Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

42 files changed, 23202 insertions, 0 deletions

diff --git a/fs/nilfs2/Kconfig b/fs/nilfs2/Kconfig
new file mode 100644
index 0000000000..7dae168e34
--- /dev/null
+++ b/fs/nilfs2/Kconfig
@@ -0,0 +1,27 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config NILFS2_FS
+	tristate "NILFS2 file system support"
+	select BUFFER_HEAD
+	select CRC32
+	select LEGACY_DIRECT_IO
+	help
+	  NILFS2 is a log-structured file system (LFS) supporting continuous
+	  snapshotting.  In addition to versioning capability of the entire
+	  file system, users can even restore files mistakenly overwritten or
+	  destroyed just a few seconds ago.  Since this file system can keep
+	  consistency like conventional LFS, it achieves quick recovery after
+	  system crashes.
+
+	  NILFS2 creates a number of checkpoints every few seconds or per
+	  synchronous write basis (unless there is no change).  Users can
+	  select significant versions among continuously created checkpoints,
+	  and can change them into snapshots which will be preserved for long
+	  periods until they are changed back to checkpoints.  Each
+	  snapshot is mountable as a read-only file system concurrently with
+	  its writable mount, and this feature is convenient for online backup.
+
+	  Some features including atime, extended attributes, and POSIX ACLs,
+	  are not supported yet.
+
+	  To compile this file system support as a module, choose M here: the
+	  module will be called nilfs2.  If unsure, say N.
diff --git a/fs/nilfs2/Makefile b/fs/nilfs2/Makefile
new file mode 100644
index 0000000000..43b60b8a4d
--- /dev/null
+++ b/fs/nilfs2/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_NILFS2_FS) += nilfs2.o
+nilfs2-y := inode.o file.o dir.o super.o namei.o page.o mdt.o \
+	btnode.o bmap.o btree.o direct.o dat.o recovery.o \
+	the_nilfs.o segbuf.o segment.o cpfile.o sufile.o \
+	ifile.o alloc.o gcinode.o ioctl.o sysfs.o
diff --git a/fs/nilfs2/alloc.c b/fs/nilfs2/alloc.c
new file mode 100644
index 0000000000..7342de296e
--- /dev/null
+++ b/fs/nilfs2/alloc.c
@@ -0,0 +1,863 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NILFS dat/inode allocator
+ *
+ * Copyright (C) 2006-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Originally written by Koji Sato.
+ * Two allocators were unified by Ryusuke Konishi and Amagai Yoshiji.
+ */
+
+#include <linux/types.h>
+#include <linux/buffer_head.h>
+#include <linux/fs.h>
+#include <linux/bitops.h>
+#include <linux/slab.h>
+#include "mdt.h"
+#include "alloc.h"
+
+
+/**
+ * nilfs_palloc_groups_per_desc_block - get the number of groups that a group
+ *					descriptor block can maintain
+ * @inode: inode of metadata file using this allocator
+ */
+static inline unsigned long
+nilfs_palloc_groups_per_desc_block(const struct inode *inode)
+{
+	return i_blocksize(inode) /
+		sizeof(struct nilfs_palloc_group_desc);
+}
+
+/**
+ * nilfs_palloc_groups_count - get maximum number of groups
+ * @inode: inode of metadata file using this allocator
+ */
+static inline unsigned long
+nilfs_palloc_groups_count(const struct inode *inode)
+{
+	return 1UL << (BITS_PER_LONG - (inode->i_blkbits + 3 /* log2(8) */));
+}
+
+/**
+ * nilfs_palloc_init_blockgroup - initialize private variables for allocator
+ * @inode: inode of metadata file using this allocator
+ * @entry_size: size of the persistent object
+ */
+int nilfs_palloc_init_blockgroup(struct inode *inode, unsigned int entry_size)
+{
+	struct nilfs_mdt_info *mi = NILFS_MDT(inode);
+
+	mi->mi_bgl = kmalloc(sizeof(*mi->mi_bgl), GFP_NOFS);
+	if (!mi->mi_bgl)
+		return -ENOMEM;
+
+	bgl_lock_init(mi->mi_bgl);
+
+	nilfs_mdt_set_entry_size(inode, entry_size, 0);
+
+	mi->mi_blocks_per_group =
+		DIV_ROUND_UP(nilfs_palloc_entries_per_group(inode),
+			     mi->mi_entries_per_block) + 1;
+		/*
+		 * Number of blocks in a group including entry blocks
+		 * and a bitmap block
+		 */
+	mi->mi_blocks_per_desc_block =
+		nilfs_palloc_groups_per_desc_block(inode) *
+		mi->mi_blocks_per_group + 1;
+		/*
+		 * Number of blocks per descriptor including the
+		 * descriptor block
+		 */
+	return 0;
+}
+
+/**
+ * nilfs_palloc_group - get group number and offset from an entry number
+ * @inode: inode of metadata file using this allocator
+ * @nr: serial number of the entry (e.g. inode number)
+ * @offset: pointer to store offset number in the group
+ */
+static unsigned long nilfs_palloc_group(const struct inode *inode, __u64 nr,
+					unsigned long *offset)
+{
+	__u64 group = nr;
+
+	*offset = do_div(group, nilfs_palloc_entries_per_group(inode));
+	return group;
+}
+
+/**
+ * nilfs_palloc_desc_blkoff - get block offset of a group descriptor block
+ * @inode: inode of metadata file using this allocator
+ * @group: group number
+ *
+ * nilfs_palloc_desc_blkoff() returns block offset of the descriptor
+ * block which contains a descriptor of the specified group.
+ */
+static unsigned long
+nilfs_palloc_desc_blkoff(const struct inode *inode, unsigned long group)
+{
+	unsigned long desc_block =
+		group / nilfs_palloc_groups_per_desc_block(inode);
+	return desc_block * NILFS_MDT(inode)->mi_blocks_per_desc_block;
+}
+
+/**
+ * nilfs_palloc_bitmap_blkoff - get block offset of a bitmap block
+ * @inode: inode of metadata file using this allocator
+ * @group: group number
+ *
+ * nilfs_palloc_bitmap_blkoff() returns block offset of the bitmap
+ * block used to allocate/deallocate entries in the specified group.
+ */
+static unsigned long
+nilfs_palloc_bitmap_blkoff(const struct inode *inode, unsigned long group)
+{
+	unsigned long desc_offset =
+		group % nilfs_palloc_groups_per_desc_block(inode);
+	return nilfs_palloc_desc_blkoff(inode, group) + 1 +
+		desc_offset * NILFS_MDT(inode)->mi_blocks_per_group;
+}
+
+/**
+ * nilfs_palloc_group_desc_nfrees - get the number of free entries in a group
+ * @desc: pointer to descriptor structure for the group
+ * @lock: spin lock protecting @desc
+ */
+static unsigned long
+nilfs_palloc_group_desc_nfrees(const struct nilfs_palloc_group_desc *desc,
+			       spinlock_t *lock)
+{
+	unsigned long nfree;
+
+	spin_lock(lock);
+	nfree = le32_to_cpu(desc->pg_nfrees);
+	spin_unlock(lock);
+	return nfree;
+}
+
+/**
+ * nilfs_palloc_group_desc_add_entries - adjust count of free entries
+ * @desc: pointer to descriptor structure for the group
+ * @lock: spin lock protecting @desc
+ * @n: delta to be added
+ */
+static u32
+nilfs_palloc_group_desc_add_entries(struct nilfs_palloc_group_desc *desc,
+				    spinlock_t *lock, u32 n)
+{
+	u32 nfree;
+
+	spin_lock(lock);
+	le32_add_cpu(&desc->pg_nfrees, n);
+	nfree = le32_to_cpu(desc->pg_nfrees);
+	spin_unlock(lock);
+	return nfree;
+}
+
+/**
+ * nilfs_palloc_entry_blkoff - get block offset of an entry block
+ * @inode: inode of metadata file using this allocator
+ * @nr: serial number of the entry (e.g. inode number)
+ */
+static unsigned long
+nilfs_palloc_entry_blkoff(const struct inode *inode, __u64 nr)
+{
+	unsigned long group, group_offset;
+
+	group = nilfs_palloc_group(inode, nr, &group_offset);
+
+	return nilfs_palloc_bitmap_blkoff(inode, group) + 1 +
+		group_offset / NILFS_MDT(inode)->mi_entries_per_block;
+}
+
+/**
+ * nilfs_palloc_desc_block_init - initialize buffer of a group descriptor block
+ * @inode: inode of metadata file
+ * @bh: buffer head of the buffer to be initialized
+ * @kaddr: kernel address mapped for the page including the buffer
+ */
+static void nilfs_palloc_desc_block_init(struct inode *inode,
+					 struct buffer_head *bh, void *kaddr)
+{
+	struct nilfs_palloc_group_desc *desc = kaddr + bh_offset(bh);
+	unsigned long n = nilfs_palloc_groups_per_desc_block(inode);
+	__le32 nfrees;
+
+	nfrees = cpu_to_le32(nilfs_palloc_entries_per_group(inode));
+	while (n-- > 0) {
+		desc->pg_nfrees = nfrees;
+		desc++;
+	}
+}
+
+static int nilfs_palloc_get_block(struct inode *inode, unsigned long blkoff,
+				  int create,
+				  void (*init_block)(struct inode *,
+						     struct buffer_head *,
+						     void *),
+				  struct buffer_head **bhp,
+				  struct nilfs_bh_assoc *prev,
+				  spinlock_t *lock)
+{
+	int ret;
+
+	spin_lock(lock);
+	if (prev->bh && blkoff == prev->blkoff &&
+	    likely(buffer_uptodate(prev->bh))) {
+		get_bh(prev->bh);
+		*bhp = prev->bh;
+		spin_unlock(lock);
+		return 0;
+	}
+	spin_unlock(lock);
+
+	ret = nilfs_mdt_get_block(inode, blkoff, create, init_block, bhp);
+	if (!ret) {
+		spin_lock(lock);
+		/*
+		 * The following code must be safe for change of the
+		 * cache contents during the get block call.
+		 */
+		brelse(prev->bh);
+		get_bh(*bhp);
+		prev->bh = *bhp;
+		prev->blkoff = blkoff;
+		spin_unlock(lock);
+	}
+	return ret;
+}
+
+/**
+ * nilfs_palloc_delete_block - delete a block on the persistent allocator file
+ * @inode: inode of metadata file using this allocator
+ * @blkoff: block offset
+ * @prev: nilfs_bh_assoc struct of the last used buffer
+ * @lock: spin lock protecting @prev
+ */
+static int nilfs_palloc_delete_block(struct inode *inode, unsigned long blkoff,
+				     struct nilfs_bh_assoc *prev,
+				     spinlock_t *lock)
+{
+	spin_lock(lock);
+	if (prev->bh && blkoff == prev->blkoff) {
+		brelse(prev->bh);
+		prev->bh = NULL;
+	}
+	spin_unlock(lock);
+	return nilfs_mdt_delete_block(inode, blkoff);
+}
+
+/**
+ * nilfs_palloc_get_desc_block - get buffer head of a group descriptor block
+ * @inode: inode of metadata file using this allocator
+ * @group: group number
+ * @create: create flag
+ * @bhp: pointer to store the resultant buffer head
+ */
+static int nilfs_palloc_get_desc_block(struct inode *inode,
+				       unsigned long group,
+				       int create, struct buffer_head **bhp)
+{
+	struct nilfs_palloc_cache *cache = NILFS_MDT(inode)->mi_palloc_cache;
+
+	return nilfs_palloc_get_block(inode,
+				      nilfs_palloc_desc_blkoff(inode, group),
+				      create, nilfs_palloc_desc_block_init,
+				      bhp, &cache->prev_desc, &cache->lock);
+}
+
+/**
+ * nilfs_palloc_get_bitmap_block - get buffer head of a bitmap block
+ * @inode: inode of metadata file using this allocator
+ * @group: group number
+ * @create: create flag
+ * @bhp: pointer to store the resultant buffer head
+ */
+static int nilfs_palloc_get_bitmap_block(struct inode *inode,
+					 unsigned long group,
+					 int create, struct buffer_head **bhp)
+{
+	struct nilfs_palloc_cache *cache = NILFS_MDT(inode)->mi_palloc_cache;
+
+	return nilfs_palloc_get_block(inode,
+				      nilfs_palloc_bitmap_blkoff(inode, group),
+				      create, NULL, bhp,
+				      &cache->prev_bitmap, &cache->lock);
+}
+
+/**
+ * nilfs_palloc_delete_bitmap_block - delete a bitmap block
+ * @inode: inode of metadata file using this allocator
+ * @group: group number
+ */
+static int nilfs_palloc_delete_bitmap_block(struct inode *inode,
+					    unsigned long group)
+{
+	struct nilfs_palloc_cache *cache = NILFS_MDT(inode)->mi_palloc_cache;
+
+	return nilfs_palloc_delete_block(inode,
+					 nilfs_palloc_bitmap_blkoff(inode,
+								    group),
+					 &cache->prev_bitmap, &cache->lock);
+}
+
+/**
+ * nilfs_palloc_get_entry_block - get buffer head of an entry block
+ * @inode: inode of metadata file using this allocator
+ * @nr: serial number of the entry (e.g. inode number)
+ * @create: create flag
+ * @bhp: pointer to store the resultant buffer head
+ */
+int nilfs_palloc_get_entry_block(struct inode *inode, __u64 nr,
+				 int create, struct buffer_head **bhp)
+{
+	struct nilfs_palloc_cache *cache = NILFS_MDT(inode)->mi_palloc_cache;
+
+	return nilfs_palloc_get_block(inode,
+				      nilfs_palloc_entry_blkoff(inode, nr),
+				      create, NULL, bhp,
+				      &cache->prev_entry, &cache->lock);
+}
+
+/**
+ * nilfs_palloc_delete_entry_block - delete an entry block
+ * @inode: inode of metadata file using this allocator
+ * @nr: serial number of the entry
+ */
+static int nilfs_palloc_delete_entry_block(struct inode *inode, __u64 nr)
+{
+	struct nilfs_palloc_cache *cache = NILFS_MDT(inode)->mi_palloc_cache;
+
+	return nilfs_palloc_delete_block(inode,
+					 nilfs_palloc_entry_blkoff(inode, nr),
+					 &cache->prev_entry, &cache->lock);
+}
+
+/**
+ * nilfs_palloc_block_get_group_desc - get kernel address of a group descriptor
+ * @inode: inode of metadata file using this allocator
+ * @group: group number
+ * @bh: buffer head of the buffer storing the group descriptor block
+ * @kaddr: kernel address mapped for the page including the buffer
+ */
+static struct nilfs_palloc_group_desc *
+nilfs_palloc_block_get_group_desc(const struct inode *inode,
+				  unsigned long group,
+				  const struct buffer_head *bh, void *kaddr)
+{
+	return (struct nilfs_palloc_group_desc *)(kaddr + bh_offset(bh)) +
+		group % nilfs_palloc_groups_per_desc_block(inode);
+}
+
+/**
+ * nilfs_palloc_block_get_entry - get kernel address of an entry
+ * @inode: inode of metadata file using this allocator
+ * @nr: serial number of the entry (e.g. inode number)
+ * @bh: buffer head of the buffer storing the entry block
+ * @kaddr: kernel address mapped for the page including the buffer
+ */
+void *nilfs_palloc_block_get_entry(const struct inode *inode, __u64 nr,
+				   const struct buffer_head *bh, void *kaddr)
+{
+	unsigned long entry_offset, group_offset;
+
+	nilfs_palloc_group(inode, nr, &group_offset);
+	entry_offset = group_offset % NILFS_MDT(inode)->mi_entries_per_block;
+
+	return kaddr + bh_offset(bh) +
+		entry_offset * NILFS_MDT(inode)->mi_entry_size;
+}
+
+/**
+ * nilfs_palloc_find_available_slot - find available slot in a group
+ * @bitmap: bitmap of the group
+ * @target: offset number of an entry in the group (start point)
+ * @bsize: size in bits
+ * @lock: spin lock protecting @bitmap
+ */
+static int nilfs_palloc_find_available_slot(unsigned char *bitmap,
+					    unsigned long target,
+					    unsigned int bsize,
+					    spinlock_t *lock)
+{
+	int pos, end = bsize;
+
+	if (likely(target < bsize)) {
+		pos = target;
+		do {
+			pos = nilfs_find_next_zero_bit(bitmap, end, pos);
+			if (pos >= end)
+				break;
+			if (!nilfs_set_bit_atomic(lock, pos, bitmap))
+				return pos;
+		} while (++pos < end);
+
+		end = target;
+	}
+
+	/* wrap around */
+	for (pos = 0; pos < end; pos++) {
+		pos = nilfs_find_next_zero_bit(bitmap, end, pos);
+		if (pos >= end)
+			break;
+		if (!nilfs_set_bit_atomic(lock, pos, bitmap))
+			return pos;
+	}
+
+	return -ENOSPC;
+}
+
+/**
+ * nilfs_palloc_rest_groups_in_desc_block - get the remaining number of groups
+ *					    in a group descriptor block
+ * @inode: inode of metadata file using this allocator
+ * @curr: current group number
+ * @max: maximum number of groups
+ */
+static unsigned long
+nilfs_palloc_rest_groups_in_desc_block(const struct inode *inode,
+				       unsigned long curr, unsigned long max)
+{
+	return min_t(unsigned long,
+		     nilfs_palloc_groups_per_desc_block(inode) -
+		     curr % nilfs_palloc_groups_per_desc_block(inode),
+		     max - curr + 1);
+}
+
+/**
+ * nilfs_palloc_count_desc_blocks - count descriptor blocks number
+ * @inode: inode of metadata file using this allocator
+ * @desc_blocks: descriptor blocks number [out]
+ */
+static int nilfs_palloc_count_desc_blocks(struct inode *inode,
+					    unsigned long *desc_blocks)
+{
+	__u64 blknum;
+	int ret;
+
+	ret = nilfs_bmap_last_key(NILFS_I(inode)->i_bmap, &blknum);
+	if (likely(!ret))
+		*desc_blocks = DIV_ROUND_UP(
+			(unsigned long)blknum,
+			NILFS_MDT(inode)->mi_blocks_per_desc_block);
+	return ret;
+}
+
+/**
+ * nilfs_palloc_mdt_file_can_grow - check potential opportunity for
+ *					MDT file growing
+ * @inode: inode of metadata file using this allocator
+ * @desc_blocks: known current descriptor blocks count
+ */
+static inline bool nilfs_palloc_mdt_file_can_grow(struct inode *inode,
+						    unsigned long desc_blocks)
+{
+	return (nilfs_palloc_groups_per_desc_block(inode) * desc_blocks) <
+			nilfs_palloc_groups_count(inode);
+}
+
+/**
+ * nilfs_palloc_count_max_entries - count max number of entries that can be
+ *					described by descriptor blocks count
+ * @inode: inode of metadata file using this allocator
+ * @nused: current number of used entries
+ * @nmaxp: max number of entries [out]
+ */
+int nilfs_palloc_count_max_entries(struct inode *inode, u64 nused, u64 *nmaxp)
+{
+	unsigned long desc_blocks = 0;
+	u64 entries_per_desc_block, nmax;
+	int err;
+
+	err = nilfs_palloc_count_desc_blocks(inode, &desc_blocks);
+	if (unlikely(err))
+		return err;
+
+	entries_per_desc_block = (u64)nilfs_palloc_entries_per_group(inode) *
+				nilfs_palloc_groups_per_desc_block(inode);
+	nmax = entries_per_desc_block * desc_blocks;
+
+	if (nused == nmax &&
+			nilfs_palloc_mdt_file_can_grow(inode, desc_blocks))
+		nmax += entries_per_desc_block;
+
+	if (nused > nmax)
+		return -ERANGE;
+
+	*nmaxp = nmax;
+	return 0;
+}
+
+/**
+ * nilfs_palloc_prepare_alloc_entry - prepare to allocate a persistent object
+ * @inode: inode of metadata file using this allocator
+ * @req: nilfs_palloc_req structure exchanged for the allocation
+ */
+int nilfs_palloc_prepare_alloc_entry(struct inode *inode,
+				     struct nilfs_palloc_req *req)
+{
+	struct buffer_head *desc_bh, *bitmap_bh;
+	struct nilfs_palloc_group_desc *desc;
+	unsigned char *bitmap;
+	void *desc_kaddr, *bitmap_kaddr;
+	unsigned long group, maxgroup, ngroups;
+	unsigned long group_offset, maxgroup_offset;
+	unsigned long n, entries_per_group;
+	unsigned long i, j;
+	spinlock_t *lock;
+	int pos, ret;
+
+	ngroups = nilfs_palloc_groups_count(inode);
+	maxgroup = ngroups - 1;
+	group = nilfs_palloc_group(inode, req->pr_entry_nr, &group_offset);
+	entries_per_group = nilfs_palloc_entries_per_group(inode);
+
+	for (i = 0; i < ngroups; i += n) {
+		if (group >= ngroups) {
+			/* wrap around */
+			group = 0;
+			maxgroup = nilfs_palloc_group(inode, req->pr_entry_nr,
+						      &maxgroup_offset) - 1;
+		}
+		ret = nilfs_palloc_get_desc_block(inode, group, 1, &desc_bh);
+		if (ret < 0)
+			return ret;
+		desc_kaddr = kmap(desc_bh->b_page);
+		desc = nilfs_palloc_block_get_group_desc(
+			inode, group, desc_bh, desc_kaddr);
+		n = nilfs_palloc_rest_groups_in_desc_block(inode, group,
+							   maxgroup);
+		for (j = 0; j < n; j++, desc++, group++) {
+			lock = nilfs_mdt_bgl_lock(inode, group);
+			if (nilfs_palloc_group_desc_nfrees(desc, lock) > 0) {
+				ret = nilfs_palloc_get_bitmap_block(
+					inode, group, 1, &bitmap_bh);
+				if (ret < 0)
+					goto out_desc;
+				bitmap_kaddr = kmap(bitmap_bh->b_page);
+				bitmap = bitmap_kaddr + bh_offset(bitmap_bh);
+				pos = nilfs_palloc_find_available_slot(
+					bitmap, group_offset,
+					entries_per_group, lock);
+				if (pos >= 0) {
+					/* found a free entry */
+					nilfs_palloc_group_desc_add_entries(
+						desc, lock, -1);
+					req->pr_entry_nr =
+						entries_per_group * group + pos;
+					kunmap(desc_bh->b_page);
+					kunmap(bitmap_bh->b_page);
+
+					req->pr_desc_bh = desc_bh;
+					req->pr_bitmap_bh = bitmap_bh;
+					return 0;
+				}
+				kunmap(bitmap_bh->b_page);
+				brelse(bitmap_bh);
+			}
+
+			group_offset = 0;
+		}
+
+		kunmap(desc_bh->b_page);
+		brelse(desc_bh);
+	}
+
+	/* no entries left */
+	return -ENOSPC;
+
+ out_desc:
+	kunmap(desc_bh->b_page);
+	brelse(desc_bh);
+	return ret;
+}
+
+/**
+ * nilfs_palloc_commit_alloc_entry - finish allocation of a persistent object
+ * @inode: inode of metadata file using this allocator
+ * @req: nilfs_palloc_req structure exchanged for the allocation
+ */
+void nilfs_palloc_commit_alloc_entry(struct inode *inode,
+				     struct nilfs_palloc_req *req)
+{
+	mark_buffer_dirty(req->pr_bitmap_bh);
+	mark_buffer_dirty(req->pr_desc_bh);
+	nilfs_mdt_mark_dirty(inode);
+
+	brelse(req->pr_bitmap_bh);
+	brelse(req->pr_desc_bh);
+}
+
+/**
+ * nilfs_palloc_commit_free_entry - finish deallocating a persistent object
+ * @inode: inode of metadata file using this allocator
+ * @req: nilfs_palloc_req structure exchanged for the removal
+ */
+void nilfs_palloc_commit_free_entry(struct inode *inode,
+				    struct nilfs_palloc_req *req)
+{
+	struct nilfs_palloc_group_desc *desc;
+	unsigned long group, group_offset;
+	unsigned char *bitmap;
+	void *desc_kaddr, *bitmap_kaddr;
+	spinlock_t *lock;
+
+	group = nilfs_palloc_group(inode, req->pr_entry_nr, &group_offset);
+	desc_kaddr = kmap(req->pr_desc_bh->b_page);
+	desc = nilfs_palloc_block_get_group_desc(inode, group,
+						 req->pr_desc_bh, desc_kaddr);
+	bitmap_kaddr = kmap(req->pr_bitmap_bh->b_page);
+	bitmap = bitmap_kaddr + bh_offset(req->pr_bitmap_bh);
+	lock = nilfs_mdt_bgl_lock(inode, group);
+
+	if (!nilfs_clear_bit_atomic(lock, group_offset, bitmap))
+		nilfs_warn(inode->i_sb,
+			   "%s (ino=%lu): entry number %llu already freed",
+			   __func__, inode->i_ino,
+			   (unsigned long long)req->pr_entry_nr);
+	else
+		nilfs_palloc_group_desc_add_entries(desc, lock, 1);
+
+	kunmap(req->pr_bitmap_bh->b_page);
+	kunmap(req->pr_desc_bh->b_page);
+
+	mark_buffer_dirty(req->pr_desc_bh);
+	mark_buffer_dirty(req->pr_bitmap_bh);
+	nilfs_mdt_mark_dirty(inode);
+
+	brelse(req->pr_bitmap_bh);
+	brelse(req->pr_desc_bh);
+}
+
+/**
+ * nilfs_palloc_abort_alloc_entry - cancel allocation of a persistent object
+ * @inode: inode of metadata file using this allocator
+ * @req: nilfs_palloc_req structure exchanged for the allocation
+ */
+void nilfs_palloc_abort_alloc_entry(struct inode *inode,
+				    struct nilfs_palloc_req *req)
+{
+	struct nilfs_palloc_group_desc *desc;
+	void *desc_kaddr, *bitmap_kaddr;
+	unsigned char *bitmap;
+	unsigned long group, group_offset;
+	spinlock_t *lock;
+
+	group = nilfs_palloc_group(inode, req->pr_entry_nr, &group_offset);
+	desc_kaddr = kmap(req->pr_desc_bh->b_page);
+	desc = nilfs_palloc_block_get_group_desc(inode, group,
+						 req->pr_desc_bh, desc_kaddr);
+	bitmap_kaddr = kmap(req->pr_bitmap_bh->b_page);
+	bitmap = bitmap_kaddr + bh_offset(req->pr_bitmap_bh);
+	lock = nilfs_mdt_bgl_lock(inode, group);
+
+	if (!nilfs_clear_bit_atomic(lock, group_offset, bitmap))
+		nilfs_warn(inode->i_sb,
+			   "%s (ino=%lu): entry number %llu already freed",
+			   __func__, inode->i_ino,
+			   (unsigned long long)req->pr_entry_nr);
+	else
+		nilfs_palloc_group_desc_add_entries(desc, lock, 1);
+
+	kunmap(req->pr_bitmap_bh->b_page);
+	kunmap(req->pr_desc_bh->b_page);
+
+	brelse(req->pr_bitmap_bh);
+	brelse(req->pr_desc_bh);
+
+	req->pr_entry_nr = 0;
+	req->pr_bitmap_bh = NULL;
+	req->pr_desc_bh = NULL;
+}
+
+/**
+ * nilfs_palloc_prepare_free_entry - prepare to deallocate a persistent object
+ * @inode: inode of metadata file using this allocator
+ * @req: nilfs_palloc_req structure exchanged for the removal
+ */
+int nilfs_palloc_prepare_free_entry(struct inode *inode,
+				    struct nilfs_palloc_req *req)
+{
+	struct buffer_head *desc_bh, *bitmap_bh;
+	unsigned long group, group_offset;
+	int ret;
+
+	group = nilfs_palloc_group(inode, req->pr_entry_nr, &group_offset);
+	ret = nilfs_palloc_get_desc_block(inode, group, 1, &desc_bh);
+	if (ret < 0)
+		return ret;
+	ret = nilfs_palloc_get_bitmap_block(inode, group, 1, &bitmap_bh);
+	if (ret < 0) {
+		brelse(desc_bh);
+		return ret;
+	}
+
+	req->pr_desc_bh = desc_bh;
+	req->pr_bitmap_bh = bitmap_bh;
+	return 0;
+}
+
+/**
+ * nilfs_palloc_abort_free_entry - cancel deallocating a persistent object
+ * @inode: inode of metadata file using this allocator
+ * @req: nilfs_palloc_req structure exchanged for the removal
+ */
+void nilfs_palloc_abort_free_entry(struct inode *inode,
+				   struct nilfs_palloc_req *req)
+{
+	brelse(req->pr_bitmap_bh);
+	brelse(req->pr_desc_bh);
+
+	req->pr_entry_nr = 0;
+	req->pr_bitmap_bh = NULL;
+	req->pr_desc_bh = NULL;
+}
+
+/**
+ * nilfs_palloc_freev - deallocate a set of persistent objects
+ * @inode: inode of metadata file using this allocator
+ * @entry_nrs: array of entry numbers to be deallocated
+ * @nitems: number of entries stored in @entry_nrs
+ */
+int nilfs_palloc_freev(struct inode *inode, __u64 *entry_nrs, size_t nitems)
+{
+	struct buffer_head *desc_bh, *bitmap_bh;
+	struct nilfs_palloc_group_desc *desc;
+	unsigned char *bitmap;
+	void *desc_kaddr, *bitmap_kaddr;
+	unsigned long group, group_offset;
+	__u64 group_min_nr, last_nrs[8];
+	const unsigned long epg = nilfs_palloc_entries_per_group(inode);
+	const unsigned int epb = NILFS_MDT(inode)->mi_entries_per_block;
+	unsigned int entry_start, end, pos;
+	spinlock_t *lock;
+	int i, j, k, ret;
+	u32 nfree;
+
+	for (i = 0; i < nitems; i = j) {
+		int change_group = false;
+		int nempties = 0, n = 0;
+
+		group = nilfs_palloc_group(inode, entry_nrs[i], &group_offset);
+		ret = nilfs_palloc_get_desc_block(inode, group, 0, &desc_bh);
+		if (ret < 0)
+			return ret;
+		ret = nilfs_palloc_get_bitmap_block(inode, group, 0,
+						    &bitmap_bh);
+		if (ret < 0) {
+			brelse(desc_bh);
+			return ret;
+		}
+
+		/* Get the first entry number of the group */
+		group_min_nr = (__u64)group * epg;
+
+		bitmap_kaddr = kmap(bitmap_bh->b_page);
+		bitmap = bitmap_kaddr + bh_offset(bitmap_bh);
+		lock = nilfs_mdt_bgl_lock(inode, group);
+
+		j = i;
+		entry_start = rounddown(group_offset, epb);
+		do {
+			if (!nilfs_clear_bit_atomic(lock, group_offset,
+						    bitmap)) {
+				nilfs_warn(inode->i_sb,
+					   "%s (ino=%lu): entry number %llu already freed",
+					   __func__, inode->i_ino,
+					   (unsigned long long)entry_nrs[j]);
+			} else {
+				n++;
+			}
+
+			j++;
+			if (j >= nitems || entry_nrs[j] < group_min_nr ||
+			    entry_nrs[j] >= group_min_nr + epg) {
+				change_group = true;
+			} else {
+				group_offset = entry_nrs[j] - group_min_nr;
+				if (group_offset >= entry_start &&
+				    group_offset < entry_start + epb) {
+					/* This entry is in the same block */
+					continue;
+				}
+			}
+
+			/* Test if the entry block is empty or not */
+			end = entry_start + epb;
+			pos = nilfs_find_next_bit(bitmap, end, entry_start);
+			if (pos >= end) {
+				last_nrs[nempties++] = entry_nrs[j - 1];
+				if (nempties >= ARRAY_SIZE(last_nrs))
+					break;
+			}
+
+			if (change_group)
+				break;
+
+			/* Go on to the next entry block */
+			entry_start = rounddown(group_offset, epb);
+		} while (true);
+
+		kunmap(bitmap_bh->b_page);
+		mark_buffer_dirty(bitmap_bh);
+		brelse(bitmap_bh);
+
+		for (k = 0; k < nempties; k++) {
+			ret = nilfs_palloc_delete_entry_block(inode,
+							      last_nrs[k]);
+			if (ret && ret != -ENOENT)
+				nilfs_warn(inode->i_sb,
+					   "error %d deleting block that object (entry=%llu, ino=%lu) belongs to",
+					   ret, (unsigned long long)last_nrs[k],
+					   inode->i_ino);
+		}
+
+		desc_kaddr = kmap_atomic(desc_bh->b_page);
+		desc = nilfs_palloc_block_get_group_desc(
+			inode, group, desc_bh, desc_kaddr);
+		nfree = nilfs_palloc_group_desc_add_entries(desc, lock, n);
+		kunmap_atomic(desc_kaddr);
+		mark_buffer_dirty(desc_bh);
+		nilfs_mdt_mark_dirty(inode);
+		brelse(desc_bh);
+
+		if (nfree == nilfs_palloc_entries_per_group(inode)) {
+			ret = nilfs_palloc_delete_bitmap_block(inode, group);
+			if (ret && ret != -ENOENT)
+				nilfs_warn(inode->i_sb,
+					   "error %d deleting bitmap block of group=%lu, ino=%lu",
+					   ret, group, inode->i_ino);
+		}
+	}
+	return 0;
+}
+
+void nilfs_palloc_setup_cache(struct inode *inode,
+			      struct nilfs_palloc_cache *cache)
+{
+	NILFS_MDT(inode)->mi_palloc_cache = cache;
+	spin_lock_init(&cache->lock);
+}
+
+void nilfs_palloc_clear_cache(struct inode *inode)
+{
+	struct nilfs_palloc_cache *cache = NILFS_MDT(inode)->mi_palloc_cache;
+
+	spin_lock(&cache->lock);
+	brelse(cache->prev_desc.bh);
+	brelse(cache->prev_bitmap.bh);
+	brelse(cache->prev_entry.bh);
+	cache->prev_desc.bh = NULL;
+	cache->prev_bitmap.bh = NULL;
+	cache->prev_entry.bh = NULL;
+	spin_unlock(&cache->lock);
+}
+
+void nilfs_palloc_destroy_cache(struct inode *inode)
+{
+	nilfs_palloc_clear_cache(inode);
+	NILFS_MDT(inode)->mi_palloc_cache = NULL;
+}
diff --git a/fs/nilfs2/alloc.h b/fs/nilfs2/alloc.h
new file mode 100644
index 0000000000..b667e869ac
--- /dev/null
+++ b/fs/nilfs2/alloc.h
@@ -0,0 +1,97 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Persistent object (dat entry/disk inode) allocator/deallocator
+ *
+ * Copyright (C) 2006-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Originally written by Koji Sato.
+ * Two allocators were unified by Ryusuke Konishi and Amagai Yoshiji.
+ */
+
+#ifndef _NILFS_ALLOC_H
+#define _NILFS_ALLOC_H
+
+#include <linux/types.h>
+#include <linux/buffer_head.h>
+#include <linux/fs.h>
+
+/**
+ * nilfs_palloc_entries_per_group - get the number of entries per group
+ * @inode: inode of metadata file using this allocator
+ *
+ * The number of entries per group is defined by the number of bits
+ * that a bitmap block can maintain.
+ */
+static inline unsigned long
+nilfs_palloc_entries_per_group(const struct inode *inode)
+{
+	return 1UL << (inode->i_blkbits + 3 /* log2(8 = CHAR_BITS) */);
+}
+
+int nilfs_palloc_init_blockgroup(struct inode *, unsigned int);
+int nilfs_palloc_get_entry_block(struct inode *, __u64, int,
+				 struct buffer_head **);
+void *nilfs_palloc_block_get_entry(const struct inode *, __u64,
+				   const struct buffer_head *, void *);
+
+int nilfs_palloc_count_max_entries(struct inode *, u64, u64 *);
+
+/**
+ * nilfs_palloc_req - persistent allocator request and reply
+ * @pr_entry_nr: entry number (vblocknr or inode number)
+ * @pr_desc_bh: buffer head of the buffer containing block group descriptors
+ * @pr_bitmap_bh: buffer head of the buffer containing a block group bitmap
+ * @pr_entry_bh: buffer head of the buffer containing translation entries
+ */
+struct nilfs_palloc_req {
+	__u64 pr_entry_nr;
+	struct buffer_head *pr_desc_bh;
+	struct buffer_head *pr_bitmap_bh;
+	struct buffer_head *pr_entry_bh;
+};
+
+int nilfs_palloc_prepare_alloc_entry(struct inode *,
+				     struct nilfs_palloc_req *);
+void nilfs_palloc_commit_alloc_entry(struct inode *,
+				     struct nilfs_palloc_req *);
+void nilfs_palloc_abort_alloc_entry(struct inode *, struct nilfs_palloc_req *);
+void nilfs_palloc_commit_free_entry(struct inode *, struct nilfs_palloc_req *);
+int nilfs_palloc_prepare_free_entry(struct inode *, struct nilfs_palloc_req *);
+void nilfs_palloc_abort_free_entry(struct inode *, struct nilfs_palloc_req *);
+int nilfs_palloc_freev(struct inode *, __u64 *, size_t);
+
+#define nilfs_set_bit_atomic		ext2_set_bit_atomic
+#define nilfs_clear_bit_atomic		ext2_clear_bit_atomic
+#define nilfs_find_next_zero_bit	find_next_zero_bit_le
+#define nilfs_find_next_bit		find_next_bit_le
+
+/**
+ * struct nilfs_bh_assoc - block offset and buffer head association
+ * @blkoff: block offset
+ * @bh: buffer head
+ */
+struct nilfs_bh_assoc {
+	unsigned long blkoff;
+	struct buffer_head *bh;
+};
+
+/**
+ * struct nilfs_palloc_cache - persistent object allocator cache
+ * @lock: cache protecting lock
+ * @prev_desc: blockgroup descriptors cache
+ * @prev_bitmap: blockgroup bitmap cache
+ * @prev_entry: translation entries cache
+ */
+struct nilfs_palloc_cache {
+	spinlock_t lock;
+	struct nilfs_bh_assoc prev_desc;
+	struct nilfs_bh_assoc prev_bitmap;
+	struct nilfs_bh_assoc prev_entry;
+};
+
+void nilfs_palloc_setup_cache(struct inode *inode,
+			      struct nilfs_palloc_cache *cache);
+void nilfs_palloc_clear_cache(struct inode *inode);
+void nilfs_palloc_destroy_cache(struct inode *inode);
+
+#endif	/* _NILFS_ALLOC_H */
diff --git a/fs/nilfs2/bmap.c b/fs/nilfs2/bmap.c
new file mode 100644
index 0000000000..7a8f166f2c
--- /dev/null
+++ b/fs/nilfs2/bmap.c
@@ -0,0 +1,588 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NILFS block mapping.
+ *
+ * Copyright (C) 2006-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Koji Sato.
+ */
+
+#include <linux/fs.h>
+#include <linux/string.h>
+#include <linux/errno.h>
+#include "nilfs.h"
+#include "bmap.h"
+#include "btree.h"
+#include "direct.h"
+#include "btnode.h"
+#include "mdt.h"
+#include "dat.h"
+#include "alloc.h"
+
+struct inode *nilfs_bmap_get_dat(const struct nilfs_bmap *bmap)
+{
+	struct the_nilfs *nilfs = bmap->b_inode->i_sb->s_fs_info;
+
+	return nilfs->ns_dat;
+}
+
+static int nilfs_bmap_convert_error(struct nilfs_bmap *bmap,
+				     const char *fname, int err)
+{
+	struct inode *inode = bmap->b_inode;
+
+	if (err == -EINVAL) {
+		__nilfs_error(inode->i_sb, fname,
+			      "broken bmap (inode number=%lu)", inode->i_ino);
+		err = -EIO;
+	}
+	return err;
+}
+
+/**
+ * nilfs_bmap_lookup_at_level - find a data block or node block
+ * @bmap: bmap
+ * @key: key
+ * @level: level
+ * @ptrp: place to store the value associated to @key
+ *
+ * Description: nilfs_bmap_lookup_at_level() finds a record whose key
+ * matches @key in the block at @level of the bmap.
+ *
+ * Return Value: On success, 0 is returned and the record associated with @key
+ * is stored in the place pointed by @ptrp. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-ENOENT - A record associated with @key does not exist.
+ */
+int nilfs_bmap_lookup_at_level(struct nilfs_bmap *bmap, __u64 key, int level,
+			       __u64 *ptrp)
+{
+	sector_t blocknr;
+	int ret;
+
+	down_read(&bmap->b_sem);
+	ret = bmap->b_ops->bop_lookup(bmap, key, level, ptrp);
+	if (ret < 0)
+		goto out;
+
+	if (NILFS_BMAP_USE_VBN(bmap)) {
+		ret = nilfs_dat_translate(nilfs_bmap_get_dat(bmap), *ptrp,
+					  &blocknr);
+		if (!ret)
+			*ptrp = blocknr;
+		else if (ret == -ENOENT) {
+			/*
+			 * If there was no valid entry in DAT for the block
+			 * address obtained by b_ops->bop_lookup, then pass
+			 * internal code -EINVAL to nilfs_bmap_convert_error
+			 * to treat it as metadata corruption.
+			 */
+			ret = -EINVAL;
+		}
+	}
+
+ out:
+	up_read(&bmap->b_sem);
+	return nilfs_bmap_convert_error(bmap, __func__, ret);
+}
+
+int nilfs_bmap_lookup_contig(struct nilfs_bmap *bmap, __u64 key, __u64 *ptrp,
+			     unsigned int maxblocks)
+{
+	int ret;
+
+	down_read(&bmap->b_sem);
+	ret = bmap->b_ops->bop_lookup_contig(bmap, key, ptrp, maxblocks);
+	up_read(&bmap->b_sem);
+
+	return nilfs_bmap_convert_error(bmap, __func__, ret);
+}
+
+static int nilfs_bmap_do_insert(struct nilfs_bmap *bmap, __u64 key, __u64 ptr)
+{
+	__u64 keys[NILFS_BMAP_SMALL_HIGH + 1];
+	__u64 ptrs[NILFS_BMAP_SMALL_HIGH + 1];
+	int ret, n;
+
+	if (bmap->b_ops->bop_check_insert != NULL) {
+		ret = bmap->b_ops->bop_check_insert(bmap, key);
+		if (ret > 0) {
+			n = bmap->b_ops->bop_gather_data(
+				bmap, keys, ptrs, NILFS_BMAP_SMALL_HIGH + 1);
+			if (n < 0)
+				return n;
+			ret = nilfs_btree_convert_and_insert(
+				bmap, key, ptr, keys, ptrs, n);
+			if (ret == 0)
+				bmap->b_u.u_flags |= NILFS_BMAP_LARGE;
+
+			return ret;
+		} else if (ret < 0)
+			return ret;
+	}
+
+	return bmap->b_ops->bop_insert(bmap, key, ptr);
+}
+
+/**
+ * nilfs_bmap_insert - insert a new key-record pair into a bmap
+ * @bmap: bmap
+ * @key: key
+ * @rec: record
+ *
+ * Description: nilfs_bmap_insert() inserts the new key-record pair specified
+ * by @key and @rec into @bmap.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-EEXIST - A record associated with @key already exist.
+ */
+int nilfs_bmap_insert(struct nilfs_bmap *bmap, __u64 key, unsigned long rec)
+{
+	int ret;
+
+	down_write(&bmap->b_sem);
+	ret = nilfs_bmap_do_insert(bmap, key, rec);
+	up_write(&bmap->b_sem);
+
+	return nilfs_bmap_convert_error(bmap, __func__, ret);
+}
+
+static int nilfs_bmap_do_delete(struct nilfs_bmap *bmap, __u64 key)
+{
+	__u64 keys[NILFS_BMAP_LARGE_LOW + 1];
+	__u64 ptrs[NILFS_BMAP_LARGE_LOW + 1];
+	int ret, n;
+
+	if (bmap->b_ops->bop_check_delete != NULL) {
+		ret = bmap->b_ops->bop_check_delete(bmap, key);
+		if (ret > 0) {
+			n = bmap->b_ops->bop_gather_data(
+				bmap, keys, ptrs, NILFS_BMAP_LARGE_LOW + 1);
+			if (n < 0)
+				return n;
+			ret = nilfs_direct_delete_and_convert(
+				bmap, key, keys, ptrs, n);
+			if (ret == 0)
+				bmap->b_u.u_flags &= ~NILFS_BMAP_LARGE;
+
+			return ret;
+		} else if (ret < 0)
+			return ret;
+	}
+
+	return bmap->b_ops->bop_delete(bmap, key);
+}
+
+/**
+ * nilfs_bmap_seek_key - seek a valid entry and return its key
+ * @bmap: bmap struct
+ * @start: start key number
+ * @keyp: place to store valid key
+ *
+ * Description: nilfs_bmap_seek_key() seeks a valid key on @bmap
+ * starting from @start, and stores it to @keyp if found.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-ENOENT - No valid entry was found
+ */
+int nilfs_bmap_seek_key(struct nilfs_bmap *bmap, __u64 start, __u64 *keyp)
+{
+	int ret;
+
+	down_read(&bmap->b_sem);
+	ret = bmap->b_ops->bop_seek_key(bmap, start, keyp);
+	up_read(&bmap->b_sem);
+
+	if (ret < 0)
+		ret = nilfs_bmap_convert_error(bmap, __func__, ret);
+	return ret;
+}
+
+int nilfs_bmap_last_key(struct nilfs_bmap *bmap, __u64 *keyp)
+{
+	int ret;
+
+	down_read(&bmap->b_sem);
+	ret = bmap->b_ops->bop_last_key(bmap, keyp);
+	up_read(&bmap->b_sem);
+
+	if (ret < 0)
+		ret = nilfs_bmap_convert_error(bmap, __func__, ret);
+	return ret;
+}
+
+/**
+ * nilfs_bmap_delete - delete a key-record pair from a bmap
+ * @bmap: bmap
+ * @key: key
+ *
+ * Description: nilfs_bmap_delete() deletes the key-record pair specified by
+ * @key from @bmap.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-ENOENT - A record associated with @key does not exist.
+ */
+int nilfs_bmap_delete(struct nilfs_bmap *bmap, __u64 key)
+{
+	int ret;
+
+	down_write(&bmap->b_sem);
+	ret = nilfs_bmap_do_delete(bmap, key);
+	up_write(&bmap->b_sem);
+
+	return nilfs_bmap_convert_error(bmap, __func__, ret);
+}
+
+static int nilfs_bmap_do_truncate(struct nilfs_bmap *bmap, __u64 key)
+{
+	__u64 lastkey;
+	int ret;
+
+	ret = bmap->b_ops->bop_last_key(bmap, &lastkey);
+	if (ret < 0) {
+		if (ret == -ENOENT)
+			ret = 0;
+		return ret;
+	}
+
+	while (key <= lastkey) {
+		ret = nilfs_bmap_do_delete(bmap, lastkey);
+		if (ret < 0)
+			return ret;
+		ret = bmap->b_ops->bop_last_key(bmap, &lastkey);
+		if (ret < 0) {
+			if (ret == -ENOENT)
+				ret = 0;
+			return ret;
+		}
+	}
+	return 0;
+}
+
+/**
+ * nilfs_bmap_truncate - truncate a bmap to a specified key
+ * @bmap: bmap
+ * @key: key
+ *
+ * Description: nilfs_bmap_truncate() removes key-record pairs whose keys are
+ * greater than or equal to @key from @bmap.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ */
+int nilfs_bmap_truncate(struct nilfs_bmap *bmap, __u64 key)
+{
+	int ret;
+
+	down_write(&bmap->b_sem);
+	ret = nilfs_bmap_do_truncate(bmap, key);
+	up_write(&bmap->b_sem);
+
+	return nilfs_bmap_convert_error(bmap, __func__, ret);
+}
+
+/**
+ * nilfs_bmap_clear - free resources a bmap holds
+ * @bmap: bmap
+ *
+ * Description: nilfs_bmap_clear() frees resources associated with @bmap.
+ */
+void nilfs_bmap_clear(struct nilfs_bmap *bmap)
+{
+	down_write(&bmap->b_sem);
+	if (bmap->b_ops->bop_clear != NULL)
+		bmap->b_ops->bop_clear(bmap);
+	up_write(&bmap->b_sem);
+}
+
+/**
+ * nilfs_bmap_propagate - propagate dirty state
+ * @bmap: bmap
+ * @bh: buffer head
+ *
+ * Description: nilfs_bmap_propagate() marks the buffers that directly or
+ * indirectly refer to the block specified by @bh dirty.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ */
+int nilfs_bmap_propagate(struct nilfs_bmap *bmap, struct buffer_head *bh)
+{
+	int ret;
+
+	down_write(&bmap->b_sem);
+	ret = bmap->b_ops->bop_propagate(bmap, bh);
+	up_write(&bmap->b_sem);
+
+	return nilfs_bmap_convert_error(bmap, __func__, ret);
+}
+
+/**
+ * nilfs_bmap_lookup_dirty_buffers -
+ * @bmap: bmap
+ * @listp: pointer to buffer head list
+ */
+void nilfs_bmap_lookup_dirty_buffers(struct nilfs_bmap *bmap,
+				     struct list_head *listp)
+{
+	if (bmap->b_ops->bop_lookup_dirty_buffers != NULL)
+		bmap->b_ops->bop_lookup_dirty_buffers(bmap, listp);
+}
+
+/**
+ * nilfs_bmap_assign - assign a new block number to a block
+ * @bmap: bmap
+ * @bh: pointer to buffer head
+ * @blocknr: block number
+ * @binfo: block information
+ *
+ * Description: nilfs_bmap_assign() assigns the block number @blocknr to the
+ * buffer specified by @bh.
+ *
+ * Return Value: On success, 0 is returned and the buffer head of a newly
+ * create buffer and the block information associated with the buffer are
+ * stored in the place pointed by @bh and @binfo, respectively. On error, one
+ * of the following negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ */
+int nilfs_bmap_assign(struct nilfs_bmap *bmap,
+		      struct buffer_head **bh,
+		      unsigned long blocknr,
+		      union nilfs_binfo *binfo)
+{
+	int ret;
+
+	down_write(&bmap->b_sem);
+	ret = bmap->b_ops->bop_assign(bmap, bh, blocknr, binfo);
+	up_write(&bmap->b_sem);
+
+	return nilfs_bmap_convert_error(bmap, __func__, ret);
+}
+
+/**
+ * nilfs_bmap_mark - mark block dirty
+ * @bmap: bmap
+ * @key: key
+ * @level: level
+ *
+ * Description: nilfs_bmap_mark() marks the block specified by @key and @level
+ * as dirty.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ */
+int nilfs_bmap_mark(struct nilfs_bmap *bmap, __u64 key, int level)
+{
+	int ret;
+
+	if (bmap->b_ops->bop_mark == NULL)
+		return 0;
+
+	down_write(&bmap->b_sem);
+	ret = bmap->b_ops->bop_mark(bmap, key, level);
+	up_write(&bmap->b_sem);
+
+	return nilfs_bmap_convert_error(bmap, __func__, ret);
+}
+
+/**
+ * nilfs_bmap_test_and_clear_dirty - test and clear a bmap dirty state
+ * @bmap: bmap
+ *
+ * Description: nilfs_test_and_clear() is the atomic operation to test and
+ * clear the dirty state of @bmap.
+ *
+ * Return Value: 1 is returned if @bmap is dirty, or 0 if clear.
+ */
+int nilfs_bmap_test_and_clear_dirty(struct nilfs_bmap *bmap)
+{
+	int ret;
+
+	down_write(&bmap->b_sem);
+	ret = nilfs_bmap_dirty(bmap);
+	nilfs_bmap_clear_dirty(bmap);
+	up_write(&bmap->b_sem);
+	return ret;
+}
+
+
+/*
+ * Internal use only
+ */
+__u64 nilfs_bmap_data_get_key(const struct nilfs_bmap *bmap,
+			      const struct buffer_head *bh)
+{
+	struct buffer_head *pbh;
+	__u64 key;
+
+	key = page_index(bh->b_page) << (PAGE_SHIFT -
+					 bmap->b_inode->i_blkbits);
+	for (pbh = page_buffers(bh->b_page); pbh != bh; pbh = pbh->b_this_page)
+		key++;
+
+	return key;
+}
+
+__u64 nilfs_bmap_find_target_seq(const struct nilfs_bmap *bmap, __u64 key)
+{
+	__s64 diff;
+
+	diff = key - bmap->b_last_allocated_key;
+	if ((nilfs_bmap_keydiff_abs(diff) < NILFS_INODE_BMAP_SIZE) &&
+	    (bmap->b_last_allocated_ptr != NILFS_BMAP_INVALID_PTR) &&
+	    (bmap->b_last_allocated_ptr + diff > 0))
+		return bmap->b_last_allocated_ptr + diff;
+	else
+		return NILFS_BMAP_INVALID_PTR;
+}
+
+#define NILFS_BMAP_GROUP_DIV	8
+__u64 nilfs_bmap_find_target_in_group(const struct nilfs_bmap *bmap)
+{
+	struct inode *dat = nilfs_bmap_get_dat(bmap);
+	unsigned long entries_per_group = nilfs_palloc_entries_per_group(dat);
+	unsigned long group = bmap->b_inode->i_ino / entries_per_group;
+
+	return group * entries_per_group +
+		(bmap->b_inode->i_ino % NILFS_BMAP_GROUP_DIV) *
+		(entries_per_group / NILFS_BMAP_GROUP_DIV);
+}
+
+static struct lock_class_key nilfs_bmap_dat_lock_key;
+static struct lock_class_key nilfs_bmap_mdt_lock_key;
+
+/**
+ * nilfs_bmap_read - read a bmap from an inode
+ * @bmap: bmap
+ * @raw_inode: on-disk inode
+ *
+ * Description: nilfs_bmap_read() initializes the bmap @bmap.
+ *
+ * Return Value: On success, 0 is returned. On error, the following negative
+ * error code is returned.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ */
+int nilfs_bmap_read(struct nilfs_bmap *bmap, struct nilfs_inode *raw_inode)
+{
+	if (raw_inode == NULL)
+		memset(bmap->b_u.u_data, 0, NILFS_BMAP_SIZE);
+	else
+		memcpy(bmap->b_u.u_data, raw_inode->i_bmap, NILFS_BMAP_SIZE);
+
+	init_rwsem(&bmap->b_sem);
+	bmap->b_state = 0;
+	bmap->b_inode = &NILFS_BMAP_I(bmap)->vfs_inode;
+	switch (bmap->b_inode->i_ino) {
+	case NILFS_DAT_INO:
+		bmap->b_ptr_type = NILFS_BMAP_PTR_P;
+		bmap->b_last_allocated_key = 0;
+		bmap->b_last_allocated_ptr = NILFS_BMAP_NEW_PTR_INIT;
+		lockdep_set_class(&bmap->b_sem, &nilfs_bmap_dat_lock_key);
+		break;
+	case NILFS_CPFILE_INO:
+	case NILFS_SUFILE_INO:
+		bmap->b_ptr_type = NILFS_BMAP_PTR_VS;
+		bmap->b_last_allocated_key = 0;
+		bmap->b_last_allocated_ptr = NILFS_BMAP_INVALID_PTR;
+		lockdep_set_class(&bmap->b_sem, &nilfs_bmap_mdt_lock_key);
+		break;
+	case NILFS_IFILE_INO:
+		lockdep_set_class(&bmap->b_sem, &nilfs_bmap_mdt_lock_key);
+		fallthrough;
+	default:
+		bmap->b_ptr_type = NILFS_BMAP_PTR_VM;
+		bmap->b_last_allocated_key = 0;
+		bmap->b_last_allocated_ptr = NILFS_BMAP_INVALID_PTR;
+		break;
+	}
+
+	return (bmap->b_u.u_flags & NILFS_BMAP_LARGE) ?
+		nilfs_btree_init(bmap) : nilfs_direct_init(bmap);
+}
+
+/**
+ * nilfs_bmap_write - write back a bmap to an inode
+ * @bmap: bmap
+ * @raw_inode: on-disk inode
+ *
+ * Description: nilfs_bmap_write() stores @bmap in @raw_inode.
+ */
+void nilfs_bmap_write(struct nilfs_bmap *bmap, struct nilfs_inode *raw_inode)
+{
+	down_write(&bmap->b_sem);
+	memcpy(raw_inode->i_bmap, bmap->b_u.u_data,
+	       NILFS_INODE_BMAP_SIZE * sizeof(__le64));
+	if (bmap->b_inode->i_ino == NILFS_DAT_INO)
+		bmap->b_last_allocated_ptr = NILFS_BMAP_NEW_PTR_INIT;
+
+	up_write(&bmap->b_sem);
+}
+
+void nilfs_bmap_init_gc(struct nilfs_bmap *bmap)
+{
+	memset(&bmap->b_u, 0, NILFS_BMAP_SIZE);
+	init_rwsem(&bmap->b_sem);
+	bmap->b_inode = &NILFS_BMAP_I(bmap)->vfs_inode;
+	bmap->b_ptr_type = NILFS_BMAP_PTR_U;
+	bmap->b_last_allocated_key = 0;
+	bmap->b_last_allocated_ptr = NILFS_BMAP_INVALID_PTR;
+	bmap->b_state = 0;
+	nilfs_btree_init_gc(bmap);
+}
+
+void nilfs_bmap_save(const struct nilfs_bmap *bmap,
+		     struct nilfs_bmap_store *store)
+{
+	memcpy(store->data, bmap->b_u.u_data, sizeof(store->data));
+	store->last_allocated_key = bmap->b_last_allocated_key;
+	store->last_allocated_ptr = bmap->b_last_allocated_ptr;
+	store->state = bmap->b_state;
+}
+
+void nilfs_bmap_restore(struct nilfs_bmap *bmap,
+			const struct nilfs_bmap_store *store)
+{
+	memcpy(bmap->b_u.u_data, store->data, sizeof(store->data));
+	bmap->b_last_allocated_key = store->last_allocated_key;
+	bmap->b_last_allocated_ptr = store->last_allocated_ptr;
+	bmap->b_state = store->state;
+}
diff --git a/fs/nilfs2/bmap.h b/fs/nilfs2/bmap.h
new file mode 100644
index 0000000000..608168a5cb
--- /dev/null
+++ b/fs/nilfs2/bmap.h
@@ -0,0 +1,271 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * NILFS block mapping.
+ *
+ * Copyright (C) 2006-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Koji Sato.
+ */
+
+#ifndef _NILFS_BMAP_H
+#define _NILFS_BMAP_H
+
+#include <linux/types.h>
+#include <linux/fs.h>
+#include <linux/buffer_head.h>
+#include <linux/nilfs2_ondisk.h>	/* nilfs_binfo, nilfs_inode, etc */
+#include "alloc.h"
+#include "dat.h"
+
+#define NILFS_BMAP_INVALID_PTR	0
+
+#define nilfs_bmap_keydiff_abs(diff)	((diff) < 0 ? -(diff) : (diff))
+
+
+struct nilfs_bmap;
+
+/**
+ * union nilfs_bmap_ptr_req - request for bmap ptr
+ * @bpr_ptr: bmap pointer
+ * @bpr_req: request for persistent allocator
+ */
+union nilfs_bmap_ptr_req {
+	__u64 bpr_ptr;
+	struct nilfs_palloc_req bpr_req;
+};
+
+/**
+ * struct nilfs_bmap_stats - bmap statistics
+ * @bs_nblocks: number of blocks created or deleted
+ */
+struct nilfs_bmap_stats {
+	unsigned int bs_nblocks;
+};
+
+/**
+ * struct nilfs_bmap_operations - bmap operation table
+ */
+struct nilfs_bmap_operations {
+	int (*bop_lookup)(const struct nilfs_bmap *, __u64, int, __u64 *);
+	int (*bop_lookup_contig)(const struct nilfs_bmap *, __u64, __u64 *,
+				 unsigned int);
+	int (*bop_insert)(struct nilfs_bmap *, __u64, __u64);
+	int (*bop_delete)(struct nilfs_bmap *, __u64);
+	void (*bop_clear)(struct nilfs_bmap *);
+
+	int (*bop_propagate)(struct nilfs_bmap *, struct buffer_head *);
+	void (*bop_lookup_dirty_buffers)(struct nilfs_bmap *,
+					 struct list_head *);
+
+	int (*bop_assign)(struct nilfs_bmap *,
+			  struct buffer_head **,
+			  sector_t,
+			  union nilfs_binfo *);
+	int (*bop_mark)(struct nilfs_bmap *, __u64, int);
+
+	int (*bop_seek_key)(const struct nilfs_bmap *, __u64, __u64 *);
+	int (*bop_last_key)(const struct nilfs_bmap *, __u64 *);
+
+	/* The following functions are internal use only. */
+	int (*bop_check_insert)(const struct nilfs_bmap *, __u64);
+	int (*bop_check_delete)(struct nilfs_bmap *, __u64);
+	int (*bop_gather_data)(struct nilfs_bmap *, __u64 *, __u64 *, int);
+};
+
+
+#define NILFS_BMAP_SIZE		(NILFS_INODE_BMAP_SIZE * sizeof(__le64))
+#define NILFS_BMAP_KEY_BIT	(sizeof(unsigned long) * 8 /* CHAR_BIT */)
+#define NILFS_BMAP_NEW_PTR_INIT	\
+	(1UL << (sizeof(unsigned long) * 8 /* CHAR_BIT */ - 1))
+
+static inline int nilfs_bmap_is_new_ptr(unsigned long ptr)
+{
+	return !!(ptr & NILFS_BMAP_NEW_PTR_INIT);
+}
+
+
+/**
+ * struct nilfs_bmap - bmap structure
+ * @b_u: raw data
+ * @b_sem: semaphore
+ * @b_inode: owner of bmap
+ * @b_ops: bmap operation table
+ * @b_last_allocated_key: last allocated key for data block
+ * @b_last_allocated_ptr: last allocated ptr for data block
+ * @b_ptr_type: pointer type
+ * @b_state: state
+ * @b_nchildren_per_block: maximum number of child nodes for non-root nodes
+ */
+struct nilfs_bmap {
+	union {
+		__u8 u_flags;
+		__le64 u_data[NILFS_BMAP_SIZE / sizeof(__le64)];
+	} b_u;
+	struct rw_semaphore b_sem;
+	struct inode *b_inode;
+	const struct nilfs_bmap_operations *b_ops;
+	__u64 b_last_allocated_key;
+	__u64 b_last_allocated_ptr;
+	int b_ptr_type;
+	int b_state;
+	__u16 b_nchildren_per_block;
+};
+
+/* pointer type */
+#define NILFS_BMAP_PTR_P	0	/* physical block number (i.e. LBN) */
+#define NILFS_BMAP_PTR_VS	1	/*
+					 * virtual block number (single
+					 * version)
+					 */
+#define NILFS_BMAP_PTR_VM	2	/*
+					 * virtual block number (has multiple
+					 * versions)
+					 */
+#define NILFS_BMAP_PTR_U	(-1)	/* never perform pointer operations */
+
+#define NILFS_BMAP_USE_VBN(bmap)	((bmap)->b_ptr_type > 0)
+
+/* state */
+#define NILFS_BMAP_DIRTY	0x00000001
+
+/**
+ * struct nilfs_bmap_store - shadow copy of bmap state
+ * @data: cached raw block mapping of on-disk inode
+ * @last_allocated_key: cached value of last allocated key for data block
+ * @last_allocated_ptr: cached value of last allocated ptr for data block
+ * @state: cached value of state field of bmap structure
+ */
+struct nilfs_bmap_store {
+	__le64 data[NILFS_BMAP_SIZE / sizeof(__le64)];
+	__u64 last_allocated_key;
+	__u64 last_allocated_ptr;
+	int state;
+};
+
+int nilfs_bmap_test_and_clear_dirty(struct nilfs_bmap *);
+int nilfs_bmap_read(struct nilfs_bmap *, struct nilfs_inode *);
+void nilfs_bmap_write(struct nilfs_bmap *, struct nilfs_inode *);
+int nilfs_bmap_lookup_contig(struct nilfs_bmap *, __u64, __u64 *, unsigned int);
+int nilfs_bmap_insert(struct nilfs_bmap *bmap, __u64 key, unsigned long rec);
+int nilfs_bmap_delete(struct nilfs_bmap *bmap, __u64 key);
+int nilfs_bmap_seek_key(struct nilfs_bmap *bmap, __u64 start, __u64 *keyp);
+int nilfs_bmap_last_key(struct nilfs_bmap *bmap, __u64 *keyp);
+int nilfs_bmap_truncate(struct nilfs_bmap *bmap, __u64 key);
+void nilfs_bmap_clear(struct nilfs_bmap *);
+int nilfs_bmap_propagate(struct nilfs_bmap *, struct buffer_head *);
+void nilfs_bmap_lookup_dirty_buffers(struct nilfs_bmap *, struct list_head *);
+int nilfs_bmap_assign(struct nilfs_bmap *, struct buffer_head **,
+		      unsigned long, union nilfs_binfo *);
+int nilfs_bmap_lookup_at_level(struct nilfs_bmap *, __u64, int, __u64 *);
+int nilfs_bmap_mark(struct nilfs_bmap *, __u64, int);
+
+void nilfs_bmap_init_gc(struct nilfs_bmap *);
+
+void nilfs_bmap_save(const struct nilfs_bmap *, struct nilfs_bmap_store *);
+void nilfs_bmap_restore(struct nilfs_bmap *, const struct nilfs_bmap_store *);
+
+static inline int nilfs_bmap_lookup(struct nilfs_bmap *bmap, __u64 key,
+				    __u64 *ptr)
+{
+	return nilfs_bmap_lookup_at_level(bmap, key, 1, ptr);
+}
+
+/*
+ * Internal use only
+ */
+struct inode *nilfs_bmap_get_dat(const struct nilfs_bmap *);
+
+static inline int nilfs_bmap_prepare_alloc_ptr(struct nilfs_bmap *bmap,
+					       union nilfs_bmap_ptr_req *req,
+					       struct inode *dat)
+{
+	if (dat)
+		return nilfs_dat_prepare_alloc(dat, &req->bpr_req);
+	/* ignore target ptr */
+	req->bpr_ptr = bmap->b_last_allocated_ptr++;
+	return 0;
+}
+
+static inline void nilfs_bmap_commit_alloc_ptr(struct nilfs_bmap *bmap,
+					       union nilfs_bmap_ptr_req *req,
+					       struct inode *dat)
+{
+	if (dat)
+		nilfs_dat_commit_alloc(dat, &req->bpr_req);
+}
+
+static inline void nilfs_bmap_abort_alloc_ptr(struct nilfs_bmap *bmap,
+					      union nilfs_bmap_ptr_req *req,
+					      struct inode *dat)
+{
+	if (dat)
+		nilfs_dat_abort_alloc(dat, &req->bpr_req);
+	else
+		bmap->b_last_allocated_ptr--;
+}
+
+static inline int nilfs_bmap_prepare_end_ptr(struct nilfs_bmap *bmap,
+					     union nilfs_bmap_ptr_req *req,
+					     struct inode *dat)
+{
+	return dat ? nilfs_dat_prepare_end(dat, &req->bpr_req) : 0;
+}
+
+static inline void nilfs_bmap_commit_end_ptr(struct nilfs_bmap *bmap,
+					     union nilfs_bmap_ptr_req *req,
+					     struct inode *dat)
+{
+	if (dat)
+		nilfs_dat_commit_end(dat, &req->bpr_req,
+				     bmap->b_ptr_type == NILFS_BMAP_PTR_VS);
+}
+
+static inline void nilfs_bmap_abort_end_ptr(struct nilfs_bmap *bmap,
+					    union nilfs_bmap_ptr_req *req,
+					    struct inode *dat)
+{
+	if (dat)
+		nilfs_dat_abort_end(dat, &req->bpr_req);
+}
+
+static inline void nilfs_bmap_set_target_v(struct nilfs_bmap *bmap, __u64 key,
+					   __u64 ptr)
+{
+	bmap->b_last_allocated_key = key;
+	bmap->b_last_allocated_ptr = ptr;
+}
+
+__u64 nilfs_bmap_data_get_key(const struct nilfs_bmap *,
+			      const struct buffer_head *);
+
+__u64 nilfs_bmap_find_target_seq(const struct nilfs_bmap *, __u64);
+__u64 nilfs_bmap_find_target_in_group(const struct nilfs_bmap *);
+
+
+/* Assume that bmap semaphore is locked. */
+static inline int nilfs_bmap_dirty(const struct nilfs_bmap *bmap)
+{
+	return !!(bmap->b_state & NILFS_BMAP_DIRTY);
+}
+
+/* Assume that bmap semaphore is locked. */
+static inline void nilfs_bmap_set_dirty(struct nilfs_bmap *bmap)
+{
+	bmap->b_state |= NILFS_BMAP_DIRTY;
+}
+
+/* Assume that bmap semaphore is locked. */
+static inline void nilfs_bmap_clear_dirty(struct nilfs_bmap *bmap)
+{
+	bmap->b_state &= ~NILFS_BMAP_DIRTY;
+}
+
+
+#define NILFS_BMAP_LARGE	0x1
+
+#define NILFS_BMAP_SMALL_LOW	NILFS_DIRECT_KEY_MIN
+#define NILFS_BMAP_SMALL_HIGH	NILFS_DIRECT_KEY_MAX
+#define NILFS_BMAP_LARGE_LOW	NILFS_BTREE_ROOT_NCHILDREN_MAX
+#define NILFS_BMAP_LARGE_HIGH	NILFS_BTREE_KEY_MAX
+
+#endif	/* _NILFS_BMAP_H */
diff --git a/fs/nilfs2/btnode.c b/fs/nilfs2/btnode.c
new file mode 100644
index 0000000000..5710833ac1
--- /dev/null
+++ b/fs/nilfs2/btnode.c
@@ -0,0 +1,298 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NILFS B-tree node cache
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Originally written by Seiji Kihara.
+ * Fully revised by Ryusuke Konishi for stabilization and simplification.
+ *
+ */
+
+#include <linux/types.h>
+#include <linux/buffer_head.h>
+#include <linux/mm.h>
+#include <linux/backing-dev.h>
+#include <linux/gfp.h>
+#include "nilfs.h"
+#include "mdt.h"
+#include "dat.h"
+#include "page.h"
+#include "btnode.h"
+
+
+/**
+ * nilfs_init_btnc_inode - initialize B-tree node cache inode
+ * @btnc_inode: inode to be initialized
+ *
+ * nilfs_init_btnc_inode() sets up an inode for B-tree node cache.
+ */
+void nilfs_init_btnc_inode(struct inode *btnc_inode)
+{
+	struct nilfs_inode_info *ii = NILFS_I(btnc_inode);
+
+	btnc_inode->i_mode = S_IFREG;
+	ii->i_flags = 0;
+	memset(&ii->i_bmap_data, 0, sizeof(struct nilfs_bmap));
+	mapping_set_gfp_mask(btnc_inode->i_mapping, GFP_NOFS);
+}
+
+void nilfs_btnode_cache_clear(struct address_space *btnc)
+{
+	invalidate_mapping_pages(btnc, 0, -1);
+	truncate_inode_pages(btnc, 0);
+}
+
+struct buffer_head *
+nilfs_btnode_create_block(struct address_space *btnc, __u64 blocknr)
+{
+	struct inode *inode = btnc->host;
+	struct buffer_head *bh;
+
+	bh = nilfs_grab_buffer(inode, btnc, blocknr, BIT(BH_NILFS_Node));
+	if (unlikely(!bh))
+		return NULL;
+
+	if (unlikely(buffer_mapped(bh) || buffer_uptodate(bh) ||
+		     buffer_dirty(bh))) {
+		brelse(bh);
+		BUG();
+	}
+	memset(bh->b_data, 0, i_blocksize(inode));
+	bh->b_bdev = inode->i_sb->s_bdev;
+	bh->b_blocknr = blocknr;
+	set_buffer_mapped(bh);
+	set_buffer_uptodate(bh);
+
+	unlock_page(bh->b_page);
+	put_page(bh->b_page);
+	return bh;
+}
+
+int nilfs_btnode_submit_block(struct address_space *btnc, __u64 blocknr,
+			      sector_t pblocknr, blk_opf_t opf,
+			      struct buffer_head **pbh, sector_t *submit_ptr)
+{
+	struct buffer_head *bh;
+	struct inode *inode = btnc->host;
+	struct page *page;
+	int err;
+
+	bh = nilfs_grab_buffer(inode, btnc, blocknr, BIT(BH_NILFS_Node));
+	if (unlikely(!bh))
+		return -ENOMEM;
+
+	err = -EEXIST; /* internal code */
+	page = bh->b_page;
+
+	if (buffer_uptodate(bh) || buffer_dirty(bh))
+		goto found;
+
+	if (pblocknr == 0) {
+		pblocknr = blocknr;
+		if (inode->i_ino != NILFS_DAT_INO) {
+			struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
+
+			/* blocknr is a virtual block number */
+			err = nilfs_dat_translate(nilfs->ns_dat, blocknr,
+						  &pblocknr);
+			if (unlikely(err)) {
+				brelse(bh);
+				goto out_locked;
+			}
+		}
+	}
+
+	if (opf & REQ_RAHEAD) {
+		if (pblocknr != *submit_ptr + 1 || !trylock_buffer(bh)) {
+			err = -EBUSY; /* internal code */
+			brelse(bh);
+			goto out_locked;
+		}
+	} else { /* opf == REQ_OP_READ */
+		lock_buffer(bh);
+	}
+	if (buffer_uptodate(bh)) {
+		unlock_buffer(bh);
+		err = -EEXIST; /* internal code */
+		goto found;
+	}
+	set_buffer_mapped(bh);
+	bh->b_bdev = inode->i_sb->s_bdev;
+	bh->b_blocknr = pblocknr; /* set block address for read */
+	bh->b_end_io = end_buffer_read_sync;
+	get_bh(bh);
+	submit_bh(opf, bh);
+	bh->b_blocknr = blocknr; /* set back to the given block address */
+	*submit_ptr = pblocknr;
+	err = 0;
+found:
+	*pbh = bh;
+
+out_locked:
+	unlock_page(page);
+	put_page(page);
+	return err;
+}
+
+/**
+ * nilfs_btnode_delete - delete B-tree node buffer
+ * @bh: buffer to be deleted
+ *
+ * nilfs_btnode_delete() invalidates the specified buffer and delete the page
+ * including the buffer if the page gets unbusy.
+ */
+void nilfs_btnode_delete(struct buffer_head *bh)
+{
+	struct address_space *mapping;
+	struct page *page = bh->b_page;
+	pgoff_t index = page_index(page);
+	int still_dirty;
+
+	get_page(page);
+	lock_page(page);
+	wait_on_page_writeback(page);
+
+	nilfs_forget_buffer(bh);
+	still_dirty = PageDirty(page);
+	mapping = page->mapping;
+	unlock_page(page);
+	put_page(page);
+
+	if (!still_dirty && mapping)
+		invalidate_inode_pages2_range(mapping, index, index);
+}
+
+/**
+ * nilfs_btnode_prepare_change_key
+ *  prepare to move contents of the block for old key to one of new key.
+ *  the old buffer will not be removed, but might be reused for new buffer.
+ *  it might return -ENOMEM because of memory allocation errors,
+ *  and might return -EIO because of disk read errors.
+ */
+int nilfs_btnode_prepare_change_key(struct address_space *btnc,
+				    struct nilfs_btnode_chkey_ctxt *ctxt)
+{
+	struct buffer_head *obh, *nbh;
+	struct inode *inode = btnc->host;
+	__u64 oldkey = ctxt->oldkey, newkey = ctxt->newkey;
+	int err;
+
+	if (oldkey == newkey)
+		return 0;
+
+	obh = ctxt->bh;
+	ctxt->newbh = NULL;
+
+	if (inode->i_blkbits == PAGE_SHIFT) {
+		struct page *opage = obh->b_page;
+		lock_page(opage);
+retry:
+		/* BUG_ON(oldkey != obh->b_folio->index); */
+		if (unlikely(oldkey != opage->index))
+			NILFS_PAGE_BUG(opage,
+				       "invalid oldkey %lld (newkey=%lld)",
+				       (unsigned long long)oldkey,
+				       (unsigned long long)newkey);
+
+		xa_lock_irq(&btnc->i_pages);
+		err = __xa_insert(&btnc->i_pages, newkey, opage, GFP_NOFS);
+		xa_unlock_irq(&btnc->i_pages);
+		/*
+		 * Note: page->index will not change to newkey until
+		 * nilfs_btnode_commit_change_key() will be called.
+		 * To protect the page in intermediate state, the page lock
+		 * is held.
+		 */
+		if (!err)
+			return 0;
+		else if (err != -EBUSY)
+			goto failed_unlock;
+
+		err = invalidate_inode_pages2_range(btnc, newkey, newkey);
+		if (!err)
+			goto retry;
+		/* fallback to copy mode */
+		unlock_page(opage);
+	}
+
+	nbh = nilfs_btnode_create_block(btnc, newkey);
+	if (!nbh)
+		return -ENOMEM;
+
+	BUG_ON(nbh == obh);
+	ctxt->newbh = nbh;
+	return 0;
+
+ failed_unlock:
+	unlock_page(obh->b_page);
+	return err;
+}
+
+/**
+ * nilfs_btnode_commit_change_key
+ *  commit the change_key operation prepared by prepare_change_key().
+ */
+void nilfs_btnode_commit_change_key(struct address_space *btnc,
+				    struct nilfs_btnode_chkey_ctxt *ctxt)
+{
+	struct buffer_head *obh = ctxt->bh, *nbh = ctxt->newbh;
+	__u64 oldkey = ctxt->oldkey, newkey = ctxt->newkey;
+	struct page *opage;
+
+	if (oldkey == newkey)
+		return;
+
+	if (nbh == NULL) {	/* blocksize == pagesize */
+		opage = obh->b_page;
+		if (unlikely(oldkey != opage->index))
+			NILFS_PAGE_BUG(opage,
+				       "invalid oldkey %lld (newkey=%lld)",
+				       (unsigned long long)oldkey,
+				       (unsigned long long)newkey);
+		mark_buffer_dirty(obh);
+
+		xa_lock_irq(&btnc->i_pages);
+		__xa_erase(&btnc->i_pages, oldkey);
+		__xa_set_mark(&btnc->i_pages, newkey, PAGECACHE_TAG_DIRTY);
+		xa_unlock_irq(&btnc->i_pages);
+
+		opage->index = obh->b_blocknr = newkey;
+		unlock_page(opage);
+	} else {
+		nilfs_copy_buffer(nbh, obh);
+		mark_buffer_dirty(nbh);
+
+		nbh->b_blocknr = newkey;
+		ctxt->bh = nbh;
+		nilfs_btnode_delete(obh); /* will decrement bh->b_count */
+	}
+}
+
+/**
+ * nilfs_btnode_abort_change_key
+ *  abort the change_key operation prepared by prepare_change_key().
+ */
+void nilfs_btnode_abort_change_key(struct address_space *btnc,
+				   struct nilfs_btnode_chkey_ctxt *ctxt)
+{
+	struct buffer_head *nbh = ctxt->newbh;
+	__u64 oldkey = ctxt->oldkey, newkey = ctxt->newkey;
+
+	if (oldkey == newkey)
+		return;
+
+	if (nbh == NULL) {	/* blocksize == pagesize */
+		xa_erase_irq(&btnc->i_pages, newkey);
+		unlock_page(ctxt->bh->b_page);
+	} else {
+		/*
+		 * When canceling a buffer that a prepare operation has
+		 * allocated to copy a node block to another location, use
+		 * nilfs_btnode_delete() to initialize and release the buffer
+		 * so that the buffer flags will not be in an inconsistent
+		 * state when it is reallocated.
+		 */
+		nilfs_btnode_delete(nbh);
+	}
+}
diff --git a/fs/nilfs2/btnode.h b/fs/nilfs2/btnode.h
new file mode 100644
index 0000000000..4bc5612dff
--- /dev/null
+++ b/fs/nilfs2/btnode.h
@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * NILFS B-tree node cache
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Seiji Kihara.
+ * Revised by Ryusuke Konishi.
+ */
+
+#ifndef _NILFS_BTNODE_H
+#define _NILFS_BTNODE_H
+
+#include <linux/types.h>
+#include <linux/buffer_head.h>
+#include <linux/fs.h>
+#include <linux/backing-dev.h>
+
+/**
+ * struct nilfs_btnode_chkey_ctxt - change key context
+ * @oldkey: old key of block's moving content
+ * @newkey: new key for block's content
+ * @bh: buffer head of old buffer
+ * @newbh: buffer head of new buffer
+ */
+struct nilfs_btnode_chkey_ctxt {
+	__u64 oldkey;
+	__u64 newkey;
+	struct buffer_head *bh;
+	struct buffer_head *newbh;
+};
+
+void nilfs_init_btnc_inode(struct inode *btnc_inode);
+void nilfs_btnode_cache_clear(struct address_space *);
+struct buffer_head *nilfs_btnode_create_block(struct address_space *btnc,
+					      __u64 blocknr);
+int nilfs_btnode_submit_block(struct address_space *, __u64, sector_t,
+			      blk_opf_t, struct buffer_head **, sector_t *);
+void nilfs_btnode_delete(struct buffer_head *);
+int nilfs_btnode_prepare_change_key(struct address_space *,
+				    struct nilfs_btnode_chkey_ctxt *);
+void nilfs_btnode_commit_change_key(struct address_space *,
+				    struct nilfs_btnode_chkey_ctxt *);
+void nilfs_btnode_abort_change_key(struct address_space *,
+				   struct nilfs_btnode_chkey_ctxt *);
+
+#endif	/* _NILFS_BTNODE_H */
diff --git a/fs/nilfs2/btree.c b/fs/nilfs2/btree.c
new file mode 100644
index 0000000000..13592e82ea
--- /dev/null
+++ b/fs/nilfs2/btree.c
@@ -0,0 +1,2428 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NILFS B-tree.
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Koji Sato.
+ */
+
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/errno.h>
+#include <linux/pagevec.h>
+#include "nilfs.h"
+#include "page.h"
+#include "btnode.h"
+#include "btree.h"
+#include "alloc.h"
+#include "dat.h"
+
+static void __nilfs_btree_init(struct nilfs_bmap *bmap);
+
+static struct nilfs_btree_path *nilfs_btree_alloc_path(void)
+{
+	struct nilfs_btree_path *path;
+	int level = NILFS_BTREE_LEVEL_DATA;
+
+	path = kmem_cache_alloc(nilfs_btree_path_cache, GFP_NOFS);
+	if (path == NULL)
+		goto out;
+
+	for (; level < NILFS_BTREE_LEVEL_MAX; level++) {
+		path[level].bp_bh = NULL;
+		path[level].bp_sib_bh = NULL;
+		path[level].bp_index = 0;
+		path[level].bp_oldreq.bpr_ptr = NILFS_BMAP_INVALID_PTR;
+		path[level].bp_newreq.bpr_ptr = NILFS_BMAP_INVALID_PTR;
+		path[level].bp_op = NULL;
+	}
+
+out:
+	return path;
+}
+
+static void nilfs_btree_free_path(struct nilfs_btree_path *path)
+{
+	int level = NILFS_BTREE_LEVEL_DATA;
+
+	for (; level < NILFS_BTREE_LEVEL_MAX; level++)
+		brelse(path[level].bp_bh);
+
+	kmem_cache_free(nilfs_btree_path_cache, path);
+}
+
+/*
+ * B-tree node operations
+ */
+static int nilfs_btree_get_new_block(const struct nilfs_bmap *btree,
+				     __u64 ptr, struct buffer_head **bhp)
+{
+	struct inode *btnc_inode = NILFS_BMAP_I(btree)->i_assoc_inode;
+	struct address_space *btnc = btnc_inode->i_mapping;
+	struct buffer_head *bh;
+
+	bh = nilfs_btnode_create_block(btnc, ptr);
+	if (!bh)
+		return -ENOMEM;
+
+	set_buffer_nilfs_volatile(bh);
+	*bhp = bh;
+	return 0;
+}
+
+static int nilfs_btree_node_get_flags(const struct nilfs_btree_node *node)
+{
+	return node->bn_flags;
+}
+
+static void
+nilfs_btree_node_set_flags(struct nilfs_btree_node *node, int flags)
+{
+	node->bn_flags = flags;
+}
+
+static int nilfs_btree_node_root(const struct nilfs_btree_node *node)
+{
+	return nilfs_btree_node_get_flags(node) & NILFS_BTREE_NODE_ROOT;
+}
+
+static int nilfs_btree_node_get_level(const struct nilfs_btree_node *node)
+{
+	return node->bn_level;
+}
+
+static void
+nilfs_btree_node_set_level(struct nilfs_btree_node *node, int level)
+{
+	node->bn_level = level;
+}
+
+static int nilfs_btree_node_get_nchildren(const struct nilfs_btree_node *node)
+{
+	return le16_to_cpu(node->bn_nchildren);
+}
+
+static void
+nilfs_btree_node_set_nchildren(struct nilfs_btree_node *node, int nchildren)
+{
+	node->bn_nchildren = cpu_to_le16(nchildren);
+}
+
+static int nilfs_btree_node_size(const struct nilfs_bmap *btree)
+{
+	return i_blocksize(btree->b_inode);
+}
+
+static int nilfs_btree_nchildren_per_block(const struct nilfs_bmap *btree)
+{
+	return btree->b_nchildren_per_block;
+}
+
+static __le64 *
+nilfs_btree_node_dkeys(const struct nilfs_btree_node *node)
+{
+	return (__le64 *)((char *)(node + 1) +
+			  (nilfs_btree_node_root(node) ?
+			   0 : NILFS_BTREE_NODE_EXTRA_PAD_SIZE));
+}
+
+static __le64 *
+nilfs_btree_node_dptrs(const struct nilfs_btree_node *node, int ncmax)
+{
+	return (__le64 *)(nilfs_btree_node_dkeys(node) + ncmax);
+}
+
+static __u64
+nilfs_btree_node_get_key(const struct nilfs_btree_node *node, int index)
+{
+	return le64_to_cpu(*(nilfs_btree_node_dkeys(node) + index));
+}
+
+static void
+nilfs_btree_node_set_key(struct nilfs_btree_node *node, int index, __u64 key)
+{
+	*(nilfs_btree_node_dkeys(node) + index) = cpu_to_le64(key);
+}
+
+static __u64
+nilfs_btree_node_get_ptr(const struct nilfs_btree_node *node, int index,
+			 int ncmax)
+{
+	return le64_to_cpu(*(nilfs_btree_node_dptrs(node, ncmax) + index));
+}
+
+static void
+nilfs_btree_node_set_ptr(struct nilfs_btree_node *node, int index, __u64 ptr,
+			 int ncmax)
+{
+	*(nilfs_btree_node_dptrs(node, ncmax) + index) = cpu_to_le64(ptr);
+}
+
+static void nilfs_btree_node_init(struct nilfs_btree_node *node, int flags,
+				  int level, int nchildren, int ncmax,
+				  const __u64 *keys, const __u64 *ptrs)
+{
+	__le64 *dkeys;
+	__le64 *dptrs;
+	int i;
+
+	nilfs_btree_node_set_flags(node, flags);
+	nilfs_btree_node_set_level(node, level);
+	nilfs_btree_node_set_nchildren(node, nchildren);
+
+	dkeys = nilfs_btree_node_dkeys(node);
+	dptrs = nilfs_btree_node_dptrs(node, ncmax);
+	for (i = 0; i < nchildren; i++) {
+		dkeys[i] = cpu_to_le64(keys[i]);
+		dptrs[i] = cpu_to_le64(ptrs[i]);
+	}
+}
+
+/* Assume the buffer heads corresponding to left and right are locked. */
+static void nilfs_btree_node_move_left(struct nilfs_btree_node *left,
+				       struct nilfs_btree_node *right,
+				       int n, int lncmax, int rncmax)
+{
+	__le64 *ldkeys, *rdkeys;
+	__le64 *ldptrs, *rdptrs;
+	int lnchildren, rnchildren;
+
+	ldkeys = nilfs_btree_node_dkeys(left);
+	ldptrs = nilfs_btree_node_dptrs(left, lncmax);
+	lnchildren = nilfs_btree_node_get_nchildren(left);
+
+	rdkeys = nilfs_btree_node_dkeys(right);
+	rdptrs = nilfs_btree_node_dptrs(right, rncmax);
+	rnchildren = nilfs_btree_node_get_nchildren(right);
+
+	memcpy(ldkeys + lnchildren, rdkeys, n * sizeof(*rdkeys));
+	memcpy(ldptrs + lnchildren, rdptrs, n * sizeof(*rdptrs));
+	memmove(rdkeys, rdkeys + n, (rnchildren - n) * sizeof(*rdkeys));
+	memmove(rdptrs, rdptrs + n, (rnchildren - n) * sizeof(*rdptrs));
+
+	lnchildren += n;
+	rnchildren -= n;
+	nilfs_btree_node_set_nchildren(left, lnchildren);
+	nilfs_btree_node_set_nchildren(right, rnchildren);
+}
+
+/* Assume that the buffer heads corresponding to left and right are locked. */
+static void nilfs_btree_node_move_right(struct nilfs_btree_node *left,
+					struct nilfs_btree_node *right,
+					int n, int lncmax, int rncmax)
+{
+	__le64 *ldkeys, *rdkeys;
+	__le64 *ldptrs, *rdptrs;
+	int lnchildren, rnchildren;
+
+	ldkeys = nilfs_btree_node_dkeys(left);
+	ldptrs = nilfs_btree_node_dptrs(left, lncmax);
+	lnchildren = nilfs_btree_node_get_nchildren(left);
+
+	rdkeys = nilfs_btree_node_dkeys(right);
+	rdptrs = nilfs_btree_node_dptrs(right, rncmax);
+	rnchildren = nilfs_btree_node_get_nchildren(right);
+
+	memmove(rdkeys + n, rdkeys, rnchildren * sizeof(*rdkeys));
+	memmove(rdptrs + n, rdptrs, rnchildren * sizeof(*rdptrs));
+	memcpy(rdkeys, ldkeys + lnchildren - n, n * sizeof(*rdkeys));
+	memcpy(rdptrs, ldptrs + lnchildren - n, n * sizeof(*rdptrs));
+
+	lnchildren -= n;
+	rnchildren += n;
+	nilfs_btree_node_set_nchildren(left, lnchildren);
+	nilfs_btree_node_set_nchildren(right, rnchildren);
+}
+
+/* Assume that the buffer head corresponding to node is locked. */
+static void nilfs_btree_node_insert(struct nilfs_btree_node *node, int index,
+				    __u64 key, __u64 ptr, int ncmax)
+{
+	__le64 *dkeys;
+	__le64 *dptrs;
+	int nchildren;
+
+	dkeys = nilfs_btree_node_dkeys(node);
+	dptrs = nilfs_btree_node_dptrs(node, ncmax);
+	nchildren = nilfs_btree_node_get_nchildren(node);
+	if (index < nchildren) {
+		memmove(dkeys + index + 1, dkeys + index,
+			(nchildren - index) * sizeof(*dkeys));
+		memmove(dptrs + index + 1, dptrs + index,
+			(nchildren - index) * sizeof(*dptrs));
+	}
+	dkeys[index] = cpu_to_le64(key);
+	dptrs[index] = cpu_to_le64(ptr);
+	nchildren++;
+	nilfs_btree_node_set_nchildren(node, nchildren);
+}
+
+/* Assume that the buffer head corresponding to node is locked. */
+static void nilfs_btree_node_delete(struct nilfs_btree_node *node, int index,
+				    __u64 *keyp, __u64 *ptrp, int ncmax)
+{
+	__u64 key;
+	__u64 ptr;
+	__le64 *dkeys;
+	__le64 *dptrs;
+	int nchildren;
+
+	dkeys = nilfs_btree_node_dkeys(node);
+	dptrs = nilfs_btree_node_dptrs(node, ncmax);
+	key = le64_to_cpu(dkeys[index]);
+	ptr = le64_to_cpu(dptrs[index]);
+	nchildren = nilfs_btree_node_get_nchildren(node);
+	if (keyp != NULL)
+		*keyp = key;
+	if (ptrp != NULL)
+		*ptrp = ptr;
+
+	if (index < nchildren - 1) {
+		memmove(dkeys + index, dkeys + index + 1,
+			(nchildren - index - 1) * sizeof(*dkeys));
+		memmove(dptrs + index, dptrs + index + 1,
+			(nchildren - index - 1) * sizeof(*dptrs));
+	}
+	nchildren--;
+	nilfs_btree_node_set_nchildren(node, nchildren);
+}
+
+static int nilfs_btree_node_lookup(const struct nilfs_btree_node *node,
+				   __u64 key, int *indexp)
+{
+	__u64 nkey;
+	int index, low, high, s;
+
+	/* binary search */
+	low = 0;
+	high = nilfs_btree_node_get_nchildren(node) - 1;
+	index = 0;
+	s = 0;
+	while (low <= high) {
+		index = (low + high) / 2;
+		nkey = nilfs_btree_node_get_key(node, index);
+		if (nkey == key) {
+			s = 0;
+			goto out;
+		} else if (nkey < key) {
+			low = index + 1;
+			s = -1;
+		} else {
+			high = index - 1;
+			s = 1;
+		}
+	}
+
+	/* adjust index */
+	if (nilfs_btree_node_get_level(node) > NILFS_BTREE_LEVEL_NODE_MIN) {
+		if (s > 0 && index > 0)
+			index--;
+	} else if (s < 0)
+		index++;
+
+ out:
+	*indexp = index;
+
+	return s == 0;
+}
+
+/**
+ * nilfs_btree_node_broken - verify consistency of btree node
+ * @node: btree node block to be examined
+ * @size: node size (in bytes)
+ * @inode: host inode of btree
+ * @blocknr: block number
+ *
+ * Return Value: If node is broken, 1 is returned. Otherwise, 0 is returned.
+ */
+static int nilfs_btree_node_broken(const struct nilfs_btree_node *node,
+				   size_t size, struct inode *inode,
+				   sector_t blocknr)
+{
+	int level, flags, nchildren;
+	int ret = 0;
+
+	level = nilfs_btree_node_get_level(node);
+	flags = nilfs_btree_node_get_flags(node);
+	nchildren = nilfs_btree_node_get_nchildren(node);
+
+	if (unlikely(level < NILFS_BTREE_LEVEL_NODE_MIN ||
+		     level >= NILFS_BTREE_LEVEL_MAX ||
+		     (flags & NILFS_BTREE_NODE_ROOT) ||
+		     nchildren < 0 ||
+		     nchildren > NILFS_BTREE_NODE_NCHILDREN_MAX(size))) {
+		nilfs_crit(inode->i_sb,
+			   "bad btree node (ino=%lu, blocknr=%llu): level = %d, flags = 0x%x, nchildren = %d",
+			   inode->i_ino, (unsigned long long)blocknr, level,
+			   flags, nchildren);
+		ret = 1;
+	}
+	return ret;
+}
+
+/**
+ * nilfs_btree_root_broken - verify consistency of btree root node
+ * @node: btree root node to be examined
+ * @inode: host inode of btree
+ *
+ * Return Value: If node is broken, 1 is returned. Otherwise, 0 is returned.
+ */
+static int nilfs_btree_root_broken(const struct nilfs_btree_node *node,
+				   struct inode *inode)
+{
+	int level, flags, nchildren;
+	int ret = 0;
+
+	level = nilfs_btree_node_get_level(node);
+	flags = nilfs_btree_node_get_flags(node);
+	nchildren = nilfs_btree_node_get_nchildren(node);
+
+	if (unlikely(level < NILFS_BTREE_LEVEL_NODE_MIN ||
+		     level >= NILFS_BTREE_LEVEL_MAX ||
+		     nchildren < 0 ||
+		     nchildren > NILFS_BTREE_ROOT_NCHILDREN_MAX)) {
+		nilfs_crit(inode->i_sb,
+			   "bad btree root (ino=%lu): level = %d, flags = 0x%x, nchildren = %d",
+			   inode->i_ino, level, flags, nchildren);
+		ret = 1;
+	}
+	return ret;
+}
+
+int nilfs_btree_broken_node_block(struct buffer_head *bh)
+{
+	struct inode *inode;
+	int ret;
+
+	if (buffer_nilfs_checked(bh))
+		return 0;
+
+	inode = bh->b_folio->mapping->host;
+	ret = nilfs_btree_node_broken((struct nilfs_btree_node *)bh->b_data,
+				      bh->b_size, inode, bh->b_blocknr);
+	if (likely(!ret))
+		set_buffer_nilfs_checked(bh);
+	return ret;
+}
+
+static struct nilfs_btree_node *
+nilfs_btree_get_root(const struct nilfs_bmap *btree)
+{
+	return (struct nilfs_btree_node *)btree->b_u.u_data;
+}
+
+static struct nilfs_btree_node *
+nilfs_btree_get_nonroot_node(const struct nilfs_btree_path *path, int level)
+{
+	return (struct nilfs_btree_node *)path[level].bp_bh->b_data;
+}
+
+static struct nilfs_btree_node *
+nilfs_btree_get_sib_node(const struct nilfs_btree_path *path, int level)
+{
+	return (struct nilfs_btree_node *)path[level].bp_sib_bh->b_data;
+}
+
+static int nilfs_btree_height(const struct nilfs_bmap *btree)
+{
+	return nilfs_btree_node_get_level(nilfs_btree_get_root(btree)) + 1;
+}
+
+static struct nilfs_btree_node *
+nilfs_btree_get_node(const struct nilfs_bmap *btree,
+		     const struct nilfs_btree_path *path,
+		     int level, int *ncmaxp)
+{
+	struct nilfs_btree_node *node;
+
+	if (level == nilfs_btree_height(btree) - 1) {
+		node = nilfs_btree_get_root(btree);
+		*ncmaxp = NILFS_BTREE_ROOT_NCHILDREN_MAX;
+	} else {
+		node = nilfs_btree_get_nonroot_node(path, level);
+		*ncmaxp = nilfs_btree_nchildren_per_block(btree);
+	}
+	return node;
+}
+
+static int nilfs_btree_bad_node(const struct nilfs_bmap *btree,
+				struct nilfs_btree_node *node, int level)
+{
+	if (unlikely(nilfs_btree_node_get_level(node) != level)) {
+		dump_stack();
+		nilfs_crit(btree->b_inode->i_sb,
+			   "btree level mismatch (ino=%lu): %d != %d",
+			   btree->b_inode->i_ino,
+			   nilfs_btree_node_get_level(node), level);
+		return 1;
+	}
+	return 0;
+}
+
+struct nilfs_btree_readahead_info {
+	struct nilfs_btree_node *node;	/* parent node */
+	int max_ra_blocks;		/* max nof blocks to read ahead */
+	int index;			/* current index on the parent node */
+	int ncmax;			/* nof children in the parent node */
+};
+
+static int __nilfs_btree_get_block(const struct nilfs_bmap *btree, __u64 ptr,
+				   struct buffer_head **bhp,
+				   const struct nilfs_btree_readahead_info *ra)
+{
+	struct inode *btnc_inode = NILFS_BMAP_I(btree)->i_assoc_inode;
+	struct address_space *btnc = btnc_inode->i_mapping;
+	struct buffer_head *bh, *ra_bh;
+	sector_t submit_ptr = 0;
+	int ret;
+
+	ret = nilfs_btnode_submit_block(btnc, ptr, 0, REQ_OP_READ, &bh,
+					&submit_ptr);
+	if (ret) {
+		if (likely(ret == -EEXIST))
+			goto out_check;
+		if (ret == -ENOENT) {
+			/*
+			 * Block address translation failed due to invalid
+			 * value of 'ptr'.  In this case, return internal code
+			 * -EINVAL (broken bmap) to notify bmap layer of fatal
+			 * metadata corruption.
+			 */
+			ret = -EINVAL;
+		}
+		return ret;
+	}
+
+	if (ra) {
+		int i, n;
+		__u64 ptr2;
+
+		/* read ahead sibling nodes */
+		for (n = ra->max_ra_blocks, i = ra->index + 1;
+		     n > 0 && i < ra->ncmax; n--, i++) {
+			ptr2 = nilfs_btree_node_get_ptr(ra->node, i, ra->ncmax);
+
+			ret = nilfs_btnode_submit_block(btnc, ptr2, 0,
+						REQ_OP_READ | REQ_RAHEAD,
+						&ra_bh, &submit_ptr);
+			if (likely(!ret || ret == -EEXIST))
+				brelse(ra_bh);
+			else if (ret != -EBUSY)
+				break;
+			if (!buffer_locked(bh))
+				goto out_no_wait;
+		}
+	}
+
+	wait_on_buffer(bh);
+
+ out_no_wait:
+	if (!buffer_uptodate(bh)) {
+		nilfs_err(btree->b_inode->i_sb,
+			  "I/O error reading b-tree node block (ino=%lu, blocknr=%llu)",
+			  btree->b_inode->i_ino, (unsigned long long)ptr);
+		brelse(bh);
+		return -EIO;
+	}
+
+ out_check:
+	if (nilfs_btree_broken_node_block(bh)) {
+		clear_buffer_uptodate(bh);
+		brelse(bh);
+		return -EINVAL;
+	}
+
+	*bhp = bh;
+	return 0;
+}
+
+static int nilfs_btree_get_block(const struct nilfs_bmap *btree, __u64 ptr,
+				   struct buffer_head **bhp)
+{
+	return __nilfs_btree_get_block(btree, ptr, bhp, NULL);
+}
+
+static int nilfs_btree_do_lookup(const struct nilfs_bmap *btree,
+				 struct nilfs_btree_path *path,
+				 __u64 key, __u64 *ptrp, int minlevel,
+				 int readahead)
+{
+	struct nilfs_btree_node *node;
+	struct nilfs_btree_readahead_info p, *ra;
+	__u64 ptr;
+	int level, index, found, ncmax, ret;
+
+	node = nilfs_btree_get_root(btree);
+	level = nilfs_btree_node_get_level(node);
+	if (level < minlevel || nilfs_btree_node_get_nchildren(node) <= 0)
+		return -ENOENT;
+
+	found = nilfs_btree_node_lookup(node, key, &index);
+	ptr = nilfs_btree_node_get_ptr(node, index,
+				       NILFS_BTREE_ROOT_NCHILDREN_MAX);
+	path[level].bp_bh = NULL;
+	path[level].bp_index = index;
+
+	ncmax = nilfs_btree_nchildren_per_block(btree);
+
+	while (--level >= minlevel) {
+		ra = NULL;
+		if (level == NILFS_BTREE_LEVEL_NODE_MIN && readahead) {
+			p.node = nilfs_btree_get_node(btree, path, level + 1,
+						      &p.ncmax);
+			p.index = index;
+			p.max_ra_blocks = 7;
+			ra = &p;
+		}
+		ret = __nilfs_btree_get_block(btree, ptr, &path[level].bp_bh,
+					      ra);
+		if (ret < 0)
+			return ret;
+
+		node = nilfs_btree_get_nonroot_node(path, level);
+		if (nilfs_btree_bad_node(btree, node, level))
+			return -EINVAL;
+		if (!found)
+			found = nilfs_btree_node_lookup(node, key, &index);
+		else
+			index = 0;
+		if (index < ncmax) {
+			ptr = nilfs_btree_node_get_ptr(node, index, ncmax);
+		} else {
+			WARN_ON(found || level != NILFS_BTREE_LEVEL_NODE_MIN);
+			/* insert */
+			ptr = NILFS_BMAP_INVALID_PTR;
+		}
+		path[level].bp_index = index;
+	}
+	if (!found)
+		return -ENOENT;
+
+	if (ptrp != NULL)
+		*ptrp = ptr;
+
+	return 0;
+}
+
+static int nilfs_btree_do_lookup_last(const struct nilfs_bmap *btree,
+				      struct nilfs_btree_path *path,
+				      __u64 *keyp, __u64 *ptrp)
+{
+	struct nilfs_btree_node *node;
+	__u64 ptr;
+	int index, level, ncmax, ret;
+
+	node = nilfs_btree_get_root(btree);
+	index = nilfs_btree_node_get_nchildren(node) - 1;
+	if (index < 0)
+		return -ENOENT;
+	level = nilfs_btree_node_get_level(node);
+	ptr = nilfs_btree_node_get_ptr(node, index,
+				       NILFS_BTREE_ROOT_NCHILDREN_MAX);
+	path[level].bp_bh = NULL;
+	path[level].bp_index = index;
+	ncmax = nilfs_btree_nchildren_per_block(btree);
+
+	for (level--; level > 0; level--) {
+		ret = nilfs_btree_get_block(btree, ptr, &path[level].bp_bh);
+		if (ret < 0)
+			return ret;
+		node = nilfs_btree_get_nonroot_node(path, level);
+		if (nilfs_btree_bad_node(btree, node, level))
+			return -EINVAL;
+		index = nilfs_btree_node_get_nchildren(node) - 1;
+		ptr = nilfs_btree_node_get_ptr(node, index, ncmax);
+		path[level].bp_index = index;
+	}
+
+	if (keyp != NULL)
+		*keyp = nilfs_btree_node_get_key(node, index);
+	if (ptrp != NULL)
+		*ptrp = ptr;
+
+	return 0;
+}
+
+/**
+ * nilfs_btree_get_next_key - get next valid key from btree path array
+ * @btree: bmap struct of btree
+ * @path: array of nilfs_btree_path struct
+ * @minlevel: start level
+ * @nextkey: place to store the next valid key
+ *
+ * Return Value: If a next key was found, 0 is returned. Otherwise,
+ * -ENOENT is returned.
+ */
+static int nilfs_btree_get_next_key(const struct nilfs_bmap *btree,
+				    const struct nilfs_btree_path *path,
+				    int minlevel, __u64 *nextkey)
+{
+	struct nilfs_btree_node *node;
+	int maxlevel = nilfs_btree_height(btree) - 1;
+	int index, next_adj, level;
+
+	/* Next index is already set to bp_index for leaf nodes. */
+	next_adj = 0;
+	for (level = minlevel; level <= maxlevel; level++) {
+		if (level == maxlevel)
+			node = nilfs_btree_get_root(btree);
+		else
+			node = nilfs_btree_get_nonroot_node(path, level);
+
+		index = path[level].bp_index + next_adj;
+		if (index < nilfs_btree_node_get_nchildren(node)) {
+			/* Next key is in this node */
+			*nextkey = nilfs_btree_node_get_key(node, index);
+			return 0;
+		}
+		/* For non-leaf nodes, next index is stored at bp_index + 1. */
+		next_adj = 1;
+	}
+	return -ENOENT;
+}
+
+static int nilfs_btree_lookup(const struct nilfs_bmap *btree,
+			      __u64 key, int level, __u64 *ptrp)
+{
+	struct nilfs_btree_path *path;
+	int ret;
+
+	path = nilfs_btree_alloc_path();
+	if (path == NULL)
+		return -ENOMEM;
+
+	ret = nilfs_btree_do_lookup(btree, path, key, ptrp, level, 0);
+
+	nilfs_btree_free_path(path);
+
+	return ret;
+}
+
+static int nilfs_btree_lookup_contig(const struct nilfs_bmap *btree,
+				     __u64 key, __u64 *ptrp,
+				     unsigned int maxblocks)
+{
+	struct nilfs_btree_path *path;
+	struct nilfs_btree_node *node;
+	struct inode *dat = NULL;
+	__u64 ptr, ptr2;
+	sector_t blocknr;
+	int level = NILFS_BTREE_LEVEL_NODE_MIN;
+	int ret, cnt, index, maxlevel, ncmax;
+	struct nilfs_btree_readahead_info p;
+
+	path = nilfs_btree_alloc_path();
+	if (path == NULL)
+		return -ENOMEM;
+
+	ret = nilfs_btree_do_lookup(btree, path, key, &ptr, level, 1);
+	if (ret < 0)
+		goto out;
+
+	if (NILFS_BMAP_USE_VBN(btree)) {
+		dat = nilfs_bmap_get_dat(btree);
+		ret = nilfs_dat_translate(dat, ptr, &blocknr);
+		if (ret < 0)
+			goto out;
+		ptr = blocknr;
+	}
+	cnt = 1;
+	if (cnt == maxblocks)
+		goto end;
+
+	maxlevel = nilfs_btree_height(btree) - 1;
+	node = nilfs_btree_get_node(btree, path, level, &ncmax);
+	index = path[level].bp_index + 1;
+	for (;;) {
+		while (index < nilfs_btree_node_get_nchildren(node)) {
+			if (nilfs_btree_node_get_key(node, index) !=
+			    key + cnt)
+				goto end;
+			ptr2 = nilfs_btree_node_get_ptr(node, index, ncmax);
+			if (dat) {
+				ret = nilfs_dat_translate(dat, ptr2, &blocknr);
+				if (ret < 0)
+					goto out;
+				ptr2 = blocknr;
+			}
+			if (ptr2 != ptr + cnt || ++cnt == maxblocks)
+				goto end;
+			index++;
+		}
+		if (level == maxlevel)
+			break;
+
+		/* look-up right sibling node */
+		p.node = nilfs_btree_get_node(btree, path, level + 1, &p.ncmax);
+		p.index = path[level + 1].bp_index + 1;
+		p.max_ra_blocks = 7;
+		if (p.index >= nilfs_btree_node_get_nchildren(p.node) ||
+		    nilfs_btree_node_get_key(p.node, p.index) != key + cnt)
+			break;
+		ptr2 = nilfs_btree_node_get_ptr(p.node, p.index, p.ncmax);
+		path[level + 1].bp_index = p.index;
+
+		brelse(path[level].bp_bh);
+		path[level].bp_bh = NULL;
+
+		ret = __nilfs_btree_get_block(btree, ptr2, &path[level].bp_bh,
+					      &p);
+		if (ret < 0)
+			goto out;
+		node = nilfs_btree_get_nonroot_node(path, level);
+		ncmax = nilfs_btree_nchildren_per_block(btree);
+		index = 0;
+		path[level].bp_index = index;
+	}
+ end:
+	*ptrp = ptr;
+	ret = cnt;
+ out:
+	nilfs_btree_free_path(path);
+	return ret;
+}
+
+static void nilfs_btree_promote_key(struct nilfs_bmap *btree,
+				    struct nilfs_btree_path *path,
+				    int level, __u64 key)
+{
+	if (level < nilfs_btree_height(btree) - 1) {
+		do {
+			nilfs_btree_node_set_key(
+				nilfs_btree_get_nonroot_node(path, level),
+				path[level].bp_index, key);
+			if (!buffer_dirty(path[level].bp_bh))
+				mark_buffer_dirty(path[level].bp_bh);
+		} while ((path[level].bp_index == 0) &&
+			 (++level < nilfs_btree_height(btree) - 1));
+	}
+
+	/* root */
+	if (level == nilfs_btree_height(btree) - 1) {
+		nilfs_btree_node_set_key(nilfs_btree_get_root(btree),
+					 path[level].bp_index, key);
+	}
+}
+
+static void nilfs_btree_do_insert(struct nilfs_bmap *btree,
+				  struct nilfs_btree_path *path,
+				  int level, __u64 *keyp, __u64 *ptrp)
+{
+	struct nilfs_btree_node *node;
+	int ncblk;
+
+	if (level < nilfs_btree_height(btree) - 1) {
+		node = nilfs_btree_get_nonroot_node(path, level);
+		ncblk = nilfs_btree_nchildren_per_block(btree);
+		nilfs_btree_node_insert(node, path[level].bp_index,
+					*keyp, *ptrp, ncblk);
+		if (!buffer_dirty(path[level].bp_bh))
+			mark_buffer_dirty(path[level].bp_bh);
+
+		if (path[level].bp_index == 0)
+			nilfs_btree_promote_key(btree, path, level + 1,
+						nilfs_btree_node_get_key(node,
+									 0));
+	} else {
+		node = nilfs_btree_get_root(btree);
+		nilfs_btree_node_insert(node, path[level].bp_index,
+					*keyp, *ptrp,
+					NILFS_BTREE_ROOT_NCHILDREN_MAX);
+	}
+}
+
+static void nilfs_btree_carry_left(struct nilfs_bmap *btree,
+				   struct nilfs_btree_path *path,
+				   int level, __u64 *keyp, __u64 *ptrp)
+{
+	struct nilfs_btree_node *node, *left;
+	int nchildren, lnchildren, n, move, ncblk;
+
+	node = nilfs_btree_get_nonroot_node(path, level);
+	left = nilfs_btree_get_sib_node(path, level);
+	nchildren = nilfs_btree_node_get_nchildren(node);
+	lnchildren = nilfs_btree_node_get_nchildren(left);
+	ncblk = nilfs_btree_nchildren_per_block(btree);
+	move = 0;
+
+	n = (nchildren + lnchildren + 1) / 2 - lnchildren;
+	if (n > path[level].bp_index) {
+		/* move insert point */
+		n--;
+		move = 1;
+	}
+
+	nilfs_btree_node_move_left(left, node, n, ncblk, ncblk);
+
+	if (!buffer_dirty(path[level].bp_bh))
+		mark_buffer_dirty(path[level].bp_bh);
+	if (!buffer_dirty(path[level].bp_sib_bh))
+		mark_buffer_dirty(path[level].bp_sib_bh);
+
+	nilfs_btree_promote_key(btree, path, level + 1,
+				nilfs_btree_node_get_key(node, 0));
+
+	if (move) {
+		brelse(path[level].bp_bh);
+		path[level].bp_bh = path[level].bp_sib_bh;
+		path[level].bp_sib_bh = NULL;
+		path[level].bp_index += lnchildren;
+		path[level + 1].bp_index--;
+	} else {
+		brelse(path[level].bp_sib_bh);
+		path[level].bp_sib_bh = NULL;
+		path[level].bp_index -= n;
+	}
+
+	nilfs_btree_do_insert(btree, path, level, keyp, ptrp);
+}
+
+static void nilfs_btree_carry_right(struct nilfs_bmap *btree,
+				    struct nilfs_btree_path *path,
+				    int level, __u64 *keyp, __u64 *ptrp)
+{
+	struct nilfs_btree_node *node, *right;
+	int nchildren, rnchildren, n, move, ncblk;
+
+	node = nilfs_btree_get_nonroot_node(path, level);
+	right = nilfs_btree_get_sib_node(path, level);
+	nchildren = nilfs_btree_node_get_nchildren(node);
+	rnchildren = nilfs_btree_node_get_nchildren(right);
+	ncblk = nilfs_btree_nchildren_per_block(btree);
+	move = 0;
+
+	n = (nchildren + rnchildren + 1) / 2 - rnchildren;
+	if (n > nchildren - path[level].bp_index) {
+		/* move insert point */
+		n--;
+		move = 1;
+	}
+
+	nilfs_btree_node_move_right(node, right, n, ncblk, ncblk);
+
+	if (!buffer_dirty(path[level].bp_bh))
+		mark_buffer_dirty(path[level].bp_bh);
+	if (!buffer_dirty(path[level].bp_sib_bh))
+		mark_buffer_dirty(path[level].bp_sib_bh);
+
+	path[level + 1].bp_index++;
+	nilfs_btree_promote_key(btree, path, level + 1,
+				nilfs_btree_node_get_key(right, 0));
+	path[level + 1].bp_index--;
+
+	if (move) {
+		brelse(path[level].bp_bh);
+		path[level].bp_bh = path[level].bp_sib_bh;
+		path[level].bp_sib_bh = NULL;
+		path[level].bp_index -= nilfs_btree_node_get_nchildren(node);
+		path[level + 1].bp_index++;
+	} else {
+		brelse(path[level].bp_sib_bh);
+		path[level].bp_sib_bh = NULL;
+	}
+
+	nilfs_btree_do_insert(btree, path, level, keyp, ptrp);
+}
+
+static void nilfs_btree_split(struct nilfs_bmap *btree,
+			      struct nilfs_btree_path *path,
+			      int level, __u64 *keyp, __u64 *ptrp)
+{
+	struct nilfs_btree_node *node, *right;
+	int nchildren, n, move, ncblk;
+
+	node = nilfs_btree_get_nonroot_node(path, level);
+	right = nilfs_btree_get_sib_node(path, level);
+	nchildren = nilfs_btree_node_get_nchildren(node);
+	ncblk = nilfs_btree_nchildren_per_block(btree);
+	move = 0;
+
+	n = (nchildren + 1) / 2;
+	if (n > nchildren - path[level].bp_index) {
+		n--;
+		move = 1;
+	}
+
+	nilfs_btree_node_move_right(node, right, n, ncblk, ncblk);
+
+	if (!buffer_dirty(path[level].bp_bh))
+		mark_buffer_dirty(path[level].bp_bh);
+	if (!buffer_dirty(path[level].bp_sib_bh))
+		mark_buffer_dirty(path[level].bp_sib_bh);
+
+	if (move) {
+		path[level].bp_index -= nilfs_btree_node_get_nchildren(node);
+		nilfs_btree_node_insert(right, path[level].bp_index,
+					*keyp, *ptrp, ncblk);
+
+		*keyp = nilfs_btree_node_get_key(right, 0);
+		*ptrp = path[level].bp_newreq.bpr_ptr;
+
+		brelse(path[level].bp_bh);
+		path[level].bp_bh = path[level].bp_sib_bh;
+		path[level].bp_sib_bh = NULL;
+	} else {
+		nilfs_btree_do_insert(btree, path, level, keyp, ptrp);
+
+		*keyp = nilfs_btree_node_get_key(right, 0);
+		*ptrp = path[level].bp_newreq.bpr_ptr;
+
+		brelse(path[level].bp_sib_bh);
+		path[level].bp_sib_bh = NULL;
+	}
+
+	path[level + 1].bp_index++;
+}
+
+static void nilfs_btree_grow(struct nilfs_bmap *btree,
+			     struct nilfs_btree_path *path,
+			     int level, __u64 *keyp, __u64 *ptrp)
+{
+	struct nilfs_btree_node *root, *child;
+	int n, ncblk;
+
+	root = nilfs_btree_get_root(btree);
+	child = nilfs_btree_get_sib_node(path, level);
+	ncblk = nilfs_btree_nchildren_per_block(btree);
+
+	n = nilfs_btree_node_get_nchildren(root);
+
+	nilfs_btree_node_move_right(root, child, n,
+				    NILFS_BTREE_ROOT_NCHILDREN_MAX, ncblk);
+	nilfs_btree_node_set_level(root, level + 1);
+
+	if (!buffer_dirty(path[level].bp_sib_bh))
+		mark_buffer_dirty(path[level].bp_sib_bh);
+
+	path[level].bp_bh = path[level].bp_sib_bh;
+	path[level].bp_sib_bh = NULL;
+
+	nilfs_btree_do_insert(btree, path, level, keyp, ptrp);
+
+	*keyp = nilfs_btree_node_get_key(child, 0);
+	*ptrp = path[level].bp_newreq.bpr_ptr;
+}
+
+static __u64 nilfs_btree_find_near(const struct nilfs_bmap *btree,
+				   const struct nilfs_btree_path *path)
+{
+	struct nilfs_btree_node *node;
+	int level, ncmax;
+
+	if (path == NULL)
+		return NILFS_BMAP_INVALID_PTR;
+
+	/* left sibling */
+	level = NILFS_BTREE_LEVEL_NODE_MIN;
+	if (path[level].bp_index > 0) {
+		node = nilfs_btree_get_node(btree, path, level, &ncmax);
+		return nilfs_btree_node_get_ptr(node,
+						path[level].bp_index - 1,
+						ncmax);
+	}
+
+	/* parent */
+	level = NILFS_BTREE_LEVEL_NODE_MIN + 1;
+	if (level <= nilfs_btree_height(btree) - 1) {
+		node = nilfs_btree_get_node(btree, path, level, &ncmax);
+		return nilfs_btree_node_get_ptr(node, path[level].bp_index,
+						ncmax);
+	}
+
+	return NILFS_BMAP_INVALID_PTR;
+}
+
+static __u64 nilfs_btree_find_target_v(const struct nilfs_bmap *btree,
+				       const struct nilfs_btree_path *path,
+				       __u64 key)
+{
+	__u64 ptr;
+
+	ptr = nilfs_bmap_find_target_seq(btree, key);
+	if (ptr != NILFS_BMAP_INVALID_PTR)
+		/* sequential access */
+		return ptr;
+
+	ptr = nilfs_btree_find_near(btree, path);
+	if (ptr != NILFS_BMAP_INVALID_PTR)
+		/* near */
+		return ptr;
+
+	/* block group */
+	return nilfs_bmap_find_target_in_group(btree);
+}
+
+static int nilfs_btree_prepare_insert(struct nilfs_bmap *btree,
+				      struct nilfs_btree_path *path,
+				      int *levelp, __u64 key, __u64 ptr,
+				      struct nilfs_bmap_stats *stats)
+{
+	struct buffer_head *bh;
+	struct nilfs_btree_node *node, *parent, *sib;
+	__u64 sibptr;
+	int pindex, level, ncmax, ncblk, ret;
+	struct inode *dat = NULL;
+
+	stats->bs_nblocks = 0;
+	level = NILFS_BTREE_LEVEL_DATA;
+
+	/* allocate a new ptr for data block */
+	if (NILFS_BMAP_USE_VBN(btree)) {
+		path[level].bp_newreq.bpr_ptr =
+			nilfs_btree_find_target_v(btree, path, key);
+		dat = nilfs_bmap_get_dat(btree);
+	}
+
+	ret = nilfs_bmap_prepare_alloc_ptr(btree, &path[level].bp_newreq, dat);
+	if (ret < 0)
+		goto err_out_data;
+
+	ncblk = nilfs_btree_nchildren_per_block(btree);
+
+	for (level = NILFS_BTREE_LEVEL_NODE_MIN;
+	     level < nilfs_btree_height(btree) - 1;
+	     level++) {
+		node = nilfs_btree_get_nonroot_node(path, level);
+		if (nilfs_btree_node_get_nchildren(node) < ncblk) {
+			path[level].bp_op = nilfs_btree_do_insert;
+			stats->bs_nblocks++;
+			goto out;
+		}
+
+		parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
+		pindex = path[level + 1].bp_index;
+
+		/* left sibling */
+		if (pindex > 0) {
+			sibptr = nilfs_btree_node_get_ptr(parent, pindex - 1,
+							  ncmax);
+			ret = nilfs_btree_get_block(btree, sibptr, &bh);
+			if (ret < 0)
+				goto err_out_child_node;
+			sib = (struct nilfs_btree_node *)bh->b_data;
+			if (nilfs_btree_node_get_nchildren(sib) < ncblk) {
+				path[level].bp_sib_bh = bh;
+				path[level].bp_op = nilfs_btree_carry_left;
+				stats->bs_nblocks++;
+				goto out;
+			} else {
+				brelse(bh);
+			}
+		}
+
+		/* right sibling */
+		if (pindex < nilfs_btree_node_get_nchildren(parent) - 1) {
+			sibptr = nilfs_btree_node_get_ptr(parent, pindex + 1,
+							  ncmax);
+			ret = nilfs_btree_get_block(btree, sibptr, &bh);
+			if (ret < 0)
+				goto err_out_child_node;
+			sib = (struct nilfs_btree_node *)bh->b_data;
+			if (nilfs_btree_node_get_nchildren(sib) < ncblk) {
+				path[level].bp_sib_bh = bh;
+				path[level].bp_op = nilfs_btree_carry_right;
+				stats->bs_nblocks++;
+				goto out;
+			} else {
+				brelse(bh);
+			}
+		}
+
+		/* split */
+		path[level].bp_newreq.bpr_ptr =
+			path[level - 1].bp_newreq.bpr_ptr + 1;
+		ret = nilfs_bmap_prepare_alloc_ptr(btree,
+						   &path[level].bp_newreq, dat);
+		if (ret < 0)
+			goto err_out_child_node;
+		ret = nilfs_btree_get_new_block(btree,
+						path[level].bp_newreq.bpr_ptr,
+						&bh);
+		if (ret < 0)
+			goto err_out_curr_node;
+
+		stats->bs_nblocks++;
+
+		sib = (struct nilfs_btree_node *)bh->b_data;
+		nilfs_btree_node_init(sib, 0, level, 0, ncblk, NULL, NULL);
+		path[level].bp_sib_bh = bh;
+		path[level].bp_op = nilfs_btree_split;
+	}
+
+	/* root */
+	node = nilfs_btree_get_root(btree);
+	if (nilfs_btree_node_get_nchildren(node) <
+	    NILFS_BTREE_ROOT_NCHILDREN_MAX) {
+		path[level].bp_op = nilfs_btree_do_insert;
+		stats->bs_nblocks++;
+		goto out;
+	}
+
+	/* grow */
+	path[level].bp_newreq.bpr_ptr = path[level - 1].bp_newreq.bpr_ptr + 1;
+	ret = nilfs_bmap_prepare_alloc_ptr(btree, &path[level].bp_newreq, dat);
+	if (ret < 0)
+		goto err_out_child_node;
+	ret = nilfs_btree_get_new_block(btree, path[level].bp_newreq.bpr_ptr,
+					&bh);
+	if (ret < 0)
+		goto err_out_curr_node;
+
+	nilfs_btree_node_init((struct nilfs_btree_node *)bh->b_data,
+			      0, level, 0, ncblk, NULL, NULL);
+	path[level].bp_sib_bh = bh;
+	path[level].bp_op = nilfs_btree_grow;
+
+	level++;
+	path[level].bp_op = nilfs_btree_do_insert;
+
+	/* a newly-created node block and a data block are added */
+	stats->bs_nblocks += 2;
+
+	/* success */
+ out:
+	*levelp = level;
+	return ret;
+
+	/* error */
+ err_out_curr_node:
+	nilfs_bmap_abort_alloc_ptr(btree, &path[level].bp_newreq, dat);
+ err_out_child_node:
+	for (level--; level > NILFS_BTREE_LEVEL_DATA; level--) {
+		nilfs_btnode_delete(path[level].bp_sib_bh);
+		nilfs_bmap_abort_alloc_ptr(btree, &path[level].bp_newreq, dat);
+
+	}
+
+	nilfs_bmap_abort_alloc_ptr(btree, &path[level].bp_newreq, dat);
+ err_out_data:
+	*levelp = level;
+	stats->bs_nblocks = 0;
+	return ret;
+}
+
+static void nilfs_btree_commit_insert(struct nilfs_bmap *btree,
+				      struct nilfs_btree_path *path,
+				      int maxlevel, __u64 key, __u64 ptr)
+{
+	struct inode *dat = NULL;
+	int level;
+
+	set_buffer_nilfs_volatile((struct buffer_head *)((unsigned long)ptr));
+	ptr = path[NILFS_BTREE_LEVEL_DATA].bp_newreq.bpr_ptr;
+	if (NILFS_BMAP_USE_VBN(btree)) {
+		nilfs_bmap_set_target_v(btree, key, ptr);
+		dat = nilfs_bmap_get_dat(btree);
+	}
+
+	for (level = NILFS_BTREE_LEVEL_NODE_MIN; level <= maxlevel; level++) {
+		nilfs_bmap_commit_alloc_ptr(btree,
+					    &path[level - 1].bp_newreq, dat);
+		path[level].bp_op(btree, path, level, &key, &ptr);
+	}
+
+	if (!nilfs_bmap_dirty(btree))
+		nilfs_bmap_set_dirty(btree);
+}
+
+static int nilfs_btree_insert(struct nilfs_bmap *btree, __u64 key, __u64 ptr)
+{
+	struct nilfs_btree_path *path;
+	struct nilfs_bmap_stats stats;
+	int level, ret;
+
+	path = nilfs_btree_alloc_path();
+	if (path == NULL)
+		return -ENOMEM;
+
+	ret = nilfs_btree_do_lookup(btree, path, key, NULL,
+				    NILFS_BTREE_LEVEL_NODE_MIN, 0);
+	if (ret != -ENOENT) {
+		if (ret == 0)
+			ret = -EEXIST;
+		goto out;
+	}
+
+	ret = nilfs_btree_prepare_insert(btree, path, &level, key, ptr, &stats);
+	if (ret < 0)
+		goto out;
+	nilfs_btree_commit_insert(btree, path, level, key, ptr);
+	nilfs_inode_add_blocks(btree->b_inode, stats.bs_nblocks);
+
+ out:
+	nilfs_btree_free_path(path);
+	return ret;
+}
+
+static void nilfs_btree_do_delete(struct nilfs_bmap *btree,
+				  struct nilfs_btree_path *path,
+				  int level, __u64 *keyp, __u64 *ptrp)
+{
+	struct nilfs_btree_node *node;
+	int ncblk;
+
+	if (level < nilfs_btree_height(btree) - 1) {
+		node = nilfs_btree_get_nonroot_node(path, level);
+		ncblk = nilfs_btree_nchildren_per_block(btree);
+		nilfs_btree_node_delete(node, path[level].bp_index,
+					keyp, ptrp, ncblk);
+		if (!buffer_dirty(path[level].bp_bh))
+			mark_buffer_dirty(path[level].bp_bh);
+		if (path[level].bp_index == 0)
+			nilfs_btree_promote_key(btree, path, level + 1,
+				nilfs_btree_node_get_key(node, 0));
+	} else {
+		node = nilfs_btree_get_root(btree);
+		nilfs_btree_node_delete(node, path[level].bp_index,
+					keyp, ptrp,
+					NILFS_BTREE_ROOT_NCHILDREN_MAX);
+	}
+}
+
+static void nilfs_btree_borrow_left(struct nilfs_bmap *btree,
+				    struct nilfs_btree_path *path,
+				    int level, __u64 *keyp, __u64 *ptrp)
+{
+	struct nilfs_btree_node *node, *left;
+	int nchildren, lnchildren, n, ncblk;
+
+	nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
+
+	node = nilfs_btree_get_nonroot_node(path, level);
+	left = nilfs_btree_get_sib_node(path, level);
+	nchildren = nilfs_btree_node_get_nchildren(node);
+	lnchildren = nilfs_btree_node_get_nchildren(left);
+	ncblk = nilfs_btree_nchildren_per_block(btree);
+
+	n = (nchildren + lnchildren) / 2 - nchildren;
+
+	nilfs_btree_node_move_right(left, node, n, ncblk, ncblk);
+
+	if (!buffer_dirty(path[level].bp_bh))
+		mark_buffer_dirty(path[level].bp_bh);
+	if (!buffer_dirty(path[level].bp_sib_bh))
+		mark_buffer_dirty(path[level].bp_sib_bh);
+
+	nilfs_btree_promote_key(btree, path, level + 1,
+				nilfs_btree_node_get_key(node, 0));
+
+	brelse(path[level].bp_sib_bh);
+	path[level].bp_sib_bh = NULL;
+	path[level].bp_index += n;
+}
+
+static void nilfs_btree_borrow_right(struct nilfs_bmap *btree,
+				     struct nilfs_btree_path *path,
+				     int level, __u64 *keyp, __u64 *ptrp)
+{
+	struct nilfs_btree_node *node, *right;
+	int nchildren, rnchildren, n, ncblk;
+
+	nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
+
+	node = nilfs_btree_get_nonroot_node(path, level);
+	right = nilfs_btree_get_sib_node(path, level);
+	nchildren = nilfs_btree_node_get_nchildren(node);
+	rnchildren = nilfs_btree_node_get_nchildren(right);
+	ncblk = nilfs_btree_nchildren_per_block(btree);
+
+	n = (nchildren + rnchildren) / 2 - nchildren;
+
+	nilfs_btree_node_move_left(node, right, n, ncblk, ncblk);
+
+	if (!buffer_dirty(path[level].bp_bh))
+		mark_buffer_dirty(path[level].bp_bh);
+	if (!buffer_dirty(path[level].bp_sib_bh))
+		mark_buffer_dirty(path[level].bp_sib_bh);
+
+	path[level + 1].bp_index++;
+	nilfs_btree_promote_key(btree, path, level + 1,
+				nilfs_btree_node_get_key(right, 0));
+	path[level + 1].bp_index--;
+
+	brelse(path[level].bp_sib_bh);
+	path[level].bp_sib_bh = NULL;
+}
+
+static void nilfs_btree_concat_left(struct nilfs_bmap *btree,
+				    struct nilfs_btree_path *path,
+				    int level, __u64 *keyp, __u64 *ptrp)
+{
+	struct nilfs_btree_node *node, *left;
+	int n, ncblk;
+
+	nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
+
+	node = nilfs_btree_get_nonroot_node(path, level);
+	left = nilfs_btree_get_sib_node(path, level);
+	ncblk = nilfs_btree_nchildren_per_block(btree);
+
+	n = nilfs_btree_node_get_nchildren(node);
+
+	nilfs_btree_node_move_left(left, node, n, ncblk, ncblk);
+
+	if (!buffer_dirty(path[level].bp_sib_bh))
+		mark_buffer_dirty(path[level].bp_sib_bh);
+
+	nilfs_btnode_delete(path[level].bp_bh);
+	path[level].bp_bh = path[level].bp_sib_bh;
+	path[level].bp_sib_bh = NULL;
+	path[level].bp_index += nilfs_btree_node_get_nchildren(left);
+}
+
+static void nilfs_btree_concat_right(struct nilfs_bmap *btree,
+				     struct nilfs_btree_path *path,
+				     int level, __u64 *keyp, __u64 *ptrp)
+{
+	struct nilfs_btree_node *node, *right;
+	int n, ncblk;
+
+	nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
+
+	node = nilfs_btree_get_nonroot_node(path, level);
+	right = nilfs_btree_get_sib_node(path, level);
+	ncblk = nilfs_btree_nchildren_per_block(btree);
+
+	n = nilfs_btree_node_get_nchildren(right);
+
+	nilfs_btree_node_move_left(node, right, n, ncblk, ncblk);
+
+	if (!buffer_dirty(path[level].bp_bh))
+		mark_buffer_dirty(path[level].bp_bh);
+
+	nilfs_btnode_delete(path[level].bp_sib_bh);
+	path[level].bp_sib_bh = NULL;
+	path[level + 1].bp_index++;
+}
+
+static void nilfs_btree_shrink(struct nilfs_bmap *btree,
+			       struct nilfs_btree_path *path,
+			       int level, __u64 *keyp, __u64 *ptrp)
+{
+	struct nilfs_btree_node *root, *child;
+	int n, ncblk;
+
+	nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
+
+	root = nilfs_btree_get_root(btree);
+	child = nilfs_btree_get_nonroot_node(path, level);
+	ncblk = nilfs_btree_nchildren_per_block(btree);
+
+	nilfs_btree_node_delete(root, 0, NULL, NULL,
+				NILFS_BTREE_ROOT_NCHILDREN_MAX);
+	nilfs_btree_node_set_level(root, level);
+	n = nilfs_btree_node_get_nchildren(child);
+	nilfs_btree_node_move_left(root, child, n,
+				   NILFS_BTREE_ROOT_NCHILDREN_MAX, ncblk);
+
+	nilfs_btnode_delete(path[level].bp_bh);
+	path[level].bp_bh = NULL;
+}
+
+static void nilfs_btree_nop(struct nilfs_bmap *btree,
+			    struct nilfs_btree_path *path,
+			    int level, __u64 *keyp, __u64 *ptrp)
+{
+}
+
+static int nilfs_btree_prepare_delete(struct nilfs_bmap *btree,
+				      struct nilfs_btree_path *path,
+				      int *levelp,
+				      struct nilfs_bmap_stats *stats,
+				      struct inode *dat)
+{
+	struct buffer_head *bh;
+	struct nilfs_btree_node *node, *parent, *sib;
+	__u64 sibptr;
+	int pindex, dindex, level, ncmin, ncmax, ncblk, ret;
+
+	ret = 0;
+	stats->bs_nblocks = 0;
+	ncmin = NILFS_BTREE_NODE_NCHILDREN_MIN(nilfs_btree_node_size(btree));
+	ncblk = nilfs_btree_nchildren_per_block(btree);
+
+	for (level = NILFS_BTREE_LEVEL_NODE_MIN, dindex = path[level].bp_index;
+	     level < nilfs_btree_height(btree) - 1;
+	     level++) {
+		node = nilfs_btree_get_nonroot_node(path, level);
+		path[level].bp_oldreq.bpr_ptr =
+			nilfs_btree_node_get_ptr(node, dindex, ncblk);
+		ret = nilfs_bmap_prepare_end_ptr(btree,
+						 &path[level].bp_oldreq, dat);
+		if (ret < 0)
+			goto err_out_child_node;
+
+		if (nilfs_btree_node_get_nchildren(node) > ncmin) {
+			path[level].bp_op = nilfs_btree_do_delete;
+			stats->bs_nblocks++;
+			goto out;
+		}
+
+		parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
+		pindex = path[level + 1].bp_index;
+		dindex = pindex;
+
+		if (pindex > 0) {
+			/* left sibling */
+			sibptr = nilfs_btree_node_get_ptr(parent, pindex - 1,
+							  ncmax);
+			ret = nilfs_btree_get_block(btree, sibptr, &bh);
+			if (ret < 0)
+				goto err_out_curr_node;
+			sib = (struct nilfs_btree_node *)bh->b_data;
+			if (nilfs_btree_node_get_nchildren(sib) > ncmin) {
+				path[level].bp_sib_bh = bh;
+				path[level].bp_op = nilfs_btree_borrow_left;
+				stats->bs_nblocks++;
+				goto out;
+			} else {
+				path[level].bp_sib_bh = bh;
+				path[level].bp_op = nilfs_btree_concat_left;
+				stats->bs_nblocks++;
+				/* continue; */
+			}
+		} else if (pindex <
+			   nilfs_btree_node_get_nchildren(parent) - 1) {
+			/* right sibling */
+			sibptr = nilfs_btree_node_get_ptr(parent, pindex + 1,
+							  ncmax);
+			ret = nilfs_btree_get_block(btree, sibptr, &bh);
+			if (ret < 0)
+				goto err_out_curr_node;
+			sib = (struct nilfs_btree_node *)bh->b_data;
+			if (nilfs_btree_node_get_nchildren(sib) > ncmin) {
+				path[level].bp_sib_bh = bh;
+				path[level].bp_op = nilfs_btree_borrow_right;
+				stats->bs_nblocks++;
+				goto out;
+			} else {
+				path[level].bp_sib_bh = bh;
+				path[level].bp_op = nilfs_btree_concat_right;
+				stats->bs_nblocks++;
+				/*
+				 * When merging right sibling node
+				 * into the current node, pointer to
+				 * the right sibling node must be
+				 * terminated instead.  The adjustment
+				 * below is required for that.
+				 */
+				dindex = pindex + 1;
+				/* continue; */
+			}
+		} else {
+			/* no siblings */
+			/* the only child of the root node */
+			WARN_ON(level != nilfs_btree_height(btree) - 2);
+			if (nilfs_btree_node_get_nchildren(node) - 1 <=
+			    NILFS_BTREE_ROOT_NCHILDREN_MAX) {
+				path[level].bp_op = nilfs_btree_shrink;
+				stats->bs_nblocks += 2;
+				level++;
+				path[level].bp_op = nilfs_btree_nop;
+				goto shrink_root_child;
+			} else {
+				path[level].bp_op = nilfs_btree_do_delete;
+				stats->bs_nblocks++;
+				goto out;
+			}
+		}
+	}
+
+	/* child of the root node is deleted */
+	path[level].bp_op = nilfs_btree_do_delete;
+	stats->bs_nblocks++;
+
+shrink_root_child:
+	node = nilfs_btree_get_root(btree);
+	path[level].bp_oldreq.bpr_ptr =
+		nilfs_btree_node_get_ptr(node, dindex,
+					 NILFS_BTREE_ROOT_NCHILDREN_MAX);
+
+	ret = nilfs_bmap_prepare_end_ptr(btree, &path[level].bp_oldreq, dat);
+	if (ret < 0)
+		goto err_out_child_node;
+
+	/* success */
+ out:
+	*levelp = level;
+	return ret;
+
+	/* error */
+ err_out_curr_node:
+	nilfs_bmap_abort_end_ptr(btree, &path[level].bp_oldreq, dat);
+ err_out_child_node:
+	for (level--; level >= NILFS_BTREE_LEVEL_NODE_MIN; level--) {
+		brelse(path[level].bp_sib_bh);
+		nilfs_bmap_abort_end_ptr(btree, &path[level].bp_oldreq, dat);
+	}
+	*levelp = level;
+	stats->bs_nblocks = 0;
+	return ret;
+}
+
+static void nilfs_btree_commit_delete(struct nilfs_bmap *btree,
+				      struct nilfs_btree_path *path,
+				      int maxlevel, struct inode *dat)
+{
+	int level;
+
+	for (level = NILFS_BTREE_LEVEL_NODE_MIN; level <= maxlevel; level++) {
+		nilfs_bmap_commit_end_ptr(btree, &path[level].bp_oldreq, dat);
+		path[level].bp_op(btree, path, level, NULL, NULL);
+	}
+
+	if (!nilfs_bmap_dirty(btree))
+		nilfs_bmap_set_dirty(btree);
+}
+
+static int nilfs_btree_delete(struct nilfs_bmap *btree, __u64 key)
+
+{
+	struct nilfs_btree_path *path;
+	struct nilfs_bmap_stats stats;
+	struct inode *dat;
+	int level, ret;
+
+	path = nilfs_btree_alloc_path();
+	if (path == NULL)
+		return -ENOMEM;
+
+	ret = nilfs_btree_do_lookup(btree, path, key, NULL,
+				    NILFS_BTREE_LEVEL_NODE_MIN, 0);
+	if (ret < 0)
+		goto out;
+
+
+	dat = NILFS_BMAP_USE_VBN(btree) ? nilfs_bmap_get_dat(btree) : NULL;
+
+	ret = nilfs_btree_prepare_delete(btree, path, &level, &stats, dat);
+	if (ret < 0)
+		goto out;
+	nilfs_btree_commit_delete(btree, path, level, dat);
+	nilfs_inode_sub_blocks(btree->b_inode, stats.bs_nblocks);
+
+out:
+	nilfs_btree_free_path(path);
+	return ret;
+}
+
+static int nilfs_btree_seek_key(const struct nilfs_bmap *btree, __u64 start,
+				__u64 *keyp)
+{
+	struct nilfs_btree_path *path;
+	const int minlevel = NILFS_BTREE_LEVEL_NODE_MIN;
+	int ret;
+
+	path = nilfs_btree_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	ret = nilfs_btree_do_lookup(btree, path, start, NULL, minlevel, 0);
+	if (!ret)
+		*keyp = start;
+	else if (ret == -ENOENT)
+		ret = nilfs_btree_get_next_key(btree, path, minlevel, keyp);
+
+	nilfs_btree_free_path(path);
+	return ret;
+}
+
+static int nilfs_btree_last_key(const struct nilfs_bmap *btree, __u64 *keyp)
+{
+	struct nilfs_btree_path *path;
+	int ret;
+
+	path = nilfs_btree_alloc_path();
+	if (path == NULL)
+		return -ENOMEM;
+
+	ret = nilfs_btree_do_lookup_last(btree, path, keyp, NULL);
+
+	nilfs_btree_free_path(path);
+
+	return ret;
+}
+
+static int nilfs_btree_check_delete(struct nilfs_bmap *btree, __u64 key)
+{
+	struct buffer_head *bh;
+	struct nilfs_btree_node *root, *node;
+	__u64 maxkey, nextmaxkey;
+	__u64 ptr;
+	int nchildren, ret;
+
+	root = nilfs_btree_get_root(btree);
+	switch (nilfs_btree_height(btree)) {
+	case 2:
+		bh = NULL;
+		node = root;
+		break;
+	case 3:
+		nchildren = nilfs_btree_node_get_nchildren(root);
+		if (nchildren > 1)
+			return 0;
+		ptr = nilfs_btree_node_get_ptr(root, nchildren - 1,
+					       NILFS_BTREE_ROOT_NCHILDREN_MAX);
+		ret = nilfs_btree_get_block(btree, ptr, &bh);
+		if (ret < 0)
+			return ret;
+		node = (struct nilfs_btree_node *)bh->b_data;
+		break;
+	default:
+		return 0;
+	}
+
+	nchildren = nilfs_btree_node_get_nchildren(node);
+	maxkey = nilfs_btree_node_get_key(node, nchildren - 1);
+	nextmaxkey = (nchildren > 1) ?
+		nilfs_btree_node_get_key(node, nchildren - 2) : 0;
+	brelse(bh);
+
+	return (maxkey == key) && (nextmaxkey < NILFS_BMAP_LARGE_LOW);
+}
+
+static int nilfs_btree_gather_data(struct nilfs_bmap *btree,
+				   __u64 *keys, __u64 *ptrs, int nitems)
+{
+	struct buffer_head *bh;
+	struct nilfs_btree_node *node, *root;
+	__le64 *dkeys;
+	__le64 *dptrs;
+	__u64 ptr;
+	int nchildren, ncmax, i, ret;
+
+	root = nilfs_btree_get_root(btree);
+	switch (nilfs_btree_height(btree)) {
+	case 2:
+		bh = NULL;
+		node = root;
+		ncmax = NILFS_BTREE_ROOT_NCHILDREN_MAX;
+		break;
+	case 3:
+		nchildren = nilfs_btree_node_get_nchildren(root);
+		WARN_ON(nchildren > 1);
+		ptr = nilfs_btree_node_get_ptr(root, nchildren - 1,
+					       NILFS_BTREE_ROOT_NCHILDREN_MAX);
+		ret = nilfs_btree_get_block(btree, ptr, &bh);
+		if (ret < 0)
+			return ret;
+		node = (struct nilfs_btree_node *)bh->b_data;
+		ncmax = nilfs_btree_nchildren_per_block(btree);
+		break;
+	default:
+		node = NULL;
+		return -EINVAL;
+	}
+
+	nchildren = nilfs_btree_node_get_nchildren(node);
+	if (nchildren < nitems)
+		nitems = nchildren;
+	dkeys = nilfs_btree_node_dkeys(node);
+	dptrs = nilfs_btree_node_dptrs(node, ncmax);
+	for (i = 0; i < nitems; i++) {
+		keys[i] = le64_to_cpu(dkeys[i]);
+		ptrs[i] = le64_to_cpu(dptrs[i]);
+	}
+
+	brelse(bh);
+
+	return nitems;
+}
+
+static int
+nilfs_btree_prepare_convert_and_insert(struct nilfs_bmap *btree, __u64 key,
+				       union nilfs_bmap_ptr_req *dreq,
+				       union nilfs_bmap_ptr_req *nreq,
+				       struct buffer_head **bhp,
+				       struct nilfs_bmap_stats *stats)
+{
+	struct buffer_head *bh;
+	struct inode *dat = NULL;
+	int ret;
+
+	stats->bs_nblocks = 0;
+
+	/* for data */
+	/* cannot find near ptr */
+	if (NILFS_BMAP_USE_VBN(btree)) {
+		dreq->bpr_ptr = nilfs_btree_find_target_v(btree, NULL, key);
+		dat = nilfs_bmap_get_dat(btree);
+	}
+
+	ret = nilfs_attach_btree_node_cache(&NILFS_BMAP_I(btree)->vfs_inode);
+	if (ret < 0)
+		return ret;
+
+	ret = nilfs_bmap_prepare_alloc_ptr(btree, dreq, dat);
+	if (ret < 0)
+		return ret;
+
+	*bhp = NULL;
+	stats->bs_nblocks++;
+	if (nreq != NULL) {
+		nreq->bpr_ptr = dreq->bpr_ptr + 1;
+		ret = nilfs_bmap_prepare_alloc_ptr(btree, nreq, dat);
+		if (ret < 0)
+			goto err_out_dreq;
+
+		ret = nilfs_btree_get_new_block(btree, nreq->bpr_ptr, &bh);
+		if (ret < 0)
+			goto err_out_nreq;
+
+		*bhp = bh;
+		stats->bs_nblocks++;
+	}
+
+	/* success */
+	return 0;
+
+	/* error */
+ err_out_nreq:
+	nilfs_bmap_abort_alloc_ptr(btree, nreq, dat);
+ err_out_dreq:
+	nilfs_bmap_abort_alloc_ptr(btree, dreq, dat);
+	stats->bs_nblocks = 0;
+	return ret;
+
+}
+
+static void
+nilfs_btree_commit_convert_and_insert(struct nilfs_bmap *btree,
+				      __u64 key, __u64 ptr,
+				      const __u64 *keys, const __u64 *ptrs,
+				      int n,
+				      union nilfs_bmap_ptr_req *dreq,
+				      union nilfs_bmap_ptr_req *nreq,
+				      struct buffer_head *bh)
+{
+	struct nilfs_btree_node *node;
+	struct inode *dat;
+	__u64 tmpptr;
+	int ncblk;
+
+	/* free resources */
+	if (btree->b_ops->bop_clear != NULL)
+		btree->b_ops->bop_clear(btree);
+
+	/* ptr must be a pointer to a buffer head. */
+	set_buffer_nilfs_volatile((struct buffer_head *)((unsigned long)ptr));
+
+	/* convert and insert */
+	dat = NILFS_BMAP_USE_VBN(btree) ? nilfs_bmap_get_dat(btree) : NULL;
+	__nilfs_btree_init(btree);
+	if (nreq != NULL) {
+		nilfs_bmap_commit_alloc_ptr(btree, dreq, dat);
+		nilfs_bmap_commit_alloc_ptr(btree, nreq, dat);
+
+		/* create child node at level 1 */
+		node = (struct nilfs_btree_node *)bh->b_data;
+		ncblk = nilfs_btree_nchildren_per_block(btree);
+		nilfs_btree_node_init(node, 0, 1, n, ncblk, keys, ptrs);
+		nilfs_btree_node_insert(node, n, key, dreq->bpr_ptr, ncblk);
+		if (!buffer_dirty(bh))
+			mark_buffer_dirty(bh);
+		if (!nilfs_bmap_dirty(btree))
+			nilfs_bmap_set_dirty(btree);
+
+		brelse(bh);
+
+		/* create root node at level 2 */
+		node = nilfs_btree_get_root(btree);
+		tmpptr = nreq->bpr_ptr;
+		nilfs_btree_node_init(node, NILFS_BTREE_NODE_ROOT, 2, 1,
+				      NILFS_BTREE_ROOT_NCHILDREN_MAX,
+				      &keys[0], &tmpptr);
+	} else {
+		nilfs_bmap_commit_alloc_ptr(btree, dreq, dat);
+
+		/* create root node at level 1 */
+		node = nilfs_btree_get_root(btree);
+		nilfs_btree_node_init(node, NILFS_BTREE_NODE_ROOT, 1, n,
+				      NILFS_BTREE_ROOT_NCHILDREN_MAX,
+				      keys, ptrs);
+		nilfs_btree_node_insert(node, n, key, dreq->bpr_ptr,
+					NILFS_BTREE_ROOT_NCHILDREN_MAX);
+		if (!nilfs_bmap_dirty(btree))
+			nilfs_bmap_set_dirty(btree);
+	}
+
+	if (NILFS_BMAP_USE_VBN(btree))
+		nilfs_bmap_set_target_v(btree, key, dreq->bpr_ptr);
+}
+
+/**
+ * nilfs_btree_convert_and_insert -
+ * @bmap:
+ * @key:
+ * @ptr:
+ * @keys:
+ * @ptrs:
+ * @n:
+ */
+int nilfs_btree_convert_and_insert(struct nilfs_bmap *btree,
+				   __u64 key, __u64 ptr,
+				   const __u64 *keys, const __u64 *ptrs, int n)
+{
+	struct buffer_head *bh = NULL;
+	union nilfs_bmap_ptr_req dreq, nreq, *di, *ni;
+	struct nilfs_bmap_stats stats;
+	int ret;
+
+	if (n + 1 <= NILFS_BTREE_ROOT_NCHILDREN_MAX) {
+		di = &dreq;
+		ni = NULL;
+	} else if ((n + 1) <= NILFS_BTREE_NODE_NCHILDREN_MAX(
+			   nilfs_btree_node_size(btree))) {
+		di = &dreq;
+		ni = &nreq;
+	} else {
+		di = NULL;
+		ni = NULL;
+		BUG();
+	}
+
+	ret = nilfs_btree_prepare_convert_and_insert(btree, key, di, ni, &bh,
+						     &stats);
+	if (ret < 0)
+		return ret;
+	nilfs_btree_commit_convert_and_insert(btree, key, ptr, keys, ptrs, n,
+					      di, ni, bh);
+	nilfs_inode_add_blocks(btree->b_inode, stats.bs_nblocks);
+	return 0;
+}
+
+static int nilfs_btree_propagate_p(struct nilfs_bmap *btree,
+				   struct nilfs_btree_path *path,
+				   int level,
+				   struct buffer_head *bh)
+{
+	while ((++level < nilfs_btree_height(btree) - 1) &&
+	       !buffer_dirty(path[level].bp_bh))
+		mark_buffer_dirty(path[level].bp_bh);
+
+	return 0;
+}
+
+static int nilfs_btree_prepare_update_v(struct nilfs_bmap *btree,
+					struct nilfs_btree_path *path,
+					int level, struct inode *dat)
+{
+	struct nilfs_btree_node *parent;
+	int ncmax, ret;
+
+	parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
+	path[level].bp_oldreq.bpr_ptr =
+		nilfs_btree_node_get_ptr(parent, path[level + 1].bp_index,
+					 ncmax);
+	path[level].bp_newreq.bpr_ptr = path[level].bp_oldreq.bpr_ptr + 1;
+	ret = nilfs_dat_prepare_update(dat, &path[level].bp_oldreq.bpr_req,
+				       &path[level].bp_newreq.bpr_req);
+	if (ret < 0)
+		return ret;
+
+	if (buffer_nilfs_node(path[level].bp_bh)) {
+		path[level].bp_ctxt.oldkey = path[level].bp_oldreq.bpr_ptr;
+		path[level].bp_ctxt.newkey = path[level].bp_newreq.bpr_ptr;
+		path[level].bp_ctxt.bh = path[level].bp_bh;
+		ret = nilfs_btnode_prepare_change_key(
+			NILFS_BMAP_I(btree)->i_assoc_inode->i_mapping,
+			&path[level].bp_ctxt);
+		if (ret < 0) {
+			nilfs_dat_abort_update(dat,
+					       &path[level].bp_oldreq.bpr_req,
+					       &path[level].bp_newreq.bpr_req);
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
+static void nilfs_btree_commit_update_v(struct nilfs_bmap *btree,
+					struct nilfs_btree_path *path,
+					int level, struct inode *dat)
+{
+	struct nilfs_btree_node *parent;
+	int ncmax;
+
+	nilfs_dat_commit_update(dat, &path[level].bp_oldreq.bpr_req,
+				&path[level].bp_newreq.bpr_req,
+				btree->b_ptr_type == NILFS_BMAP_PTR_VS);
+
+	if (buffer_nilfs_node(path[level].bp_bh)) {
+		nilfs_btnode_commit_change_key(
+			NILFS_BMAP_I(btree)->i_assoc_inode->i_mapping,
+			&path[level].bp_ctxt);
+		path[level].bp_bh = path[level].bp_ctxt.bh;
+	}
+	set_buffer_nilfs_volatile(path[level].bp_bh);
+
+	parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
+	nilfs_btree_node_set_ptr(parent, path[level + 1].bp_index,
+				 path[level].bp_newreq.bpr_ptr, ncmax);
+}
+
+static void nilfs_btree_abort_update_v(struct nilfs_bmap *btree,
+				       struct nilfs_btree_path *path,
+				       int level, struct inode *dat)
+{
+	nilfs_dat_abort_update(dat, &path[level].bp_oldreq.bpr_req,
+			       &path[level].bp_newreq.bpr_req);
+	if (buffer_nilfs_node(path[level].bp_bh))
+		nilfs_btnode_abort_change_key(
+			NILFS_BMAP_I(btree)->i_assoc_inode->i_mapping,
+			&path[level].bp_ctxt);
+}
+
+static int nilfs_btree_prepare_propagate_v(struct nilfs_bmap *btree,
+					   struct nilfs_btree_path *path,
+					   int minlevel, int *maxlevelp,
+					   struct inode *dat)
+{
+	int level, ret;
+
+	level = minlevel;
+	if (!buffer_nilfs_volatile(path[level].bp_bh)) {
+		ret = nilfs_btree_prepare_update_v(btree, path, level, dat);
+		if (ret < 0)
+			return ret;
+	}
+	while ((++level < nilfs_btree_height(btree) - 1) &&
+	       !buffer_dirty(path[level].bp_bh)) {
+
+		WARN_ON(buffer_nilfs_volatile(path[level].bp_bh));
+		ret = nilfs_btree_prepare_update_v(btree, path, level, dat);
+		if (ret < 0)
+			goto out;
+	}
+
+	/* success */
+	*maxlevelp = level - 1;
+	return 0;
+
+	/* error */
+ out:
+	while (--level > minlevel)
+		nilfs_btree_abort_update_v(btree, path, level, dat);
+	if (!buffer_nilfs_volatile(path[level].bp_bh))
+		nilfs_btree_abort_update_v(btree, path, level, dat);
+	return ret;
+}
+
+static void nilfs_btree_commit_propagate_v(struct nilfs_bmap *btree,
+					   struct nilfs_btree_path *path,
+					   int minlevel, int maxlevel,
+					   struct buffer_head *bh,
+					   struct inode *dat)
+{
+	int level;
+
+	if (!buffer_nilfs_volatile(path[minlevel].bp_bh))
+		nilfs_btree_commit_update_v(btree, path, minlevel, dat);
+
+	for (level = minlevel + 1; level <= maxlevel; level++)
+		nilfs_btree_commit_update_v(btree, path, level, dat);
+}
+
+static int nilfs_btree_propagate_v(struct nilfs_bmap *btree,
+				   struct nilfs_btree_path *path,
+				   int level, struct buffer_head *bh)
+{
+	int maxlevel = 0, ret;
+	struct nilfs_btree_node *parent;
+	struct inode *dat = nilfs_bmap_get_dat(btree);
+	__u64 ptr;
+	int ncmax;
+
+	get_bh(bh);
+	path[level].bp_bh = bh;
+	ret = nilfs_btree_prepare_propagate_v(btree, path, level, &maxlevel,
+					      dat);
+	if (ret < 0)
+		goto out;
+
+	if (buffer_nilfs_volatile(path[level].bp_bh)) {
+		parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
+		ptr = nilfs_btree_node_get_ptr(parent,
+					       path[level + 1].bp_index,
+					       ncmax);
+		ret = nilfs_dat_mark_dirty(dat, ptr);
+		if (ret < 0)
+			goto out;
+	}
+
+	nilfs_btree_commit_propagate_v(btree, path, level, maxlevel, bh, dat);
+
+ out:
+	brelse(path[level].bp_bh);
+	path[level].bp_bh = NULL;
+	return ret;
+}
+
+static int nilfs_btree_propagate(struct nilfs_bmap *btree,
+				 struct buffer_head *bh)
+{
+	struct nilfs_btree_path *path;
+	struct nilfs_btree_node *node;
+	__u64 key;
+	int level, ret;
+
+	WARN_ON(!buffer_dirty(bh));
+
+	path = nilfs_btree_alloc_path();
+	if (path == NULL)
+		return -ENOMEM;
+
+	if (buffer_nilfs_node(bh)) {
+		node = (struct nilfs_btree_node *)bh->b_data;
+		key = nilfs_btree_node_get_key(node, 0);
+		level = nilfs_btree_node_get_level(node);
+	} else {
+		key = nilfs_bmap_data_get_key(btree, bh);
+		level = NILFS_BTREE_LEVEL_DATA;
+	}
+
+	ret = nilfs_btree_do_lookup(btree, path, key, NULL, level + 1, 0);
+	if (ret < 0) {
+		if (unlikely(ret == -ENOENT))
+			nilfs_crit(btree->b_inode->i_sb,
+				   "writing node/leaf block does not appear in b-tree (ino=%lu) at key=%llu, level=%d",
+				   btree->b_inode->i_ino,
+				   (unsigned long long)key, level);
+		goto out;
+	}
+
+	ret = NILFS_BMAP_USE_VBN(btree) ?
+		nilfs_btree_propagate_v(btree, path, level, bh) :
+		nilfs_btree_propagate_p(btree, path, level, bh);
+
+ out:
+	nilfs_btree_free_path(path);
+
+	return ret;
+}
+
+static int nilfs_btree_propagate_gc(struct nilfs_bmap *btree,
+				    struct buffer_head *bh)
+{
+	return nilfs_dat_mark_dirty(nilfs_bmap_get_dat(btree), bh->b_blocknr);
+}
+
+static void nilfs_btree_add_dirty_buffer(struct nilfs_bmap *btree,
+					 struct list_head *lists,
+					 struct buffer_head *bh)
+{
+	struct list_head *head;
+	struct buffer_head *cbh;
+	struct nilfs_btree_node *node, *cnode;
+	__u64 key, ckey;
+	int level;
+
+	get_bh(bh);
+	node = (struct nilfs_btree_node *)bh->b_data;
+	key = nilfs_btree_node_get_key(node, 0);
+	level = nilfs_btree_node_get_level(node);
+	if (level < NILFS_BTREE_LEVEL_NODE_MIN ||
+	    level >= NILFS_BTREE_LEVEL_MAX) {
+		dump_stack();
+		nilfs_warn(btree->b_inode->i_sb,
+			   "invalid btree level: %d (key=%llu, ino=%lu, blocknr=%llu)",
+			   level, (unsigned long long)key,
+			   btree->b_inode->i_ino,
+			   (unsigned long long)bh->b_blocknr);
+		return;
+	}
+
+	list_for_each(head, &lists[level]) {
+		cbh = list_entry(head, struct buffer_head, b_assoc_buffers);
+		cnode = (struct nilfs_btree_node *)cbh->b_data;
+		ckey = nilfs_btree_node_get_key(cnode, 0);
+		if (key < ckey)
+			break;
+	}
+	list_add_tail(&bh->b_assoc_buffers, head);
+}
+
+static void nilfs_btree_lookup_dirty_buffers(struct nilfs_bmap *btree,
+					     struct list_head *listp)
+{
+	struct inode *btnc_inode = NILFS_BMAP_I(btree)->i_assoc_inode;
+	struct address_space *btcache = btnc_inode->i_mapping;
+	struct list_head lists[NILFS_BTREE_LEVEL_MAX];
+	struct folio_batch fbatch;
+	struct buffer_head *bh, *head;
+	pgoff_t index = 0;
+	int level, i;
+
+	for (level = NILFS_BTREE_LEVEL_NODE_MIN;
+	     level < NILFS_BTREE_LEVEL_MAX;
+	     level++)
+		INIT_LIST_HEAD(&lists[level]);
+
+	folio_batch_init(&fbatch);
+
+	while (filemap_get_folios_tag(btcache, &index, (pgoff_t)-1,
+				PAGECACHE_TAG_DIRTY, &fbatch)) {
+		for (i = 0; i < folio_batch_count(&fbatch); i++) {
+			bh = head = folio_buffers(fbatch.folios[i]);
+			do {
+				if (buffer_dirty(bh))
+					nilfs_btree_add_dirty_buffer(btree,
+								     lists, bh);
+			} while ((bh = bh->b_this_page) != head);
+		}
+		folio_batch_release(&fbatch);
+		cond_resched();
+	}
+
+	for (level = NILFS_BTREE_LEVEL_NODE_MIN;
+	     level < NILFS_BTREE_LEVEL_MAX;
+	     level++)
+		list_splice_tail(&lists[level], listp);
+}
+
+static int nilfs_btree_assign_p(struct nilfs_bmap *btree,
+				struct nilfs_btree_path *path,
+				int level,
+				struct buffer_head **bh,
+				sector_t blocknr,
+				union nilfs_binfo *binfo)
+{
+	struct nilfs_btree_node *parent;
+	__u64 key;
+	__u64 ptr;
+	int ncmax, ret;
+
+	parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
+	ptr = nilfs_btree_node_get_ptr(parent, path[level + 1].bp_index,
+				       ncmax);
+	if (buffer_nilfs_node(*bh)) {
+		path[level].bp_ctxt.oldkey = ptr;
+		path[level].bp_ctxt.newkey = blocknr;
+		path[level].bp_ctxt.bh = *bh;
+		ret = nilfs_btnode_prepare_change_key(
+			NILFS_BMAP_I(btree)->i_assoc_inode->i_mapping,
+			&path[level].bp_ctxt);
+		if (ret < 0)
+			return ret;
+		nilfs_btnode_commit_change_key(
+			NILFS_BMAP_I(btree)->i_assoc_inode->i_mapping,
+			&path[level].bp_ctxt);
+		*bh = path[level].bp_ctxt.bh;
+	}
+
+	nilfs_btree_node_set_ptr(parent, path[level + 1].bp_index, blocknr,
+				 ncmax);
+
+	key = nilfs_btree_node_get_key(parent, path[level + 1].bp_index);
+	/* on-disk format */
+	binfo->bi_dat.bi_blkoff = cpu_to_le64(key);
+	binfo->bi_dat.bi_level = level;
+	memset(binfo->bi_dat.bi_pad, 0, sizeof(binfo->bi_dat.bi_pad));
+
+	return 0;
+}
+
+static int nilfs_btree_assign_v(struct nilfs_bmap *btree,
+				struct nilfs_btree_path *path,
+				int level,
+				struct buffer_head **bh,
+				sector_t blocknr,
+				union nilfs_binfo *binfo)
+{
+	struct nilfs_btree_node *parent;
+	struct inode *dat = nilfs_bmap_get_dat(btree);
+	__u64 key;
+	__u64 ptr;
+	union nilfs_bmap_ptr_req req;
+	int ncmax, ret;
+
+	parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
+	ptr = nilfs_btree_node_get_ptr(parent, path[level + 1].bp_index,
+				       ncmax);
+	req.bpr_ptr = ptr;
+	ret = nilfs_dat_prepare_start(dat, &req.bpr_req);
+	if (ret < 0)
+		return ret;
+	nilfs_dat_commit_start(dat, &req.bpr_req, blocknr);
+
+	key = nilfs_btree_node_get_key(parent, path[level + 1].bp_index);
+	/* on-disk format */
+	binfo->bi_v.bi_vblocknr = cpu_to_le64(ptr);
+	binfo->bi_v.bi_blkoff = cpu_to_le64(key);
+
+	return 0;
+}
+
+static int nilfs_btree_assign(struct nilfs_bmap *btree,
+			      struct buffer_head **bh,
+			      sector_t blocknr,
+			      union nilfs_binfo *binfo)
+{
+	struct nilfs_btree_path *path;
+	struct nilfs_btree_node *node;
+	__u64 key;
+	int level, ret;
+
+	path = nilfs_btree_alloc_path();
+	if (path == NULL)
+		return -ENOMEM;
+
+	if (buffer_nilfs_node(*bh)) {
+		node = (struct nilfs_btree_node *)(*bh)->b_data;
+		key = nilfs_btree_node_get_key(node, 0);
+		level = nilfs_btree_node_get_level(node);
+	} else {
+		key = nilfs_bmap_data_get_key(btree, *bh);
+		level = NILFS_BTREE_LEVEL_DATA;
+	}
+
+	ret = nilfs_btree_do_lookup(btree, path, key, NULL, level + 1, 0);
+	if (ret < 0) {
+		WARN_ON(ret == -ENOENT);
+		goto out;
+	}
+
+	ret = NILFS_BMAP_USE_VBN(btree) ?
+		nilfs_btree_assign_v(btree, path, level, bh, blocknr, binfo) :
+		nilfs_btree_assign_p(btree, path, level, bh, blocknr, binfo);
+
+ out:
+	nilfs_btree_free_path(path);
+
+	return ret;
+}
+
+static int nilfs_btree_assign_gc(struct nilfs_bmap *btree,
+				 struct buffer_head **bh,
+				 sector_t blocknr,
+				 union nilfs_binfo *binfo)
+{
+	struct nilfs_btree_node *node;
+	__u64 key;
+	int ret;
+
+	ret = nilfs_dat_move(nilfs_bmap_get_dat(btree), (*bh)->b_blocknr,
+			     blocknr);
+	if (ret < 0)
+		return ret;
+
+	if (buffer_nilfs_node(*bh)) {
+		node = (struct nilfs_btree_node *)(*bh)->b_data;
+		key = nilfs_btree_node_get_key(node, 0);
+	} else
+		key = nilfs_bmap_data_get_key(btree, *bh);
+
+	/* on-disk format */
+	binfo->bi_v.bi_vblocknr = cpu_to_le64((*bh)->b_blocknr);
+	binfo->bi_v.bi_blkoff = cpu_to_le64(key);
+
+	return 0;
+}
+
+static int nilfs_btree_mark(struct nilfs_bmap *btree, __u64 key, int level)
+{
+	struct buffer_head *bh;
+	struct nilfs_btree_path *path;
+	__u64 ptr;
+	int ret;
+
+	path = nilfs_btree_alloc_path();
+	if (path == NULL)
+		return -ENOMEM;
+
+	ret = nilfs_btree_do_lookup(btree, path, key, &ptr, level + 1, 0);
+	if (ret < 0) {
+		WARN_ON(ret == -ENOENT);
+		goto out;
+	}
+	ret = nilfs_btree_get_block(btree, ptr, &bh);
+	if (ret < 0) {
+		WARN_ON(ret == -ENOENT);
+		goto out;
+	}
+
+	if (!buffer_dirty(bh))
+		mark_buffer_dirty(bh);
+	brelse(bh);
+	if (!nilfs_bmap_dirty(btree))
+		nilfs_bmap_set_dirty(btree);
+
+ out:
+	nilfs_btree_free_path(path);
+	return ret;
+}
+
+static const struct nilfs_bmap_operations nilfs_btree_ops = {
+	.bop_lookup		=	nilfs_btree_lookup,
+	.bop_lookup_contig	=	nilfs_btree_lookup_contig,
+	.bop_insert		=	nilfs_btree_insert,
+	.bop_delete		=	nilfs_btree_delete,
+	.bop_clear		=	NULL,
+
+	.bop_propagate		=	nilfs_btree_propagate,
+
+	.bop_lookup_dirty_buffers =	nilfs_btree_lookup_dirty_buffers,
+
+	.bop_assign		=	nilfs_btree_assign,
+	.bop_mark		=	nilfs_btree_mark,
+
+	.bop_seek_key		=	nilfs_btree_seek_key,
+	.bop_last_key		=	nilfs_btree_last_key,
+
+	.bop_check_insert	=	NULL,
+	.bop_check_delete	=	nilfs_btree_check_delete,
+	.bop_gather_data	=	nilfs_btree_gather_data,
+};
+
+static const struct nilfs_bmap_operations nilfs_btree_ops_gc = {
+	.bop_lookup		=	NULL,
+	.bop_lookup_contig	=	NULL,
+	.bop_insert		=	NULL,
+	.bop_delete		=	NULL,
+	.bop_clear		=	NULL,
+
+	.bop_propagate		=	nilfs_btree_propagate_gc,
+
+	.bop_lookup_dirty_buffers =	nilfs_btree_lookup_dirty_buffers,
+
+	.bop_assign		=	nilfs_btree_assign_gc,
+	.bop_mark		=	NULL,
+
+	.bop_seek_key		=	NULL,
+	.bop_last_key		=	NULL,
+
+	.bop_check_insert	=	NULL,
+	.bop_check_delete	=	NULL,
+	.bop_gather_data	=	NULL,
+};
+
+static void __nilfs_btree_init(struct nilfs_bmap *bmap)
+{
+	bmap->b_ops = &nilfs_btree_ops;
+	bmap->b_nchildren_per_block =
+		NILFS_BTREE_NODE_NCHILDREN_MAX(nilfs_btree_node_size(bmap));
+}
+
+int nilfs_btree_init(struct nilfs_bmap *bmap)
+{
+	int ret = 0;
+
+	__nilfs_btree_init(bmap);
+
+	if (nilfs_btree_root_broken(nilfs_btree_get_root(bmap), bmap->b_inode))
+		ret = -EIO;
+	else
+		ret = nilfs_attach_btree_node_cache(
+			&NILFS_BMAP_I(bmap)->vfs_inode);
+
+	return ret;
+}
+
+void nilfs_btree_init_gc(struct nilfs_bmap *bmap)
+{
+	bmap->b_ops = &nilfs_btree_ops_gc;
+	bmap->b_nchildren_per_block =
+		NILFS_BTREE_NODE_NCHILDREN_MAX(nilfs_btree_node_size(bmap));
+}
diff --git a/fs/nilfs2/btree.h b/fs/nilfs2/btree.h
new file mode 100644
index 0000000000..92868e1a48
--- /dev/null
+++ b/fs/nilfs2/btree.h
@@ -0,0 +1,64 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * NILFS B-tree.
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Koji Sato.
+ */
+
+#ifndef _NILFS_BTREE_H
+#define _NILFS_BTREE_H
+
+#include <linux/types.h>
+#include <linux/buffer_head.h>
+#include <linux/list.h>
+#include <linux/nilfs2_ondisk.h>	/* nilfs_btree_node */
+#include "btnode.h"
+#include "bmap.h"
+
+/**
+ * struct nilfs_btree_path - A path on which B-tree operations are executed
+ * @bp_bh: buffer head of node block
+ * @bp_sib_bh: buffer head of sibling node block
+ * @bp_index: index of child node
+ * @bp_oldreq: ptr end request for old ptr
+ * @bp_newreq: ptr alloc request for new ptr
+ * @bp_op: rebalance operation
+ */
+struct nilfs_btree_path {
+	struct buffer_head *bp_bh;
+	struct buffer_head *bp_sib_bh;
+	int bp_index;
+	union nilfs_bmap_ptr_req bp_oldreq;
+	union nilfs_bmap_ptr_req bp_newreq;
+	struct nilfs_btnode_chkey_ctxt bp_ctxt;
+	void (*bp_op)(struct nilfs_bmap *, struct nilfs_btree_path *,
+		      int, __u64 *, __u64 *);
+};
+
+#define NILFS_BTREE_ROOT_SIZE		NILFS_BMAP_SIZE
+#define NILFS_BTREE_ROOT_NCHILDREN_MAX					\
+	((NILFS_BTREE_ROOT_SIZE - sizeof(struct nilfs_btree_node)) /	\
+	 (sizeof(__le64 /* dkey */) + sizeof(__le64 /* dptr */)))
+#define NILFS_BTREE_ROOT_NCHILDREN_MIN	0
+#define NILFS_BTREE_NODE_EXTRA_PAD_SIZE	(sizeof(__le64))
+#define NILFS_BTREE_NODE_NCHILDREN_MAX(nodesize)			\
+	(((nodesize) - sizeof(struct nilfs_btree_node) -		\
+		NILFS_BTREE_NODE_EXTRA_PAD_SIZE) /			\
+	 (sizeof(__le64 /* dkey */) + sizeof(__le64 /* dptr */)))
+#define NILFS_BTREE_NODE_NCHILDREN_MIN(nodesize)			\
+	((NILFS_BTREE_NODE_NCHILDREN_MAX(nodesize) - 1) / 2 + 1)
+#define NILFS_BTREE_KEY_MIN	((__u64)0)
+#define NILFS_BTREE_KEY_MAX	(~(__u64)0)
+
+extern struct kmem_cache *nilfs_btree_path_cache;
+
+int nilfs_btree_init(struct nilfs_bmap *);
+int nilfs_btree_convert_and_insert(struct nilfs_bmap *, __u64, __u64,
+				   const __u64 *, const __u64 *, int);
+void nilfs_btree_init_gc(struct nilfs_bmap *);
+
+int nilfs_btree_broken_node_block(struct buffer_head *bh);
+
+#endif	/* _NILFS_BTREE_H */
diff --git a/fs/nilfs2/cpfile.c b/fs/nilfs2/cpfile.c
new file mode 100644
index 0000000000..9ebefb3acb
--- /dev/null
+++ b/fs/nilfs2/cpfile.c
@@ -0,0 +1,1015 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NILFS checkpoint file.
+ *
+ * Copyright (C) 2006-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Koji Sato.
+ */
+
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/string.h>
+#include <linux/buffer_head.h>
+#include <linux/errno.h>
+#include "mdt.h"
+#include "cpfile.h"
+
+
+static inline unsigned long
+nilfs_cpfile_checkpoints_per_block(const struct inode *cpfile)
+{
+	return NILFS_MDT(cpfile)->mi_entries_per_block;
+}
+
+/* block number from the beginning of the file */
+static unsigned long
+nilfs_cpfile_get_blkoff(const struct inode *cpfile, __u64 cno)
+{
+	__u64 tcno = cno + NILFS_MDT(cpfile)->mi_first_entry_offset - 1;
+
+	do_div(tcno, nilfs_cpfile_checkpoints_per_block(cpfile));
+	return (unsigned long)tcno;
+}
+
+/* offset in block */
+static unsigned long
+nilfs_cpfile_get_offset(const struct inode *cpfile, __u64 cno)
+{
+	__u64 tcno = cno + NILFS_MDT(cpfile)->mi_first_entry_offset - 1;
+
+	return do_div(tcno, nilfs_cpfile_checkpoints_per_block(cpfile));
+}
+
+static __u64 nilfs_cpfile_first_checkpoint_in_block(const struct inode *cpfile,
+						    unsigned long blkoff)
+{
+	return (__u64)nilfs_cpfile_checkpoints_per_block(cpfile) * blkoff
+		+ 1 - NILFS_MDT(cpfile)->mi_first_entry_offset;
+}
+
+static unsigned long
+nilfs_cpfile_checkpoints_in_block(const struct inode *cpfile,
+				  __u64 curr,
+				  __u64 max)
+{
+	return min_t(__u64,
+		     nilfs_cpfile_checkpoints_per_block(cpfile) -
+		     nilfs_cpfile_get_offset(cpfile, curr),
+		     max - curr);
+}
+
+static inline int nilfs_cpfile_is_in_first(const struct inode *cpfile,
+					   __u64 cno)
+{
+	return nilfs_cpfile_get_blkoff(cpfile, cno) == 0;
+}
+
+static unsigned int
+nilfs_cpfile_block_add_valid_checkpoints(const struct inode *cpfile,
+					 struct buffer_head *bh,
+					 void *kaddr,
+					 unsigned int n)
+{
+	struct nilfs_checkpoint *cp = kaddr + bh_offset(bh);
+	unsigned int count;
+
+	count = le32_to_cpu(cp->cp_checkpoints_count) + n;
+	cp->cp_checkpoints_count = cpu_to_le32(count);
+	return count;
+}
+
+static unsigned int
+nilfs_cpfile_block_sub_valid_checkpoints(const struct inode *cpfile,
+					 struct buffer_head *bh,
+					 void *kaddr,
+					 unsigned int n)
+{
+	struct nilfs_checkpoint *cp = kaddr + bh_offset(bh);
+	unsigned int count;
+
+	WARN_ON(le32_to_cpu(cp->cp_checkpoints_count) < n);
+	count = le32_to_cpu(cp->cp_checkpoints_count) - n;
+	cp->cp_checkpoints_count = cpu_to_le32(count);
+	return count;
+}
+
+static inline struct nilfs_cpfile_header *
+nilfs_cpfile_block_get_header(const struct inode *cpfile,
+			      struct buffer_head *bh,
+			      void *kaddr)
+{
+	return kaddr + bh_offset(bh);
+}
+
+static struct nilfs_checkpoint *
+nilfs_cpfile_block_get_checkpoint(const struct inode *cpfile, __u64 cno,
+				  struct buffer_head *bh,
+				  void *kaddr)
+{
+	return kaddr + bh_offset(bh) + nilfs_cpfile_get_offset(cpfile, cno) *
+		NILFS_MDT(cpfile)->mi_entry_size;
+}
+
+static void nilfs_cpfile_block_init(struct inode *cpfile,
+				    struct buffer_head *bh,
+				    void *kaddr)
+{
+	struct nilfs_checkpoint *cp = kaddr + bh_offset(bh);
+	size_t cpsz = NILFS_MDT(cpfile)->mi_entry_size;
+	int n = nilfs_cpfile_checkpoints_per_block(cpfile);
+
+	while (n-- > 0) {
+		nilfs_checkpoint_set_invalid(cp);
+		cp = (void *)cp + cpsz;
+	}
+}
+
+static inline int nilfs_cpfile_get_header_block(struct inode *cpfile,
+						struct buffer_head **bhp)
+{
+	return nilfs_mdt_get_block(cpfile, 0, 0, NULL, bhp);
+}
+
+static inline int nilfs_cpfile_get_checkpoint_block(struct inode *cpfile,
+						    __u64 cno,
+						    int create,
+						    struct buffer_head **bhp)
+{
+	return nilfs_mdt_get_block(cpfile,
+				   nilfs_cpfile_get_blkoff(cpfile, cno),
+				   create, nilfs_cpfile_block_init, bhp);
+}
+
+/**
+ * nilfs_cpfile_find_checkpoint_block - find and get a buffer on cpfile
+ * @cpfile: inode of cpfile
+ * @start_cno: start checkpoint number (inclusive)
+ * @end_cno: end checkpoint number (inclusive)
+ * @cnop: place to store the next checkpoint number
+ * @bhp: place to store a pointer to buffer_head struct
+ *
+ * Return Value: On success, it returns 0. On error, the following negative
+ * error code is returned.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ *
+ * %-EIO - I/O error
+ *
+ * %-ENOENT - no block exists in the range.
+ */
+static int nilfs_cpfile_find_checkpoint_block(struct inode *cpfile,
+					      __u64 start_cno, __u64 end_cno,
+					      __u64 *cnop,
+					      struct buffer_head **bhp)
+{
+	unsigned long start, end, blkoff;
+	int ret;
+
+	if (unlikely(start_cno > end_cno))
+		return -ENOENT;
+
+	start = nilfs_cpfile_get_blkoff(cpfile, start_cno);
+	end = nilfs_cpfile_get_blkoff(cpfile, end_cno);
+
+	ret = nilfs_mdt_find_block(cpfile, start, end, &blkoff, bhp);
+	if (!ret)
+		*cnop = (blkoff == start) ? start_cno :
+			nilfs_cpfile_first_checkpoint_in_block(cpfile, blkoff);
+	return ret;
+}
+
+static inline int nilfs_cpfile_delete_checkpoint_block(struct inode *cpfile,
+						       __u64 cno)
+{
+	return nilfs_mdt_delete_block(cpfile,
+				      nilfs_cpfile_get_blkoff(cpfile, cno));
+}
+
+/**
+ * nilfs_cpfile_get_checkpoint - get a checkpoint
+ * @cpfile: inode of checkpoint file
+ * @cno: checkpoint number
+ * @create: create flag
+ * @cpp: pointer to a checkpoint
+ * @bhp: pointer to a buffer head
+ *
+ * Description: nilfs_cpfile_get_checkpoint() acquires the checkpoint
+ * specified by @cno. A new checkpoint will be created if @cno is the current
+ * checkpoint number and @create is nonzero.
+ *
+ * Return Value: On success, 0 is returned, and the checkpoint and the
+ * buffer head of the buffer on which the checkpoint is located are stored in
+ * the place pointed by @cpp and @bhp, respectively. On error, one of the
+ * following negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-ENOENT - No such checkpoint.
+ *
+ * %-EINVAL - invalid checkpoint.
+ */
+int nilfs_cpfile_get_checkpoint(struct inode *cpfile,
+				__u64 cno,
+				int create,
+				struct nilfs_checkpoint **cpp,
+				struct buffer_head **bhp)
+{
+	struct buffer_head *header_bh, *cp_bh;
+	struct nilfs_cpfile_header *header;
+	struct nilfs_checkpoint *cp;
+	void *kaddr;
+	int ret;
+
+	if (unlikely(cno < 1 || cno > nilfs_mdt_cno(cpfile) ||
+		     (cno < nilfs_mdt_cno(cpfile) && create)))
+		return -EINVAL;
+
+	down_write(&NILFS_MDT(cpfile)->mi_sem);
+
+	ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
+	if (ret < 0)
+		goto out_sem;
+	ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, create, &cp_bh);
+	if (ret < 0)
+		goto out_header;
+	kaddr = kmap(cp_bh->b_page);
+	cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
+	if (nilfs_checkpoint_invalid(cp)) {
+		if (!create) {
+			kunmap(cp_bh->b_page);
+			brelse(cp_bh);
+			ret = -ENOENT;
+			goto out_header;
+		}
+		/* a newly-created checkpoint */
+		nilfs_checkpoint_clear_invalid(cp);
+		if (!nilfs_cpfile_is_in_first(cpfile, cno))
+			nilfs_cpfile_block_add_valid_checkpoints(cpfile, cp_bh,
+								 kaddr, 1);
+		mark_buffer_dirty(cp_bh);
+
+		kaddr = kmap_atomic(header_bh->b_page);
+		header = nilfs_cpfile_block_get_header(cpfile, header_bh,
+						       kaddr);
+		le64_add_cpu(&header->ch_ncheckpoints, 1);
+		kunmap_atomic(kaddr);
+		mark_buffer_dirty(header_bh);
+		nilfs_mdt_mark_dirty(cpfile);
+	}
+
+	if (cpp != NULL)
+		*cpp = cp;
+	*bhp = cp_bh;
+
+ out_header:
+	brelse(header_bh);
+
+ out_sem:
+	up_write(&NILFS_MDT(cpfile)->mi_sem);
+	return ret;
+}
+
+/**
+ * nilfs_cpfile_put_checkpoint - put a checkpoint
+ * @cpfile: inode of checkpoint file
+ * @cno: checkpoint number
+ * @bh: buffer head
+ *
+ * Description: nilfs_cpfile_put_checkpoint() releases the checkpoint
+ * specified by @cno. @bh must be the buffer head which has been returned by
+ * a previous call to nilfs_cpfile_get_checkpoint() with @cno.
+ */
+void nilfs_cpfile_put_checkpoint(struct inode *cpfile, __u64 cno,
+				 struct buffer_head *bh)
+{
+	kunmap(bh->b_page);
+	brelse(bh);
+}
+
+/**
+ * nilfs_cpfile_delete_checkpoints - delete checkpoints
+ * @cpfile: inode of checkpoint file
+ * @start: start checkpoint number
+ * @end: end checkpoint number
+ *
+ * Description: nilfs_cpfile_delete_checkpoints() deletes the checkpoints in
+ * the period from @start to @end, excluding @end itself. The checkpoints
+ * which have been already deleted are ignored.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-EINVAL - invalid checkpoints.
+ */
+int nilfs_cpfile_delete_checkpoints(struct inode *cpfile,
+				    __u64 start,
+				    __u64 end)
+{
+	struct buffer_head *header_bh, *cp_bh;
+	struct nilfs_cpfile_header *header;
+	struct nilfs_checkpoint *cp;
+	size_t cpsz = NILFS_MDT(cpfile)->mi_entry_size;
+	__u64 cno;
+	void *kaddr;
+	unsigned long tnicps;
+	int ret, ncps, nicps, nss, count, i;
+
+	if (unlikely(start == 0 || start > end)) {
+		nilfs_err(cpfile->i_sb,
+			  "cannot delete checkpoints: invalid range [%llu, %llu)",
+			  (unsigned long long)start, (unsigned long long)end);
+		return -EINVAL;
+	}
+
+	down_write(&NILFS_MDT(cpfile)->mi_sem);
+
+	ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
+	if (ret < 0)
+		goto out_sem;
+	tnicps = 0;
+	nss = 0;
+
+	for (cno = start; cno < end; cno += ncps) {
+		ncps = nilfs_cpfile_checkpoints_in_block(cpfile, cno, end);
+		ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
+		if (ret < 0) {
+			if (ret != -ENOENT)
+				break;
+			/* skip hole */
+			ret = 0;
+			continue;
+		}
+
+		kaddr = kmap_atomic(cp_bh->b_page);
+		cp = nilfs_cpfile_block_get_checkpoint(
+			cpfile, cno, cp_bh, kaddr);
+		nicps = 0;
+		for (i = 0; i < ncps; i++, cp = (void *)cp + cpsz) {
+			if (nilfs_checkpoint_snapshot(cp)) {
+				nss++;
+			} else if (!nilfs_checkpoint_invalid(cp)) {
+				nilfs_checkpoint_set_invalid(cp);
+				nicps++;
+			}
+		}
+		if (nicps > 0) {
+			tnicps += nicps;
+			mark_buffer_dirty(cp_bh);
+			nilfs_mdt_mark_dirty(cpfile);
+			if (!nilfs_cpfile_is_in_first(cpfile, cno)) {
+				count =
+				  nilfs_cpfile_block_sub_valid_checkpoints(
+						cpfile, cp_bh, kaddr, nicps);
+				if (count == 0) {
+					/* make hole */
+					kunmap_atomic(kaddr);
+					brelse(cp_bh);
+					ret =
+					  nilfs_cpfile_delete_checkpoint_block(
+								   cpfile, cno);
+					if (ret == 0)
+						continue;
+					nilfs_err(cpfile->i_sb,
+						  "error %d deleting checkpoint block",
+						  ret);
+					break;
+				}
+			}
+		}
+
+		kunmap_atomic(kaddr);
+		brelse(cp_bh);
+	}
+
+	if (tnicps > 0) {
+		kaddr = kmap_atomic(header_bh->b_page);
+		header = nilfs_cpfile_block_get_header(cpfile, header_bh,
+						       kaddr);
+		le64_add_cpu(&header->ch_ncheckpoints, -(u64)tnicps);
+		mark_buffer_dirty(header_bh);
+		nilfs_mdt_mark_dirty(cpfile);
+		kunmap_atomic(kaddr);
+	}
+
+	brelse(header_bh);
+	if (nss > 0)
+		ret = -EBUSY;
+
+ out_sem:
+	up_write(&NILFS_MDT(cpfile)->mi_sem);
+	return ret;
+}
+
+static void nilfs_cpfile_checkpoint_to_cpinfo(struct inode *cpfile,
+					      struct nilfs_checkpoint *cp,
+					      struct nilfs_cpinfo *ci)
+{
+	ci->ci_flags = le32_to_cpu(cp->cp_flags);
+	ci->ci_cno = le64_to_cpu(cp->cp_cno);
+	ci->ci_create = le64_to_cpu(cp->cp_create);
+	ci->ci_nblk_inc = le64_to_cpu(cp->cp_nblk_inc);
+	ci->ci_inodes_count = le64_to_cpu(cp->cp_inodes_count);
+	ci->ci_blocks_count = le64_to_cpu(cp->cp_blocks_count);
+	ci->ci_next = le64_to_cpu(cp->cp_snapshot_list.ssl_next);
+}
+
+static ssize_t nilfs_cpfile_do_get_cpinfo(struct inode *cpfile, __u64 *cnop,
+					  void *buf, unsigned int cisz,
+					  size_t nci)
+{
+	struct nilfs_checkpoint *cp;
+	struct nilfs_cpinfo *ci = buf;
+	struct buffer_head *bh;
+	size_t cpsz = NILFS_MDT(cpfile)->mi_entry_size;
+	__u64 cur_cno = nilfs_mdt_cno(cpfile), cno = *cnop;
+	void *kaddr;
+	int n, ret;
+	int ncps, i;
+
+	if (cno == 0)
+		return -ENOENT; /* checkpoint number 0 is invalid */
+	down_read(&NILFS_MDT(cpfile)->mi_sem);
+
+	for (n = 0; n < nci; cno += ncps) {
+		ret = nilfs_cpfile_find_checkpoint_block(
+			cpfile, cno, cur_cno - 1, &cno, &bh);
+		if (ret < 0) {
+			if (likely(ret == -ENOENT))
+				break;
+			goto out;
+		}
+		ncps = nilfs_cpfile_checkpoints_in_block(cpfile, cno, cur_cno);
+
+		kaddr = kmap_atomic(bh->b_page);
+		cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
+		for (i = 0; i < ncps && n < nci; i++, cp = (void *)cp + cpsz) {
+			if (!nilfs_checkpoint_invalid(cp)) {
+				nilfs_cpfile_checkpoint_to_cpinfo(cpfile, cp,
+								  ci);
+				ci = (void *)ci + cisz;
+				n++;
+			}
+		}
+		kunmap_atomic(kaddr);
+		brelse(bh);
+	}
+
+	ret = n;
+	if (n > 0) {
+		ci = (void *)ci - cisz;
+		*cnop = ci->ci_cno + 1;
+	}
+
+ out:
+	up_read(&NILFS_MDT(cpfile)->mi_sem);
+	return ret;
+}
+
+static ssize_t nilfs_cpfile_do_get_ssinfo(struct inode *cpfile, __u64 *cnop,
+					  void *buf, unsigned int cisz,
+					  size_t nci)
+{
+	struct buffer_head *bh;
+	struct nilfs_cpfile_header *header;
+	struct nilfs_checkpoint *cp;
+	struct nilfs_cpinfo *ci = buf;
+	__u64 curr = *cnop, next;
+	unsigned long curr_blkoff, next_blkoff;
+	void *kaddr;
+	int n = 0, ret;
+
+	down_read(&NILFS_MDT(cpfile)->mi_sem);
+
+	if (curr == 0) {
+		ret = nilfs_cpfile_get_header_block(cpfile, &bh);
+		if (ret < 0)
+			goto out;
+		kaddr = kmap_atomic(bh->b_page);
+		header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
+		curr = le64_to_cpu(header->ch_snapshot_list.ssl_next);
+		kunmap_atomic(kaddr);
+		brelse(bh);
+		if (curr == 0) {
+			ret = 0;
+			goto out;
+		}
+	} else if (unlikely(curr == ~(__u64)0)) {
+		ret = 0;
+		goto out;
+	}
+
+	curr_blkoff = nilfs_cpfile_get_blkoff(cpfile, curr);
+	ret = nilfs_cpfile_get_checkpoint_block(cpfile, curr, 0, &bh);
+	if (unlikely(ret < 0)) {
+		if (ret == -ENOENT)
+			ret = 0; /* No snapshots (started from a hole block) */
+		goto out;
+	}
+	kaddr = kmap_atomic(bh->b_page);
+	while (n < nci) {
+		cp = nilfs_cpfile_block_get_checkpoint(cpfile, curr, bh, kaddr);
+		curr = ~(__u64)0; /* Terminator */
+		if (unlikely(nilfs_checkpoint_invalid(cp) ||
+			     !nilfs_checkpoint_snapshot(cp)))
+			break;
+		nilfs_cpfile_checkpoint_to_cpinfo(cpfile, cp, ci);
+		ci = (void *)ci + cisz;
+		n++;
+		next = le64_to_cpu(cp->cp_snapshot_list.ssl_next);
+		if (next == 0)
+			break; /* reach end of the snapshot list */
+
+		next_blkoff = nilfs_cpfile_get_blkoff(cpfile, next);
+		if (curr_blkoff != next_blkoff) {
+			kunmap_atomic(kaddr);
+			brelse(bh);
+			ret = nilfs_cpfile_get_checkpoint_block(cpfile, next,
+								0, &bh);
+			if (unlikely(ret < 0)) {
+				WARN_ON(ret == -ENOENT);
+				goto out;
+			}
+			kaddr = kmap_atomic(bh->b_page);
+		}
+		curr = next;
+		curr_blkoff = next_blkoff;
+	}
+	kunmap_atomic(kaddr);
+	brelse(bh);
+	*cnop = curr;
+	ret = n;
+
+ out:
+	up_read(&NILFS_MDT(cpfile)->mi_sem);
+	return ret;
+}
+
+/**
+ * nilfs_cpfile_get_cpinfo -
+ * @cpfile:
+ * @cno:
+ * @ci:
+ * @nci:
+ */
+
+ssize_t nilfs_cpfile_get_cpinfo(struct inode *cpfile, __u64 *cnop, int mode,
+				void *buf, unsigned int cisz, size_t nci)
+{
+	switch (mode) {
+	case NILFS_CHECKPOINT:
+		return nilfs_cpfile_do_get_cpinfo(cpfile, cnop, buf, cisz, nci);
+	case NILFS_SNAPSHOT:
+		return nilfs_cpfile_do_get_ssinfo(cpfile, cnop, buf, cisz, nci);
+	default:
+		return -EINVAL;
+	}
+}
+
+/**
+ * nilfs_cpfile_delete_checkpoint -
+ * @cpfile:
+ * @cno:
+ */
+int nilfs_cpfile_delete_checkpoint(struct inode *cpfile, __u64 cno)
+{
+	struct nilfs_cpinfo ci;
+	__u64 tcno = cno;
+	ssize_t nci;
+
+	nci = nilfs_cpfile_do_get_cpinfo(cpfile, &tcno, &ci, sizeof(ci), 1);
+	if (nci < 0)
+		return nci;
+	else if (nci == 0 || ci.ci_cno != cno)
+		return -ENOENT;
+	else if (nilfs_cpinfo_snapshot(&ci))
+		return -EBUSY;
+
+	return nilfs_cpfile_delete_checkpoints(cpfile, cno, cno + 1);
+}
+
+static struct nilfs_snapshot_list *
+nilfs_cpfile_block_get_snapshot_list(const struct inode *cpfile,
+				     __u64 cno,
+				     struct buffer_head *bh,
+				     void *kaddr)
+{
+	struct nilfs_cpfile_header *header;
+	struct nilfs_checkpoint *cp;
+	struct nilfs_snapshot_list *list;
+
+	if (cno != 0) {
+		cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
+		list = &cp->cp_snapshot_list;
+	} else {
+		header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
+		list = &header->ch_snapshot_list;
+	}
+	return list;
+}
+
+static int nilfs_cpfile_set_snapshot(struct inode *cpfile, __u64 cno)
+{
+	struct buffer_head *header_bh, *curr_bh, *prev_bh, *cp_bh;
+	struct nilfs_cpfile_header *header;
+	struct nilfs_checkpoint *cp;
+	struct nilfs_snapshot_list *list;
+	__u64 curr, prev;
+	unsigned long curr_blkoff, prev_blkoff;
+	void *kaddr;
+	int ret;
+
+	if (cno == 0)
+		return -ENOENT; /* checkpoint number 0 is invalid */
+	down_write(&NILFS_MDT(cpfile)->mi_sem);
+
+	ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
+	if (ret < 0)
+		goto out_sem;
+	kaddr = kmap_atomic(cp_bh->b_page);
+	cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
+	if (nilfs_checkpoint_invalid(cp)) {
+		ret = -ENOENT;
+		kunmap_atomic(kaddr);
+		goto out_cp;
+	}
+	if (nilfs_checkpoint_snapshot(cp)) {
+		ret = 0;
+		kunmap_atomic(kaddr);
+		goto out_cp;
+	}
+	kunmap_atomic(kaddr);
+
+	ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
+	if (ret < 0)
+		goto out_cp;
+	kaddr = kmap_atomic(header_bh->b_page);
+	header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
+	list = &header->ch_snapshot_list;
+	curr_bh = header_bh;
+	get_bh(curr_bh);
+	curr = 0;
+	curr_blkoff = 0;
+	prev = le64_to_cpu(list->ssl_prev);
+	while (prev > cno) {
+		prev_blkoff = nilfs_cpfile_get_blkoff(cpfile, prev);
+		curr = prev;
+		if (curr_blkoff != prev_blkoff) {
+			kunmap_atomic(kaddr);
+			brelse(curr_bh);
+			ret = nilfs_cpfile_get_checkpoint_block(cpfile, curr,
+								0, &curr_bh);
+			if (ret < 0)
+				goto out_header;
+			kaddr = kmap_atomic(curr_bh->b_page);
+		}
+		curr_blkoff = prev_blkoff;
+		cp = nilfs_cpfile_block_get_checkpoint(
+			cpfile, curr, curr_bh, kaddr);
+		list = &cp->cp_snapshot_list;
+		prev = le64_to_cpu(list->ssl_prev);
+	}
+	kunmap_atomic(kaddr);
+
+	if (prev != 0) {
+		ret = nilfs_cpfile_get_checkpoint_block(cpfile, prev, 0,
+							&prev_bh);
+		if (ret < 0)
+			goto out_curr;
+	} else {
+		prev_bh = header_bh;
+		get_bh(prev_bh);
+	}
+
+	kaddr = kmap_atomic(curr_bh->b_page);
+	list = nilfs_cpfile_block_get_snapshot_list(
+		cpfile, curr, curr_bh, kaddr);
+	list->ssl_prev = cpu_to_le64(cno);
+	kunmap_atomic(kaddr);
+
+	kaddr = kmap_atomic(cp_bh->b_page);
+	cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
+	cp->cp_snapshot_list.ssl_next = cpu_to_le64(curr);
+	cp->cp_snapshot_list.ssl_prev = cpu_to_le64(prev);
+	nilfs_checkpoint_set_snapshot(cp);
+	kunmap_atomic(kaddr);
+
+	kaddr = kmap_atomic(prev_bh->b_page);
+	list = nilfs_cpfile_block_get_snapshot_list(
+		cpfile, prev, prev_bh, kaddr);
+	list->ssl_next = cpu_to_le64(cno);
+	kunmap_atomic(kaddr);
+
+	kaddr = kmap_atomic(header_bh->b_page);
+	header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
+	le64_add_cpu(&header->ch_nsnapshots, 1);
+	kunmap_atomic(kaddr);
+
+	mark_buffer_dirty(prev_bh);
+	mark_buffer_dirty(curr_bh);
+	mark_buffer_dirty(cp_bh);
+	mark_buffer_dirty(header_bh);
+	nilfs_mdt_mark_dirty(cpfile);
+
+	brelse(prev_bh);
+
+ out_curr:
+	brelse(curr_bh);
+
+ out_header:
+	brelse(header_bh);
+
+ out_cp:
+	brelse(cp_bh);
+
+ out_sem:
+	up_write(&NILFS_MDT(cpfile)->mi_sem);
+	return ret;
+}
+
+static int nilfs_cpfile_clear_snapshot(struct inode *cpfile, __u64 cno)
+{
+	struct buffer_head *header_bh, *next_bh, *prev_bh, *cp_bh;
+	struct nilfs_cpfile_header *header;
+	struct nilfs_checkpoint *cp;
+	struct nilfs_snapshot_list *list;
+	__u64 next, prev;
+	void *kaddr;
+	int ret;
+
+	if (cno == 0)
+		return -ENOENT; /* checkpoint number 0 is invalid */
+	down_write(&NILFS_MDT(cpfile)->mi_sem);
+
+	ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &cp_bh);
+	if (ret < 0)
+		goto out_sem;
+	kaddr = kmap_atomic(cp_bh->b_page);
+	cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
+	if (nilfs_checkpoint_invalid(cp)) {
+		ret = -ENOENT;
+		kunmap_atomic(kaddr);
+		goto out_cp;
+	}
+	if (!nilfs_checkpoint_snapshot(cp)) {
+		ret = 0;
+		kunmap_atomic(kaddr);
+		goto out_cp;
+	}
+
+	list = &cp->cp_snapshot_list;
+	next = le64_to_cpu(list->ssl_next);
+	prev = le64_to_cpu(list->ssl_prev);
+	kunmap_atomic(kaddr);
+
+	ret = nilfs_cpfile_get_header_block(cpfile, &header_bh);
+	if (ret < 0)
+		goto out_cp;
+	if (next != 0) {
+		ret = nilfs_cpfile_get_checkpoint_block(cpfile, next, 0,
+							&next_bh);
+		if (ret < 0)
+			goto out_header;
+	} else {
+		next_bh = header_bh;
+		get_bh(next_bh);
+	}
+	if (prev != 0) {
+		ret = nilfs_cpfile_get_checkpoint_block(cpfile, prev, 0,
+							&prev_bh);
+		if (ret < 0)
+			goto out_next;
+	} else {
+		prev_bh = header_bh;
+		get_bh(prev_bh);
+	}
+
+	kaddr = kmap_atomic(next_bh->b_page);
+	list = nilfs_cpfile_block_get_snapshot_list(
+		cpfile, next, next_bh, kaddr);
+	list->ssl_prev = cpu_to_le64(prev);
+	kunmap_atomic(kaddr);
+
+	kaddr = kmap_atomic(prev_bh->b_page);
+	list = nilfs_cpfile_block_get_snapshot_list(
+		cpfile, prev, prev_bh, kaddr);
+	list->ssl_next = cpu_to_le64(next);
+	kunmap_atomic(kaddr);
+
+	kaddr = kmap_atomic(cp_bh->b_page);
+	cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, cp_bh, kaddr);
+	cp->cp_snapshot_list.ssl_next = cpu_to_le64(0);
+	cp->cp_snapshot_list.ssl_prev = cpu_to_le64(0);
+	nilfs_checkpoint_clear_snapshot(cp);
+	kunmap_atomic(kaddr);
+
+	kaddr = kmap_atomic(header_bh->b_page);
+	header = nilfs_cpfile_block_get_header(cpfile, header_bh, kaddr);
+	le64_add_cpu(&header->ch_nsnapshots, -1);
+	kunmap_atomic(kaddr);
+
+	mark_buffer_dirty(next_bh);
+	mark_buffer_dirty(prev_bh);
+	mark_buffer_dirty(cp_bh);
+	mark_buffer_dirty(header_bh);
+	nilfs_mdt_mark_dirty(cpfile);
+
+	brelse(prev_bh);
+
+ out_next:
+	brelse(next_bh);
+
+ out_header:
+	brelse(header_bh);
+
+ out_cp:
+	brelse(cp_bh);
+
+ out_sem:
+	up_write(&NILFS_MDT(cpfile)->mi_sem);
+	return ret;
+}
+
+/**
+ * nilfs_cpfile_is_snapshot -
+ * @cpfile: inode of checkpoint file
+ * @cno: checkpoint number
+ *
+ * Description:
+ *
+ * Return Value: On success, 1 is returned if the checkpoint specified by
+ * @cno is a snapshot, or 0 if not. On error, one of the following negative
+ * error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-ENOENT - No such checkpoint.
+ */
+int nilfs_cpfile_is_snapshot(struct inode *cpfile, __u64 cno)
+{
+	struct buffer_head *bh;
+	struct nilfs_checkpoint *cp;
+	void *kaddr;
+	int ret;
+
+	/*
+	 * CP number is invalid if it's zero or larger than the
+	 * largest existing one.
+	 */
+	if (cno == 0 || cno >= nilfs_mdt_cno(cpfile))
+		return -ENOENT;
+	down_read(&NILFS_MDT(cpfile)->mi_sem);
+
+	ret = nilfs_cpfile_get_checkpoint_block(cpfile, cno, 0, &bh);
+	if (ret < 0)
+		goto out;
+	kaddr = kmap_atomic(bh->b_page);
+	cp = nilfs_cpfile_block_get_checkpoint(cpfile, cno, bh, kaddr);
+	if (nilfs_checkpoint_invalid(cp))
+		ret = -ENOENT;
+	else
+		ret = nilfs_checkpoint_snapshot(cp);
+	kunmap_atomic(kaddr);
+	brelse(bh);
+
+ out:
+	up_read(&NILFS_MDT(cpfile)->mi_sem);
+	return ret;
+}
+
+/**
+ * nilfs_cpfile_change_cpmode - change checkpoint mode
+ * @cpfile: inode of checkpoint file
+ * @cno: checkpoint number
+ * @mode: mode of checkpoint
+ *
+ * Description: nilfs_change_cpmode() changes the mode of the checkpoint
+ * specified by @cno. The mode @mode is NILFS_CHECKPOINT or NILFS_SNAPSHOT.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-ENOENT - No such checkpoint.
+ */
+int nilfs_cpfile_change_cpmode(struct inode *cpfile, __u64 cno, int mode)
+{
+	int ret;
+
+	switch (mode) {
+	case NILFS_CHECKPOINT:
+		if (nilfs_checkpoint_is_mounted(cpfile->i_sb, cno))
+			/*
+			 * Current implementation does not have to protect
+			 * plain read-only mounts since they are exclusive
+			 * with a read/write mount and are protected from the
+			 * cleaner.
+			 */
+			ret = -EBUSY;
+		else
+			ret = nilfs_cpfile_clear_snapshot(cpfile, cno);
+		return ret;
+	case NILFS_SNAPSHOT:
+		return nilfs_cpfile_set_snapshot(cpfile, cno);
+	default:
+		return -EINVAL;
+	}
+}
+
+/**
+ * nilfs_cpfile_get_stat - get checkpoint statistics
+ * @cpfile: inode of checkpoint file
+ * @cpstat: pointer to a structure of checkpoint statistics
+ *
+ * Description: nilfs_cpfile_get_stat() returns information about checkpoints.
+ *
+ * Return Value: On success, 0 is returned, and checkpoints information is
+ * stored in the place pointed by @cpstat. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ */
+int nilfs_cpfile_get_stat(struct inode *cpfile, struct nilfs_cpstat *cpstat)
+{
+	struct buffer_head *bh;
+	struct nilfs_cpfile_header *header;
+	void *kaddr;
+	int ret;
+
+	down_read(&NILFS_MDT(cpfile)->mi_sem);
+
+	ret = nilfs_cpfile_get_header_block(cpfile, &bh);
+	if (ret < 0)
+		goto out_sem;
+	kaddr = kmap_atomic(bh->b_page);
+	header = nilfs_cpfile_block_get_header(cpfile, bh, kaddr);
+	cpstat->cs_cno = nilfs_mdt_cno(cpfile);
+	cpstat->cs_ncps = le64_to_cpu(header->ch_ncheckpoints);
+	cpstat->cs_nsss = le64_to_cpu(header->ch_nsnapshots);
+	kunmap_atomic(kaddr);
+	brelse(bh);
+
+ out_sem:
+	up_read(&NILFS_MDT(cpfile)->mi_sem);
+	return ret;
+}
+
+/**
+ * nilfs_cpfile_read - read or get cpfile inode
+ * @sb: super block instance
+ * @cpsize: size of a checkpoint entry
+ * @raw_inode: on-disk cpfile inode
+ * @inodep: buffer to store the inode
+ */
+int nilfs_cpfile_read(struct super_block *sb, size_t cpsize,
+		      struct nilfs_inode *raw_inode, struct inode **inodep)
+{
+	struct inode *cpfile;
+	int err;
+
+	if (cpsize > sb->s_blocksize) {
+		nilfs_err(sb, "too large checkpoint size: %zu bytes", cpsize);
+		return -EINVAL;
+	} else if (cpsize < NILFS_MIN_CHECKPOINT_SIZE) {
+		nilfs_err(sb, "too small checkpoint size: %zu bytes", cpsize);
+		return -EINVAL;
+	}
+
+	cpfile = nilfs_iget_locked(sb, NULL, NILFS_CPFILE_INO);
+	if (unlikely(!cpfile))
+		return -ENOMEM;
+	if (!(cpfile->i_state & I_NEW))
+		goto out;
+
+	err = nilfs_mdt_init(cpfile, NILFS_MDT_GFP, 0);
+	if (err)
+		goto failed;
+
+	nilfs_mdt_set_entry_size(cpfile, cpsize,
+				 sizeof(struct nilfs_cpfile_header));
+
+	err = nilfs_read_inode_common(cpfile, raw_inode);
+	if (err)
+		goto failed;
+
+	unlock_new_inode(cpfile);
+ out:
+	*inodep = cpfile;
+	return 0;
+ failed:
+	iget_failed(cpfile);
+	return err;
+}
diff --git a/fs/nilfs2/cpfile.h b/fs/nilfs2/cpfile.h
new file mode 100644
index 0000000000..edabb2dc57
--- /dev/null
+++ b/fs/nilfs2/cpfile.h
@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * NILFS checkpoint file.
+ *
+ * Copyright (C) 2006-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Koji Sato.
+ */
+
+#ifndef _NILFS_CPFILE_H
+#define _NILFS_CPFILE_H
+
+#include <linux/fs.h>
+#include <linux/buffer_head.h>
+#include <linux/nilfs2_api.h>		/* nilfs_cpstat */
+#include <linux/nilfs2_ondisk.h>	/* nilfs_inode, nilfs_checkpoint */
+
+
+int nilfs_cpfile_get_checkpoint(struct inode *, __u64, int,
+				struct nilfs_checkpoint **,
+				struct buffer_head **);
+void nilfs_cpfile_put_checkpoint(struct inode *, __u64, struct buffer_head *);
+int nilfs_cpfile_delete_checkpoints(struct inode *, __u64, __u64);
+int nilfs_cpfile_delete_checkpoint(struct inode *, __u64);
+int nilfs_cpfile_change_cpmode(struct inode *, __u64, int);
+int nilfs_cpfile_is_snapshot(struct inode *, __u64);
+int nilfs_cpfile_get_stat(struct inode *, struct nilfs_cpstat *);
+ssize_t nilfs_cpfile_get_cpinfo(struct inode *, __u64 *, int, void *,
+				unsigned int, size_t);
+
+int nilfs_cpfile_read(struct super_block *sb, size_t cpsize,
+		      struct nilfs_inode *raw_inode, struct inode **inodep);
+
+#endif	/* _NILFS_CPFILE_H */
diff --git a/fs/nilfs2/dat.c b/fs/nilfs2/dat.c
new file mode 100644
index 0000000000..9cf6ba58f5
--- /dev/null
+++ b/fs/nilfs2/dat.c
@@ -0,0 +1,540 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NILFS disk address translation.
+ *
+ * Copyright (C) 2006-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Koji Sato.
+ */
+
+#include <linux/types.h>
+#include <linux/buffer_head.h>
+#include <linux/string.h>
+#include <linux/errno.h>
+#include "nilfs.h"
+#include "mdt.h"
+#include "alloc.h"
+#include "dat.h"
+
+
+#define NILFS_CNO_MIN	((__u64)1)
+#define NILFS_CNO_MAX	(~(__u64)0)
+
+/**
+ * struct nilfs_dat_info - on-memory private data of DAT file
+ * @mi: on-memory private data of metadata file
+ * @palloc_cache: persistent object allocator cache of DAT file
+ * @shadow: shadow map of DAT file
+ */
+struct nilfs_dat_info {
+	struct nilfs_mdt_info mi;
+	struct nilfs_palloc_cache palloc_cache;
+	struct nilfs_shadow_map shadow;
+};
+
+static inline struct nilfs_dat_info *NILFS_DAT_I(struct inode *dat)
+{
+	return (struct nilfs_dat_info *)NILFS_MDT(dat);
+}
+
+static int nilfs_dat_prepare_entry(struct inode *dat,
+				   struct nilfs_palloc_req *req, int create)
+{
+	int ret;
+
+	ret = nilfs_palloc_get_entry_block(dat, req->pr_entry_nr,
+					   create, &req->pr_entry_bh);
+	if (unlikely(ret == -ENOENT)) {
+		nilfs_err(dat->i_sb,
+			  "DAT doesn't have a block to manage vblocknr = %llu",
+			  (unsigned long long)req->pr_entry_nr);
+		/*
+		 * Return internal code -EINVAL to notify bmap layer of
+		 * metadata corruption.
+		 */
+		ret = -EINVAL;
+	}
+	return ret;
+}
+
+static void nilfs_dat_commit_entry(struct inode *dat,
+				   struct nilfs_palloc_req *req)
+{
+	mark_buffer_dirty(req->pr_entry_bh);
+	nilfs_mdt_mark_dirty(dat);
+	brelse(req->pr_entry_bh);
+}
+
+static void nilfs_dat_abort_entry(struct inode *dat,
+				  struct nilfs_palloc_req *req)
+{
+	brelse(req->pr_entry_bh);
+}
+
+int nilfs_dat_prepare_alloc(struct inode *dat, struct nilfs_palloc_req *req)
+{
+	int ret;
+
+	ret = nilfs_palloc_prepare_alloc_entry(dat, req);
+	if (ret < 0)
+		return ret;
+
+	ret = nilfs_dat_prepare_entry(dat, req, 1);
+	if (ret < 0)
+		nilfs_palloc_abort_alloc_entry(dat, req);
+
+	return ret;
+}
+
+void nilfs_dat_commit_alloc(struct inode *dat, struct nilfs_palloc_req *req)
+{
+	struct nilfs_dat_entry *entry;
+	void *kaddr;
+
+	kaddr = kmap_atomic(req->pr_entry_bh->b_page);
+	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
+					     req->pr_entry_bh, kaddr);
+	entry->de_start = cpu_to_le64(NILFS_CNO_MIN);
+	entry->de_end = cpu_to_le64(NILFS_CNO_MAX);
+	entry->de_blocknr = cpu_to_le64(0);
+	kunmap_atomic(kaddr);
+
+	nilfs_palloc_commit_alloc_entry(dat, req);
+	nilfs_dat_commit_entry(dat, req);
+}
+
+void nilfs_dat_abort_alloc(struct inode *dat, struct nilfs_palloc_req *req)
+{
+	nilfs_dat_abort_entry(dat, req);
+	nilfs_palloc_abort_alloc_entry(dat, req);
+}
+
+static void nilfs_dat_commit_free(struct inode *dat,
+				  struct nilfs_palloc_req *req)
+{
+	struct nilfs_dat_entry *entry;
+	void *kaddr;
+
+	kaddr = kmap_atomic(req->pr_entry_bh->b_page);
+	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
+					     req->pr_entry_bh, kaddr);
+	entry->de_start = cpu_to_le64(NILFS_CNO_MIN);
+	entry->de_end = cpu_to_le64(NILFS_CNO_MIN);
+	entry->de_blocknr = cpu_to_le64(0);
+	kunmap_atomic(kaddr);
+
+	nilfs_dat_commit_entry(dat, req);
+
+	if (unlikely(req->pr_desc_bh == NULL || req->pr_bitmap_bh == NULL)) {
+		nilfs_error(dat->i_sb,
+			    "state inconsistency probably due to duplicate use of vblocknr = %llu",
+			    (unsigned long long)req->pr_entry_nr);
+		return;
+	}
+	nilfs_palloc_commit_free_entry(dat, req);
+}
+
+int nilfs_dat_prepare_start(struct inode *dat, struct nilfs_palloc_req *req)
+{
+	return nilfs_dat_prepare_entry(dat, req, 0);
+}
+
+void nilfs_dat_commit_start(struct inode *dat, struct nilfs_palloc_req *req,
+			    sector_t blocknr)
+{
+	struct nilfs_dat_entry *entry;
+	void *kaddr;
+
+	kaddr = kmap_atomic(req->pr_entry_bh->b_page);
+	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
+					     req->pr_entry_bh, kaddr);
+	entry->de_start = cpu_to_le64(nilfs_mdt_cno(dat));
+	entry->de_blocknr = cpu_to_le64(blocknr);
+	kunmap_atomic(kaddr);
+
+	nilfs_dat_commit_entry(dat, req);
+}
+
+int nilfs_dat_prepare_end(struct inode *dat, struct nilfs_palloc_req *req)
+{
+	struct nilfs_dat_entry *entry;
+	__u64 start;
+	sector_t blocknr;
+	void *kaddr;
+	int ret;
+
+	ret = nilfs_dat_prepare_entry(dat, req, 0);
+	if (ret < 0)
+		return ret;
+
+	kaddr = kmap_atomic(req->pr_entry_bh->b_page);
+	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
+					     req->pr_entry_bh, kaddr);
+	start = le64_to_cpu(entry->de_start);
+	blocknr = le64_to_cpu(entry->de_blocknr);
+	kunmap_atomic(kaddr);
+
+	if (blocknr == 0) {
+		ret = nilfs_palloc_prepare_free_entry(dat, req);
+		if (ret < 0) {
+			nilfs_dat_abort_entry(dat, req);
+			return ret;
+		}
+	}
+	if (unlikely(start > nilfs_mdt_cno(dat))) {
+		nilfs_err(dat->i_sb,
+			  "vblocknr = %llu has abnormal lifetime: start cno (= %llu) > current cno (= %llu)",
+			  (unsigned long long)req->pr_entry_nr,
+			  (unsigned long long)start,
+			  (unsigned long long)nilfs_mdt_cno(dat));
+		nilfs_dat_abort_entry(dat, req);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+void nilfs_dat_commit_end(struct inode *dat, struct nilfs_palloc_req *req,
+			  int dead)
+{
+	struct nilfs_dat_entry *entry;
+	__u64 start, end;
+	sector_t blocknr;
+	void *kaddr;
+
+	kaddr = kmap_atomic(req->pr_entry_bh->b_page);
+	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
+					     req->pr_entry_bh, kaddr);
+	end = start = le64_to_cpu(entry->de_start);
+	if (!dead) {
+		end = nilfs_mdt_cno(dat);
+		WARN_ON(start > end);
+	}
+	entry->de_end = cpu_to_le64(end);
+	blocknr = le64_to_cpu(entry->de_blocknr);
+	kunmap_atomic(kaddr);
+
+	if (blocknr == 0)
+		nilfs_dat_commit_free(dat, req);
+	else
+		nilfs_dat_commit_entry(dat, req);
+}
+
+void nilfs_dat_abort_end(struct inode *dat, struct nilfs_palloc_req *req)
+{
+	struct nilfs_dat_entry *entry;
+	__u64 start;
+	sector_t blocknr;
+	void *kaddr;
+
+	kaddr = kmap_atomic(req->pr_entry_bh->b_page);
+	entry = nilfs_palloc_block_get_entry(dat, req->pr_entry_nr,
+					     req->pr_entry_bh, kaddr);
+	start = le64_to_cpu(entry->de_start);
+	blocknr = le64_to_cpu(entry->de_blocknr);
+	kunmap_atomic(kaddr);
+
+	if (start == nilfs_mdt_cno(dat) && blocknr == 0)
+		nilfs_palloc_abort_free_entry(dat, req);
+	nilfs_dat_abort_entry(dat, req);
+}
+
+int nilfs_dat_prepare_update(struct inode *dat,
+			     struct nilfs_palloc_req *oldreq,
+			     struct nilfs_palloc_req *newreq)
+{
+	int ret;
+
+	ret = nilfs_dat_prepare_end(dat, oldreq);
+	if (!ret) {
+		ret = nilfs_dat_prepare_alloc(dat, newreq);
+		if (ret < 0)
+			nilfs_dat_abort_end(dat, oldreq);
+	}
+	return ret;
+}
+
+void nilfs_dat_commit_update(struct inode *dat,
+			     struct nilfs_palloc_req *oldreq,
+			     struct nilfs_palloc_req *newreq, int dead)
+{
+	nilfs_dat_commit_end(dat, oldreq, dead);
+	nilfs_dat_commit_alloc(dat, newreq);
+}
+
+void nilfs_dat_abort_update(struct inode *dat,
+			    struct nilfs_palloc_req *oldreq,
+			    struct nilfs_palloc_req *newreq)
+{
+	nilfs_dat_abort_end(dat, oldreq);
+	nilfs_dat_abort_alloc(dat, newreq);
+}
+
+/**
+ * nilfs_dat_mark_dirty -
+ * @dat: DAT file inode
+ * @vblocknr: virtual block number
+ *
+ * Description:
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ */
+int nilfs_dat_mark_dirty(struct inode *dat, __u64 vblocknr)
+{
+	struct nilfs_palloc_req req;
+	int ret;
+
+	req.pr_entry_nr = vblocknr;
+	ret = nilfs_dat_prepare_entry(dat, &req, 0);
+	if (ret == 0)
+		nilfs_dat_commit_entry(dat, &req);
+	return ret;
+}
+
+/**
+ * nilfs_dat_freev - free virtual block numbers
+ * @dat: DAT file inode
+ * @vblocknrs: array of virtual block numbers
+ * @nitems: number of virtual block numbers
+ *
+ * Description: nilfs_dat_freev() frees the virtual block numbers specified by
+ * @vblocknrs and @nitems.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-ENOENT - The virtual block number have not been allocated.
+ */
+int nilfs_dat_freev(struct inode *dat, __u64 *vblocknrs, size_t nitems)
+{
+	return nilfs_palloc_freev(dat, vblocknrs, nitems);
+}
+
+/**
+ * nilfs_dat_move - change a block number
+ * @dat: DAT file inode
+ * @vblocknr: virtual block number
+ * @blocknr: block number
+ *
+ * Description: nilfs_dat_move() changes the block number associated with
+ * @vblocknr to @blocknr.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ */
+int nilfs_dat_move(struct inode *dat, __u64 vblocknr, sector_t blocknr)
+{
+	struct buffer_head *entry_bh;
+	struct nilfs_dat_entry *entry;
+	void *kaddr;
+	int ret;
+
+	ret = nilfs_palloc_get_entry_block(dat, vblocknr, 0, &entry_bh);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * The given disk block number (blocknr) is not yet written to
+	 * the device at this point.
+	 *
+	 * To prevent nilfs_dat_translate() from returning the
+	 * uncommitted block number, this makes a copy of the entry
+	 * buffer and redirects nilfs_dat_translate() to the copy.
+	 */
+	if (!buffer_nilfs_redirected(entry_bh)) {
+		ret = nilfs_mdt_freeze_buffer(dat, entry_bh);
+		if (ret) {
+			brelse(entry_bh);
+			return ret;
+		}
+	}
+
+	kaddr = kmap_atomic(entry_bh->b_page);
+	entry = nilfs_palloc_block_get_entry(dat, vblocknr, entry_bh, kaddr);
+	if (unlikely(entry->de_blocknr == cpu_to_le64(0))) {
+		nilfs_crit(dat->i_sb,
+			   "%s: invalid vblocknr = %llu, [%llu, %llu)",
+			   __func__, (unsigned long long)vblocknr,
+			   (unsigned long long)le64_to_cpu(entry->de_start),
+			   (unsigned long long)le64_to_cpu(entry->de_end));
+		kunmap_atomic(kaddr);
+		brelse(entry_bh);
+		return -EINVAL;
+	}
+	WARN_ON(blocknr == 0);
+	entry->de_blocknr = cpu_to_le64(blocknr);
+	kunmap_atomic(kaddr);
+
+	mark_buffer_dirty(entry_bh);
+	nilfs_mdt_mark_dirty(dat);
+
+	brelse(entry_bh);
+
+	return 0;
+}
+
+/**
+ * nilfs_dat_translate - translate a virtual block number to a block number
+ * @dat: DAT file inode
+ * @vblocknr: virtual block number
+ * @blocknrp: pointer to a block number
+ *
+ * Description: nilfs_dat_translate() maps the virtual block number @vblocknr
+ * to the corresponding block number.
+ *
+ * Return Value: On success, 0 is returned and the block number associated
+ * with @vblocknr is stored in the place pointed by @blocknrp. On error, one
+ * of the following negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-ENOENT - A block number associated with @vblocknr does not exist.
+ */
+int nilfs_dat_translate(struct inode *dat, __u64 vblocknr, sector_t *blocknrp)
+{
+	struct buffer_head *entry_bh, *bh;
+	struct nilfs_dat_entry *entry;
+	sector_t blocknr;
+	void *kaddr;
+	int ret;
+
+	ret = nilfs_palloc_get_entry_block(dat, vblocknr, 0, &entry_bh);
+	if (ret < 0)
+		return ret;
+
+	if (!nilfs_doing_gc() && buffer_nilfs_redirected(entry_bh)) {
+		bh = nilfs_mdt_get_frozen_buffer(dat, entry_bh);
+		if (bh) {
+			WARN_ON(!buffer_uptodate(bh));
+			brelse(entry_bh);
+			entry_bh = bh;
+		}
+	}
+
+	kaddr = kmap_atomic(entry_bh->b_page);
+	entry = nilfs_palloc_block_get_entry(dat, vblocknr, entry_bh, kaddr);
+	blocknr = le64_to_cpu(entry->de_blocknr);
+	if (blocknr == 0) {
+		ret = -ENOENT;
+		goto out;
+	}
+	*blocknrp = blocknr;
+
+ out:
+	kunmap_atomic(kaddr);
+	brelse(entry_bh);
+	return ret;
+}
+
+ssize_t nilfs_dat_get_vinfo(struct inode *dat, void *buf, unsigned int visz,
+			    size_t nvi)
+{
+	struct buffer_head *entry_bh;
+	struct nilfs_dat_entry *entry;
+	struct nilfs_vinfo *vinfo = buf;
+	__u64 first, last;
+	void *kaddr;
+	unsigned long entries_per_block = NILFS_MDT(dat)->mi_entries_per_block;
+	int i, j, n, ret;
+
+	for (i = 0; i < nvi; i += n) {
+		ret = nilfs_palloc_get_entry_block(dat, vinfo->vi_vblocknr,
+						   0, &entry_bh);
+		if (ret < 0)
+			return ret;
+		kaddr = kmap_atomic(entry_bh->b_page);
+		/* last virtual block number in this block */
+		first = vinfo->vi_vblocknr;
+		do_div(first, entries_per_block);
+		first *= entries_per_block;
+		last = first + entries_per_block - 1;
+		for (j = i, n = 0;
+		     j < nvi && vinfo->vi_vblocknr >= first &&
+			     vinfo->vi_vblocknr <= last;
+		     j++, n++, vinfo = (void *)vinfo + visz) {
+			entry = nilfs_palloc_block_get_entry(
+				dat, vinfo->vi_vblocknr, entry_bh, kaddr);
+			vinfo->vi_start = le64_to_cpu(entry->de_start);
+			vinfo->vi_end = le64_to_cpu(entry->de_end);
+			vinfo->vi_blocknr = le64_to_cpu(entry->de_blocknr);
+		}
+		kunmap_atomic(kaddr);
+		brelse(entry_bh);
+	}
+
+	return nvi;
+}
+
+/**
+ * nilfs_dat_read - read or get dat inode
+ * @sb: super block instance
+ * @entry_size: size of a dat entry
+ * @raw_inode: on-disk dat inode
+ * @inodep: buffer to store the inode
+ */
+int nilfs_dat_read(struct super_block *sb, size_t entry_size,
+		   struct nilfs_inode *raw_inode, struct inode **inodep)
+{
+	static struct lock_class_key dat_lock_key;
+	struct inode *dat;
+	struct nilfs_dat_info *di;
+	int err;
+
+	if (entry_size > sb->s_blocksize) {
+		nilfs_err(sb, "too large DAT entry size: %zu bytes",
+			  entry_size);
+		return -EINVAL;
+	} else if (entry_size < NILFS_MIN_DAT_ENTRY_SIZE) {
+		nilfs_err(sb, "too small DAT entry size: %zu bytes",
+			  entry_size);
+		return -EINVAL;
+	}
+
+	dat = nilfs_iget_locked(sb, NULL, NILFS_DAT_INO);
+	if (unlikely(!dat))
+		return -ENOMEM;
+	if (!(dat->i_state & I_NEW))
+		goto out;
+
+	err = nilfs_mdt_init(dat, NILFS_MDT_GFP, sizeof(*di));
+	if (err)
+		goto failed;
+
+	err = nilfs_palloc_init_blockgroup(dat, entry_size);
+	if (err)
+		goto failed;
+
+	di = NILFS_DAT_I(dat);
+	lockdep_set_class(&di->mi.mi_sem, &dat_lock_key);
+	nilfs_palloc_setup_cache(dat, &di->palloc_cache);
+	err = nilfs_mdt_setup_shadow_map(dat, &di->shadow);
+	if (err)
+		goto failed;
+
+	err = nilfs_read_inode_common(dat, raw_inode);
+	if (err)
+		goto failed;
+
+	unlock_new_inode(dat);
+ out:
+	*inodep = dat;
+	return 0;
+ failed:
+	iget_failed(dat);
+	return err;
+}
diff --git a/fs/nilfs2/dat.h b/fs/nilfs2/dat.h
new file mode 100644
index 0000000000..468c82d261
--- /dev/null
+++ b/fs/nilfs2/dat.h
@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * NILFS disk address translation.
+ *
+ * Copyright (C) 2006-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Koji Sato.
+ */
+
+#ifndef _NILFS_DAT_H
+#define _NILFS_DAT_H
+
+#include <linux/types.h>
+#include <linux/buffer_head.h>
+#include <linux/fs.h>
+#include <linux/nilfs2_ondisk.h>	/* nilfs_inode, nilfs_checkpoint */
+
+
+struct nilfs_palloc_req;
+
+int nilfs_dat_translate(struct inode *, __u64, sector_t *);
+
+int nilfs_dat_prepare_alloc(struct inode *, struct nilfs_palloc_req *);
+void nilfs_dat_commit_alloc(struct inode *, struct nilfs_palloc_req *);
+void nilfs_dat_abort_alloc(struct inode *, struct nilfs_palloc_req *);
+int nilfs_dat_prepare_start(struct inode *, struct nilfs_palloc_req *);
+void nilfs_dat_commit_start(struct inode *, struct nilfs_palloc_req *,
+			    sector_t);
+int nilfs_dat_prepare_end(struct inode *, struct nilfs_palloc_req *);
+void nilfs_dat_commit_end(struct inode *, struct nilfs_palloc_req *, int);
+void nilfs_dat_abort_end(struct inode *, struct nilfs_palloc_req *);
+int nilfs_dat_prepare_update(struct inode *, struct nilfs_palloc_req *,
+			     struct nilfs_palloc_req *);
+void nilfs_dat_commit_update(struct inode *, struct nilfs_palloc_req *,
+			     struct nilfs_palloc_req *, int);
+void nilfs_dat_abort_update(struct inode *, struct nilfs_palloc_req *,
+			    struct nilfs_palloc_req *);
+
+int nilfs_dat_mark_dirty(struct inode *, __u64);
+int nilfs_dat_freev(struct inode *, __u64 *, size_t);
+int nilfs_dat_move(struct inode *, __u64, sector_t);
+ssize_t nilfs_dat_get_vinfo(struct inode *, void *, unsigned int, size_t);
+
+int nilfs_dat_read(struct super_block *sb, size_t entry_size,
+		   struct nilfs_inode *raw_inode, struct inode **inodep);
+
+#endif	/* _NILFS_DAT_H */
diff --git a/fs/nilfs2/dir.c b/fs/nilfs2/dir.c
new file mode 100644
index 0000000000..bce734b68f
--- /dev/null
+++ b/fs/nilfs2/dir.c
@@ -0,0 +1,679 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NILFS directory entry operations
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Modified for NILFS by Amagai Yoshiji.
+ */
+/*
+ *  linux/fs/ext2/dir.c
+ *
+ * Copyright (C) 1992, 1993, 1994, 1995
+ * Remy Card (card@masi.ibp.fr)
+ * Laboratoire MASI - Institut Blaise Pascal
+ * Universite Pierre et Marie Curie (Paris VI)
+ *
+ *  from
+ *
+ *  linux/fs/minix/dir.c
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ *
+ *  ext2 directory handling functions
+ *
+ *  Big-endian to little-endian byte-swapping/bitmaps by
+ *        David S. Miller (davem@caip.rutgers.edu), 1995
+ *
+ * All code that works with directory layout had been switched to pagecache
+ * and moved here. AV
+ */
+
+#include <linux/pagemap.h>
+#include "nilfs.h"
+#include "page.h"
+
+static inline unsigned int nilfs_rec_len_from_disk(__le16 dlen)
+{
+	unsigned int len = le16_to_cpu(dlen);
+
+#if (PAGE_SIZE >= 65536)
+	if (len == NILFS_MAX_REC_LEN)
+		return 1 << 16;
+#endif
+	return len;
+}
+
+static inline __le16 nilfs_rec_len_to_disk(unsigned int len)
+{
+#if (PAGE_SIZE >= 65536)
+	if (len == (1 << 16))
+		return cpu_to_le16(NILFS_MAX_REC_LEN);
+
+	BUG_ON(len > (1 << 16));
+#endif
+	return cpu_to_le16(len);
+}
+
+/*
+ * nilfs uses block-sized chunks. Arguably, sector-sized ones would be
+ * more robust, but we have what we have
+ */
+static inline unsigned int nilfs_chunk_size(struct inode *inode)
+{
+	return inode->i_sb->s_blocksize;
+}
+
+static inline void nilfs_put_page(struct page *page)
+{
+	kunmap(page);
+	put_page(page);
+}
+
+/*
+ * Return the offset into page `page_nr' of the last valid
+ * byte in that page, plus one.
+ */
+static unsigned int nilfs_last_byte(struct inode *inode, unsigned long page_nr)
+{
+	unsigned int last_byte = inode->i_size;
+
+	last_byte -= page_nr << PAGE_SHIFT;
+	if (last_byte > PAGE_SIZE)
+		last_byte = PAGE_SIZE;
+	return last_byte;
+}
+
+static int nilfs_prepare_chunk(struct page *page, unsigned int from,
+			       unsigned int to)
+{
+	loff_t pos = page_offset(page) + from;
+
+	return __block_write_begin(page, pos, to - from, nilfs_get_block);
+}
+
+static void nilfs_commit_chunk(struct page *page,
+			       struct address_space *mapping,
+			       unsigned int from, unsigned int to)
+{
+	struct inode *dir = mapping->host;
+	loff_t pos = page_offset(page) + from;
+	unsigned int len = to - from;
+	unsigned int nr_dirty, copied;
+	int err;
+
+	nr_dirty = nilfs_page_count_clean_buffers(page, from, to);
+	copied = block_write_end(NULL, mapping, pos, len, len, page, NULL);
+	if (pos + copied > dir->i_size)
+		i_size_write(dir, pos + copied);
+	if (IS_DIRSYNC(dir))
+		nilfs_set_transaction_flag(NILFS_TI_SYNC);
+	err = nilfs_set_file_dirty(dir, nr_dirty);
+	WARN_ON(err); /* do not happen */
+	unlock_page(page);
+}
+
+static bool nilfs_check_page(struct page *page)
+{
+	struct inode *dir = page->mapping->host;
+	struct super_block *sb = dir->i_sb;
+	unsigned int chunk_size = nilfs_chunk_size(dir);
+	char *kaddr = page_address(page);
+	unsigned int offs, rec_len;
+	unsigned int limit = PAGE_SIZE;
+	struct nilfs_dir_entry *p;
+	char *error;
+
+	if ((dir->i_size >> PAGE_SHIFT) == page->index) {
+		limit = dir->i_size & ~PAGE_MASK;
+		if (limit & (chunk_size - 1))
+			goto Ebadsize;
+		if (!limit)
+			goto out;
+	}
+	for (offs = 0; offs <= limit - NILFS_DIR_REC_LEN(1); offs += rec_len) {
+		p = (struct nilfs_dir_entry *)(kaddr + offs);
+		rec_len = nilfs_rec_len_from_disk(p->rec_len);
+
+		if (rec_len < NILFS_DIR_REC_LEN(1))
+			goto Eshort;
+		if (rec_len & 3)
+			goto Ealign;
+		if (rec_len < NILFS_DIR_REC_LEN(p->name_len))
+			goto Enamelen;
+		if (((offs + rec_len - 1) ^ offs) & ~(chunk_size-1))
+			goto Espan;
+	}
+	if (offs != limit)
+		goto Eend;
+out:
+	SetPageChecked(page);
+	return true;
+
+	/* Too bad, we had an error */
+
+Ebadsize:
+	nilfs_error(sb,
+		    "size of directory #%lu is not a multiple of chunk size",
+		    dir->i_ino);
+	goto fail;
+Eshort:
+	error = "rec_len is smaller than minimal";
+	goto bad_entry;
+Ealign:
+	error = "unaligned directory entry";
+	goto bad_entry;
+Enamelen:
+	error = "rec_len is too small for name_len";
+	goto bad_entry;
+Espan:
+	error = "directory entry across blocks";
+bad_entry:
+	nilfs_error(sb,
+		    "bad entry in directory #%lu: %s - offset=%lu, inode=%lu, rec_len=%d, name_len=%d",
+		    dir->i_ino, error, (page->index << PAGE_SHIFT) + offs,
+		    (unsigned long)le64_to_cpu(p->inode),
+		    rec_len, p->name_len);
+	goto fail;
+Eend:
+	p = (struct nilfs_dir_entry *)(kaddr + offs);
+	nilfs_error(sb,
+		    "entry in directory #%lu spans the page boundary offset=%lu, inode=%lu",
+		    dir->i_ino, (page->index << PAGE_SHIFT) + offs,
+		    (unsigned long)le64_to_cpu(p->inode));
+fail:
+	SetPageError(page);
+	return false;
+}
+
+static struct page *nilfs_get_page(struct inode *dir, unsigned long n)
+{
+	struct address_space *mapping = dir->i_mapping;
+	struct page *page = read_mapping_page(mapping, n, NULL);
+
+	if (!IS_ERR(page)) {
+		kmap(page);
+		if (unlikely(!PageChecked(page))) {
+			if (!nilfs_check_page(page))
+				goto fail;
+		}
+	}
+	return page;
+
+fail:
+	nilfs_put_page(page);
+	return ERR_PTR(-EIO);
+}
+
+/*
+ * NOTE! unlike strncmp, nilfs_match returns 1 for success, 0 for failure.
+ *
+ * len <= NILFS_NAME_LEN and de != NULL are guaranteed by caller.
+ */
+static int
+nilfs_match(int len, const unsigned char *name, struct nilfs_dir_entry *de)
+{
+	if (len != de->name_len)
+		return 0;
+	if (!de->inode)
+		return 0;
+	return !memcmp(name, de->name, len);
+}
+
+/*
+ * p is at least 6 bytes before the end of page
+ */
+static struct nilfs_dir_entry *nilfs_next_entry(struct nilfs_dir_entry *p)
+{
+	return (struct nilfs_dir_entry *)((char *)p +
+					  nilfs_rec_len_from_disk(p->rec_len));
+}
+
+static unsigned char
+nilfs_filetype_table[NILFS_FT_MAX] = {
+	[NILFS_FT_UNKNOWN]	= DT_UNKNOWN,
+	[NILFS_FT_REG_FILE]	= DT_REG,
+	[NILFS_FT_DIR]		= DT_DIR,
+	[NILFS_FT_CHRDEV]	= DT_CHR,
+	[NILFS_FT_BLKDEV]	= DT_BLK,
+	[NILFS_FT_FIFO]		= DT_FIFO,
+	[NILFS_FT_SOCK]		= DT_SOCK,
+	[NILFS_FT_SYMLINK]	= DT_LNK,
+};
+
+#define S_SHIFT 12
+static unsigned char
+nilfs_type_by_mode[S_IFMT >> S_SHIFT] = {
+	[S_IFREG >> S_SHIFT]	= NILFS_FT_REG_FILE,
+	[S_IFDIR >> S_SHIFT]	= NILFS_FT_DIR,
+	[S_IFCHR >> S_SHIFT]	= NILFS_FT_CHRDEV,
+	[S_IFBLK >> S_SHIFT]	= NILFS_FT_BLKDEV,
+	[S_IFIFO >> S_SHIFT]	= NILFS_FT_FIFO,
+	[S_IFSOCK >> S_SHIFT]	= NILFS_FT_SOCK,
+	[S_IFLNK >> S_SHIFT]	= NILFS_FT_SYMLINK,
+};
+
+static void nilfs_set_de_type(struct nilfs_dir_entry *de, struct inode *inode)
+{
+	umode_t mode = inode->i_mode;
+
+	de->file_type = nilfs_type_by_mode[(mode & S_IFMT)>>S_SHIFT];
+}
+
+static int nilfs_readdir(struct file *file, struct dir_context *ctx)
+{
+	loff_t pos = ctx->pos;
+	struct inode *inode = file_inode(file);
+	struct super_block *sb = inode->i_sb;
+	unsigned int offset = pos & ~PAGE_MASK;
+	unsigned long n = pos >> PAGE_SHIFT;
+	unsigned long npages = dir_pages(inode);
+
+	if (pos > inode->i_size - NILFS_DIR_REC_LEN(1))
+		return 0;
+
+	for ( ; n < npages; n++, offset = 0) {
+		char *kaddr, *limit;
+		struct nilfs_dir_entry *de;
+		struct page *page = nilfs_get_page(inode, n);
+
+		if (IS_ERR(page)) {
+			nilfs_error(sb, "bad page in #%lu", inode->i_ino);
+			ctx->pos += PAGE_SIZE - offset;
+			return -EIO;
+		}
+		kaddr = page_address(page);
+		de = (struct nilfs_dir_entry *)(kaddr + offset);
+		limit = kaddr + nilfs_last_byte(inode, n) -
+			NILFS_DIR_REC_LEN(1);
+		for ( ; (char *)de <= limit; de = nilfs_next_entry(de)) {
+			if (de->rec_len == 0) {
+				nilfs_error(sb, "zero-length directory entry");
+				nilfs_put_page(page);
+				return -EIO;
+			}
+			if (de->inode) {
+				unsigned char t;
+
+				if (de->file_type < NILFS_FT_MAX)
+					t = nilfs_filetype_table[de->file_type];
+				else
+					t = DT_UNKNOWN;
+
+				if (!dir_emit(ctx, de->name, de->name_len,
+						le64_to_cpu(de->inode), t)) {
+					nilfs_put_page(page);
+					return 0;
+				}
+			}
+			ctx->pos += nilfs_rec_len_from_disk(de->rec_len);
+		}
+		nilfs_put_page(page);
+	}
+	return 0;
+}
+
+/*
+ *	nilfs_find_entry()
+ *
+ * finds an entry in the specified directory with the wanted name. It
+ * returns the page in which the entry was found, and the entry itself
+ * (as a parameter - res_dir). Page is returned mapped and unlocked.
+ * Entry is guaranteed to be valid.
+ */
+struct nilfs_dir_entry *
+nilfs_find_entry(struct inode *dir, const struct qstr *qstr,
+		 struct page **res_page)
+{
+	const unsigned char *name = qstr->name;
+	int namelen = qstr->len;
+	unsigned int reclen = NILFS_DIR_REC_LEN(namelen);
+	unsigned long start, n;
+	unsigned long npages = dir_pages(dir);
+	struct page *page = NULL;
+	struct nilfs_inode_info *ei = NILFS_I(dir);
+	struct nilfs_dir_entry *de;
+
+	if (npages == 0)
+		goto out;
+
+	/* OFFSET_CACHE */
+	*res_page = NULL;
+
+	start = ei->i_dir_start_lookup;
+	if (start >= npages)
+		start = 0;
+	n = start;
+	do {
+		char *kaddr;
+
+		page = nilfs_get_page(dir, n);
+		if (!IS_ERR(page)) {
+			kaddr = page_address(page);
+			de = (struct nilfs_dir_entry *)kaddr;
+			kaddr += nilfs_last_byte(dir, n) - reclen;
+			while ((char *) de <= kaddr) {
+				if (de->rec_len == 0) {
+					nilfs_error(dir->i_sb,
+						"zero-length directory entry");
+					nilfs_put_page(page);
+					goto out;
+				}
+				if (nilfs_match(namelen, name, de))
+					goto found;
+				de = nilfs_next_entry(de);
+			}
+			nilfs_put_page(page);
+		}
+		if (++n >= npages)
+			n = 0;
+		/* next page is past the blocks we've got */
+		if (unlikely(n > (dir->i_blocks >> (PAGE_SHIFT - 9)))) {
+			nilfs_error(dir->i_sb,
+			       "dir %lu size %lld exceeds block count %llu",
+			       dir->i_ino, dir->i_size,
+			       (unsigned long long)dir->i_blocks);
+			goto out;
+		}
+	} while (n != start);
+out:
+	return NULL;
+
+found:
+	*res_page = page;
+	ei->i_dir_start_lookup = n;
+	return de;
+}
+
+struct nilfs_dir_entry *nilfs_dotdot(struct inode *dir, struct page **p)
+{
+	struct page *page = nilfs_get_page(dir, 0);
+	struct nilfs_dir_entry *de = NULL;
+
+	if (!IS_ERR(page)) {
+		de = nilfs_next_entry(
+			(struct nilfs_dir_entry *)page_address(page));
+		*p = page;
+	}
+	return de;
+}
+
+ino_t nilfs_inode_by_name(struct inode *dir, const struct qstr *qstr)
+{
+	ino_t res = 0;
+	struct nilfs_dir_entry *de;
+	struct page *page;
+
+	de = nilfs_find_entry(dir, qstr, &page);
+	if (de) {
+		res = le64_to_cpu(de->inode);
+		kunmap(page);
+		put_page(page);
+	}
+	return res;
+}
+
+/* Releases the page */
+void nilfs_set_link(struct inode *dir, struct nilfs_dir_entry *de,
+		    struct page *page, struct inode *inode)
+{
+	unsigned int from = (char *)de - (char *)page_address(page);
+	unsigned int to = from + nilfs_rec_len_from_disk(de->rec_len);
+	struct address_space *mapping = page->mapping;
+	int err;
+
+	lock_page(page);
+	err = nilfs_prepare_chunk(page, from, to);
+	BUG_ON(err);
+	de->inode = cpu_to_le64(inode->i_ino);
+	nilfs_set_de_type(de, inode);
+	nilfs_commit_chunk(page, mapping, from, to);
+	nilfs_put_page(page);
+	dir->i_mtime = inode_set_ctime_current(dir);
+}
+
+/*
+ *	Parent is locked.
+ */
+int nilfs_add_link(struct dentry *dentry, struct inode *inode)
+{
+	struct inode *dir = d_inode(dentry->d_parent);
+	const unsigned char *name = dentry->d_name.name;
+	int namelen = dentry->d_name.len;
+	unsigned int chunk_size = nilfs_chunk_size(dir);
+	unsigned int reclen = NILFS_DIR_REC_LEN(namelen);
+	unsigned short rec_len, name_len;
+	struct page *page = NULL;
+	struct nilfs_dir_entry *de;
+	unsigned long npages = dir_pages(dir);
+	unsigned long n;
+	char *kaddr;
+	unsigned int from, to;
+	int err;
+
+	/*
+	 * We take care of directory expansion in the same loop.
+	 * This code plays outside i_size, so it locks the page
+	 * to protect that region.
+	 */
+	for (n = 0; n <= npages; n++) {
+		char *dir_end;
+
+		page = nilfs_get_page(dir, n);
+		err = PTR_ERR(page);
+		if (IS_ERR(page))
+			goto out;
+		lock_page(page);
+		kaddr = page_address(page);
+		dir_end = kaddr + nilfs_last_byte(dir, n);
+		de = (struct nilfs_dir_entry *)kaddr;
+		kaddr += PAGE_SIZE - reclen;
+		while ((char *)de <= kaddr) {
+			if ((char *)de == dir_end) {
+				/* We hit i_size */
+				name_len = 0;
+				rec_len = chunk_size;
+				de->rec_len = nilfs_rec_len_to_disk(chunk_size);
+				de->inode = 0;
+				goto got_it;
+			}
+			if (de->rec_len == 0) {
+				nilfs_error(dir->i_sb,
+					    "zero-length directory entry");
+				err = -EIO;
+				goto out_unlock;
+			}
+			err = -EEXIST;
+			if (nilfs_match(namelen, name, de))
+				goto out_unlock;
+			name_len = NILFS_DIR_REC_LEN(de->name_len);
+			rec_len = nilfs_rec_len_from_disk(de->rec_len);
+			if (!de->inode && rec_len >= reclen)
+				goto got_it;
+			if (rec_len >= name_len + reclen)
+				goto got_it;
+			de = (struct nilfs_dir_entry *)((char *)de + rec_len);
+		}
+		unlock_page(page);
+		nilfs_put_page(page);
+	}
+	BUG();
+	return -EINVAL;
+
+got_it:
+	from = (char *)de - (char *)page_address(page);
+	to = from + rec_len;
+	err = nilfs_prepare_chunk(page, from, to);
+	if (err)
+		goto out_unlock;
+	if (de->inode) {
+		struct nilfs_dir_entry *de1;
+
+		de1 = (struct nilfs_dir_entry *)((char *)de + name_len);
+		de1->rec_len = nilfs_rec_len_to_disk(rec_len - name_len);
+		de->rec_len = nilfs_rec_len_to_disk(name_len);
+		de = de1;
+	}
+	de->name_len = namelen;
+	memcpy(de->name, name, namelen);
+	de->inode = cpu_to_le64(inode->i_ino);
+	nilfs_set_de_type(de, inode);
+	nilfs_commit_chunk(page, page->mapping, from, to);
+	dir->i_mtime = inode_set_ctime_current(dir);
+	nilfs_mark_inode_dirty(dir);
+	/* OFFSET_CACHE */
+out_put:
+	nilfs_put_page(page);
+out:
+	return err;
+out_unlock:
+	unlock_page(page);
+	goto out_put;
+}
+
+/*
+ * nilfs_delete_entry deletes a directory entry by merging it with the
+ * previous entry. Page is up-to-date. Releases the page.
+ */
+int nilfs_delete_entry(struct nilfs_dir_entry *dir, struct page *page)
+{
+	struct address_space *mapping = page->mapping;
+	struct inode *inode = mapping->host;
+	char *kaddr = page_address(page);
+	unsigned int from, to;
+	struct nilfs_dir_entry *de, *pde = NULL;
+	int err;
+
+	from = ((char *)dir - kaddr) & ~(nilfs_chunk_size(inode) - 1);
+	to = ((char *)dir - kaddr) + nilfs_rec_len_from_disk(dir->rec_len);
+	de = (struct nilfs_dir_entry *)(kaddr + from);
+
+	while ((char *)de < (char *)dir) {
+		if (de->rec_len == 0) {
+			nilfs_error(inode->i_sb,
+				    "zero-length directory entry");
+			err = -EIO;
+			goto out;
+		}
+		pde = de;
+		de = nilfs_next_entry(de);
+	}
+	if (pde)
+		from = (char *)pde - (char *)page_address(page);
+	lock_page(page);
+	err = nilfs_prepare_chunk(page, from, to);
+	BUG_ON(err);
+	if (pde)
+		pde->rec_len = nilfs_rec_len_to_disk(to - from);
+	dir->inode = 0;
+	nilfs_commit_chunk(page, mapping, from, to);
+	inode->i_mtime = inode_set_ctime_current(inode);
+out:
+	nilfs_put_page(page);
+	return err;
+}
+
+/*
+ * Set the first fragment of directory.
+ */
+int nilfs_make_empty(struct inode *inode, struct inode *parent)
+{
+	struct address_space *mapping = inode->i_mapping;
+	struct page *page = grab_cache_page(mapping, 0);
+	unsigned int chunk_size = nilfs_chunk_size(inode);
+	struct nilfs_dir_entry *de;
+	int err;
+	void *kaddr;
+
+	if (!page)
+		return -ENOMEM;
+
+	err = nilfs_prepare_chunk(page, 0, chunk_size);
+	if (unlikely(err)) {
+		unlock_page(page);
+		goto fail;
+	}
+	kaddr = kmap_atomic(page);
+	memset(kaddr, 0, chunk_size);
+	de = (struct nilfs_dir_entry *)kaddr;
+	de->name_len = 1;
+	de->rec_len = nilfs_rec_len_to_disk(NILFS_DIR_REC_LEN(1));
+	memcpy(de->name, ".\0\0", 4);
+	de->inode = cpu_to_le64(inode->i_ino);
+	nilfs_set_de_type(de, inode);
+
+	de = (struct nilfs_dir_entry *)(kaddr + NILFS_DIR_REC_LEN(1));
+	de->name_len = 2;
+	de->rec_len = nilfs_rec_len_to_disk(chunk_size - NILFS_DIR_REC_LEN(1));
+	de->inode = cpu_to_le64(parent->i_ino);
+	memcpy(de->name, "..\0", 4);
+	nilfs_set_de_type(de, inode);
+	kunmap_atomic(kaddr);
+	nilfs_commit_chunk(page, mapping, 0, chunk_size);
+fail:
+	put_page(page);
+	return err;
+}
+
+/*
+ * routine to check that the specified directory is empty (for rmdir)
+ */
+int nilfs_empty_dir(struct inode *inode)
+{
+	struct page *page = NULL;
+	unsigned long i, npages = dir_pages(inode);
+
+	for (i = 0; i < npages; i++) {
+		char *kaddr;
+		struct nilfs_dir_entry *de;
+
+		page = nilfs_get_page(inode, i);
+		if (IS_ERR(page))
+			continue;
+
+		kaddr = page_address(page);
+		de = (struct nilfs_dir_entry *)kaddr;
+		kaddr += nilfs_last_byte(inode, i) - NILFS_DIR_REC_LEN(1);
+
+		while ((char *)de <= kaddr) {
+			if (de->rec_len == 0) {
+				nilfs_error(inode->i_sb,
+					    "zero-length directory entry (kaddr=%p, de=%p)",
+					    kaddr, de);
+				goto not_empty;
+			}
+			if (de->inode != 0) {
+				/* check for . and .. */
+				if (de->name[0] != '.')
+					goto not_empty;
+				if (de->name_len > 2)
+					goto not_empty;
+				if (de->name_len < 2) {
+					if (de->inode !=
+					    cpu_to_le64(inode->i_ino))
+						goto not_empty;
+				} else if (de->name[1] != '.')
+					goto not_empty;
+			}
+			de = nilfs_next_entry(de);
+		}
+		nilfs_put_page(page);
+	}
+	return 1;
+
+not_empty:
+	nilfs_put_page(page);
+	return 0;
+}
+
+const struct file_operations nilfs_dir_operations = {
+	.llseek		= generic_file_llseek,
+	.read		= generic_read_dir,
+	.iterate_shared	= nilfs_readdir,
+	.unlocked_ioctl	= nilfs_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	= nilfs_compat_ioctl,
+#endif	/* CONFIG_COMPAT */
+	.fsync		= nilfs_sync_file,
+
+};
diff --git a/fs/nilfs2/direct.c b/fs/nilfs2/direct.c
new file mode 100644
index 0000000000..4c85914f2a
--- /dev/null
+++ b/fs/nilfs2/direct.c
@@ -0,0 +1,379 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NILFS direct block pointer.
+ *
+ * Copyright (C) 2006-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Koji Sato.
+ */
+
+#include <linux/errno.h>
+#include "nilfs.h"
+#include "page.h"
+#include "direct.h"
+#include "alloc.h"
+#include "dat.h"
+
+static inline __le64 *nilfs_direct_dptrs(const struct nilfs_bmap *direct)
+{
+	return (__le64 *)
+		((struct nilfs_direct_node *)direct->b_u.u_data + 1);
+}
+
+static inline __u64
+nilfs_direct_get_ptr(const struct nilfs_bmap *direct, __u64 key)
+{
+	return le64_to_cpu(*(nilfs_direct_dptrs(direct) + key));
+}
+
+static inline void nilfs_direct_set_ptr(struct nilfs_bmap *direct,
+					__u64 key, __u64 ptr)
+{
+	*(nilfs_direct_dptrs(direct) + key) = cpu_to_le64(ptr);
+}
+
+static int nilfs_direct_lookup(const struct nilfs_bmap *direct,
+			       __u64 key, int level, __u64 *ptrp)
+{
+	__u64 ptr;
+
+	if (key > NILFS_DIRECT_KEY_MAX || level != 1)
+		return -ENOENT;
+	ptr = nilfs_direct_get_ptr(direct, key);
+	if (ptr == NILFS_BMAP_INVALID_PTR)
+		return -ENOENT;
+
+	*ptrp = ptr;
+	return 0;
+}
+
+static int nilfs_direct_lookup_contig(const struct nilfs_bmap *direct,
+				      __u64 key, __u64 *ptrp,
+				      unsigned int maxblocks)
+{
+	struct inode *dat = NULL;
+	__u64 ptr, ptr2;
+	sector_t blocknr;
+	int ret, cnt;
+
+	if (key > NILFS_DIRECT_KEY_MAX)
+		return -ENOENT;
+	ptr = nilfs_direct_get_ptr(direct, key);
+	if (ptr == NILFS_BMAP_INVALID_PTR)
+		return -ENOENT;
+
+	if (NILFS_BMAP_USE_VBN(direct)) {
+		dat = nilfs_bmap_get_dat(direct);
+		ret = nilfs_dat_translate(dat, ptr, &blocknr);
+		if (ret < 0)
+			return ret;
+		ptr = blocknr;
+	}
+
+	maxblocks = min_t(unsigned int, maxblocks,
+			  NILFS_DIRECT_KEY_MAX - key + 1);
+	for (cnt = 1; cnt < maxblocks &&
+		     (ptr2 = nilfs_direct_get_ptr(direct, key + cnt)) !=
+		     NILFS_BMAP_INVALID_PTR;
+	     cnt++) {
+		if (dat) {
+			ret = nilfs_dat_translate(dat, ptr2, &blocknr);
+			if (ret < 0)
+				return ret;
+			ptr2 = blocknr;
+		}
+		if (ptr2 != ptr + cnt)
+			break;
+	}
+	*ptrp = ptr;
+	return cnt;
+}
+
+static __u64
+nilfs_direct_find_target_v(const struct nilfs_bmap *direct, __u64 key)
+{
+	__u64 ptr;
+
+	ptr = nilfs_bmap_find_target_seq(direct, key);
+	if (ptr != NILFS_BMAP_INVALID_PTR)
+		/* sequential access */
+		return ptr;
+
+	/* block group */
+	return nilfs_bmap_find_target_in_group(direct);
+}
+
+static int nilfs_direct_insert(struct nilfs_bmap *bmap, __u64 key, __u64 ptr)
+{
+	union nilfs_bmap_ptr_req req;
+	struct inode *dat = NULL;
+	struct buffer_head *bh;
+	int ret;
+
+	if (key > NILFS_DIRECT_KEY_MAX)
+		return -ENOENT;
+	if (nilfs_direct_get_ptr(bmap, key) != NILFS_BMAP_INVALID_PTR)
+		return -EEXIST;
+
+	if (NILFS_BMAP_USE_VBN(bmap)) {
+		req.bpr_ptr = nilfs_direct_find_target_v(bmap, key);
+		dat = nilfs_bmap_get_dat(bmap);
+	}
+	ret = nilfs_bmap_prepare_alloc_ptr(bmap, &req, dat);
+	if (!ret) {
+		/* ptr must be a pointer to a buffer head. */
+		bh = (struct buffer_head *)((unsigned long)ptr);
+		set_buffer_nilfs_volatile(bh);
+
+		nilfs_bmap_commit_alloc_ptr(bmap, &req, dat);
+		nilfs_direct_set_ptr(bmap, key, req.bpr_ptr);
+
+		if (!nilfs_bmap_dirty(bmap))
+			nilfs_bmap_set_dirty(bmap);
+
+		if (NILFS_BMAP_USE_VBN(bmap))
+			nilfs_bmap_set_target_v(bmap, key, req.bpr_ptr);
+
+		nilfs_inode_add_blocks(bmap->b_inode, 1);
+	}
+	return ret;
+}
+
+static int nilfs_direct_delete(struct nilfs_bmap *bmap, __u64 key)
+{
+	union nilfs_bmap_ptr_req req;
+	struct inode *dat;
+	int ret;
+
+	if (key > NILFS_DIRECT_KEY_MAX ||
+	    nilfs_direct_get_ptr(bmap, key) == NILFS_BMAP_INVALID_PTR)
+		return -ENOENT;
+
+	dat = NILFS_BMAP_USE_VBN(bmap) ? nilfs_bmap_get_dat(bmap) : NULL;
+	req.bpr_ptr = nilfs_direct_get_ptr(bmap, key);
+
+	ret = nilfs_bmap_prepare_end_ptr(bmap, &req, dat);
+	if (!ret) {
+		nilfs_bmap_commit_end_ptr(bmap, &req, dat);
+		nilfs_direct_set_ptr(bmap, key, NILFS_BMAP_INVALID_PTR);
+		nilfs_inode_sub_blocks(bmap->b_inode, 1);
+	}
+	return ret;
+}
+
+static int nilfs_direct_seek_key(const struct nilfs_bmap *direct, __u64 start,
+				 __u64 *keyp)
+{
+	__u64 key;
+
+	for (key = start; key <= NILFS_DIRECT_KEY_MAX; key++) {
+		if (nilfs_direct_get_ptr(direct, key) !=
+		    NILFS_BMAP_INVALID_PTR) {
+			*keyp = key;
+			return 0;
+		}
+	}
+	return -ENOENT;
+}
+
+static int nilfs_direct_last_key(const struct nilfs_bmap *direct, __u64 *keyp)
+{
+	__u64 key, lastkey;
+
+	lastkey = NILFS_DIRECT_KEY_MAX + 1;
+	for (key = NILFS_DIRECT_KEY_MIN; key <= NILFS_DIRECT_KEY_MAX; key++)
+		if (nilfs_direct_get_ptr(direct, key) !=
+		    NILFS_BMAP_INVALID_PTR)
+			lastkey = key;
+
+	if (lastkey == NILFS_DIRECT_KEY_MAX + 1)
+		return -ENOENT;
+
+	*keyp = lastkey;
+
+	return 0;
+}
+
+static int nilfs_direct_check_insert(const struct nilfs_bmap *bmap, __u64 key)
+{
+	return key > NILFS_DIRECT_KEY_MAX;
+}
+
+static int nilfs_direct_gather_data(struct nilfs_bmap *direct,
+				    __u64 *keys, __u64 *ptrs, int nitems)
+{
+	__u64 key;
+	__u64 ptr;
+	int n;
+
+	if (nitems > NILFS_DIRECT_NBLOCKS)
+		nitems = NILFS_DIRECT_NBLOCKS;
+	n = 0;
+	for (key = 0; key < nitems; key++) {
+		ptr = nilfs_direct_get_ptr(direct, key);
+		if (ptr != NILFS_BMAP_INVALID_PTR) {
+			keys[n] = key;
+			ptrs[n] = ptr;
+			n++;
+		}
+	}
+	return n;
+}
+
+int nilfs_direct_delete_and_convert(struct nilfs_bmap *bmap,
+				    __u64 key, __u64 *keys, __u64 *ptrs, int n)
+{
+	__le64 *dptrs;
+	int ret, i, j;
+
+	/* no need to allocate any resource for conversion */
+
+	/* delete */
+	ret = bmap->b_ops->bop_delete(bmap, key);
+	if (ret < 0)
+		return ret;
+
+	/* free resources */
+	if (bmap->b_ops->bop_clear != NULL)
+		bmap->b_ops->bop_clear(bmap);
+
+	/* convert */
+	dptrs = nilfs_direct_dptrs(bmap);
+	for (i = 0, j = 0; i < NILFS_DIRECT_NBLOCKS; i++) {
+		if ((j < n) && (i == keys[j])) {
+			dptrs[i] = (i != key) ?
+				cpu_to_le64(ptrs[j]) :
+				NILFS_BMAP_INVALID_PTR;
+			j++;
+		} else
+			dptrs[i] = NILFS_BMAP_INVALID_PTR;
+	}
+
+	nilfs_direct_init(bmap);
+	return 0;
+}
+
+static int nilfs_direct_propagate(struct nilfs_bmap *bmap,
+				  struct buffer_head *bh)
+{
+	struct nilfs_palloc_req oldreq, newreq;
+	struct inode *dat;
+	__u64 key;
+	__u64 ptr;
+	int ret;
+
+	if (!NILFS_BMAP_USE_VBN(bmap))
+		return 0;
+
+	dat = nilfs_bmap_get_dat(bmap);
+	key = nilfs_bmap_data_get_key(bmap, bh);
+	ptr = nilfs_direct_get_ptr(bmap, key);
+	if (!buffer_nilfs_volatile(bh)) {
+		oldreq.pr_entry_nr = ptr;
+		newreq.pr_entry_nr = ptr;
+		ret = nilfs_dat_prepare_update(dat, &oldreq, &newreq);
+		if (ret < 0)
+			return ret;
+		nilfs_dat_commit_update(dat, &oldreq, &newreq,
+					bmap->b_ptr_type == NILFS_BMAP_PTR_VS);
+		set_buffer_nilfs_volatile(bh);
+		nilfs_direct_set_ptr(bmap, key, newreq.pr_entry_nr);
+	} else
+		ret = nilfs_dat_mark_dirty(dat, ptr);
+
+	return ret;
+}
+
+static int nilfs_direct_assign_v(struct nilfs_bmap *direct,
+				 __u64 key, __u64 ptr,
+				 struct buffer_head **bh,
+				 sector_t blocknr,
+				 union nilfs_binfo *binfo)
+{
+	struct inode *dat = nilfs_bmap_get_dat(direct);
+	union nilfs_bmap_ptr_req req;
+	int ret;
+
+	req.bpr_ptr = ptr;
+	ret = nilfs_dat_prepare_start(dat, &req.bpr_req);
+	if (!ret) {
+		nilfs_dat_commit_start(dat, &req.bpr_req, blocknr);
+		binfo->bi_v.bi_vblocknr = cpu_to_le64(ptr);
+		binfo->bi_v.bi_blkoff = cpu_to_le64(key);
+	}
+	return ret;
+}
+
+static int nilfs_direct_assign_p(struct nilfs_bmap *direct,
+				 __u64 key, __u64 ptr,
+				 struct buffer_head **bh,
+				 sector_t blocknr,
+				 union nilfs_binfo *binfo)
+{
+	nilfs_direct_set_ptr(direct, key, blocknr);
+
+	binfo->bi_dat.bi_blkoff = cpu_to_le64(key);
+	binfo->bi_dat.bi_level = 0;
+	memset(binfo->bi_dat.bi_pad, 0, sizeof(binfo->bi_dat.bi_pad));
+
+	return 0;
+}
+
+static int nilfs_direct_assign(struct nilfs_bmap *bmap,
+			       struct buffer_head **bh,
+			       sector_t blocknr,
+			       union nilfs_binfo *binfo)
+{
+	__u64 key;
+	__u64 ptr;
+
+	key = nilfs_bmap_data_get_key(bmap, *bh);
+	if (unlikely(key > NILFS_DIRECT_KEY_MAX)) {
+		nilfs_crit(bmap->b_inode->i_sb,
+			   "%s (ino=%lu): invalid key: %llu",
+			   __func__,
+			   bmap->b_inode->i_ino, (unsigned long long)key);
+		return -EINVAL;
+	}
+	ptr = nilfs_direct_get_ptr(bmap, key);
+	if (unlikely(ptr == NILFS_BMAP_INVALID_PTR)) {
+		nilfs_crit(bmap->b_inode->i_sb,
+			   "%s (ino=%lu): invalid pointer: %llu",
+			   __func__,
+			   bmap->b_inode->i_ino, (unsigned long long)ptr);
+		return -EINVAL;
+	}
+
+	return NILFS_BMAP_USE_VBN(bmap) ?
+		nilfs_direct_assign_v(bmap, key, ptr, bh, blocknr, binfo) :
+		nilfs_direct_assign_p(bmap, key, ptr, bh, blocknr, binfo);
+}
+
+static const struct nilfs_bmap_operations nilfs_direct_ops = {
+	.bop_lookup		=	nilfs_direct_lookup,
+	.bop_lookup_contig	=	nilfs_direct_lookup_contig,
+	.bop_insert		=	nilfs_direct_insert,
+	.bop_delete		=	nilfs_direct_delete,
+	.bop_clear		=	NULL,
+
+	.bop_propagate		=	nilfs_direct_propagate,
+
+	.bop_lookup_dirty_buffers	=	NULL,
+
+	.bop_assign		=	nilfs_direct_assign,
+	.bop_mark		=	NULL,
+
+	.bop_seek_key		=	nilfs_direct_seek_key,
+	.bop_last_key		=	nilfs_direct_last_key,
+
+	.bop_check_insert	=	nilfs_direct_check_insert,
+	.bop_check_delete	=	NULL,
+	.bop_gather_data	=	nilfs_direct_gather_data,
+};
+
+
+int nilfs_direct_init(struct nilfs_bmap *bmap)
+{
+	bmap->b_ops = &nilfs_direct_ops;
+	return 0;
+}
diff --git a/fs/nilfs2/direct.h b/fs/nilfs2/direct.h
new file mode 100644
index 0000000000..b7ca896269
--- /dev/null
+++ b/fs/nilfs2/direct.h
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * NILFS direct block pointer.
+ *
+ * Copyright (C) 2006-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Koji Sato.
+ */
+
+#ifndef _NILFS_DIRECT_H
+#define _NILFS_DIRECT_H
+
+#include <linux/types.h>
+#include <linux/buffer_head.h>
+#include "bmap.h"
+
+
+#define NILFS_DIRECT_NBLOCKS	(NILFS_BMAP_SIZE / sizeof(__le64) - 1)
+#define NILFS_DIRECT_KEY_MIN	0
+#define NILFS_DIRECT_KEY_MAX	(NILFS_DIRECT_NBLOCKS - 1)
+
+
+int nilfs_direct_init(struct nilfs_bmap *);
+int nilfs_direct_delete_and_convert(struct nilfs_bmap *, __u64, __u64 *,
+				    __u64 *, int);
+
+
+#endif	/* _NILFS_DIRECT_H */
diff --git a/fs/nilfs2/export.h b/fs/nilfs2/export.h
new file mode 100644
index 0000000000..d29fd837c4
--- /dev/null
+++ b/fs/nilfs2/export.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef NILFS_EXPORT_H
+#define NILFS_EXPORT_H
+
+#include <linux/exportfs.h>
+
+extern const struct export_operations nilfs_export_ops;
+
+/**
+ * struct nilfs_fid - NILFS file id type
+ * @cno: checkpoint number
+ * @ino: inode number
+ * @gen: file generation (version) for NFS
+ * @parent_gen: parent generation (version) for NFS
+ * @parent_ino: parent inode number
+ */
+struct nilfs_fid {
+	u64 cno;
+	u64 ino;
+	u32 gen;
+
+	u32 parent_gen;
+	u64 parent_ino;
+} __packed;
+
+#endif
diff --git a/fs/nilfs2/file.c b/fs/nilfs2/file.c
new file mode 100644
index 0000000000..740ce26d1e
--- /dev/null
+++ b/fs/nilfs2/file.c
@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NILFS regular file handling primitives including fsync().
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Amagai Yoshiji and Ryusuke Konishi.
+ */
+
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/writeback.h>
+#include "nilfs.h"
+#include "segment.h"
+
+int nilfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
+{
+	/*
+	 * Called from fsync() system call
+	 * This is the only entry point that can catch write and synch
+	 * timing for both data blocks and intermediate blocks.
+	 *
+	 * This function should be implemented when the writeback function
+	 * will be implemented.
+	 */
+	struct the_nilfs *nilfs;
+	struct inode *inode = file->f_mapping->host;
+	int err = 0;
+
+	if (nilfs_inode_dirty(inode)) {
+		if (datasync)
+			err = nilfs_construct_dsync_segment(inode->i_sb, inode,
+							    start, end);
+		else
+			err = nilfs_construct_segment(inode->i_sb);
+	}
+
+	nilfs = inode->i_sb->s_fs_info;
+	if (!err)
+		err = nilfs_flush_device(nilfs);
+
+	return err;
+}
+
+static vm_fault_t nilfs_page_mkwrite(struct vm_fault *vmf)
+{
+	struct vm_area_struct *vma = vmf->vma;
+	struct page *page = vmf->page;
+	struct inode *inode = file_inode(vma->vm_file);
+	struct nilfs_transaction_info ti;
+	int ret = 0;
+
+	if (unlikely(nilfs_near_disk_full(inode->i_sb->s_fs_info)))
+		return VM_FAULT_SIGBUS; /* -ENOSPC */
+
+	sb_start_pagefault(inode->i_sb);
+	lock_page(page);
+	if (page->mapping != inode->i_mapping ||
+	    page_offset(page) >= i_size_read(inode) || !PageUptodate(page)) {
+		unlock_page(page);
+		ret = -EFAULT;	/* make the VM retry the fault */
+		goto out;
+	}
+
+	/*
+	 * check to see if the page is mapped already (no holes)
+	 */
+	if (PageMappedToDisk(page))
+		goto mapped;
+
+	if (page_has_buffers(page)) {
+		struct buffer_head *bh, *head;
+		int fully_mapped = 1;
+
+		bh = head = page_buffers(page);
+		do {
+			if (!buffer_mapped(bh)) {
+				fully_mapped = 0;
+				break;
+			}
+		} while (bh = bh->b_this_page, bh != head);
+
+		if (fully_mapped) {
+			SetPageMappedToDisk(page);
+			goto mapped;
+		}
+	}
+	unlock_page(page);
+
+	/*
+	 * fill hole blocks
+	 */
+	ret = nilfs_transaction_begin(inode->i_sb, &ti, 1);
+	/* never returns -ENOMEM, but may return -ENOSPC */
+	if (unlikely(ret))
+		goto out;
+
+	file_update_time(vma->vm_file);
+	ret = block_page_mkwrite(vma, vmf, nilfs_get_block);
+	if (ret) {
+		nilfs_transaction_abort(inode->i_sb);
+		goto out;
+	}
+	nilfs_set_file_dirty(inode, 1 << (PAGE_SHIFT - inode->i_blkbits));
+	nilfs_transaction_commit(inode->i_sb);
+
+ mapped:
+	wait_for_stable_page(page);
+ out:
+	sb_end_pagefault(inode->i_sb);
+	return vmf_fs_error(ret);
+}
+
+static const struct vm_operations_struct nilfs_file_vm_ops = {
+	.fault		= filemap_fault,
+	.map_pages	= filemap_map_pages,
+	.page_mkwrite	= nilfs_page_mkwrite,
+};
+
+static int nilfs_file_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	file_accessed(file);
+	vma->vm_ops = &nilfs_file_vm_ops;
+	return 0;
+}
+
+/*
+ * We have mostly NULL's here: the current defaults are ok for
+ * the nilfs filesystem.
+ */
+const struct file_operations nilfs_file_operations = {
+	.llseek		= generic_file_llseek,
+	.read_iter	= generic_file_read_iter,
+	.write_iter	= generic_file_write_iter,
+	.unlocked_ioctl	= nilfs_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	= nilfs_compat_ioctl,
+#endif	/* CONFIG_COMPAT */
+	.mmap		= nilfs_file_mmap,
+	.open		= generic_file_open,
+	/* .release	= nilfs_release_file, */
+	.fsync		= nilfs_sync_file,
+	.splice_read	= filemap_splice_read,
+	.splice_write   = iter_file_splice_write,
+};
+
+const struct inode_operations nilfs_file_inode_operations = {
+	.setattr	= nilfs_setattr,
+	.permission     = nilfs_permission,
+	.fiemap		= nilfs_fiemap,
+	.fileattr_get	= nilfs_fileattr_get,
+	.fileattr_set	= nilfs_fileattr_set,
+};
+
+/* end of file */
diff --git a/fs/nilfs2/gcinode.c b/fs/nilfs2/gcinode.c
new file mode 100644
index 0000000000..8beb273092
--- /dev/null
+++ b/fs/nilfs2/gcinode.c
@@ -0,0 +1,191 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Dummy inodes to buffer blocks for garbage collection
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Seiji Kihara, Amagai Yoshiji, and Ryusuke Konishi.
+ * Revised by Ryusuke Konishi.
+ *
+ */
+/*
+ * This file adds the cache of on-disk blocks to be moved in garbage
+ * collection.  The disk blocks are held with dummy inodes (called
+ * gcinodes), and this file provides lookup function of the dummy
+ * inodes and their buffer read function.
+ *
+ * Buffers and pages held by the dummy inodes will be released each
+ * time after they are copied to a new log.  Dirty blocks made on the
+ * current generation and the blocks to be moved by GC never overlap
+ * because the dirty blocks make a new generation; they rather must be
+ * written individually.
+ */
+
+#include <linux/buffer_head.h>
+#include <linux/mpage.h>
+#include <linux/hash.h>
+#include <linux/slab.h>
+#include <linux/swap.h>
+#include "nilfs.h"
+#include "btree.h"
+#include "btnode.h"
+#include "page.h"
+#include "mdt.h"
+#include "dat.h"
+#include "ifile.h"
+
+/*
+ * nilfs_gccache_submit_read_data() - add data buffer and submit read request
+ * @inode - gc inode
+ * @blkoff - dummy offset treated as the key for the page cache
+ * @pbn - physical block number of the block
+ * @vbn - virtual block number of the block, 0 for non-virtual block
+ * @out_bh - indirect pointer to a buffer_head struct to receive the results
+ *
+ * Description: nilfs_gccache_submit_read_data() registers the data buffer
+ * specified by @pbn to the GC pagecache with the key @blkoff.
+ * This function sets @vbn (@pbn if @vbn is zero) in b_blocknr of the buffer.
+ *
+ * Return Value: On success, 0 is returned. On Error, one of the following
+ * negative error code is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-ENOENT - The block specified with @pbn does not exist.
+ */
+int nilfs_gccache_submit_read_data(struct inode *inode, sector_t blkoff,
+				   sector_t pbn, __u64 vbn,
+				   struct buffer_head **out_bh)
+{
+	struct buffer_head *bh;
+	int err;
+
+	bh = nilfs_grab_buffer(inode, inode->i_mapping, blkoff, 0);
+	if (unlikely(!bh))
+		return -ENOMEM;
+
+	if (buffer_uptodate(bh))
+		goto out;
+
+	if (pbn == 0) {
+		struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
+
+		err = nilfs_dat_translate(nilfs->ns_dat, vbn, &pbn);
+		if (unlikely(err)) /* -EIO, -ENOMEM, -ENOENT */
+			goto failed;
+	}
+
+	lock_buffer(bh);
+	if (buffer_uptodate(bh)) {
+		unlock_buffer(bh);
+		goto out;
+	}
+
+	if (!buffer_mapped(bh)) {
+		bh->b_bdev = inode->i_sb->s_bdev;
+		set_buffer_mapped(bh);
+	}
+	bh->b_blocknr = pbn;
+	bh->b_end_io = end_buffer_read_sync;
+	get_bh(bh);
+	submit_bh(REQ_OP_READ, bh);
+	if (vbn)
+		bh->b_blocknr = vbn;
+ out:
+	err = 0;
+	*out_bh = bh;
+
+ failed:
+	unlock_page(bh->b_page);
+	put_page(bh->b_page);
+	if (unlikely(err))
+		brelse(bh);
+	return err;
+}
+
+/*
+ * nilfs_gccache_submit_read_node() - add node buffer and submit read request
+ * @inode - gc inode
+ * @pbn - physical block number for the block
+ * @vbn - virtual block number for the block
+ * @out_bh - indirect pointer to a buffer_head struct to receive the results
+ *
+ * Description: nilfs_gccache_submit_read_node() registers the node buffer
+ * specified by @vbn to the GC pagecache.  @pbn can be supplied by the
+ * caller to avoid translation of the disk block address.
+ *
+ * Return Value: On success, 0 is returned. On Error, one of the following
+ * negative error code is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ */
+int nilfs_gccache_submit_read_node(struct inode *inode, sector_t pbn,
+				   __u64 vbn, struct buffer_head **out_bh)
+{
+	struct inode *btnc_inode = NILFS_I(inode)->i_assoc_inode;
+	int ret;
+
+	ret = nilfs_btnode_submit_block(btnc_inode->i_mapping, vbn ? : pbn, pbn,
+					REQ_OP_READ, out_bh, &pbn);
+	if (ret == -EEXIST) /* internal code (cache hit) */
+		ret = 0;
+	return ret;
+}
+
+int nilfs_gccache_wait_and_mark_dirty(struct buffer_head *bh)
+{
+	wait_on_buffer(bh);
+	if (!buffer_uptodate(bh)) {
+		struct inode *inode = bh->b_folio->mapping->host;
+
+		nilfs_err(inode->i_sb,
+			  "I/O error reading %s block for GC (ino=%lu, vblocknr=%llu)",
+			  buffer_nilfs_node(bh) ? "node" : "data",
+			  inode->i_ino, (unsigned long long)bh->b_blocknr);
+		return -EIO;
+	}
+	if (buffer_dirty(bh))
+		return -EEXIST;
+
+	if (buffer_nilfs_node(bh) && nilfs_btree_broken_node_block(bh)) {
+		clear_buffer_uptodate(bh);
+		return -EIO;
+	}
+	mark_buffer_dirty(bh);
+	return 0;
+}
+
+int nilfs_init_gcinode(struct inode *inode)
+{
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+
+	inode->i_mode = S_IFREG;
+	mapping_set_gfp_mask(inode->i_mapping, GFP_NOFS);
+	inode->i_mapping->a_ops = &empty_aops;
+
+	ii->i_flags = 0;
+	nilfs_bmap_init_gc(ii->i_bmap);
+
+	return nilfs_attach_btree_node_cache(inode);
+}
+
+/**
+ * nilfs_remove_all_gcinodes() - remove all unprocessed gc inodes
+ */
+void nilfs_remove_all_gcinodes(struct the_nilfs *nilfs)
+{
+	struct list_head *head = &nilfs->ns_gc_inodes;
+	struct nilfs_inode_info *ii;
+
+	while (!list_empty(head)) {
+		ii = list_first_entry(head, struct nilfs_inode_info, i_dirty);
+		list_del_init(&ii->i_dirty);
+		truncate_inode_pages(&ii->vfs_inode.i_data, 0);
+		nilfs_btnode_cache_clear(ii->i_assoc_inode->i_mapping);
+		iput(&ii->vfs_inode);
+	}
+}
diff --git a/fs/nilfs2/ifile.c b/fs/nilfs2/ifile.c
new file mode 100644
index 0000000000..a8a4bc8490
--- /dev/null
+++ b/fs/nilfs2/ifile.c
@@ -0,0 +1,215 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NILFS inode file
+ *
+ * Copyright (C) 2006-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Amagai Yoshiji.
+ * Revised by Ryusuke Konishi.
+ *
+ */
+
+#include <linux/types.h>
+#include <linux/buffer_head.h>
+#include "nilfs.h"
+#include "mdt.h"
+#include "alloc.h"
+#include "ifile.h"
+
+/**
+ * struct nilfs_ifile_info - on-memory private data of ifile
+ * @mi: on-memory private data of metadata file
+ * @palloc_cache: persistent object allocator cache of ifile
+ */
+struct nilfs_ifile_info {
+	struct nilfs_mdt_info mi;
+	struct nilfs_palloc_cache palloc_cache;
+};
+
+static inline struct nilfs_ifile_info *NILFS_IFILE_I(struct inode *ifile)
+{
+	return (struct nilfs_ifile_info *)NILFS_MDT(ifile);
+}
+
+/**
+ * nilfs_ifile_create_inode - create a new disk inode
+ * @ifile: ifile inode
+ * @out_ino: pointer to a variable to store inode number
+ * @out_bh: buffer_head contains newly allocated disk inode
+ *
+ * Return Value: On success, 0 is returned and the newly allocated inode
+ * number is stored in the place pointed by @ino, and buffer_head pointer
+ * that contains newly allocated disk inode structure is stored in the
+ * place pointed by @out_bh
+ * On error, one of the following negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-ENOSPC - No inode left.
+ */
+int nilfs_ifile_create_inode(struct inode *ifile, ino_t *out_ino,
+			     struct buffer_head **out_bh)
+{
+	struct nilfs_palloc_req req;
+	int ret;
+
+	req.pr_entry_nr = 0;  /*
+			       * 0 says find free inode from beginning
+			       * of a group. dull code!!
+			       */
+	req.pr_entry_bh = NULL;
+
+	ret = nilfs_palloc_prepare_alloc_entry(ifile, &req);
+	if (!ret) {
+		ret = nilfs_palloc_get_entry_block(ifile, req.pr_entry_nr, 1,
+						   &req.pr_entry_bh);
+		if (ret < 0)
+			nilfs_palloc_abort_alloc_entry(ifile, &req);
+	}
+	if (ret < 0) {
+		brelse(req.pr_entry_bh);
+		return ret;
+	}
+	nilfs_palloc_commit_alloc_entry(ifile, &req);
+	mark_buffer_dirty(req.pr_entry_bh);
+	nilfs_mdt_mark_dirty(ifile);
+	*out_ino = (ino_t)req.pr_entry_nr;
+	*out_bh = req.pr_entry_bh;
+	return 0;
+}
+
+/**
+ * nilfs_ifile_delete_inode - delete a disk inode
+ * @ifile: ifile inode
+ * @ino: inode number
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-ENOENT - The inode number @ino have not been allocated.
+ */
+int nilfs_ifile_delete_inode(struct inode *ifile, ino_t ino)
+{
+	struct nilfs_palloc_req req = {
+		.pr_entry_nr = ino, .pr_entry_bh = NULL
+	};
+	struct nilfs_inode *raw_inode;
+	void *kaddr;
+	int ret;
+
+	ret = nilfs_palloc_prepare_free_entry(ifile, &req);
+	if (!ret) {
+		ret = nilfs_palloc_get_entry_block(ifile, req.pr_entry_nr, 0,
+						   &req.pr_entry_bh);
+		if (ret < 0)
+			nilfs_palloc_abort_free_entry(ifile, &req);
+	}
+	if (ret < 0) {
+		brelse(req.pr_entry_bh);
+		return ret;
+	}
+
+	kaddr = kmap_atomic(req.pr_entry_bh->b_page);
+	raw_inode = nilfs_palloc_block_get_entry(ifile, req.pr_entry_nr,
+						 req.pr_entry_bh, kaddr);
+	raw_inode->i_flags = 0;
+	kunmap_atomic(kaddr);
+
+	mark_buffer_dirty(req.pr_entry_bh);
+	brelse(req.pr_entry_bh);
+
+	nilfs_palloc_commit_free_entry(ifile, &req);
+
+	return 0;
+}
+
+int nilfs_ifile_get_inode_block(struct inode *ifile, ino_t ino,
+				struct buffer_head **out_bh)
+{
+	struct super_block *sb = ifile->i_sb;
+	int err;
+
+	if (unlikely(!NILFS_VALID_INODE(sb, ino))) {
+		nilfs_error(sb, "bad inode number: %lu", (unsigned long)ino);
+		return -EINVAL;
+	}
+
+	err = nilfs_palloc_get_entry_block(ifile, ino, 0, out_bh);
+	if (unlikely(err))
+		nilfs_warn(sb, "error %d reading inode: ino=%lu",
+			   err, (unsigned long)ino);
+	return err;
+}
+
+/**
+ * nilfs_ifile_count_free_inodes - calculate free inodes count
+ * @ifile: ifile inode
+ * @nmaxinodes: current maximum of available inodes count [out]
+ * @nfreeinodes: free inodes count [out]
+ */
+int nilfs_ifile_count_free_inodes(struct inode *ifile,
+				    u64 *nmaxinodes, u64 *nfreeinodes)
+{
+	u64 nused;
+	int err;
+
+	*nmaxinodes = 0;
+	*nfreeinodes = 0;
+
+	nused = atomic64_read(&NILFS_I(ifile)->i_root->inodes_count);
+	err = nilfs_palloc_count_max_entries(ifile, nused, nmaxinodes);
+	if (likely(!err))
+		*nfreeinodes = *nmaxinodes - nused;
+	return err;
+}
+
+/**
+ * nilfs_ifile_read - read or get ifile inode
+ * @sb: super block instance
+ * @root: root object
+ * @inode_size: size of an inode
+ * @raw_inode: on-disk ifile inode
+ * @inodep: buffer to store the inode
+ */
+int nilfs_ifile_read(struct super_block *sb, struct nilfs_root *root,
+		     size_t inode_size, struct nilfs_inode *raw_inode,
+		     struct inode **inodep)
+{
+	struct inode *ifile;
+	int err;
+
+	ifile = nilfs_iget_locked(sb, root, NILFS_IFILE_INO);
+	if (unlikely(!ifile))
+		return -ENOMEM;
+	if (!(ifile->i_state & I_NEW))
+		goto out;
+
+	err = nilfs_mdt_init(ifile, NILFS_MDT_GFP,
+			     sizeof(struct nilfs_ifile_info));
+	if (err)
+		goto failed;
+
+	err = nilfs_palloc_init_blockgroup(ifile, inode_size);
+	if (err)
+		goto failed;
+
+	nilfs_palloc_setup_cache(ifile, &NILFS_IFILE_I(ifile)->palloc_cache);
+
+	err = nilfs_read_inode_common(ifile, raw_inode);
+	if (err)
+		goto failed;
+
+	unlock_new_inode(ifile);
+ out:
+	*inodep = ifile;
+	return 0;
+ failed:
+	iget_failed(ifile);
+	return err;
+}
diff --git a/fs/nilfs2/ifile.h b/fs/nilfs2/ifile.h
new file mode 100644
index 0000000000..35c5273f48
--- /dev/null
+++ b/fs/nilfs2/ifile.h
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * NILFS inode file
+ *
+ * Copyright (C) 2006-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Amagai Yoshiji.
+ * Revised by Ryusuke Konishi.
+ *
+ */
+
+#ifndef _NILFS_IFILE_H
+#define _NILFS_IFILE_H
+
+#include <linux/fs.h>
+#include <linux/buffer_head.h>
+#include "mdt.h"
+#include "alloc.h"
+
+
+static inline struct nilfs_inode *
+nilfs_ifile_map_inode(struct inode *ifile, ino_t ino, struct buffer_head *ibh)
+{
+	void *kaddr = kmap(ibh->b_page);
+
+	return nilfs_palloc_block_get_entry(ifile, ino, ibh, kaddr);
+}
+
+static inline void nilfs_ifile_unmap_inode(struct inode *ifile, ino_t ino,
+					   struct buffer_head *ibh)
+{
+	kunmap(ibh->b_page);
+}
+
+int nilfs_ifile_create_inode(struct inode *, ino_t *, struct buffer_head **);
+int nilfs_ifile_delete_inode(struct inode *, ino_t);
+int nilfs_ifile_get_inode_block(struct inode *, ino_t, struct buffer_head **);
+
+int nilfs_ifile_count_free_inodes(struct inode *, u64 *, u64 *);
+
+int nilfs_ifile_read(struct super_block *sb, struct nilfs_root *root,
+		     size_t inode_size, struct nilfs_inode *raw_inode,
+		     struct inode **inodep);
+
+#endif	/* _NILFS_IFILE_H */
diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
new file mode 100644
index 0000000000..1a8bd59934
--- /dev/null
+++ b/fs/nilfs2/inode.c
@@ -0,0 +1,1292 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NILFS inode operations.
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Ryusuke Konishi.
+ *
+ */
+
+#include <linux/buffer_head.h>
+#include <linux/gfp.h>
+#include <linux/mpage.h>
+#include <linux/pagemap.h>
+#include <linux/writeback.h>
+#include <linux/uio.h>
+#include <linux/fiemap.h>
+#include "nilfs.h"
+#include "btnode.h"
+#include "segment.h"
+#include "page.h"
+#include "mdt.h"
+#include "cpfile.h"
+#include "ifile.h"
+
+/**
+ * struct nilfs_iget_args - arguments used during comparison between inodes
+ * @ino: inode number
+ * @cno: checkpoint number
+ * @root: pointer on NILFS root object (mounted checkpoint)
+ * @for_gc: inode for GC flag
+ * @for_btnc: inode for B-tree node cache flag
+ * @for_shadow: inode for shadowed page cache flag
+ */
+struct nilfs_iget_args {
+	u64 ino;
+	__u64 cno;
+	struct nilfs_root *root;
+	bool for_gc;
+	bool for_btnc;
+	bool for_shadow;
+};
+
+static int nilfs_iget_test(struct inode *inode, void *opaque);
+
+void nilfs_inode_add_blocks(struct inode *inode, int n)
+{
+	struct nilfs_root *root = NILFS_I(inode)->i_root;
+
+	inode_add_bytes(inode, i_blocksize(inode) * n);
+	if (root)
+		atomic64_add(n, &root->blocks_count);
+}
+
+void nilfs_inode_sub_blocks(struct inode *inode, int n)
+{
+	struct nilfs_root *root = NILFS_I(inode)->i_root;
+
+	inode_sub_bytes(inode, i_blocksize(inode) * n);
+	if (root)
+		atomic64_sub(n, &root->blocks_count);
+}
+
+/**
+ * nilfs_get_block() - get a file block on the filesystem (callback function)
+ * @inode: inode struct of the target file
+ * @blkoff: file block number
+ * @bh_result: buffer head to be mapped on
+ * @create: indicate whether allocating the block or not when it has not
+ *      been allocated yet.
+ *
+ * This function does not issue actual read request of the specified data
+ * block. It is done by VFS.
+ */
+int nilfs_get_block(struct inode *inode, sector_t blkoff,
+		    struct buffer_head *bh_result, int create)
+{
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+	struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
+	__u64 blknum = 0;
+	int err = 0, ret;
+	unsigned int maxblocks = bh_result->b_size >> inode->i_blkbits;
+
+	down_read(&NILFS_MDT(nilfs->ns_dat)->mi_sem);
+	ret = nilfs_bmap_lookup_contig(ii->i_bmap, blkoff, &blknum, maxblocks);
+	up_read(&NILFS_MDT(nilfs->ns_dat)->mi_sem);
+	if (ret >= 0) {	/* found */
+		map_bh(bh_result, inode->i_sb, blknum);
+		if (ret > 0)
+			bh_result->b_size = (ret << inode->i_blkbits);
+		goto out;
+	}
+	/* data block was not found */
+	if (ret == -ENOENT && create) {
+		struct nilfs_transaction_info ti;
+
+		bh_result->b_blocknr = 0;
+		err = nilfs_transaction_begin(inode->i_sb, &ti, 1);
+		if (unlikely(err))
+			goto out;
+		err = nilfs_bmap_insert(ii->i_bmap, blkoff,
+					(unsigned long)bh_result);
+		if (unlikely(err != 0)) {
+			if (err == -EEXIST) {
+				/*
+				 * The get_block() function could be called
+				 * from multiple callers for an inode.
+				 * However, the page having this block must
+				 * be locked in this case.
+				 */
+				nilfs_warn(inode->i_sb,
+					   "%s (ino=%lu): a race condition while inserting a data block at offset=%llu",
+					   __func__, inode->i_ino,
+					   (unsigned long long)blkoff);
+				err = 0;
+			}
+			nilfs_transaction_abort(inode->i_sb);
+			goto out;
+		}
+		nilfs_mark_inode_dirty_sync(inode);
+		nilfs_transaction_commit(inode->i_sb); /* never fails */
+		/* Error handling should be detailed */
+		set_buffer_new(bh_result);
+		set_buffer_delay(bh_result);
+		map_bh(bh_result, inode->i_sb, 0);
+		/* Disk block number must be changed to proper value */
+
+	} else if (ret == -ENOENT) {
+		/*
+		 * not found is not error (e.g. hole); must return without
+		 * the mapped state flag.
+		 */
+		;
+	} else {
+		err = ret;
+	}
+
+ out:
+	return err;
+}
+
+/**
+ * nilfs_read_folio() - implement read_folio() method of nilfs_aops {}
+ * address_space_operations.
+ * @file: file struct of the file to be read
+ * @folio: the folio to be read
+ */
+static int nilfs_read_folio(struct file *file, struct folio *folio)
+{
+	return mpage_read_folio(folio, nilfs_get_block);
+}
+
+static void nilfs_readahead(struct readahead_control *rac)
+{
+	mpage_readahead(rac, nilfs_get_block);
+}
+
+static int nilfs_writepages(struct address_space *mapping,
+			    struct writeback_control *wbc)
+{
+	struct inode *inode = mapping->host;
+	int err = 0;
+
+	if (sb_rdonly(inode->i_sb)) {
+		nilfs_clear_dirty_pages(mapping, false);
+		return -EROFS;
+	}
+
+	if (wbc->sync_mode == WB_SYNC_ALL)
+		err = nilfs_construct_dsync_segment(inode->i_sb, inode,
+						    wbc->range_start,
+						    wbc->range_end);
+	return err;
+}
+
+static int nilfs_writepage(struct page *page, struct writeback_control *wbc)
+{
+	struct inode *inode = page->mapping->host;
+	int err;
+
+	if (sb_rdonly(inode->i_sb)) {
+		/*
+		 * It means that filesystem was remounted in read-only
+		 * mode because of error or metadata corruption. But we
+		 * have dirty pages that try to be flushed in background.
+		 * So, here we simply discard this dirty page.
+		 */
+		nilfs_clear_dirty_page(page, false);
+		unlock_page(page);
+		return -EROFS;
+	}
+
+	redirty_page_for_writepage(wbc, page);
+	unlock_page(page);
+
+	if (wbc->sync_mode == WB_SYNC_ALL) {
+		err = nilfs_construct_segment(inode->i_sb);
+		if (unlikely(err))
+			return err;
+	} else if (wbc->for_reclaim)
+		nilfs_flush_segment(inode->i_sb, inode->i_ino);
+
+	return 0;
+}
+
+static bool nilfs_dirty_folio(struct address_space *mapping,
+		struct folio *folio)
+{
+	struct inode *inode = mapping->host;
+	struct buffer_head *head;
+	unsigned int nr_dirty = 0;
+	bool ret = filemap_dirty_folio(mapping, folio);
+
+	/*
+	 * The page may not be locked, eg if called from try_to_unmap_one()
+	 */
+	spin_lock(&mapping->private_lock);
+	head = folio_buffers(folio);
+	if (head) {
+		struct buffer_head *bh = head;
+
+		do {
+			/* Do not mark hole blocks dirty */
+			if (buffer_dirty(bh) || !buffer_mapped(bh))
+				continue;
+
+			set_buffer_dirty(bh);
+			nr_dirty++;
+		} while (bh = bh->b_this_page, bh != head);
+	} else if (ret) {
+		nr_dirty = 1 << (folio_shift(folio) - inode->i_blkbits);
+	}
+	spin_unlock(&mapping->private_lock);
+
+	if (nr_dirty)
+		nilfs_set_file_dirty(inode, nr_dirty);
+	return ret;
+}
+
+void nilfs_write_failed(struct address_space *mapping, loff_t to)
+{
+	struct inode *inode = mapping->host;
+
+	if (to > inode->i_size) {
+		truncate_pagecache(inode, inode->i_size);
+		nilfs_truncate(inode);
+	}
+}
+
+static int nilfs_write_begin(struct file *file, struct address_space *mapping,
+			     loff_t pos, unsigned len,
+			     struct page **pagep, void **fsdata)
+
+{
+	struct inode *inode = mapping->host;
+	int err = nilfs_transaction_begin(inode->i_sb, NULL, 1);
+
+	if (unlikely(err))
+		return err;
+
+	err = block_write_begin(mapping, pos, len, pagep, nilfs_get_block);
+	if (unlikely(err)) {
+		nilfs_write_failed(mapping, pos + len);
+		nilfs_transaction_abort(inode->i_sb);
+	}
+	return err;
+}
+
+static int nilfs_write_end(struct file *file, struct address_space *mapping,
+			   loff_t pos, unsigned len, unsigned copied,
+			   struct page *page, void *fsdata)
+{
+	struct inode *inode = mapping->host;
+	unsigned int start = pos & (PAGE_SIZE - 1);
+	unsigned int nr_dirty;
+	int err;
+
+	nr_dirty = nilfs_page_count_clean_buffers(page, start,
+						  start + copied);
+	copied = generic_write_end(file, mapping, pos, len, copied, page,
+				   fsdata);
+	nilfs_set_file_dirty(inode, nr_dirty);
+	err = nilfs_transaction_commit(inode->i_sb);
+	return err ? : copied;
+}
+
+static ssize_t
+nilfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
+{
+	struct inode *inode = file_inode(iocb->ki_filp);
+
+	if (iov_iter_rw(iter) == WRITE)
+		return 0;
+
+	/* Needs synchronization with the cleaner */
+	return blockdev_direct_IO(iocb, inode, iter, nilfs_get_block);
+}
+
+const struct address_space_operations nilfs_aops = {
+	.writepage		= nilfs_writepage,
+	.read_folio		= nilfs_read_folio,
+	.writepages		= nilfs_writepages,
+	.dirty_folio		= nilfs_dirty_folio,
+	.readahead		= nilfs_readahead,
+	.write_begin		= nilfs_write_begin,
+	.write_end		= nilfs_write_end,
+	.invalidate_folio	= block_invalidate_folio,
+	.direct_IO		= nilfs_direct_IO,
+	.is_partially_uptodate  = block_is_partially_uptodate,
+};
+
+static int nilfs_insert_inode_locked(struct inode *inode,
+				     struct nilfs_root *root,
+				     unsigned long ino)
+{
+	struct nilfs_iget_args args = {
+		.ino = ino, .root = root, .cno = 0, .for_gc = false,
+		.for_btnc = false, .for_shadow = false
+	};
+
+	return insert_inode_locked4(inode, ino, nilfs_iget_test, &args);
+}
+
+struct inode *nilfs_new_inode(struct inode *dir, umode_t mode)
+{
+	struct super_block *sb = dir->i_sb;
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct inode *inode;
+	struct nilfs_inode_info *ii;
+	struct nilfs_root *root;
+	struct buffer_head *bh;
+	int err = -ENOMEM;
+	ino_t ino;
+
+	inode = new_inode(sb);
+	if (unlikely(!inode))
+		goto failed;
+
+	mapping_set_gfp_mask(inode->i_mapping,
+			   mapping_gfp_constraint(inode->i_mapping, ~__GFP_FS));
+
+	root = NILFS_I(dir)->i_root;
+	ii = NILFS_I(inode);
+	ii->i_state = BIT(NILFS_I_NEW);
+	ii->i_root = root;
+
+	err = nilfs_ifile_create_inode(root->ifile, &ino, &bh);
+	if (unlikely(err))
+		goto failed_ifile_create_inode;
+	/* reference count of i_bh inherits from nilfs_mdt_read_block() */
+
+	if (unlikely(ino < NILFS_USER_INO)) {
+		nilfs_warn(sb,
+			   "inode bitmap is inconsistent for reserved inodes");
+		do {
+			brelse(bh);
+			err = nilfs_ifile_create_inode(root->ifile, &ino, &bh);
+			if (unlikely(err))
+				goto failed_ifile_create_inode;
+		} while (ino < NILFS_USER_INO);
+
+		nilfs_info(sb, "repaired inode bitmap for reserved inodes");
+	}
+	ii->i_bh = bh;
+
+	atomic64_inc(&root->inodes_count);
+	inode_init_owner(&nop_mnt_idmap, inode, dir, mode);
+	inode->i_ino = ino;
+	inode->i_mtime = inode->i_atime = inode_set_ctime_current(inode);
+
+	if (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)) {
+		err = nilfs_bmap_read(ii->i_bmap, NULL);
+		if (err < 0)
+			goto failed_after_creation;
+
+		set_bit(NILFS_I_BMAP, &ii->i_state);
+		/* No lock is needed; iget() ensures it. */
+	}
+
+	ii->i_flags = nilfs_mask_flags(
+		mode, NILFS_I(dir)->i_flags & NILFS_FL_INHERITED);
+
+	/* ii->i_file_acl = 0; */
+	/* ii->i_dir_acl = 0; */
+	ii->i_dir_start_lookup = 0;
+	nilfs_set_inode_flags(inode);
+	spin_lock(&nilfs->ns_next_gen_lock);
+	inode->i_generation = nilfs->ns_next_generation++;
+	spin_unlock(&nilfs->ns_next_gen_lock);
+	if (nilfs_insert_inode_locked(inode, root, ino) < 0) {
+		err = -EIO;
+		goto failed_after_creation;
+	}
+
+	err = nilfs_init_acl(inode, dir);
+	if (unlikely(err))
+		/*
+		 * Never occur.  When supporting nilfs_init_acl(),
+		 * proper cancellation of above jobs should be considered.
+		 */
+		goto failed_after_creation;
+
+	return inode;
+
+ failed_after_creation:
+	clear_nlink(inode);
+	if (inode->i_state & I_NEW)
+		unlock_new_inode(inode);
+	iput(inode);  /*
+		       * raw_inode will be deleted through
+		       * nilfs_evict_inode().
+		       */
+	goto failed;
+
+ failed_ifile_create_inode:
+	make_bad_inode(inode);
+	iput(inode);
+ failed:
+	return ERR_PTR(err);
+}
+
+void nilfs_set_inode_flags(struct inode *inode)
+{
+	unsigned int flags = NILFS_I(inode)->i_flags;
+	unsigned int new_fl = 0;
+
+	if (flags & FS_SYNC_FL)
+		new_fl |= S_SYNC;
+	if (flags & FS_APPEND_FL)
+		new_fl |= S_APPEND;
+	if (flags & FS_IMMUTABLE_FL)
+		new_fl |= S_IMMUTABLE;
+	if (flags & FS_NOATIME_FL)
+		new_fl |= S_NOATIME;
+	if (flags & FS_DIRSYNC_FL)
+		new_fl |= S_DIRSYNC;
+	inode_set_flags(inode, new_fl, S_SYNC | S_APPEND | S_IMMUTABLE |
+			S_NOATIME | S_DIRSYNC);
+}
+
+int nilfs_read_inode_common(struct inode *inode,
+			    struct nilfs_inode *raw_inode)
+{
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+	int err;
+
+	inode->i_mode = le16_to_cpu(raw_inode->i_mode);
+	i_uid_write(inode, le32_to_cpu(raw_inode->i_uid));
+	i_gid_write(inode, le32_to_cpu(raw_inode->i_gid));
+	set_nlink(inode, le16_to_cpu(raw_inode->i_links_count));
+	inode->i_size = le64_to_cpu(raw_inode->i_size);
+	inode->i_atime.tv_sec = le64_to_cpu(raw_inode->i_mtime);
+	inode_set_ctime(inode, le64_to_cpu(raw_inode->i_ctime),
+			le32_to_cpu(raw_inode->i_ctime_nsec));
+	inode->i_mtime.tv_sec = le64_to_cpu(raw_inode->i_mtime);
+	inode->i_atime.tv_nsec = le32_to_cpu(raw_inode->i_mtime_nsec);
+	inode->i_mtime.tv_nsec = le32_to_cpu(raw_inode->i_mtime_nsec);
+	if (nilfs_is_metadata_file_inode(inode) && !S_ISREG(inode->i_mode))
+		return -EIO; /* this inode is for metadata and corrupted */
+	if (inode->i_nlink == 0)
+		return -ESTALE; /* this inode is deleted */
+
+	inode->i_blocks = le64_to_cpu(raw_inode->i_blocks);
+	ii->i_flags = le32_to_cpu(raw_inode->i_flags);
+#if 0
+	ii->i_file_acl = le32_to_cpu(raw_inode->i_file_acl);
+	ii->i_dir_acl = S_ISREG(inode->i_mode) ?
+		0 : le32_to_cpu(raw_inode->i_dir_acl);
+#endif
+	ii->i_dir_start_lookup = 0;
+	inode->i_generation = le32_to_cpu(raw_inode->i_generation);
+
+	if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
+	    S_ISLNK(inode->i_mode)) {
+		err = nilfs_bmap_read(ii->i_bmap, raw_inode);
+		if (err < 0)
+			return err;
+		set_bit(NILFS_I_BMAP, &ii->i_state);
+		/* No lock is needed; iget() ensures it. */
+	}
+	return 0;
+}
+
+static int __nilfs_read_inode(struct super_block *sb,
+			      struct nilfs_root *root, unsigned long ino,
+			      struct inode *inode)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct buffer_head *bh;
+	struct nilfs_inode *raw_inode;
+	int err;
+
+	down_read(&NILFS_MDT(nilfs->ns_dat)->mi_sem);
+	err = nilfs_ifile_get_inode_block(root->ifile, ino, &bh);
+	if (unlikely(err))
+		goto bad_inode;
+
+	raw_inode = nilfs_ifile_map_inode(root->ifile, ino, bh);
+
+	err = nilfs_read_inode_common(inode, raw_inode);
+	if (err)
+		goto failed_unmap;
+
+	if (S_ISREG(inode->i_mode)) {
+		inode->i_op = &nilfs_file_inode_operations;
+		inode->i_fop = &nilfs_file_operations;
+		inode->i_mapping->a_ops = &nilfs_aops;
+	} else if (S_ISDIR(inode->i_mode)) {
+		inode->i_op = &nilfs_dir_inode_operations;
+		inode->i_fop = &nilfs_dir_operations;
+		inode->i_mapping->a_ops = &nilfs_aops;
+	} else if (S_ISLNK(inode->i_mode)) {
+		inode->i_op = &nilfs_symlink_inode_operations;
+		inode_nohighmem(inode);
+		inode->i_mapping->a_ops = &nilfs_aops;
+	} else {
+		inode->i_op = &nilfs_special_inode_operations;
+		init_special_inode(
+			inode, inode->i_mode,
+			huge_decode_dev(le64_to_cpu(raw_inode->i_device_code)));
+	}
+	nilfs_ifile_unmap_inode(root->ifile, ino, bh);
+	brelse(bh);
+	up_read(&NILFS_MDT(nilfs->ns_dat)->mi_sem);
+	nilfs_set_inode_flags(inode);
+	mapping_set_gfp_mask(inode->i_mapping,
+			   mapping_gfp_constraint(inode->i_mapping, ~__GFP_FS));
+	return 0;
+
+ failed_unmap:
+	nilfs_ifile_unmap_inode(root->ifile, ino, bh);
+	brelse(bh);
+
+ bad_inode:
+	up_read(&NILFS_MDT(nilfs->ns_dat)->mi_sem);
+	return err;
+}
+
+static int nilfs_iget_test(struct inode *inode, void *opaque)
+{
+	struct nilfs_iget_args *args = opaque;
+	struct nilfs_inode_info *ii;
+
+	if (args->ino != inode->i_ino || args->root != NILFS_I(inode)->i_root)
+		return 0;
+
+	ii = NILFS_I(inode);
+	if (test_bit(NILFS_I_BTNC, &ii->i_state)) {
+		if (!args->for_btnc)
+			return 0;
+	} else if (args->for_btnc) {
+		return 0;
+	}
+	if (test_bit(NILFS_I_SHADOW, &ii->i_state)) {
+		if (!args->for_shadow)
+			return 0;
+	} else if (args->for_shadow) {
+		return 0;
+	}
+
+	if (!test_bit(NILFS_I_GCINODE, &ii->i_state))
+		return !args->for_gc;
+
+	return args->for_gc && args->cno == ii->i_cno;
+}
+
+static int nilfs_iget_set(struct inode *inode, void *opaque)
+{
+	struct nilfs_iget_args *args = opaque;
+
+	inode->i_ino = args->ino;
+	NILFS_I(inode)->i_cno = args->cno;
+	NILFS_I(inode)->i_root = args->root;
+	if (args->root && args->ino == NILFS_ROOT_INO)
+		nilfs_get_root(args->root);
+
+	if (args->for_gc)
+		NILFS_I(inode)->i_state = BIT(NILFS_I_GCINODE);
+	if (args->for_btnc)
+		NILFS_I(inode)->i_state |= BIT(NILFS_I_BTNC);
+	if (args->for_shadow)
+		NILFS_I(inode)->i_state |= BIT(NILFS_I_SHADOW);
+	return 0;
+}
+
+struct inode *nilfs_ilookup(struct super_block *sb, struct nilfs_root *root,
+			    unsigned long ino)
+{
+	struct nilfs_iget_args args = {
+		.ino = ino, .root = root, .cno = 0, .for_gc = false,
+		.for_btnc = false, .for_shadow = false
+	};
+
+	return ilookup5(sb, ino, nilfs_iget_test, &args);
+}
+
+struct inode *nilfs_iget_locked(struct super_block *sb, struct nilfs_root *root,
+				unsigned long ino)
+{
+	struct nilfs_iget_args args = {
+		.ino = ino, .root = root, .cno = 0, .for_gc = false,
+		.for_btnc = false, .for_shadow = false
+	};
+
+	return iget5_locked(sb, ino, nilfs_iget_test, nilfs_iget_set, &args);
+}
+
+struct inode *nilfs_iget(struct super_block *sb, struct nilfs_root *root,
+			 unsigned long ino)
+{
+	struct inode *inode;
+	int err;
+
+	inode = nilfs_iget_locked(sb, root, ino);
+	if (unlikely(!inode))
+		return ERR_PTR(-ENOMEM);
+	if (!(inode->i_state & I_NEW))
+		return inode;
+
+	err = __nilfs_read_inode(sb, root, ino, inode);
+	if (unlikely(err)) {
+		iget_failed(inode);
+		return ERR_PTR(err);
+	}
+	unlock_new_inode(inode);
+	return inode;
+}
+
+struct inode *nilfs_iget_for_gc(struct super_block *sb, unsigned long ino,
+				__u64 cno)
+{
+	struct nilfs_iget_args args = {
+		.ino = ino, .root = NULL, .cno = cno, .for_gc = true,
+		.for_btnc = false, .for_shadow = false
+	};
+	struct inode *inode;
+	int err;
+
+	inode = iget5_locked(sb, ino, nilfs_iget_test, nilfs_iget_set, &args);
+	if (unlikely(!inode))
+		return ERR_PTR(-ENOMEM);
+	if (!(inode->i_state & I_NEW))
+		return inode;
+
+	err = nilfs_init_gcinode(inode);
+	if (unlikely(err)) {
+		iget_failed(inode);
+		return ERR_PTR(err);
+	}
+	unlock_new_inode(inode);
+	return inode;
+}
+
+/**
+ * nilfs_attach_btree_node_cache - attach a B-tree node cache to the inode
+ * @inode: inode object
+ *
+ * nilfs_attach_btree_node_cache() attaches a B-tree node cache to @inode,
+ * or does nothing if the inode already has it.  This function allocates
+ * an additional inode to maintain page cache of B-tree nodes one-on-one.
+ *
+ * Return Value: On success, 0 is returned. On errors, one of the following
+ * negative error code is returned.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ */
+int nilfs_attach_btree_node_cache(struct inode *inode)
+{
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+	struct inode *btnc_inode;
+	struct nilfs_iget_args args;
+
+	if (ii->i_assoc_inode)
+		return 0;
+
+	args.ino = inode->i_ino;
+	args.root = ii->i_root;
+	args.cno = ii->i_cno;
+	args.for_gc = test_bit(NILFS_I_GCINODE, &ii->i_state) != 0;
+	args.for_btnc = true;
+	args.for_shadow = test_bit(NILFS_I_SHADOW, &ii->i_state) != 0;
+
+	btnc_inode = iget5_locked(inode->i_sb, inode->i_ino, nilfs_iget_test,
+				  nilfs_iget_set, &args);
+	if (unlikely(!btnc_inode))
+		return -ENOMEM;
+	if (btnc_inode->i_state & I_NEW) {
+		nilfs_init_btnc_inode(btnc_inode);
+		unlock_new_inode(btnc_inode);
+	}
+	NILFS_I(btnc_inode)->i_assoc_inode = inode;
+	NILFS_I(btnc_inode)->i_bmap = ii->i_bmap;
+	ii->i_assoc_inode = btnc_inode;
+
+	return 0;
+}
+
+/**
+ * nilfs_detach_btree_node_cache - detach the B-tree node cache from the inode
+ * @inode: inode object
+ *
+ * nilfs_detach_btree_node_cache() detaches the B-tree node cache and its
+ * holder inode bound to @inode, or does nothing if @inode doesn't have it.
+ */
+void nilfs_detach_btree_node_cache(struct inode *inode)
+{
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+	struct inode *btnc_inode = ii->i_assoc_inode;
+
+	if (btnc_inode) {
+		NILFS_I(btnc_inode)->i_assoc_inode = NULL;
+		ii->i_assoc_inode = NULL;
+		iput(btnc_inode);
+	}
+}
+
+/**
+ * nilfs_iget_for_shadow - obtain inode for shadow mapping
+ * @inode: inode object that uses shadow mapping
+ *
+ * nilfs_iget_for_shadow() allocates a pair of inodes that holds page
+ * caches for shadow mapping.  The page cache for data pages is set up
+ * in one inode and the one for b-tree node pages is set up in the
+ * other inode, which is attached to the former inode.
+ *
+ * Return Value: On success, a pointer to the inode for data pages is
+ * returned. On errors, one of the following negative error code is returned
+ * in a pointer type.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ */
+struct inode *nilfs_iget_for_shadow(struct inode *inode)
+{
+	struct nilfs_iget_args args = {
+		.ino = inode->i_ino, .root = NULL, .cno = 0, .for_gc = false,
+		.for_btnc = false, .for_shadow = true
+	};
+	struct inode *s_inode;
+	int err;
+
+	s_inode = iget5_locked(inode->i_sb, inode->i_ino, nilfs_iget_test,
+			       nilfs_iget_set, &args);
+	if (unlikely(!s_inode))
+		return ERR_PTR(-ENOMEM);
+	if (!(s_inode->i_state & I_NEW))
+		return inode;
+
+	NILFS_I(s_inode)->i_flags = 0;
+	memset(NILFS_I(s_inode)->i_bmap, 0, sizeof(struct nilfs_bmap));
+	mapping_set_gfp_mask(s_inode->i_mapping, GFP_NOFS);
+
+	err = nilfs_attach_btree_node_cache(s_inode);
+	if (unlikely(err)) {
+		iget_failed(s_inode);
+		return ERR_PTR(err);
+	}
+	unlock_new_inode(s_inode);
+	return s_inode;
+}
+
+void nilfs_write_inode_common(struct inode *inode,
+			      struct nilfs_inode *raw_inode, int has_bmap)
+{
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+
+	raw_inode->i_mode = cpu_to_le16(inode->i_mode);
+	raw_inode->i_uid = cpu_to_le32(i_uid_read(inode));
+	raw_inode->i_gid = cpu_to_le32(i_gid_read(inode));
+	raw_inode->i_links_count = cpu_to_le16(inode->i_nlink);
+	raw_inode->i_size = cpu_to_le64(inode->i_size);
+	raw_inode->i_ctime = cpu_to_le64(inode_get_ctime(inode).tv_sec);
+	raw_inode->i_mtime = cpu_to_le64(inode->i_mtime.tv_sec);
+	raw_inode->i_ctime_nsec = cpu_to_le32(inode_get_ctime(inode).tv_nsec);
+	raw_inode->i_mtime_nsec = cpu_to_le32(inode->i_mtime.tv_nsec);
+	raw_inode->i_blocks = cpu_to_le64(inode->i_blocks);
+
+	raw_inode->i_flags = cpu_to_le32(ii->i_flags);
+	raw_inode->i_generation = cpu_to_le32(inode->i_generation);
+
+	if (NILFS_ROOT_METADATA_FILE(inode->i_ino)) {
+		struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
+
+		/* zero-fill unused portion in the case of super root block */
+		raw_inode->i_xattr = 0;
+		raw_inode->i_pad = 0;
+		memset((void *)raw_inode + sizeof(*raw_inode), 0,
+		       nilfs->ns_inode_size - sizeof(*raw_inode));
+	}
+
+	if (has_bmap)
+		nilfs_bmap_write(ii->i_bmap, raw_inode);
+	else if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode))
+		raw_inode->i_device_code =
+			cpu_to_le64(huge_encode_dev(inode->i_rdev));
+	/*
+	 * When extending inode, nilfs->ns_inode_size should be checked
+	 * for substitutions of appended fields.
+	 */
+}
+
+void nilfs_update_inode(struct inode *inode, struct buffer_head *ibh, int flags)
+{
+	ino_t ino = inode->i_ino;
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+	struct inode *ifile = ii->i_root->ifile;
+	struct nilfs_inode *raw_inode;
+
+	raw_inode = nilfs_ifile_map_inode(ifile, ino, ibh);
+
+	if (test_and_clear_bit(NILFS_I_NEW, &ii->i_state))
+		memset(raw_inode, 0, NILFS_MDT(ifile)->mi_entry_size);
+	if (flags & I_DIRTY_DATASYNC)
+		set_bit(NILFS_I_INODE_SYNC, &ii->i_state);
+
+	nilfs_write_inode_common(inode, raw_inode, 0);
+		/*
+		 * XXX: call with has_bmap = 0 is a workaround to avoid
+		 * deadlock of bmap.  This delays update of i_bmap to just
+		 * before writing.
+		 */
+
+	nilfs_ifile_unmap_inode(ifile, ino, ibh);
+}
+
+#define NILFS_MAX_TRUNCATE_BLOCKS	16384  /* 64MB for 4KB block */
+
+static void nilfs_truncate_bmap(struct nilfs_inode_info *ii,
+				unsigned long from)
+{
+	__u64 b;
+	int ret;
+
+	if (!test_bit(NILFS_I_BMAP, &ii->i_state))
+		return;
+repeat:
+	ret = nilfs_bmap_last_key(ii->i_bmap, &b);
+	if (ret == -ENOENT)
+		return;
+	else if (ret < 0)
+		goto failed;
+
+	if (b < from)
+		return;
+
+	b -= min_t(__u64, NILFS_MAX_TRUNCATE_BLOCKS, b - from);
+	ret = nilfs_bmap_truncate(ii->i_bmap, b);
+	nilfs_relax_pressure_in_lock(ii->vfs_inode.i_sb);
+	if (!ret || (ret == -ENOMEM &&
+		     nilfs_bmap_truncate(ii->i_bmap, b) == 0))
+		goto repeat;
+
+failed:
+	nilfs_warn(ii->vfs_inode.i_sb, "error %d truncating bmap (ino=%lu)",
+		   ret, ii->vfs_inode.i_ino);
+}
+
+void nilfs_truncate(struct inode *inode)
+{
+	unsigned long blkoff;
+	unsigned int blocksize;
+	struct nilfs_transaction_info ti;
+	struct super_block *sb = inode->i_sb;
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+
+	if (!test_bit(NILFS_I_BMAP, &ii->i_state))
+		return;
+	if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
+		return;
+
+	blocksize = sb->s_blocksize;
+	blkoff = (inode->i_size + blocksize - 1) >> sb->s_blocksize_bits;
+	nilfs_transaction_begin(sb, &ti, 0); /* never fails */
+
+	block_truncate_page(inode->i_mapping, inode->i_size, nilfs_get_block);
+
+	nilfs_truncate_bmap(ii, blkoff);
+
+	inode->i_mtime = inode_set_ctime_current(inode);
+	if (IS_SYNC(inode))
+		nilfs_set_transaction_flag(NILFS_TI_SYNC);
+
+	nilfs_mark_inode_dirty(inode);
+	nilfs_set_file_dirty(inode, 0);
+	nilfs_transaction_commit(sb);
+	/*
+	 * May construct a logical segment and may fail in sync mode.
+	 * But truncate has no return value.
+	 */
+}
+
+static void nilfs_clear_inode(struct inode *inode)
+{
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+
+	/*
+	 * Free resources allocated in nilfs_read_inode(), here.
+	 */
+	BUG_ON(!list_empty(&ii->i_dirty));
+	brelse(ii->i_bh);
+	ii->i_bh = NULL;
+
+	if (nilfs_is_metadata_file_inode(inode))
+		nilfs_mdt_clear(inode);
+
+	if (test_bit(NILFS_I_BMAP, &ii->i_state))
+		nilfs_bmap_clear(ii->i_bmap);
+
+	if (!test_bit(NILFS_I_BTNC, &ii->i_state))
+		nilfs_detach_btree_node_cache(inode);
+
+	if (ii->i_root && inode->i_ino == NILFS_ROOT_INO)
+		nilfs_put_root(ii->i_root);
+}
+
+void nilfs_evict_inode(struct inode *inode)
+{
+	struct nilfs_transaction_info ti;
+	struct super_block *sb = inode->i_sb;
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+	struct the_nilfs *nilfs;
+	int ret;
+
+	if (inode->i_nlink || !ii->i_root || unlikely(is_bad_inode(inode))) {
+		truncate_inode_pages_final(&inode->i_data);
+		clear_inode(inode);
+		nilfs_clear_inode(inode);
+		return;
+	}
+	nilfs_transaction_begin(sb, &ti, 0); /* never fails */
+
+	truncate_inode_pages_final(&inode->i_data);
+
+	nilfs = sb->s_fs_info;
+	if (unlikely(sb_rdonly(sb) || !nilfs->ns_writer)) {
+		/*
+		 * If this inode is about to be disposed after the file system
+		 * has been degraded to read-only due to file system corruption
+		 * or after the writer has been detached, do not make any
+		 * changes that cause writes, just clear it.
+		 * Do this check after read-locking ns_segctor_sem by
+		 * nilfs_transaction_begin() in order to avoid a race with
+		 * the writer detach operation.
+		 */
+		clear_inode(inode);
+		nilfs_clear_inode(inode);
+		nilfs_transaction_abort(sb);
+		return;
+	}
+
+	/* TODO: some of the following operations may fail.  */
+	nilfs_truncate_bmap(ii, 0);
+	nilfs_mark_inode_dirty(inode);
+	clear_inode(inode);
+
+	ret = nilfs_ifile_delete_inode(ii->i_root->ifile, inode->i_ino);
+	if (!ret)
+		atomic64_dec(&ii->i_root->inodes_count);
+
+	nilfs_clear_inode(inode);
+
+	if (IS_SYNC(inode))
+		nilfs_set_transaction_flag(NILFS_TI_SYNC);
+	nilfs_transaction_commit(sb);
+	/*
+	 * May construct a logical segment and may fail in sync mode.
+	 * But delete_inode has no return value.
+	 */
+}
+
+int nilfs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
+		  struct iattr *iattr)
+{
+	struct nilfs_transaction_info ti;
+	struct inode *inode = d_inode(dentry);
+	struct super_block *sb = inode->i_sb;
+	int err;
+
+	err = setattr_prepare(&nop_mnt_idmap, dentry, iattr);
+	if (err)
+		return err;
+
+	err = nilfs_transaction_begin(sb, &ti, 0);
+	if (unlikely(err))
+		return err;
+
+	if ((iattr->ia_valid & ATTR_SIZE) &&
+	    iattr->ia_size != i_size_read(inode)) {
+		inode_dio_wait(inode);
+		truncate_setsize(inode, iattr->ia_size);
+		nilfs_truncate(inode);
+	}
+
+	setattr_copy(&nop_mnt_idmap, inode, iattr);
+	mark_inode_dirty(inode);
+
+	if (iattr->ia_valid & ATTR_MODE) {
+		err = nilfs_acl_chmod(inode);
+		if (unlikely(err))
+			goto out_err;
+	}
+
+	return nilfs_transaction_commit(sb);
+
+out_err:
+	nilfs_transaction_abort(sb);
+	return err;
+}
+
+int nilfs_permission(struct mnt_idmap *idmap, struct inode *inode,
+		     int mask)
+{
+	struct nilfs_root *root = NILFS_I(inode)->i_root;
+
+	if ((mask & MAY_WRITE) && root &&
+	    root->cno != NILFS_CPTREE_CURRENT_CNO)
+		return -EROFS; /* snapshot is not writable */
+
+	return generic_permission(&nop_mnt_idmap, inode, mask);
+}
+
+int nilfs_load_inode_block(struct inode *inode, struct buffer_head **pbh)
+{
+	struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+	int err;
+
+	spin_lock(&nilfs->ns_inode_lock);
+	if (ii->i_bh == NULL || unlikely(!buffer_uptodate(ii->i_bh))) {
+		spin_unlock(&nilfs->ns_inode_lock);
+		err = nilfs_ifile_get_inode_block(ii->i_root->ifile,
+						  inode->i_ino, pbh);
+		if (unlikely(err))
+			return err;
+		spin_lock(&nilfs->ns_inode_lock);
+		if (ii->i_bh == NULL)
+			ii->i_bh = *pbh;
+		else if (unlikely(!buffer_uptodate(ii->i_bh))) {
+			__brelse(ii->i_bh);
+			ii->i_bh = *pbh;
+		} else {
+			brelse(*pbh);
+			*pbh = ii->i_bh;
+		}
+	} else
+		*pbh = ii->i_bh;
+
+	get_bh(*pbh);
+	spin_unlock(&nilfs->ns_inode_lock);
+	return 0;
+}
+
+int nilfs_inode_dirty(struct inode *inode)
+{
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+	struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
+	int ret = 0;
+
+	if (!list_empty(&ii->i_dirty)) {
+		spin_lock(&nilfs->ns_inode_lock);
+		ret = test_bit(NILFS_I_DIRTY, &ii->i_state) ||
+			test_bit(NILFS_I_BUSY, &ii->i_state);
+		spin_unlock(&nilfs->ns_inode_lock);
+	}
+	return ret;
+}
+
+int nilfs_set_file_dirty(struct inode *inode, unsigned int nr_dirty)
+{
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+	struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
+
+	atomic_add(nr_dirty, &nilfs->ns_ndirtyblks);
+
+	if (test_and_set_bit(NILFS_I_DIRTY, &ii->i_state))
+		return 0;
+
+	spin_lock(&nilfs->ns_inode_lock);
+	if (!test_bit(NILFS_I_QUEUED, &ii->i_state) &&
+	    !test_bit(NILFS_I_BUSY, &ii->i_state)) {
+		/*
+		 * Because this routine may race with nilfs_dispose_list(),
+		 * we have to check NILFS_I_QUEUED here, too.
+		 */
+		if (list_empty(&ii->i_dirty) && igrab(inode) == NULL) {
+			/*
+			 * This will happen when somebody is freeing
+			 * this inode.
+			 */
+			nilfs_warn(inode->i_sb,
+				   "cannot set file dirty (ino=%lu): the file is being freed",
+				   inode->i_ino);
+			spin_unlock(&nilfs->ns_inode_lock);
+			return -EINVAL; /*
+					 * NILFS_I_DIRTY may remain for
+					 * freeing inode.
+					 */
+		}
+		list_move_tail(&ii->i_dirty, &nilfs->ns_dirty_files);
+		set_bit(NILFS_I_QUEUED, &ii->i_state);
+	}
+	spin_unlock(&nilfs->ns_inode_lock);
+	return 0;
+}
+
+int __nilfs_mark_inode_dirty(struct inode *inode, int flags)
+{
+	struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
+	struct buffer_head *ibh;
+	int err;
+
+	/*
+	 * Do not dirty inodes after the log writer has been detached
+	 * and its nilfs_root struct has been freed.
+	 */
+	if (unlikely(nilfs_purging(nilfs)))
+		return 0;
+
+	err = nilfs_load_inode_block(inode, &ibh);
+	if (unlikely(err)) {
+		nilfs_warn(inode->i_sb,
+			   "cannot mark inode dirty (ino=%lu): error %d loading inode block",
+			   inode->i_ino, err);
+		return err;
+	}
+	nilfs_update_inode(inode, ibh, flags);
+	mark_buffer_dirty(ibh);
+	nilfs_mdt_mark_dirty(NILFS_I(inode)->i_root->ifile);
+	brelse(ibh);
+	return 0;
+}
+
+/**
+ * nilfs_dirty_inode - reflect changes on given inode to an inode block.
+ * @inode: inode of the file to be registered.
+ * @flags: flags to determine the dirty state of the inode
+ *
+ * nilfs_dirty_inode() loads a inode block containing the specified
+ * @inode and copies data from a nilfs_inode to a corresponding inode
+ * entry in the inode block. This operation is excluded from the segment
+ * construction. This function can be called both as a single operation
+ * and as a part of indivisible file operations.
+ */
+void nilfs_dirty_inode(struct inode *inode, int flags)
+{
+	struct nilfs_transaction_info ti;
+	struct nilfs_mdt_info *mdi = NILFS_MDT(inode);
+
+	if (is_bad_inode(inode)) {
+		nilfs_warn(inode->i_sb,
+			   "tried to mark bad_inode dirty. ignored.");
+		dump_stack();
+		return;
+	}
+	if (mdi) {
+		nilfs_mdt_mark_dirty(inode);
+		return;
+	}
+	nilfs_transaction_begin(inode->i_sb, &ti, 0);
+	__nilfs_mark_inode_dirty(inode, flags);
+	nilfs_transaction_commit(inode->i_sb); /* never fails */
+}
+
+int nilfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
+		 __u64 start, __u64 len)
+{
+	struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
+	__u64 logical = 0, phys = 0, size = 0;
+	__u32 flags = 0;
+	loff_t isize;
+	sector_t blkoff, end_blkoff;
+	sector_t delalloc_blkoff;
+	unsigned long delalloc_blklen;
+	unsigned int blkbits = inode->i_blkbits;
+	int ret, n;
+
+	ret = fiemap_prep(inode, fieinfo, start, &len, 0);
+	if (ret)
+		return ret;
+
+	inode_lock(inode);
+
+	isize = i_size_read(inode);
+
+	blkoff = start >> blkbits;
+	end_blkoff = (start + len - 1) >> blkbits;
+
+	delalloc_blklen = nilfs_find_uncommitted_extent(inode, blkoff,
+							&delalloc_blkoff);
+
+	do {
+		__u64 blkphy;
+		unsigned int maxblocks;
+
+		if (delalloc_blklen && blkoff == delalloc_blkoff) {
+			if (size) {
+				/* End of the current extent */
+				ret = fiemap_fill_next_extent(
+					fieinfo, logical, phys, size, flags);
+				if (ret)
+					break;
+			}
+			if (blkoff > end_blkoff)
+				break;
+
+			flags = FIEMAP_EXTENT_MERGED | FIEMAP_EXTENT_DELALLOC;
+			logical = blkoff << blkbits;
+			phys = 0;
+			size = delalloc_blklen << blkbits;
+
+			blkoff = delalloc_blkoff + delalloc_blklen;
+			delalloc_blklen = nilfs_find_uncommitted_extent(
+				inode, blkoff, &delalloc_blkoff);
+			continue;
+		}
+
+		/*
+		 * Limit the number of blocks that we look up so as
+		 * not to get into the next delayed allocation extent.
+		 */
+		maxblocks = INT_MAX;
+		if (delalloc_blklen)
+			maxblocks = min_t(sector_t, delalloc_blkoff - blkoff,
+					  maxblocks);
+		blkphy = 0;
+
+		down_read(&NILFS_MDT(nilfs->ns_dat)->mi_sem);
+		n = nilfs_bmap_lookup_contig(
+			NILFS_I(inode)->i_bmap, blkoff, &blkphy, maxblocks);
+		up_read(&NILFS_MDT(nilfs->ns_dat)->mi_sem);
+
+		if (n < 0) {
+			int past_eof;
+
+			if (unlikely(n != -ENOENT))
+				break; /* error */
+
+			/* HOLE */
+			blkoff++;
+			past_eof = ((blkoff << blkbits) >= isize);
+
+			if (size) {
+				/* End of the current extent */
+
+				if (past_eof)
+					flags |= FIEMAP_EXTENT_LAST;
+
+				ret = fiemap_fill_next_extent(
+					fieinfo, logical, phys, size, flags);
+				if (ret)
+					break;
+				size = 0;
+			}
+			if (blkoff > end_blkoff || past_eof)
+				break;
+		} else {
+			if (size) {
+				if (phys && blkphy << blkbits == phys + size) {
+					/* The current extent goes on */
+					size += n << blkbits;
+				} else {
+					/* Terminate the current extent */
+					ret = fiemap_fill_next_extent(
+						fieinfo, logical, phys, size,
+						flags);
+					if (ret || blkoff > end_blkoff)
+						break;
+
+					/* Start another extent */
+					flags = FIEMAP_EXTENT_MERGED;
+					logical = blkoff << blkbits;
+					phys = blkphy << blkbits;
+					size = n << blkbits;
+				}
+			} else {
+				/* Start a new extent */
+				flags = FIEMAP_EXTENT_MERGED;
+				logical = blkoff << blkbits;
+				phys = blkphy << blkbits;
+				size = n << blkbits;
+			}
+			blkoff += n;
+		}
+		cond_resched();
+	} while (true);
+
+	/* If ret is 1 then we just hit the end of the extent array */
+	if (ret == 1)
+		ret = 0;
+
+	inode_unlock(inode);
+	return ret;
+}
diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
new file mode 100644
index 0000000000..40ffade49f
--- /dev/null
+++ b/fs/nilfs2/ioctl.c
@@ -0,0 +1,1345 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NILFS ioctl operations.
+ *
+ * Copyright (C) 2007, 2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Koji Sato.
+ */
+
+#include <linux/fs.h>
+#include <linux/wait.h>
+#include <linux/slab.h>
+#include <linux/capability.h>	/* capable() */
+#include <linux/uaccess.h>	/* copy_from_user(), copy_to_user() */
+#include <linux/vmalloc.h>
+#include <linux/compat.h>	/* compat_ptr() */
+#include <linux/mount.h>	/* mnt_want_write_file(), mnt_drop_write_file() */
+#include <linux/buffer_head.h>
+#include <linux/fileattr.h>
+#include "nilfs.h"
+#include "segment.h"
+#include "bmap.h"
+#include "cpfile.h"
+#include "sufile.h"
+#include "dat.h"
+
+/**
+ * nilfs_ioctl_wrap_copy - wrapping function of get/set metadata info
+ * @nilfs: nilfs object
+ * @argv: vector of arguments from userspace
+ * @dir: set of direction flags
+ * @dofunc: concrete function of get/set metadata info
+ *
+ * Description: nilfs_ioctl_wrap_copy() gets/sets metadata info by means of
+ * calling dofunc() function on the basis of @argv argument.
+ *
+ * Return Value: On success, 0 is returned and requested metadata info
+ * is copied into userspace. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EINVAL - Invalid arguments from userspace.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-EFAULT - Failure during execution of requested operation.
+ */
+static int nilfs_ioctl_wrap_copy(struct the_nilfs *nilfs,
+				 struct nilfs_argv *argv, int dir,
+				 ssize_t (*dofunc)(struct the_nilfs *,
+						   __u64 *, int,
+						   void *, size_t, size_t))
+{
+	void *buf;
+	void __user *base = (void __user *)(unsigned long)argv->v_base;
+	size_t maxmembs, total, n;
+	ssize_t nr;
+	int ret, i;
+	__u64 pos, ppos;
+
+	if (argv->v_nmembs == 0)
+		return 0;
+
+	if (argv->v_size > PAGE_SIZE)
+		return -EINVAL;
+
+	/*
+	 * Reject pairs of a start item position (argv->v_index) and a
+	 * total count (argv->v_nmembs) which leads position 'pos' to
+	 * overflow by the increment at the end of the loop.
+	 */
+	if (argv->v_index > ~(__u64)0 - argv->v_nmembs)
+		return -EINVAL;
+
+	buf = (void *)get_zeroed_page(GFP_NOFS);
+	if (unlikely(!buf))
+		return -ENOMEM;
+	maxmembs = PAGE_SIZE / argv->v_size;
+
+	ret = 0;
+	total = 0;
+	pos = argv->v_index;
+	for (i = 0; i < argv->v_nmembs; i += n) {
+		n = (argv->v_nmembs - i < maxmembs) ?
+			argv->v_nmembs - i : maxmembs;
+		if ((dir & _IOC_WRITE) &&
+		    copy_from_user(buf, base + argv->v_size * i,
+				   argv->v_size * n)) {
+			ret = -EFAULT;
+			break;
+		}
+		ppos = pos;
+		nr = dofunc(nilfs, &pos, argv->v_flags, buf, argv->v_size,
+			       n);
+		if (nr < 0) {
+			ret = nr;
+			break;
+		}
+		if ((dir & _IOC_READ) &&
+		    copy_to_user(base + argv->v_size * i, buf,
+				 argv->v_size * nr)) {
+			ret = -EFAULT;
+			break;
+		}
+		total += nr;
+		if ((size_t)nr < n)
+			break;
+		if (pos == ppos)
+			pos += n;
+	}
+	argv->v_nmembs = total;
+
+	free_pages((unsigned long)buf, 0);
+	return ret;
+}
+
+/**
+ * nilfs_fileattr_get - ioctl to support lsattr
+ */
+int nilfs_fileattr_get(struct dentry *dentry, struct fileattr *fa)
+{
+	struct inode *inode = d_inode(dentry);
+
+	fileattr_fill_flags(fa, NILFS_I(inode)->i_flags & FS_FL_USER_VISIBLE);
+
+	return 0;
+}
+
+/**
+ * nilfs_fileattr_set - ioctl to support chattr
+ */
+int nilfs_fileattr_set(struct mnt_idmap *idmap,
+		       struct dentry *dentry, struct fileattr *fa)
+{
+	struct inode *inode = d_inode(dentry);
+	struct nilfs_transaction_info ti;
+	unsigned int flags, oldflags;
+	int ret;
+
+	if (fileattr_has_fsx(fa))
+		return -EOPNOTSUPP;
+
+	flags = nilfs_mask_flags(inode->i_mode, fa->flags);
+
+	ret = nilfs_transaction_begin(inode->i_sb, &ti, 0);
+	if (ret)
+		return ret;
+
+	oldflags = NILFS_I(inode)->i_flags & ~FS_FL_USER_MODIFIABLE;
+	NILFS_I(inode)->i_flags = oldflags | (flags & FS_FL_USER_MODIFIABLE);
+
+	nilfs_set_inode_flags(inode);
+	inode_set_ctime_current(inode);
+	if (IS_SYNC(inode))
+		nilfs_set_transaction_flag(NILFS_TI_SYNC);
+
+	nilfs_mark_inode_dirty(inode);
+	return nilfs_transaction_commit(inode->i_sb);
+}
+
+/**
+ * nilfs_ioctl_getversion - get info about a file's version (generation number)
+ */
+static int nilfs_ioctl_getversion(struct inode *inode, void __user *argp)
+{
+	return put_user(inode->i_generation, (int __user *)argp);
+}
+
+/**
+ * nilfs_ioctl_change_cpmode - change checkpoint mode (checkpoint/snapshot)
+ * @inode: inode object
+ * @filp: file object
+ * @cmd: ioctl's request code
+ * @argp: pointer on argument from userspace
+ *
+ * Description: nilfs_ioctl_change_cpmode() function changes mode of
+ * given checkpoint between checkpoint and snapshot state. This ioctl
+ * is used in chcp and mkcp utilities.
+ *
+ * Return Value: On success, 0 is returned and mode of a checkpoint is
+ * changed. On error, one of the following negative error codes
+ * is returned.
+ *
+ * %-EPERM - Operation not permitted.
+ *
+ * %-EFAULT - Failure during checkpoint mode changing.
+ */
+static int nilfs_ioctl_change_cpmode(struct inode *inode, struct file *filp,
+				     unsigned int cmd, void __user *argp)
+{
+	struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
+	struct nilfs_transaction_info ti;
+	struct nilfs_cpmode cpmode;
+	int ret;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	ret = mnt_want_write_file(filp);
+	if (ret)
+		return ret;
+
+	ret = -EFAULT;
+	if (copy_from_user(&cpmode, argp, sizeof(cpmode)))
+		goto out;
+
+	mutex_lock(&nilfs->ns_snapshot_mount_mutex);
+
+	nilfs_transaction_begin(inode->i_sb, &ti, 0);
+	ret = nilfs_cpfile_change_cpmode(
+		nilfs->ns_cpfile, cpmode.cm_cno, cpmode.cm_mode);
+	if (unlikely(ret < 0))
+		nilfs_transaction_abort(inode->i_sb);
+	else
+		nilfs_transaction_commit(inode->i_sb); /* never fails */
+
+	mutex_unlock(&nilfs->ns_snapshot_mount_mutex);
+out:
+	mnt_drop_write_file(filp);
+	return ret;
+}
+
+/**
+ * nilfs_ioctl_delete_checkpoint - remove checkpoint
+ * @inode: inode object
+ * @filp: file object
+ * @cmd: ioctl's request code
+ * @argp: pointer on argument from userspace
+ *
+ * Description: nilfs_ioctl_delete_checkpoint() function removes
+ * checkpoint from NILFS2 file system. This ioctl is used in rmcp
+ * utility.
+ *
+ * Return Value: On success, 0 is returned and a checkpoint is
+ * removed. On error, one of the following negative error codes
+ * is returned.
+ *
+ * %-EPERM - Operation not permitted.
+ *
+ * %-EFAULT - Failure during checkpoint removing.
+ */
+static int
+nilfs_ioctl_delete_checkpoint(struct inode *inode, struct file *filp,
+			      unsigned int cmd, void __user *argp)
+{
+	struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
+	struct nilfs_transaction_info ti;
+	__u64 cno;
+	int ret;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	ret = mnt_want_write_file(filp);
+	if (ret)
+		return ret;
+
+	ret = -EFAULT;
+	if (copy_from_user(&cno, argp, sizeof(cno)))
+		goto out;
+
+	nilfs_transaction_begin(inode->i_sb, &ti, 0);
+	ret = nilfs_cpfile_delete_checkpoint(nilfs->ns_cpfile, cno);
+	if (unlikely(ret < 0))
+		nilfs_transaction_abort(inode->i_sb);
+	else
+		nilfs_transaction_commit(inode->i_sb); /* never fails */
+out:
+	mnt_drop_write_file(filp);
+	return ret;
+}
+
+/**
+ * nilfs_ioctl_do_get_cpinfo - callback method getting info about checkpoints
+ * @nilfs: nilfs object
+ * @posp: pointer on array of checkpoint's numbers
+ * @flags: checkpoint mode (checkpoint or snapshot)
+ * @buf: buffer for storing checkponts' info
+ * @size: size in bytes of one checkpoint info item in array
+ * @nmembs: number of checkpoints in array (numbers and infos)
+ *
+ * Description: nilfs_ioctl_do_get_cpinfo() function returns info about
+ * requested checkpoints. The NILFS_IOCTL_GET_CPINFO ioctl is used in
+ * lscp utility and by nilfs_cleanerd daemon.
+ *
+ * Return value: count of nilfs_cpinfo structures in output buffer.
+ */
+static ssize_t
+nilfs_ioctl_do_get_cpinfo(struct the_nilfs *nilfs, __u64 *posp, int flags,
+			  void *buf, size_t size, size_t nmembs)
+{
+	int ret;
+
+	down_read(&nilfs->ns_segctor_sem);
+	ret = nilfs_cpfile_get_cpinfo(nilfs->ns_cpfile, posp, flags, buf,
+				      size, nmembs);
+	up_read(&nilfs->ns_segctor_sem);
+	return ret;
+}
+
+/**
+ * nilfs_ioctl_get_cpstat - get checkpoints statistics
+ * @inode: inode object
+ * @filp: file object
+ * @cmd: ioctl's request code
+ * @argp: pointer on argument from userspace
+ *
+ * Description: nilfs_ioctl_get_cpstat() returns information about checkpoints.
+ * The NILFS_IOCTL_GET_CPSTAT ioctl is used by lscp, rmcp utilities
+ * and by nilfs_cleanerd daemon.
+ *
+ * Return Value: On success, 0 is returned, and checkpoints information is
+ * copied into userspace pointer @argp. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-EFAULT - Failure during getting checkpoints statistics.
+ */
+static int nilfs_ioctl_get_cpstat(struct inode *inode, struct file *filp,
+				  unsigned int cmd, void __user *argp)
+{
+	struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
+	struct nilfs_cpstat cpstat;
+	int ret;
+
+	down_read(&nilfs->ns_segctor_sem);
+	ret = nilfs_cpfile_get_stat(nilfs->ns_cpfile, &cpstat);
+	up_read(&nilfs->ns_segctor_sem);
+	if (ret < 0)
+		return ret;
+
+	if (copy_to_user(argp, &cpstat, sizeof(cpstat)))
+		ret = -EFAULT;
+	return ret;
+}
+
+/**
+ * nilfs_ioctl_do_get_suinfo - callback method getting segment usage info
+ * @nilfs: nilfs object
+ * @posp: pointer on array of segment numbers
+ * @flags: *not used*
+ * @buf: buffer for storing suinfo array
+ * @size: size in bytes of one suinfo item in array
+ * @nmembs: count of segment numbers and suinfos in array
+ *
+ * Description: nilfs_ioctl_do_get_suinfo() function returns segment usage
+ * info about requested segments. The NILFS_IOCTL_GET_SUINFO ioctl is used
+ * in lssu, nilfs_resize utilities and by nilfs_cleanerd daemon.
+ *
+ * Return value: count of nilfs_suinfo structures in output buffer.
+ */
+static ssize_t
+nilfs_ioctl_do_get_suinfo(struct the_nilfs *nilfs, __u64 *posp, int flags,
+			  void *buf, size_t size, size_t nmembs)
+{
+	int ret;
+
+	down_read(&nilfs->ns_segctor_sem);
+	ret = nilfs_sufile_get_suinfo(nilfs->ns_sufile, *posp, buf, size,
+				      nmembs);
+	up_read(&nilfs->ns_segctor_sem);
+	return ret;
+}
+
+/**
+ * nilfs_ioctl_get_sustat - get segment usage statistics
+ * @inode: inode object
+ * @filp: file object
+ * @cmd: ioctl's request code
+ * @argp: pointer on argument from userspace
+ *
+ * Description: nilfs_ioctl_get_sustat() returns segment usage statistics.
+ * The NILFS_IOCTL_GET_SUSTAT ioctl is used in lssu, nilfs_resize utilities
+ * and by nilfs_cleanerd daemon.
+ *
+ * Return Value: On success, 0 is returned, and segment usage information is
+ * copied into userspace pointer @argp. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-EFAULT - Failure during getting segment usage statistics.
+ */
+static int nilfs_ioctl_get_sustat(struct inode *inode, struct file *filp,
+				  unsigned int cmd, void __user *argp)
+{
+	struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
+	struct nilfs_sustat sustat;
+	int ret;
+
+	down_read(&nilfs->ns_segctor_sem);
+	ret = nilfs_sufile_get_stat(nilfs->ns_sufile, &sustat);
+	up_read(&nilfs->ns_segctor_sem);
+	if (ret < 0)
+		return ret;
+
+	if (copy_to_user(argp, &sustat, sizeof(sustat)))
+		ret = -EFAULT;
+	return ret;
+}
+
+/**
+ * nilfs_ioctl_do_get_vinfo - callback method getting virtual blocks info
+ * @nilfs: nilfs object
+ * @posp: *not used*
+ * @flags: *not used*
+ * @buf: buffer for storing array of nilfs_vinfo structures
+ * @size: size in bytes of one vinfo item in array
+ * @nmembs: count of vinfos in array
+ *
+ * Description: nilfs_ioctl_do_get_vinfo() function returns information
+ * on virtual block addresses. The NILFS_IOCTL_GET_VINFO ioctl is used
+ * by nilfs_cleanerd daemon.
+ *
+ * Return value: count of nilfs_vinfo structures in output buffer.
+ */
+static ssize_t
+nilfs_ioctl_do_get_vinfo(struct the_nilfs *nilfs, __u64 *posp, int flags,
+			 void *buf, size_t size, size_t nmembs)
+{
+	int ret;
+
+	down_read(&nilfs->ns_segctor_sem);
+	ret = nilfs_dat_get_vinfo(nilfs->ns_dat, buf, size, nmembs);
+	up_read(&nilfs->ns_segctor_sem);
+	return ret;
+}
+
+/**
+ * nilfs_ioctl_do_get_bdescs - callback method getting disk block descriptors
+ * @nilfs: nilfs object
+ * @posp: *not used*
+ * @flags: *not used*
+ * @buf: buffer for storing array of nilfs_bdesc structures
+ * @size: size in bytes of one bdesc item in array
+ * @nmembs: count of bdescs in array
+ *
+ * Description: nilfs_ioctl_do_get_bdescs() function returns information
+ * about descriptors of disk block numbers. The NILFS_IOCTL_GET_BDESCS ioctl
+ * is used by nilfs_cleanerd daemon.
+ *
+ * Return value: count of nilfs_bdescs structures in output buffer.
+ */
+static ssize_t
+nilfs_ioctl_do_get_bdescs(struct the_nilfs *nilfs, __u64 *posp, int flags,
+			  void *buf, size_t size, size_t nmembs)
+{
+	struct nilfs_bmap *bmap = NILFS_I(nilfs->ns_dat)->i_bmap;
+	struct nilfs_bdesc *bdescs = buf;
+	int ret, i;
+
+	down_read(&nilfs->ns_segctor_sem);
+	for (i = 0; i < nmembs; i++) {
+		ret = nilfs_bmap_lookup_at_level(bmap,
+						 bdescs[i].bd_offset,
+						 bdescs[i].bd_level + 1,
+						 &bdescs[i].bd_blocknr);
+		if (ret < 0) {
+			if (ret != -ENOENT) {
+				up_read(&nilfs->ns_segctor_sem);
+				return ret;
+			}
+			bdescs[i].bd_blocknr = 0;
+		}
+	}
+	up_read(&nilfs->ns_segctor_sem);
+	return nmembs;
+}
+
+/**
+ * nilfs_ioctl_get_bdescs - get disk block descriptors
+ * @inode: inode object
+ * @filp: file object
+ * @cmd: ioctl's request code
+ * @argp: pointer on argument from userspace
+ *
+ * Description: nilfs_ioctl_do_get_bdescs() function returns information
+ * about descriptors of disk block numbers. The NILFS_IOCTL_GET_BDESCS ioctl
+ * is used by nilfs_cleanerd daemon.
+ *
+ * Return Value: On success, 0 is returned, and disk block descriptors are
+ * copied into userspace pointer @argp. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EINVAL - Invalid arguments from userspace.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-EFAULT - Failure during getting disk block descriptors.
+ */
+static int nilfs_ioctl_get_bdescs(struct inode *inode, struct file *filp,
+				  unsigned int cmd, void __user *argp)
+{
+	struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
+	struct nilfs_argv argv;
+	int ret;
+
+	if (copy_from_user(&argv, argp, sizeof(argv)))
+		return -EFAULT;
+
+	if (argv.v_size != sizeof(struct nilfs_bdesc))
+		return -EINVAL;
+
+	ret = nilfs_ioctl_wrap_copy(nilfs, &argv, _IOC_DIR(cmd),
+				    nilfs_ioctl_do_get_bdescs);
+	if (ret < 0)
+		return ret;
+
+	if (copy_to_user(argp, &argv, sizeof(argv)))
+		ret = -EFAULT;
+	return ret;
+}
+
+/**
+ * nilfs_ioctl_move_inode_block - prepare data/node block for moving by GC
+ * @inode: inode object
+ * @vdesc: descriptor of virtual block number
+ * @buffers: list of moving buffers
+ *
+ * Description: nilfs_ioctl_move_inode_block() function registers data/node
+ * buffer in the GC pagecache and submit read request.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-ENOENT - Requested block doesn't exist.
+ *
+ * %-EEXIST - Blocks conflict is detected.
+ */
+static int nilfs_ioctl_move_inode_block(struct inode *inode,
+					struct nilfs_vdesc *vdesc,
+					struct list_head *buffers)
+{
+	struct buffer_head *bh;
+	int ret;
+
+	if (vdesc->vd_flags == 0)
+		ret = nilfs_gccache_submit_read_data(
+			inode, vdesc->vd_offset, vdesc->vd_blocknr,
+			vdesc->vd_vblocknr, &bh);
+	else
+		ret = nilfs_gccache_submit_read_node(
+			inode, vdesc->vd_blocknr, vdesc->vd_vblocknr, &bh);
+
+	if (unlikely(ret < 0)) {
+		if (ret == -ENOENT)
+			nilfs_crit(inode->i_sb,
+				   "%s: invalid virtual block address (%s): ino=%llu, cno=%llu, offset=%llu, blocknr=%llu, vblocknr=%llu",
+				   __func__, vdesc->vd_flags ? "node" : "data",
+				   (unsigned long long)vdesc->vd_ino,
+				   (unsigned long long)vdesc->vd_cno,
+				   (unsigned long long)vdesc->vd_offset,
+				   (unsigned long long)vdesc->vd_blocknr,
+				   (unsigned long long)vdesc->vd_vblocknr);
+		return ret;
+	}
+	if (unlikely(!list_empty(&bh->b_assoc_buffers))) {
+		nilfs_crit(inode->i_sb,
+			   "%s: conflicting %s buffer: ino=%llu, cno=%llu, offset=%llu, blocknr=%llu, vblocknr=%llu",
+			   __func__, vdesc->vd_flags ? "node" : "data",
+			   (unsigned long long)vdesc->vd_ino,
+			   (unsigned long long)vdesc->vd_cno,
+			   (unsigned long long)vdesc->vd_offset,
+			   (unsigned long long)vdesc->vd_blocknr,
+			   (unsigned long long)vdesc->vd_vblocknr);
+		brelse(bh);
+		return -EEXIST;
+	}
+	list_add_tail(&bh->b_assoc_buffers, buffers);
+	return 0;
+}
+
+/**
+ * nilfs_ioctl_move_blocks - move valid inode's blocks during garbage collection
+ * @sb: superblock object
+ * @argv: vector of arguments from userspace
+ * @buf: array of nilfs_vdesc structures
+ *
+ * Description: nilfs_ioctl_move_blocks() function reads valid data/node
+ * blocks that garbage collector specified with the array of nilfs_vdesc
+ * structures and stores them into page caches of GC inodes.
+ *
+ * Return Value: Number of processed nilfs_vdesc structures or
+ * error code, otherwise.
+ */
+static int nilfs_ioctl_move_blocks(struct super_block *sb,
+				   struct nilfs_argv *argv, void *buf)
+{
+	size_t nmembs = argv->v_nmembs;
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct inode *inode;
+	struct nilfs_vdesc *vdesc;
+	struct buffer_head *bh, *n;
+	LIST_HEAD(buffers);
+	ino_t ino;
+	__u64 cno;
+	int i, ret;
+
+	for (i = 0, vdesc = buf; i < nmembs; ) {
+		ino = vdesc->vd_ino;
+		cno = vdesc->vd_cno;
+		inode = nilfs_iget_for_gc(sb, ino, cno);
+		if (IS_ERR(inode)) {
+			ret = PTR_ERR(inode);
+			goto failed;
+		}
+		if (list_empty(&NILFS_I(inode)->i_dirty)) {
+			/*
+			 * Add the inode to GC inode list. Garbage Collection
+			 * is serialized and no two processes manipulate the
+			 * list simultaneously.
+			 */
+			igrab(inode);
+			list_add(&NILFS_I(inode)->i_dirty,
+				 &nilfs->ns_gc_inodes);
+		}
+
+		do {
+			ret = nilfs_ioctl_move_inode_block(inode, vdesc,
+							   &buffers);
+			if (unlikely(ret < 0)) {
+				iput(inode);
+				goto failed;
+			}
+			vdesc++;
+		} while (++i < nmembs &&
+			 vdesc->vd_ino == ino && vdesc->vd_cno == cno);
+
+		iput(inode); /* The inode still remains in GC inode list */
+	}
+
+	list_for_each_entry_safe(bh, n, &buffers, b_assoc_buffers) {
+		ret = nilfs_gccache_wait_and_mark_dirty(bh);
+		if (unlikely(ret < 0)) {
+			WARN_ON(ret == -EEXIST);
+			goto failed;
+		}
+		list_del_init(&bh->b_assoc_buffers);
+		brelse(bh);
+	}
+	return nmembs;
+
+ failed:
+	list_for_each_entry_safe(bh, n, &buffers, b_assoc_buffers) {
+		list_del_init(&bh->b_assoc_buffers);
+		brelse(bh);
+	}
+	return ret;
+}
+
+/**
+ * nilfs_ioctl_delete_checkpoints - delete checkpoints
+ * @nilfs: nilfs object
+ * @argv: vector of arguments from userspace
+ * @buf: array of periods of checkpoints numbers
+ *
+ * Description: nilfs_ioctl_delete_checkpoints() function deletes checkpoints
+ * in the period from p_start to p_end, excluding p_end itself. The checkpoints
+ * which have been already deleted are ignored.
+ *
+ * Return Value: Number of processed nilfs_period structures or
+ * error code, otherwise.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-EINVAL - invalid checkpoints.
+ */
+static int nilfs_ioctl_delete_checkpoints(struct the_nilfs *nilfs,
+					  struct nilfs_argv *argv, void *buf)
+{
+	size_t nmembs = argv->v_nmembs;
+	struct inode *cpfile = nilfs->ns_cpfile;
+	struct nilfs_period *periods = buf;
+	int ret, i;
+
+	for (i = 0; i < nmembs; i++) {
+		ret = nilfs_cpfile_delete_checkpoints(
+			cpfile, periods[i].p_start, periods[i].p_end);
+		if (ret < 0)
+			return ret;
+	}
+	return nmembs;
+}
+
+/**
+ * nilfs_ioctl_free_vblocknrs - free virtual block numbers
+ * @nilfs: nilfs object
+ * @argv: vector of arguments from userspace
+ * @buf: array of virtual block numbers
+ *
+ * Description: nilfs_ioctl_free_vblocknrs() function frees
+ * the virtual block numbers specified by @buf and @argv->v_nmembs.
+ *
+ * Return Value: Number of processed virtual block numbers or
+ * error code, otherwise.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-ENOENT - The virtual block number have not been allocated.
+ */
+static int nilfs_ioctl_free_vblocknrs(struct the_nilfs *nilfs,
+				      struct nilfs_argv *argv, void *buf)
+{
+	size_t nmembs = argv->v_nmembs;
+	int ret;
+
+	ret = nilfs_dat_freev(nilfs->ns_dat, buf, nmembs);
+
+	return (ret < 0) ? ret : nmembs;
+}
+
+/**
+ * nilfs_ioctl_mark_blocks_dirty - mark blocks dirty
+ * @nilfs: nilfs object
+ * @argv: vector of arguments from userspace
+ * @buf: array of block descriptors
+ *
+ * Description: nilfs_ioctl_mark_blocks_dirty() function marks
+ * metadata file or data blocks as dirty.
+ *
+ * Return Value: Number of processed block descriptors or
+ * error code, otherwise.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ *
+ * %-EIO - I/O error
+ *
+ * %-ENOENT - the specified block does not exist (hole block)
+ */
+static int nilfs_ioctl_mark_blocks_dirty(struct the_nilfs *nilfs,
+					 struct nilfs_argv *argv, void *buf)
+{
+	size_t nmembs = argv->v_nmembs;
+	struct nilfs_bmap *bmap = NILFS_I(nilfs->ns_dat)->i_bmap;
+	struct nilfs_bdesc *bdescs = buf;
+	struct buffer_head *bh;
+	int ret, i;
+
+	for (i = 0; i < nmembs; i++) {
+		/* XXX: use macro or inline func to check liveness */
+		ret = nilfs_bmap_lookup_at_level(bmap,
+						 bdescs[i].bd_offset,
+						 bdescs[i].bd_level + 1,
+						 &bdescs[i].bd_blocknr);
+		if (ret < 0) {
+			if (ret != -ENOENT)
+				return ret;
+			bdescs[i].bd_blocknr = 0;
+		}
+		if (bdescs[i].bd_blocknr != bdescs[i].bd_oblocknr)
+			/* skip dead block */
+			continue;
+		if (bdescs[i].bd_level == 0) {
+			ret = nilfs_mdt_get_block(nilfs->ns_dat,
+						  bdescs[i].bd_offset,
+						  false, NULL, &bh);
+			if (unlikely(ret)) {
+				WARN_ON(ret == -ENOENT);
+				return ret;
+			}
+			mark_buffer_dirty(bh);
+			nilfs_mdt_mark_dirty(nilfs->ns_dat);
+			put_bh(bh);
+		} else {
+			ret = nilfs_bmap_mark(bmap, bdescs[i].bd_offset,
+					      bdescs[i].bd_level);
+			if (ret < 0) {
+				WARN_ON(ret == -ENOENT);
+				return ret;
+			}
+		}
+	}
+	return nmembs;
+}
+
+int nilfs_ioctl_prepare_clean_segments(struct the_nilfs *nilfs,
+				       struct nilfs_argv *argv, void **kbufs)
+{
+	const char *msg;
+	int ret;
+
+	ret = nilfs_ioctl_delete_checkpoints(nilfs, &argv[1], kbufs[1]);
+	if (ret < 0) {
+		/*
+		 * can safely abort because checkpoints can be removed
+		 * independently.
+		 */
+		msg = "cannot delete checkpoints";
+		goto failed;
+	}
+	ret = nilfs_ioctl_free_vblocknrs(nilfs, &argv[2], kbufs[2]);
+	if (ret < 0) {
+		/*
+		 * can safely abort because DAT file is updated atomically
+		 * using a copy-on-write technique.
+		 */
+		msg = "cannot delete virtual blocks from DAT file";
+		goto failed;
+	}
+	ret = nilfs_ioctl_mark_blocks_dirty(nilfs, &argv[3], kbufs[3]);
+	if (ret < 0) {
+		/*
+		 * can safely abort because the operation is nondestructive.
+		 */
+		msg = "cannot mark copying blocks dirty";
+		goto failed;
+	}
+	return 0;
+
+ failed:
+	nilfs_err(nilfs->ns_sb, "error %d preparing GC: %s", ret, msg);
+	return ret;
+}
+
+/**
+ * nilfs_ioctl_clean_segments - clean segments
+ * @inode: inode object
+ * @filp: file object
+ * @cmd: ioctl's request code
+ * @argp: pointer on argument from userspace
+ *
+ * Description: nilfs_ioctl_clean_segments() function makes garbage
+ * collection operation in the environment of requested parameters
+ * from userspace. The NILFS_IOCTL_CLEAN_SEGMENTS ioctl is used by
+ * nilfs_cleanerd daemon.
+ *
+ * Return Value: On success, 0 is returned or error code, otherwise.
+ */
+static int nilfs_ioctl_clean_segments(struct inode *inode, struct file *filp,
+				      unsigned int cmd, void __user *argp)
+{
+	struct nilfs_argv argv[5];
+	static const size_t argsz[5] = {
+		sizeof(struct nilfs_vdesc),
+		sizeof(struct nilfs_period),
+		sizeof(__u64),
+		sizeof(struct nilfs_bdesc),
+		sizeof(__u64),
+	};
+	void __user *base;
+	void *kbufs[5];
+	struct the_nilfs *nilfs;
+	size_t len, nsegs;
+	int n, ret;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	ret = mnt_want_write_file(filp);
+	if (ret)
+		return ret;
+
+	ret = -EFAULT;
+	if (copy_from_user(argv, argp, sizeof(argv)))
+		goto out;
+
+	ret = -EINVAL;
+	nsegs = argv[4].v_nmembs;
+	if (argv[4].v_size != argsz[4])
+		goto out;
+	if (nsegs > UINT_MAX / sizeof(__u64))
+		goto out;
+
+	/*
+	 * argv[4] points to segment numbers this ioctl cleans.  We
+	 * use kmalloc() for its buffer because memory used for the
+	 * segment numbers is enough small.
+	 */
+	kbufs[4] = memdup_user((void __user *)(unsigned long)argv[4].v_base,
+			       nsegs * sizeof(__u64));
+	if (IS_ERR(kbufs[4])) {
+		ret = PTR_ERR(kbufs[4]);
+		goto out;
+	}
+	nilfs = inode->i_sb->s_fs_info;
+
+	for (n = 0; n < 4; n++) {
+		ret = -EINVAL;
+		if (argv[n].v_size != argsz[n])
+			goto out_free;
+
+		if (argv[n].v_nmembs > nsegs * nilfs->ns_blocks_per_segment)
+			goto out_free;
+
+		if (argv[n].v_nmembs >= UINT_MAX / argv[n].v_size)
+			goto out_free;
+
+		len = argv[n].v_size * argv[n].v_nmembs;
+		base = (void __user *)(unsigned long)argv[n].v_base;
+		if (len == 0) {
+			kbufs[n] = NULL;
+			continue;
+		}
+
+		kbufs[n] = vmalloc(len);
+		if (!kbufs[n]) {
+			ret = -ENOMEM;
+			goto out_free;
+		}
+		if (copy_from_user(kbufs[n], base, len)) {
+			ret = -EFAULT;
+			vfree(kbufs[n]);
+			goto out_free;
+		}
+	}
+
+	/*
+	 * nilfs_ioctl_move_blocks() will call nilfs_iget_for_gc(),
+	 * which will operates an inode list without blocking.
+	 * To protect the list from concurrent operations,
+	 * nilfs_ioctl_move_blocks should be atomic operation.
+	 */
+	if (test_and_set_bit(THE_NILFS_GC_RUNNING, &nilfs->ns_flags)) {
+		ret = -EBUSY;
+		goto out_free;
+	}
+
+	ret = nilfs_ioctl_move_blocks(inode->i_sb, &argv[0], kbufs[0]);
+	if (ret < 0) {
+		nilfs_err(inode->i_sb,
+			  "error %d preparing GC: cannot read source blocks",
+			  ret);
+	} else {
+		if (nilfs_sb_need_update(nilfs))
+			set_nilfs_discontinued(nilfs);
+		ret = nilfs_clean_segments(inode->i_sb, argv, kbufs);
+	}
+
+	nilfs_remove_all_gcinodes(nilfs);
+	clear_nilfs_gc_running(nilfs);
+
+out_free:
+	while (--n >= 0)
+		vfree(kbufs[n]);
+	kfree(kbufs[4]);
+out:
+	mnt_drop_write_file(filp);
+	return ret;
+}
+
+/**
+ * nilfs_ioctl_sync - make a checkpoint
+ * @inode: inode object
+ * @filp: file object
+ * @cmd: ioctl's request code
+ * @argp: pointer on argument from userspace
+ *
+ * Description: nilfs_ioctl_sync() function constructs a logical segment
+ * for checkpointing.  This function guarantees that all modified data
+ * and metadata are written out to the device when it successfully
+ * returned.
+ *
+ * Return Value: On success, 0 is retured. On errors, one of the following
+ * negative error code is returned.
+ *
+ * %-EROFS - Read only filesystem.
+ *
+ * %-EIO - I/O error
+ *
+ * %-ENOSPC - No space left on device (only in a panic state).
+ *
+ * %-ERESTARTSYS - Interrupted.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ *
+ * %-EFAULT - Failure during execution of requested operation.
+ */
+static int nilfs_ioctl_sync(struct inode *inode, struct file *filp,
+			    unsigned int cmd, void __user *argp)
+{
+	__u64 cno;
+	int ret;
+	struct the_nilfs *nilfs;
+
+	ret = nilfs_construct_segment(inode->i_sb);
+	if (ret < 0)
+		return ret;
+
+	nilfs = inode->i_sb->s_fs_info;
+	ret = nilfs_flush_device(nilfs);
+	if (ret < 0)
+		return ret;
+
+	if (argp != NULL) {
+		down_read(&nilfs->ns_segctor_sem);
+		cno = nilfs->ns_cno - 1;
+		up_read(&nilfs->ns_segctor_sem);
+		if (copy_to_user(argp, &cno, sizeof(cno)))
+			return -EFAULT;
+	}
+	return 0;
+}
+
+/**
+ * nilfs_ioctl_resize - resize NILFS2 volume
+ * @inode: inode object
+ * @filp: file object
+ * @argp: pointer on argument from userspace
+ *
+ * Return Value: On success, 0 is returned or error code, otherwise.
+ */
+static int nilfs_ioctl_resize(struct inode *inode, struct file *filp,
+			      void __user *argp)
+{
+	__u64 newsize;
+	int ret = -EPERM;
+
+	if (!capable(CAP_SYS_ADMIN))
+		goto out;
+
+	ret = mnt_want_write_file(filp);
+	if (ret)
+		goto out;
+
+	ret = -EFAULT;
+	if (copy_from_user(&newsize, argp, sizeof(newsize)))
+		goto out_drop_write;
+
+	ret = nilfs_resize_fs(inode->i_sb, newsize);
+
+out_drop_write:
+	mnt_drop_write_file(filp);
+out:
+	return ret;
+}
+
+/**
+ * nilfs_ioctl_trim_fs() - trim ioctl handle function
+ * @inode: inode object
+ * @argp: pointer on argument from userspace
+ *
+ * Description: nilfs_ioctl_trim_fs is the FITRIM ioctl handle function. It
+ * checks the arguments from userspace and calls nilfs_sufile_trim_fs, which
+ * performs the actual trim operation.
+ *
+ * Return Value: On success, 0 is returned or negative error code, otherwise.
+ */
+static int nilfs_ioctl_trim_fs(struct inode *inode, void __user *argp)
+{
+	struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
+	struct fstrim_range range;
+	int ret;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if (!bdev_max_discard_sectors(nilfs->ns_bdev))
+		return -EOPNOTSUPP;
+
+	if (copy_from_user(&range, argp, sizeof(range)))
+		return -EFAULT;
+
+	range.minlen = max_t(u64, range.minlen,
+			     bdev_discard_granularity(nilfs->ns_bdev));
+
+	down_read(&nilfs->ns_segctor_sem);
+	ret = nilfs_sufile_trim_fs(nilfs->ns_sufile, &range);
+	up_read(&nilfs->ns_segctor_sem);
+
+	if (ret < 0)
+		return ret;
+
+	if (copy_to_user(argp, &range, sizeof(range)))
+		return -EFAULT;
+
+	return 0;
+}
+
+/**
+ * nilfs_ioctl_set_alloc_range - limit range of segments to be allocated
+ * @inode: inode object
+ * @argp: pointer on argument from userspace
+ *
+ * Description: nilfs_ioctl_set_alloc_range() function defines lower limit
+ * of segments in bytes and upper limit of segments in bytes.
+ * The NILFS_IOCTL_SET_ALLOC_RANGE is used by nilfs_resize utility.
+ *
+ * Return Value: On success, 0 is returned or error code, otherwise.
+ */
+static int nilfs_ioctl_set_alloc_range(struct inode *inode, void __user *argp)
+{
+	struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
+	__u64 range[2];
+	__u64 minseg, maxseg;
+	unsigned long segbytes;
+	int ret = -EPERM;
+
+	if (!capable(CAP_SYS_ADMIN))
+		goto out;
+
+	ret = -EFAULT;
+	if (copy_from_user(range, argp, sizeof(__u64[2])))
+		goto out;
+
+	ret = -ERANGE;
+	if (range[1] > bdev_nr_bytes(inode->i_sb->s_bdev))
+		goto out;
+
+	segbytes = nilfs->ns_blocks_per_segment * nilfs->ns_blocksize;
+
+	minseg = range[0] + segbytes - 1;
+	do_div(minseg, segbytes);
+
+	if (range[1] < 4096)
+		goto out;
+
+	maxseg = NILFS_SB2_OFFSET_BYTES(range[1]);
+	if (maxseg < segbytes)
+		goto out;
+
+	do_div(maxseg, segbytes);
+	maxseg--;
+
+	ret = nilfs_sufile_set_alloc_range(nilfs->ns_sufile, minseg, maxseg);
+out:
+	return ret;
+}
+
+/**
+ * nilfs_ioctl_get_info - wrapping function of get metadata info
+ * @inode: inode object
+ * @filp: file object
+ * @cmd: ioctl's request code
+ * @argp: pointer on argument from userspace
+ * @membsz: size of an item in bytes
+ * @dofunc: concrete function of getting metadata info
+ *
+ * Description: nilfs_ioctl_get_info() gets metadata info by means of
+ * calling dofunc() function.
+ *
+ * Return Value: On success, 0 is returned and requested metadata info
+ * is copied into userspace. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EINVAL - Invalid arguments from userspace.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-EFAULT - Failure during execution of requested operation.
+ */
+static int nilfs_ioctl_get_info(struct inode *inode, struct file *filp,
+				unsigned int cmd, void __user *argp,
+				size_t membsz,
+				ssize_t (*dofunc)(struct the_nilfs *,
+						  __u64 *, int,
+						  void *, size_t, size_t))
+
+{
+	struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
+	struct nilfs_argv argv;
+	int ret;
+
+	if (copy_from_user(&argv, argp, sizeof(argv)))
+		return -EFAULT;
+
+	if (argv.v_size < membsz)
+		return -EINVAL;
+
+	ret = nilfs_ioctl_wrap_copy(nilfs, &argv, _IOC_DIR(cmd), dofunc);
+	if (ret < 0)
+		return ret;
+
+	if (copy_to_user(argp, &argv, sizeof(argv)))
+		ret = -EFAULT;
+	return ret;
+}
+
+/**
+ * nilfs_ioctl_set_suinfo - set segment usage info
+ * @inode: inode object
+ * @filp: file object
+ * @cmd: ioctl's request code
+ * @argp: pointer on argument from userspace
+ *
+ * Description: Expects an array of nilfs_suinfo_update structures
+ * encapsulated in nilfs_argv and updates the segment usage info
+ * according to the flags in nilfs_suinfo_update.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the
+ * following negative error codes is returned.
+ *
+ * %-EPERM - Not enough permissions
+ *
+ * %-EFAULT - Error copying input data
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-EINVAL - Invalid values in input (segment number, flags or nblocks)
+ */
+static int nilfs_ioctl_set_suinfo(struct inode *inode, struct file *filp,
+				unsigned int cmd, void __user *argp)
+{
+	struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
+	struct nilfs_transaction_info ti;
+	struct nilfs_argv argv;
+	size_t len;
+	void __user *base;
+	void *kbuf;
+	int ret;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	ret = mnt_want_write_file(filp);
+	if (ret)
+		return ret;
+
+	ret = -EFAULT;
+	if (copy_from_user(&argv, argp, sizeof(argv)))
+		goto out;
+
+	ret = -EINVAL;
+	if (argv.v_size < sizeof(struct nilfs_suinfo_update))
+		goto out;
+
+	if (argv.v_nmembs > nilfs->ns_nsegments)
+		goto out;
+
+	if (argv.v_nmembs >= UINT_MAX / argv.v_size)
+		goto out;
+
+	len = argv.v_size * argv.v_nmembs;
+	if (!len) {
+		ret = 0;
+		goto out;
+	}
+
+	base = (void __user *)(unsigned long)argv.v_base;
+	kbuf = vmalloc(len);
+	if (!kbuf) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	if (copy_from_user(kbuf, base, len)) {
+		ret = -EFAULT;
+		goto out_free;
+	}
+
+	nilfs_transaction_begin(inode->i_sb, &ti, 0);
+	ret = nilfs_sufile_set_suinfo(nilfs->ns_sufile, kbuf, argv.v_size,
+			argv.v_nmembs);
+	if (unlikely(ret < 0))
+		nilfs_transaction_abort(inode->i_sb);
+	else
+		nilfs_transaction_commit(inode->i_sb); /* never fails */
+
+out_free:
+	vfree(kbuf);
+out:
+	mnt_drop_write_file(filp);
+	return ret;
+}
+
+long nilfs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+{
+	struct inode *inode = file_inode(filp);
+	void __user *argp = (void __user *)arg;
+
+	switch (cmd) {
+	case FS_IOC_GETVERSION:
+		return nilfs_ioctl_getversion(inode, argp);
+	case NILFS_IOCTL_CHANGE_CPMODE:
+		return nilfs_ioctl_change_cpmode(inode, filp, cmd, argp);
+	case NILFS_IOCTL_DELETE_CHECKPOINT:
+		return nilfs_ioctl_delete_checkpoint(inode, filp, cmd, argp);
+	case NILFS_IOCTL_GET_CPINFO:
+		return nilfs_ioctl_get_info(inode, filp, cmd, argp,
+					    sizeof(struct nilfs_cpinfo),
+					    nilfs_ioctl_do_get_cpinfo);
+	case NILFS_IOCTL_GET_CPSTAT:
+		return nilfs_ioctl_get_cpstat(inode, filp, cmd, argp);
+	case NILFS_IOCTL_GET_SUINFO:
+		return nilfs_ioctl_get_info(inode, filp, cmd, argp,
+					    sizeof(struct nilfs_suinfo),
+					    nilfs_ioctl_do_get_suinfo);
+	case NILFS_IOCTL_SET_SUINFO:
+		return nilfs_ioctl_set_suinfo(inode, filp, cmd, argp);
+	case NILFS_IOCTL_GET_SUSTAT:
+		return nilfs_ioctl_get_sustat(inode, filp, cmd, argp);
+	case NILFS_IOCTL_GET_VINFO:
+		return nilfs_ioctl_get_info(inode, filp, cmd, argp,
+					    sizeof(struct nilfs_vinfo),
+					    nilfs_ioctl_do_get_vinfo);
+	case NILFS_IOCTL_GET_BDESCS:
+		return nilfs_ioctl_get_bdescs(inode, filp, cmd, argp);
+	case NILFS_IOCTL_CLEAN_SEGMENTS:
+		return nilfs_ioctl_clean_segments(inode, filp, cmd, argp);
+	case NILFS_IOCTL_SYNC:
+		return nilfs_ioctl_sync(inode, filp, cmd, argp);
+	case NILFS_IOCTL_RESIZE:
+		return nilfs_ioctl_resize(inode, filp, argp);
+	case NILFS_IOCTL_SET_ALLOC_RANGE:
+		return nilfs_ioctl_set_alloc_range(inode, argp);
+	case FITRIM:
+		return nilfs_ioctl_trim_fs(inode, argp);
+	default:
+		return -ENOTTY;
+	}
+}
+
+#ifdef CONFIG_COMPAT
+long nilfs_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+{
+	switch (cmd) {
+	case FS_IOC32_GETVERSION:
+		cmd = FS_IOC_GETVERSION;
+		break;
+	case NILFS_IOCTL_CHANGE_CPMODE:
+	case NILFS_IOCTL_DELETE_CHECKPOINT:
+	case NILFS_IOCTL_GET_CPINFO:
+	case NILFS_IOCTL_GET_CPSTAT:
+	case NILFS_IOCTL_GET_SUINFO:
+	case NILFS_IOCTL_SET_SUINFO:
+	case NILFS_IOCTL_GET_SUSTAT:
+	case NILFS_IOCTL_GET_VINFO:
+	case NILFS_IOCTL_GET_BDESCS:
+	case NILFS_IOCTL_CLEAN_SEGMENTS:
+	case NILFS_IOCTL_SYNC:
+	case NILFS_IOCTL_RESIZE:
+	case NILFS_IOCTL_SET_ALLOC_RANGE:
+	case FITRIM:
+		break;
+	default:
+		return -ENOIOCTLCMD;
+	}
+	return nilfs_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
+}
+#endif
diff --git a/fs/nilfs2/mdt.c b/fs/nilfs2/mdt.c
new file mode 100644
index 0000000000..19c8158605
--- /dev/null
+++ b/fs/nilfs2/mdt.c
@@ -0,0 +1,665 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Meta data file for NILFS
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Ryusuke Konishi.
+ */
+
+#include <linux/buffer_head.h>
+#include <linux/mpage.h>
+#include <linux/mm.h>
+#include <linux/writeback.h>
+#include <linux/backing-dev.h>
+#include <linux/swap.h>
+#include <linux/slab.h>
+#include "nilfs.h"
+#include "btnode.h"
+#include "segment.h"
+#include "page.h"
+#include "mdt.h"
+#include "alloc.h"		/* nilfs_palloc_destroy_cache() */
+
+#include <trace/events/nilfs2.h>
+
+#define NILFS_MDT_MAX_RA_BLOCKS		(16 - 1)
+
+
+static int
+nilfs_mdt_insert_new_block(struct inode *inode, unsigned long block,
+			   struct buffer_head *bh,
+			   void (*init_block)(struct inode *,
+					      struct buffer_head *, void *))
+{
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+	void *kaddr;
+	int ret;
+
+	/* Caller exclude read accesses using page lock */
+
+	/* set_buffer_new(bh); */
+	bh->b_blocknr = 0;
+
+	ret = nilfs_bmap_insert(ii->i_bmap, block, (unsigned long)bh);
+	if (unlikely(ret))
+		return ret;
+
+	set_buffer_mapped(bh);
+
+	kaddr = kmap_atomic(bh->b_page);
+	memset(kaddr + bh_offset(bh), 0, i_blocksize(inode));
+	if (init_block)
+		init_block(inode, bh, kaddr);
+	flush_dcache_page(bh->b_page);
+	kunmap_atomic(kaddr);
+
+	set_buffer_uptodate(bh);
+	mark_buffer_dirty(bh);
+	nilfs_mdt_mark_dirty(inode);
+
+	trace_nilfs2_mdt_insert_new_block(inode, inode->i_ino, block);
+
+	return 0;
+}
+
+static int nilfs_mdt_create_block(struct inode *inode, unsigned long block,
+				  struct buffer_head **out_bh,
+				  void (*init_block)(struct inode *,
+						     struct buffer_head *,
+						     void *))
+{
+	struct super_block *sb = inode->i_sb;
+	struct nilfs_transaction_info ti;
+	struct buffer_head *bh;
+	int err;
+
+	nilfs_transaction_begin(sb, &ti, 0);
+
+	err = -ENOMEM;
+	bh = nilfs_grab_buffer(inode, inode->i_mapping, block, 0);
+	if (unlikely(!bh))
+		goto failed_unlock;
+
+	err = -EEXIST;
+	if (buffer_uptodate(bh))
+		goto failed_bh;
+
+	wait_on_buffer(bh);
+	if (buffer_uptodate(bh))
+		goto failed_bh;
+
+	bh->b_bdev = sb->s_bdev;
+	err = nilfs_mdt_insert_new_block(inode, block, bh, init_block);
+	if (likely(!err)) {
+		get_bh(bh);
+		*out_bh = bh;
+	}
+
+ failed_bh:
+	unlock_page(bh->b_page);
+	put_page(bh->b_page);
+	brelse(bh);
+
+ failed_unlock:
+	if (likely(!err))
+		err = nilfs_transaction_commit(sb);
+	else
+		nilfs_transaction_abort(sb);
+
+	return err;
+}
+
+static int
+nilfs_mdt_submit_block(struct inode *inode, unsigned long blkoff, blk_opf_t opf,
+		       struct buffer_head **out_bh)
+{
+	struct buffer_head *bh;
+	__u64 blknum = 0;
+	int ret = -ENOMEM;
+
+	bh = nilfs_grab_buffer(inode, inode->i_mapping, blkoff, 0);
+	if (unlikely(!bh))
+		goto failed;
+
+	ret = -EEXIST; /* internal code */
+	if (buffer_uptodate(bh))
+		goto out;
+
+	if (opf & REQ_RAHEAD) {
+		if (!trylock_buffer(bh)) {
+			ret = -EBUSY;
+			goto failed_bh;
+		}
+	} else /* opf == REQ_OP_READ */
+		lock_buffer(bh);
+
+	if (buffer_uptodate(bh)) {
+		unlock_buffer(bh);
+		goto out;
+	}
+
+	ret = nilfs_bmap_lookup(NILFS_I(inode)->i_bmap, blkoff, &blknum);
+	if (unlikely(ret)) {
+		unlock_buffer(bh);
+		goto failed_bh;
+	}
+	map_bh(bh, inode->i_sb, (sector_t)blknum);
+
+	bh->b_end_io = end_buffer_read_sync;
+	get_bh(bh);
+	submit_bh(opf, bh);
+	ret = 0;
+
+	trace_nilfs2_mdt_submit_block(inode, inode->i_ino, blkoff,
+				      opf & REQ_OP_MASK);
+ out:
+	get_bh(bh);
+	*out_bh = bh;
+
+ failed_bh:
+	unlock_page(bh->b_page);
+	put_page(bh->b_page);
+	brelse(bh);
+ failed:
+	return ret;
+}
+
+static int nilfs_mdt_read_block(struct inode *inode, unsigned long block,
+				int readahead, struct buffer_head **out_bh)
+{
+	struct buffer_head *first_bh, *bh;
+	unsigned long blkoff;
+	int i, nr_ra_blocks = NILFS_MDT_MAX_RA_BLOCKS;
+	int err;
+
+	err = nilfs_mdt_submit_block(inode, block, REQ_OP_READ, &first_bh);
+	if (err == -EEXIST) /* internal code */
+		goto out;
+
+	if (unlikely(err))
+		goto failed;
+
+	if (readahead) {
+		blkoff = block + 1;
+		for (i = 0; i < nr_ra_blocks; i++, blkoff++) {
+			err = nilfs_mdt_submit_block(inode, blkoff,
+						REQ_OP_READ | REQ_RAHEAD, &bh);
+			if (likely(!err || err == -EEXIST))
+				brelse(bh);
+			else if (err != -EBUSY)
+				break;
+				/* abort readahead if bmap lookup failed */
+			if (!buffer_locked(first_bh))
+				goto out_no_wait;
+		}
+	}
+
+	wait_on_buffer(first_bh);
+
+ out_no_wait:
+	err = -EIO;
+	if (!buffer_uptodate(first_bh)) {
+		nilfs_err(inode->i_sb,
+			  "I/O error reading meta-data file (ino=%lu, block-offset=%lu)",
+			  inode->i_ino, block);
+		goto failed_bh;
+	}
+ out:
+	*out_bh = first_bh;
+	return 0;
+
+ failed_bh:
+	brelse(first_bh);
+ failed:
+	return err;
+}
+
+/**
+ * nilfs_mdt_get_block - read or create a buffer on meta data file.
+ * @inode: inode of the meta data file
+ * @blkoff: block offset
+ * @create: create flag
+ * @init_block: initializer used for newly allocated block
+ * @out_bh: output of a pointer to the buffer_head
+ *
+ * nilfs_mdt_get_block() looks up the specified buffer and tries to create
+ * a new buffer if @create is not zero.  On success, the returned buffer is
+ * assured to be either existing or formatted using a buffer lock on success.
+ * @out_bh is substituted only when zero is returned.
+ *
+ * Return Value: On success, it returns 0. On error, the following negative
+ * error code is returned.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ *
+ * %-EIO - I/O error
+ *
+ * %-ENOENT - the specified block does not exist (hole block)
+ *
+ * %-EROFS - Read only filesystem (for create mode)
+ */
+int nilfs_mdt_get_block(struct inode *inode, unsigned long blkoff, int create,
+			void (*init_block)(struct inode *,
+					   struct buffer_head *, void *),
+			struct buffer_head **out_bh)
+{
+	int ret;
+
+	/* Should be rewritten with merging nilfs_mdt_read_block() */
+ retry:
+	ret = nilfs_mdt_read_block(inode, blkoff, !create, out_bh);
+	if (!create || ret != -ENOENT)
+		return ret;
+
+	ret = nilfs_mdt_create_block(inode, blkoff, out_bh, init_block);
+	if (unlikely(ret == -EEXIST)) {
+		/* create = 0; */  /* limit read-create loop retries */
+		goto retry;
+	}
+	return ret;
+}
+
+/**
+ * nilfs_mdt_find_block - find and get a buffer on meta data file.
+ * @inode: inode of the meta data file
+ * @start: start block offset (inclusive)
+ * @end: end block offset (inclusive)
+ * @blkoff: block offset
+ * @out_bh: place to store a pointer to buffer_head struct
+ *
+ * nilfs_mdt_find_block() looks up an existing block in range of
+ * [@start, @end] and stores pointer to a buffer head of the block to
+ * @out_bh, and block offset to @blkoff, respectively.  @out_bh and
+ * @blkoff are substituted only when zero is returned.
+ *
+ * Return Value: On success, it returns 0. On error, the following negative
+ * error code is returned.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ *
+ * %-EIO - I/O error
+ *
+ * %-ENOENT - no block was found in the range
+ */
+int nilfs_mdt_find_block(struct inode *inode, unsigned long start,
+			 unsigned long end, unsigned long *blkoff,
+			 struct buffer_head **out_bh)
+{
+	__u64 next;
+	int ret;
+
+	if (unlikely(start > end))
+		return -ENOENT;
+
+	ret = nilfs_mdt_read_block(inode, start, true, out_bh);
+	if (!ret) {
+		*blkoff = start;
+		goto out;
+	}
+	if (unlikely(ret != -ENOENT || start == ULONG_MAX))
+		goto out;
+
+	ret = nilfs_bmap_seek_key(NILFS_I(inode)->i_bmap, start + 1, &next);
+	if (!ret) {
+		if (next <= end) {
+			ret = nilfs_mdt_read_block(inode, next, true, out_bh);
+			if (!ret)
+				*blkoff = next;
+		} else {
+			ret = -ENOENT;
+		}
+	}
+out:
+	return ret;
+}
+
+/**
+ * nilfs_mdt_delete_block - make a hole on the meta data file.
+ * @inode: inode of the meta data file
+ * @block: block offset
+ *
+ * Return Value: On success, zero is returned.
+ * On error, one of the following negative error code is returned.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ *
+ * %-EIO - I/O error
+ */
+int nilfs_mdt_delete_block(struct inode *inode, unsigned long block)
+{
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+	int err;
+
+	err = nilfs_bmap_delete(ii->i_bmap, block);
+	if (!err || err == -ENOENT) {
+		nilfs_mdt_mark_dirty(inode);
+		nilfs_mdt_forget_block(inode, block);
+	}
+	return err;
+}
+
+/**
+ * nilfs_mdt_forget_block - discard dirty state and try to remove the page
+ * @inode: inode of the meta data file
+ * @block: block offset
+ *
+ * nilfs_mdt_forget_block() clears a dirty flag of the specified buffer, and
+ * tries to release the page including the buffer from a page cache.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error code is returned.
+ *
+ * %-EBUSY - page has an active buffer.
+ *
+ * %-ENOENT - page cache has no page addressed by the offset.
+ */
+int nilfs_mdt_forget_block(struct inode *inode, unsigned long block)
+{
+	pgoff_t index = (pgoff_t)block >>
+		(PAGE_SHIFT - inode->i_blkbits);
+	struct page *page;
+	unsigned long first_block;
+	int ret = 0;
+	int still_dirty;
+
+	page = find_lock_page(inode->i_mapping, index);
+	if (!page)
+		return -ENOENT;
+
+	wait_on_page_writeback(page);
+
+	first_block = (unsigned long)index <<
+		(PAGE_SHIFT - inode->i_blkbits);
+	if (page_has_buffers(page)) {
+		struct buffer_head *bh;
+
+		bh = nilfs_page_get_nth_block(page, block - first_block);
+		nilfs_forget_buffer(bh);
+	}
+	still_dirty = PageDirty(page);
+	unlock_page(page);
+	put_page(page);
+
+	if (still_dirty ||
+	    invalidate_inode_pages2_range(inode->i_mapping, index, index) != 0)
+		ret = -EBUSY;
+	return ret;
+}
+
+int nilfs_mdt_fetch_dirty(struct inode *inode)
+{
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+
+	if (nilfs_bmap_test_and_clear_dirty(ii->i_bmap)) {
+		set_bit(NILFS_I_DIRTY, &ii->i_state);
+		return 1;
+	}
+	return test_bit(NILFS_I_DIRTY, &ii->i_state);
+}
+
+static int
+nilfs_mdt_write_page(struct page *page, struct writeback_control *wbc)
+{
+	struct inode *inode = page->mapping->host;
+	struct super_block *sb;
+	int err = 0;
+
+	if (inode && sb_rdonly(inode->i_sb)) {
+		/*
+		 * It means that filesystem was remounted in read-only
+		 * mode because of error or metadata corruption. But we
+		 * have dirty pages that try to be flushed in background.
+		 * So, here we simply discard this dirty page.
+		 */
+		nilfs_clear_dirty_page(page, false);
+		unlock_page(page);
+		return -EROFS;
+	}
+
+	redirty_page_for_writepage(wbc, page);
+	unlock_page(page);
+
+	if (!inode)
+		return 0;
+
+	sb = inode->i_sb;
+
+	if (wbc->sync_mode == WB_SYNC_ALL)
+		err = nilfs_construct_segment(sb);
+	else if (wbc->for_reclaim)
+		nilfs_flush_segment(sb, inode->i_ino);
+
+	return err;
+}
+
+
+static const struct address_space_operations def_mdt_aops = {
+	.dirty_folio		= block_dirty_folio,
+	.invalidate_folio	= block_invalidate_folio,
+	.writepage		= nilfs_mdt_write_page,
+};
+
+static const struct inode_operations def_mdt_iops;
+static const struct file_operations def_mdt_fops;
+
+
+int nilfs_mdt_init(struct inode *inode, gfp_t gfp_mask, size_t objsz)
+{
+	struct nilfs_mdt_info *mi;
+
+	mi = kzalloc(max(sizeof(*mi), objsz), GFP_NOFS);
+	if (!mi)
+		return -ENOMEM;
+
+	init_rwsem(&mi->mi_sem);
+	inode->i_private = mi;
+
+	inode->i_mode = S_IFREG;
+	mapping_set_gfp_mask(inode->i_mapping, gfp_mask);
+
+	inode->i_op = &def_mdt_iops;
+	inode->i_fop = &def_mdt_fops;
+	inode->i_mapping->a_ops = &def_mdt_aops;
+
+	return 0;
+}
+
+/**
+ * nilfs_mdt_clear - do cleanup for the metadata file
+ * @inode: inode of the metadata file
+ */
+void nilfs_mdt_clear(struct inode *inode)
+{
+	struct nilfs_mdt_info *mdi = NILFS_MDT(inode);
+	struct nilfs_shadow_map *shadow = mdi->mi_shadow;
+
+	if (mdi->mi_palloc_cache)
+		nilfs_palloc_destroy_cache(inode);
+
+	if (shadow) {
+		struct inode *s_inode = shadow->inode;
+
+		shadow->inode = NULL;
+		iput(s_inode);
+		mdi->mi_shadow = NULL;
+	}
+}
+
+/**
+ * nilfs_mdt_destroy - release resources used by the metadata file
+ * @inode: inode of the metadata file
+ */
+void nilfs_mdt_destroy(struct inode *inode)
+{
+	struct nilfs_mdt_info *mdi = NILFS_MDT(inode);
+
+	kfree(mdi->mi_bgl); /* kfree(NULL) is safe */
+	kfree(mdi);
+}
+
+void nilfs_mdt_set_entry_size(struct inode *inode, unsigned int entry_size,
+			      unsigned int header_size)
+{
+	struct nilfs_mdt_info *mi = NILFS_MDT(inode);
+
+	mi->mi_entry_size = entry_size;
+	mi->mi_entries_per_block = i_blocksize(inode) / entry_size;
+	mi->mi_first_entry_offset = DIV_ROUND_UP(header_size, entry_size);
+}
+
+/**
+ * nilfs_mdt_setup_shadow_map - setup shadow map and bind it to metadata file
+ * @inode: inode of the metadata file
+ * @shadow: shadow mapping
+ */
+int nilfs_mdt_setup_shadow_map(struct inode *inode,
+			       struct nilfs_shadow_map *shadow)
+{
+	struct nilfs_mdt_info *mi = NILFS_MDT(inode);
+	struct inode *s_inode;
+
+	INIT_LIST_HEAD(&shadow->frozen_buffers);
+
+	s_inode = nilfs_iget_for_shadow(inode);
+	if (IS_ERR(s_inode))
+		return PTR_ERR(s_inode);
+
+	shadow->inode = s_inode;
+	mi->mi_shadow = shadow;
+	return 0;
+}
+
+/**
+ * nilfs_mdt_save_to_shadow_map - copy bmap and dirty pages to shadow map
+ * @inode: inode of the metadata file
+ */
+int nilfs_mdt_save_to_shadow_map(struct inode *inode)
+{
+	struct nilfs_mdt_info *mi = NILFS_MDT(inode);
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+	struct nilfs_shadow_map *shadow = mi->mi_shadow;
+	struct inode *s_inode = shadow->inode;
+	int ret;
+
+	ret = nilfs_copy_dirty_pages(s_inode->i_mapping, inode->i_mapping);
+	if (ret)
+		goto out;
+
+	ret = nilfs_copy_dirty_pages(NILFS_I(s_inode)->i_assoc_inode->i_mapping,
+				     ii->i_assoc_inode->i_mapping);
+	if (ret)
+		goto out;
+
+	nilfs_bmap_save(ii->i_bmap, &shadow->bmap_store);
+ out:
+	return ret;
+}
+
+int nilfs_mdt_freeze_buffer(struct inode *inode, struct buffer_head *bh)
+{
+	struct nilfs_shadow_map *shadow = NILFS_MDT(inode)->mi_shadow;
+	struct buffer_head *bh_frozen;
+	struct page *page;
+	int blkbits = inode->i_blkbits;
+
+	page = grab_cache_page(shadow->inode->i_mapping, bh->b_folio->index);
+	if (!page)
+		return -ENOMEM;
+
+	if (!page_has_buffers(page))
+		create_empty_buffers(page, 1 << blkbits, 0);
+
+	bh_frozen = nilfs_page_get_nth_block(page, bh_offset(bh) >> blkbits);
+
+	if (!buffer_uptodate(bh_frozen))
+		nilfs_copy_buffer(bh_frozen, bh);
+	if (list_empty(&bh_frozen->b_assoc_buffers)) {
+		list_add_tail(&bh_frozen->b_assoc_buffers,
+			      &shadow->frozen_buffers);
+		set_buffer_nilfs_redirected(bh);
+	} else {
+		brelse(bh_frozen); /* already frozen */
+	}
+
+	unlock_page(page);
+	put_page(page);
+	return 0;
+}
+
+struct buffer_head *
+nilfs_mdt_get_frozen_buffer(struct inode *inode, struct buffer_head *bh)
+{
+	struct nilfs_shadow_map *shadow = NILFS_MDT(inode)->mi_shadow;
+	struct buffer_head *bh_frozen = NULL;
+	struct page *page;
+	int n;
+
+	page = find_lock_page(shadow->inode->i_mapping, bh->b_folio->index);
+	if (page) {
+		if (page_has_buffers(page)) {
+			n = bh_offset(bh) >> inode->i_blkbits;
+			bh_frozen = nilfs_page_get_nth_block(page, n);
+		}
+		unlock_page(page);
+		put_page(page);
+	}
+	return bh_frozen;
+}
+
+static void nilfs_release_frozen_buffers(struct nilfs_shadow_map *shadow)
+{
+	struct list_head *head = &shadow->frozen_buffers;
+	struct buffer_head *bh;
+
+	while (!list_empty(head)) {
+		bh = list_first_entry(head, struct buffer_head,
+				      b_assoc_buffers);
+		list_del_init(&bh->b_assoc_buffers);
+		brelse(bh); /* drop ref-count to make it releasable */
+	}
+}
+
+/**
+ * nilfs_mdt_restore_from_shadow_map - restore dirty pages and bmap state
+ * @inode: inode of the metadata file
+ */
+void nilfs_mdt_restore_from_shadow_map(struct inode *inode)
+{
+	struct nilfs_mdt_info *mi = NILFS_MDT(inode);
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+	struct nilfs_shadow_map *shadow = mi->mi_shadow;
+
+	down_write(&mi->mi_sem);
+
+	if (mi->mi_palloc_cache)
+		nilfs_palloc_clear_cache(inode);
+
+	nilfs_clear_dirty_pages(inode->i_mapping, true);
+	nilfs_copy_back_pages(inode->i_mapping, shadow->inode->i_mapping);
+
+	nilfs_clear_dirty_pages(ii->i_assoc_inode->i_mapping, true);
+	nilfs_copy_back_pages(ii->i_assoc_inode->i_mapping,
+			      NILFS_I(shadow->inode)->i_assoc_inode->i_mapping);
+
+	nilfs_bmap_restore(ii->i_bmap, &shadow->bmap_store);
+
+	up_write(&mi->mi_sem);
+}
+
+/**
+ * nilfs_mdt_clear_shadow_map - truncate pages in shadow map caches
+ * @inode: inode of the metadata file
+ */
+void nilfs_mdt_clear_shadow_map(struct inode *inode)
+{
+	struct nilfs_mdt_info *mi = NILFS_MDT(inode);
+	struct nilfs_shadow_map *shadow = mi->mi_shadow;
+	struct inode *shadow_btnc_inode = NILFS_I(shadow->inode)->i_assoc_inode;
+
+	down_write(&mi->mi_sem);
+	nilfs_release_frozen_buffers(shadow);
+	truncate_inode_pages(shadow->inode->i_mapping, 0);
+	truncate_inode_pages(shadow_btnc_inode->i_mapping, 0);
+	up_write(&mi->mi_sem);
+}
diff --git a/fs/nilfs2/mdt.h b/fs/nilfs2/mdt.h
new file mode 100644
index 0000000000..9e23bab3ff
--- /dev/null
+++ b/fs/nilfs2/mdt.h
@@ -0,0 +1,115 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * NILFS meta data file prototype and definitions
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Ryusuke Konishi.
+ */
+
+#ifndef _NILFS_MDT_H
+#define _NILFS_MDT_H
+
+#include <linux/buffer_head.h>
+#include <linux/blockgroup_lock.h>
+#include "nilfs.h"
+#include "page.h"
+
+/**
+ * struct nilfs_shadow_map - shadow mapping of meta data file
+ * @bmap_store: shadow copy of bmap state
+ * @inode: holder of page caches used in shadow mapping
+ * @frozen_buffers: list of frozen buffers
+ */
+struct nilfs_shadow_map {
+	struct nilfs_bmap_store bmap_store;
+	struct inode *inode;
+	struct list_head frozen_buffers;
+};
+
+/**
+ * struct nilfs_mdt_info - on-memory private data of meta data files
+ * @mi_sem: reader/writer semaphore for meta data operations
+ * @mi_bgl: per-blockgroup locking
+ * @mi_entry_size: size of an entry
+ * @mi_first_entry_offset: offset to the first entry
+ * @mi_entries_per_block: number of entries in a block
+ * @mi_palloc_cache: persistent object allocator cache
+ * @mi_shadow: shadow of bmap and page caches
+ * @mi_blocks_per_group: number of blocks in a group
+ * @mi_blocks_per_desc_block: number of blocks per descriptor block
+ */
+struct nilfs_mdt_info {
+	struct rw_semaphore	mi_sem;
+	struct blockgroup_lock *mi_bgl;
+	unsigned int		mi_entry_size;
+	unsigned int		mi_first_entry_offset;
+	unsigned long		mi_entries_per_block;
+	struct nilfs_palloc_cache *mi_palloc_cache;
+	struct nilfs_shadow_map *mi_shadow;
+	unsigned long		mi_blocks_per_group;
+	unsigned long		mi_blocks_per_desc_block;
+};
+
+static inline struct nilfs_mdt_info *NILFS_MDT(const struct inode *inode)
+{
+	return inode->i_private;
+}
+
+static inline int nilfs_is_metadata_file_inode(const struct inode *inode)
+{
+	return inode->i_private != NULL;
+}
+
+/* Default GFP flags using highmem */
+#define NILFS_MDT_GFP      (__GFP_RECLAIM | __GFP_IO | __GFP_HIGHMEM)
+
+int nilfs_mdt_get_block(struct inode *, unsigned long, int,
+			void (*init_block)(struct inode *,
+					   struct buffer_head *, void *),
+			struct buffer_head **);
+int nilfs_mdt_find_block(struct inode *inode, unsigned long start,
+			 unsigned long end, unsigned long *blkoff,
+			 struct buffer_head **out_bh);
+int nilfs_mdt_delete_block(struct inode *, unsigned long);
+int nilfs_mdt_forget_block(struct inode *, unsigned long);
+int nilfs_mdt_fetch_dirty(struct inode *);
+
+int nilfs_mdt_init(struct inode *inode, gfp_t gfp_mask, size_t objsz);
+void nilfs_mdt_clear(struct inode *inode);
+void nilfs_mdt_destroy(struct inode *inode);
+
+void nilfs_mdt_set_entry_size(struct inode *, unsigned int, unsigned int);
+
+int nilfs_mdt_setup_shadow_map(struct inode *inode,
+			       struct nilfs_shadow_map *shadow);
+int nilfs_mdt_save_to_shadow_map(struct inode *inode);
+void nilfs_mdt_restore_from_shadow_map(struct inode *inode);
+void nilfs_mdt_clear_shadow_map(struct inode *inode);
+int nilfs_mdt_freeze_buffer(struct inode *inode, struct buffer_head *bh);
+struct buffer_head *nilfs_mdt_get_frozen_buffer(struct inode *inode,
+						struct buffer_head *bh);
+
+static inline void nilfs_mdt_mark_dirty(struct inode *inode)
+{
+	if (!test_bit(NILFS_I_DIRTY, &NILFS_I(inode)->i_state))
+		set_bit(NILFS_I_DIRTY, &NILFS_I(inode)->i_state);
+}
+
+static inline void nilfs_mdt_clear_dirty(struct inode *inode)
+{
+	clear_bit(NILFS_I_DIRTY, &NILFS_I(inode)->i_state);
+}
+
+static inline __u64 nilfs_mdt_cno(struct inode *inode)
+{
+	return ((struct the_nilfs *)inode->i_sb->s_fs_info)->ns_cno;
+}
+
+static inline spinlock_t *
+nilfs_mdt_bgl_lock(struct inode *inode, unsigned int block_group)
+{
+	return bgl_lock_ptr(NILFS_MDT(inode)->mi_bgl, block_group);
+}
+
+#endif /* _NILFS_MDT_H */
diff --git a/fs/nilfs2/namei.c b/fs/nilfs2/namei.c
new file mode 100644
index 0000000000..2a4e7f4a81
--- /dev/null
+++ b/fs/nilfs2/namei.c
@@ -0,0 +1,573 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NILFS pathname lookup operations.
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Modified for NILFS by Amagai Yoshiji and Ryusuke Konishi.
+ */
+/*
+ *  linux/fs/ext2/namei.c
+ *
+ * Copyright (C) 1992, 1993, 1994, 1995
+ * Remy Card (card@masi.ibp.fr)
+ * Laboratoire MASI - Institut Blaise Pascal
+ * Universite Pierre et Marie Curie (Paris VI)
+ *
+ *  from
+ *
+ *  linux/fs/minix/namei.c
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ *
+ *  Big-endian to little-endian byte-swapping/bitmaps by
+ *        David S. Miller (davem@caip.rutgers.edu), 1995
+ */
+
+#include <linux/pagemap.h>
+#include "nilfs.h"
+#include "export.h"
+
+#define NILFS_FID_SIZE_NON_CONNECTABLE \
+	(offsetof(struct nilfs_fid, parent_gen) / 4)
+#define NILFS_FID_SIZE_CONNECTABLE	(sizeof(struct nilfs_fid) / 4)
+
+static inline int nilfs_add_nondir(struct dentry *dentry, struct inode *inode)
+{
+	int err = nilfs_add_link(dentry, inode);
+
+	if (!err) {
+		d_instantiate_new(dentry, inode);
+		return 0;
+	}
+	inode_dec_link_count(inode);
+	unlock_new_inode(inode);
+	iput(inode);
+	return err;
+}
+
+/*
+ * Methods themselves.
+ */
+
+static struct dentry *
+nilfs_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
+{
+	struct inode *inode;
+	ino_t ino;
+
+	if (dentry->d_name.len > NILFS_NAME_LEN)
+		return ERR_PTR(-ENAMETOOLONG);
+
+	ino = nilfs_inode_by_name(dir, &dentry->d_name);
+	inode = ino ? nilfs_iget(dir->i_sb, NILFS_I(dir)->i_root, ino) : NULL;
+	return d_splice_alias(inode, dentry);
+}
+
+/*
+ * By the time this is called, we already have created
+ * the directory cache entry for the new file, but it
+ * is so far negative - it has no inode.
+ *
+ * If the create succeeds, we fill in the inode information
+ * with d_instantiate().
+ */
+static int nilfs_create(struct mnt_idmap *idmap, struct inode *dir,
+			struct dentry *dentry, umode_t mode, bool excl)
+{
+	struct inode *inode;
+	struct nilfs_transaction_info ti;
+	int err;
+
+	err = nilfs_transaction_begin(dir->i_sb, &ti, 1);
+	if (err)
+		return err;
+	inode = nilfs_new_inode(dir, mode);
+	err = PTR_ERR(inode);
+	if (!IS_ERR(inode)) {
+		inode->i_op = &nilfs_file_inode_operations;
+		inode->i_fop = &nilfs_file_operations;
+		inode->i_mapping->a_ops = &nilfs_aops;
+		nilfs_mark_inode_dirty(inode);
+		err = nilfs_add_nondir(dentry, inode);
+	}
+	if (!err)
+		err = nilfs_transaction_commit(dir->i_sb);
+	else
+		nilfs_transaction_abort(dir->i_sb);
+
+	return err;
+}
+
+static int
+nilfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
+	    struct dentry *dentry, umode_t mode, dev_t rdev)
+{
+	struct inode *inode;
+	struct nilfs_transaction_info ti;
+	int err;
+
+	err = nilfs_transaction_begin(dir->i_sb, &ti, 1);
+	if (err)
+		return err;
+	inode = nilfs_new_inode(dir, mode);
+	err = PTR_ERR(inode);
+	if (!IS_ERR(inode)) {
+		init_special_inode(inode, inode->i_mode, rdev);
+		nilfs_mark_inode_dirty(inode);
+		err = nilfs_add_nondir(dentry, inode);
+	}
+	if (!err)
+		err = nilfs_transaction_commit(dir->i_sb);
+	else
+		nilfs_transaction_abort(dir->i_sb);
+
+	return err;
+}
+
+static int nilfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
+			 struct dentry *dentry, const char *symname)
+{
+	struct nilfs_transaction_info ti;
+	struct super_block *sb = dir->i_sb;
+	unsigned int l = strlen(symname) + 1;
+	struct inode *inode;
+	int err;
+
+	if (l > sb->s_blocksize)
+		return -ENAMETOOLONG;
+
+	err = nilfs_transaction_begin(dir->i_sb, &ti, 1);
+	if (err)
+		return err;
+
+	inode = nilfs_new_inode(dir, S_IFLNK | 0777);
+	err = PTR_ERR(inode);
+	if (IS_ERR(inode))
+		goto out;
+
+	/* slow symlink */
+	inode->i_op = &nilfs_symlink_inode_operations;
+	inode_nohighmem(inode);
+	inode->i_mapping->a_ops = &nilfs_aops;
+	err = page_symlink(inode, symname, l);
+	if (err)
+		goto out_fail;
+
+	/* mark_inode_dirty(inode); */
+	/* page_symlink() do this */
+
+	err = nilfs_add_nondir(dentry, inode);
+out:
+	if (!err)
+		err = nilfs_transaction_commit(dir->i_sb);
+	else
+		nilfs_transaction_abort(dir->i_sb);
+
+	return err;
+
+out_fail:
+	drop_nlink(inode);
+	nilfs_mark_inode_dirty(inode);
+	unlock_new_inode(inode);
+	iput(inode);
+	goto out;
+}
+
+static int nilfs_link(struct dentry *old_dentry, struct inode *dir,
+		      struct dentry *dentry)
+{
+	struct inode *inode = d_inode(old_dentry);
+	struct nilfs_transaction_info ti;
+	int err;
+
+	err = nilfs_transaction_begin(dir->i_sb, &ti, 1);
+	if (err)
+		return err;
+
+	inode_set_ctime_current(inode);
+	inode_inc_link_count(inode);
+	ihold(inode);
+
+	err = nilfs_add_link(dentry, inode);
+	if (!err) {
+		d_instantiate(dentry, inode);
+		err = nilfs_transaction_commit(dir->i_sb);
+	} else {
+		inode_dec_link_count(inode);
+		iput(inode);
+		nilfs_transaction_abort(dir->i_sb);
+	}
+
+	return err;
+}
+
+static int nilfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
+		       struct dentry *dentry, umode_t mode)
+{
+	struct inode *inode;
+	struct nilfs_transaction_info ti;
+	int err;
+
+	err = nilfs_transaction_begin(dir->i_sb, &ti, 1);
+	if (err)
+		return err;
+
+	inc_nlink(dir);
+
+	inode = nilfs_new_inode(dir, S_IFDIR | mode);
+	err = PTR_ERR(inode);
+	if (IS_ERR(inode))
+		goto out_dir;
+
+	inode->i_op = &nilfs_dir_inode_operations;
+	inode->i_fop = &nilfs_dir_operations;
+	inode->i_mapping->a_ops = &nilfs_aops;
+
+	inc_nlink(inode);
+
+	err = nilfs_make_empty(inode, dir);
+	if (err)
+		goto out_fail;
+
+	err = nilfs_add_link(dentry, inode);
+	if (err)
+		goto out_fail;
+
+	nilfs_mark_inode_dirty(inode);
+	d_instantiate_new(dentry, inode);
+out:
+	if (!err)
+		err = nilfs_transaction_commit(dir->i_sb);
+	else
+		nilfs_transaction_abort(dir->i_sb);
+
+	return err;
+
+out_fail:
+	drop_nlink(inode);
+	drop_nlink(inode);
+	nilfs_mark_inode_dirty(inode);
+	unlock_new_inode(inode);
+	iput(inode);
+out_dir:
+	drop_nlink(dir);
+	nilfs_mark_inode_dirty(dir);
+	goto out;
+}
+
+static int nilfs_do_unlink(struct inode *dir, struct dentry *dentry)
+{
+	struct inode *inode;
+	struct nilfs_dir_entry *de;
+	struct page *page;
+	int err;
+
+	err = -ENOENT;
+	de = nilfs_find_entry(dir, &dentry->d_name, &page);
+	if (!de)
+		goto out;
+
+	inode = d_inode(dentry);
+	err = -EIO;
+	if (le64_to_cpu(de->inode) != inode->i_ino)
+		goto out;
+
+	if (!inode->i_nlink) {
+		nilfs_warn(inode->i_sb,
+			   "deleting nonexistent file (ino=%lu), %d",
+			   inode->i_ino, inode->i_nlink);
+		set_nlink(inode, 1);
+	}
+	err = nilfs_delete_entry(de, page);
+	if (err)
+		goto out;
+
+	inode_set_ctime_to_ts(inode, inode_get_ctime(dir));
+	drop_nlink(inode);
+	err = 0;
+out:
+	return err;
+}
+
+static int nilfs_unlink(struct inode *dir, struct dentry *dentry)
+{
+	struct nilfs_transaction_info ti;
+	int err;
+
+	err = nilfs_transaction_begin(dir->i_sb, &ti, 0);
+	if (err)
+		return err;
+
+	err = nilfs_do_unlink(dir, dentry);
+
+	if (!err) {
+		nilfs_mark_inode_dirty(dir);
+		nilfs_mark_inode_dirty(d_inode(dentry));
+		err = nilfs_transaction_commit(dir->i_sb);
+	} else
+		nilfs_transaction_abort(dir->i_sb);
+
+	return err;
+}
+
+static int nilfs_rmdir(struct inode *dir, struct dentry *dentry)
+{
+	struct inode *inode = d_inode(dentry);
+	struct nilfs_transaction_info ti;
+	int err;
+
+	err = nilfs_transaction_begin(dir->i_sb, &ti, 0);
+	if (err)
+		return err;
+
+	err = -ENOTEMPTY;
+	if (nilfs_empty_dir(inode)) {
+		err = nilfs_do_unlink(dir, dentry);
+		if (!err) {
+			inode->i_size = 0;
+			drop_nlink(inode);
+			nilfs_mark_inode_dirty(inode);
+			drop_nlink(dir);
+			nilfs_mark_inode_dirty(dir);
+		}
+	}
+	if (!err)
+		err = nilfs_transaction_commit(dir->i_sb);
+	else
+		nilfs_transaction_abort(dir->i_sb);
+
+	return err;
+}
+
+static int nilfs_rename(struct mnt_idmap *idmap,
+			struct inode *old_dir, struct dentry *old_dentry,
+			struct inode *new_dir, struct dentry *new_dentry,
+			unsigned int flags)
+{
+	struct inode *old_inode = d_inode(old_dentry);
+	struct inode *new_inode = d_inode(new_dentry);
+	struct page *dir_page = NULL;
+	struct nilfs_dir_entry *dir_de = NULL;
+	struct page *old_page;
+	struct nilfs_dir_entry *old_de;
+	struct nilfs_transaction_info ti;
+	int err;
+
+	if (flags & ~RENAME_NOREPLACE)
+		return -EINVAL;
+
+	err = nilfs_transaction_begin(old_dir->i_sb, &ti, 1);
+	if (unlikely(err))
+		return err;
+
+	err = -ENOENT;
+	old_de = nilfs_find_entry(old_dir, &old_dentry->d_name, &old_page);
+	if (!old_de)
+		goto out;
+
+	if (S_ISDIR(old_inode->i_mode)) {
+		err = -EIO;
+		dir_de = nilfs_dotdot(old_inode, &dir_page);
+		if (!dir_de)
+			goto out_old;
+	}
+
+	if (new_inode) {
+		struct page *new_page;
+		struct nilfs_dir_entry *new_de;
+
+		err = -ENOTEMPTY;
+		if (dir_de && !nilfs_empty_dir(new_inode))
+			goto out_dir;
+
+		err = -ENOENT;
+		new_de = nilfs_find_entry(new_dir, &new_dentry->d_name, &new_page);
+		if (!new_de)
+			goto out_dir;
+		nilfs_set_link(new_dir, new_de, new_page, old_inode);
+		nilfs_mark_inode_dirty(new_dir);
+		inode_set_ctime_current(new_inode);
+		if (dir_de)
+			drop_nlink(new_inode);
+		drop_nlink(new_inode);
+		nilfs_mark_inode_dirty(new_inode);
+	} else {
+		err = nilfs_add_link(new_dentry, old_inode);
+		if (err)
+			goto out_dir;
+		if (dir_de) {
+			inc_nlink(new_dir);
+			nilfs_mark_inode_dirty(new_dir);
+		}
+	}
+
+	/*
+	 * Like most other Unix systems, set the ctime for inodes on a
+	 * rename.
+	 */
+	inode_set_ctime_current(old_inode);
+
+	nilfs_delete_entry(old_de, old_page);
+
+	if (dir_de) {
+		nilfs_set_link(old_inode, dir_de, dir_page, new_dir);
+		drop_nlink(old_dir);
+	}
+	nilfs_mark_inode_dirty(old_dir);
+	nilfs_mark_inode_dirty(old_inode);
+
+	err = nilfs_transaction_commit(old_dir->i_sb);
+	return err;
+
+out_dir:
+	if (dir_de) {
+		kunmap(dir_page);
+		put_page(dir_page);
+	}
+out_old:
+	kunmap(old_page);
+	put_page(old_page);
+out:
+	nilfs_transaction_abort(old_dir->i_sb);
+	return err;
+}
+
+/*
+ * Export operations
+ */
+static struct dentry *nilfs_get_parent(struct dentry *child)
+{
+	unsigned long ino;
+	struct inode *inode;
+	struct nilfs_root *root;
+
+	ino = nilfs_inode_by_name(d_inode(child), &dotdot_name);
+	if (!ino)
+		return ERR_PTR(-ENOENT);
+
+	root = NILFS_I(d_inode(child))->i_root;
+
+	inode = nilfs_iget(child->d_sb, root, ino);
+	if (IS_ERR(inode))
+		return ERR_CAST(inode);
+
+	return d_obtain_alias(inode);
+}
+
+static struct dentry *nilfs_get_dentry(struct super_block *sb, u64 cno,
+				       u64 ino, u32 gen)
+{
+	struct nilfs_root *root;
+	struct inode *inode;
+
+	if (ino < NILFS_FIRST_INO(sb) && ino != NILFS_ROOT_INO)
+		return ERR_PTR(-ESTALE);
+
+	root = nilfs_lookup_root(sb->s_fs_info, cno);
+	if (!root)
+		return ERR_PTR(-ESTALE);
+
+	inode = nilfs_iget(sb, root, ino);
+	nilfs_put_root(root);
+
+	if (IS_ERR(inode))
+		return ERR_CAST(inode);
+	if (gen && inode->i_generation != gen) {
+		iput(inode);
+		return ERR_PTR(-ESTALE);
+	}
+	return d_obtain_alias(inode);
+}
+
+static struct dentry *nilfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
+					 int fh_len, int fh_type)
+{
+	struct nilfs_fid *fid = (struct nilfs_fid *)fh;
+
+	if (fh_len < NILFS_FID_SIZE_NON_CONNECTABLE ||
+	    (fh_type != FILEID_NILFS_WITH_PARENT &&
+	     fh_type != FILEID_NILFS_WITHOUT_PARENT))
+		return NULL;
+
+	return nilfs_get_dentry(sb, fid->cno, fid->ino, fid->gen);
+}
+
+static struct dentry *nilfs_fh_to_parent(struct super_block *sb, struct fid *fh,
+					 int fh_len, int fh_type)
+{
+	struct nilfs_fid *fid = (struct nilfs_fid *)fh;
+
+	if (fh_len < NILFS_FID_SIZE_CONNECTABLE ||
+	    fh_type != FILEID_NILFS_WITH_PARENT)
+		return NULL;
+
+	return nilfs_get_dentry(sb, fid->cno, fid->parent_ino, fid->parent_gen);
+}
+
+static int nilfs_encode_fh(struct inode *inode, __u32 *fh, int *lenp,
+			   struct inode *parent)
+{
+	struct nilfs_fid *fid = (struct nilfs_fid *)fh;
+	struct nilfs_root *root = NILFS_I(inode)->i_root;
+	int type;
+
+	if (parent && *lenp < NILFS_FID_SIZE_CONNECTABLE) {
+		*lenp = NILFS_FID_SIZE_CONNECTABLE;
+		return FILEID_INVALID;
+	}
+	if (*lenp < NILFS_FID_SIZE_NON_CONNECTABLE) {
+		*lenp = NILFS_FID_SIZE_NON_CONNECTABLE;
+		return FILEID_INVALID;
+	}
+
+	fid->cno = root->cno;
+	fid->ino = inode->i_ino;
+	fid->gen = inode->i_generation;
+
+	if (parent) {
+		fid->parent_ino = parent->i_ino;
+		fid->parent_gen = parent->i_generation;
+		type = FILEID_NILFS_WITH_PARENT;
+		*lenp = NILFS_FID_SIZE_CONNECTABLE;
+	} else {
+		type = FILEID_NILFS_WITHOUT_PARENT;
+		*lenp = NILFS_FID_SIZE_NON_CONNECTABLE;
+	}
+
+	return type;
+}
+
+const struct inode_operations nilfs_dir_inode_operations = {
+	.create		= nilfs_create,
+	.lookup		= nilfs_lookup,
+	.link		= nilfs_link,
+	.unlink		= nilfs_unlink,
+	.symlink	= nilfs_symlink,
+	.mkdir		= nilfs_mkdir,
+	.rmdir		= nilfs_rmdir,
+	.mknod		= nilfs_mknod,
+	.rename		= nilfs_rename,
+	.setattr	= nilfs_setattr,
+	.permission	= nilfs_permission,
+	.fiemap		= nilfs_fiemap,
+	.fileattr_get	= nilfs_fileattr_get,
+	.fileattr_set	= nilfs_fileattr_set,
+};
+
+const struct inode_operations nilfs_special_inode_operations = {
+	.setattr	= nilfs_setattr,
+	.permission	= nilfs_permission,
+};
+
+const struct inode_operations nilfs_symlink_inode_operations = {
+	.get_link	= page_get_link,
+	.permission     = nilfs_permission,
+};
+
+const struct export_operations nilfs_export_ops = {
+	.encode_fh = nilfs_encode_fh,
+	.fh_to_dentry = nilfs_fh_to_dentry,
+	.fh_to_parent = nilfs_fh_to_parent,
+	.get_parent = nilfs_get_parent,
+};
diff --git a/fs/nilfs2/nilfs.h b/fs/nilfs2/nilfs.h
new file mode 100644
index 0000000000..8046490cd7
--- /dev/null
+++ b/fs/nilfs2/nilfs.h
@@ -0,0 +1,386 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * NILFS local header file.
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Koji Sato and Ryusuke Konishi.
+ */
+
+#ifndef _NILFS_H
+#define _NILFS_H
+
+#include <linux/kernel.h>
+#include <linux/buffer_head.h>
+#include <linux/spinlock.h>
+#include <linux/blkdev.h>
+#include <linux/nilfs2_api.h>
+#include <linux/nilfs2_ondisk.h>
+#include "the_nilfs.h"
+#include "bmap.h"
+
+/**
+ * struct nilfs_inode_info - nilfs inode data in memory
+ * @i_flags: inode flags
+ * @i_state: dynamic state flags
+ * @i_bmap: pointer on i_bmap_data
+ * @i_bmap_data: raw block mapping
+ * @i_xattr: <TODO>
+ * @i_dir_start_lookup: page index of last successful search
+ * @i_cno: checkpoint number for GC inode
+ * @i_assoc_inode: associated inode (B-tree node cache holder or back pointer)
+ * @i_dirty: list for connecting dirty files
+ * @xattr_sem: semaphore for extended attributes processing
+ * @i_bh: buffer contains disk inode
+ * @i_root: root object of the current filesystem tree
+ * @vfs_inode: VFS inode object
+ */
+struct nilfs_inode_info {
+	__u32 i_flags;
+	unsigned long  i_state;		/* Dynamic state flags */
+	struct nilfs_bmap *i_bmap;
+	struct nilfs_bmap i_bmap_data;
+	__u64 i_xattr;	/* sector_t ??? */
+	__u32 i_dir_start_lookup;
+	__u64 i_cno;		/* check point number for GC inode */
+	struct inode *i_assoc_inode;
+	struct list_head i_dirty;	/* List for connecting dirty files */
+
+#ifdef CONFIG_NILFS_XATTR
+	/*
+	 * Extended attributes can be read independently of the main file
+	 * data. Taking i_sem even when reading would cause contention
+	 * between readers of EAs and writers of regular file data, so
+	 * instead we synchronize on xattr_sem when reading or changing
+	 * EAs.
+	 */
+	struct rw_semaphore xattr_sem;
+#endif
+	struct buffer_head *i_bh;	/*
+					 * i_bh contains a new or dirty
+					 * disk inode.
+					 */
+	struct nilfs_root *i_root;
+	struct inode vfs_inode;
+};
+
+static inline struct nilfs_inode_info *NILFS_I(const struct inode *inode)
+{
+	return container_of(inode, struct nilfs_inode_info, vfs_inode);
+}
+
+static inline struct nilfs_inode_info *
+NILFS_BMAP_I(const struct nilfs_bmap *bmap)
+{
+	return container_of(bmap, struct nilfs_inode_info, i_bmap_data);
+}
+
+/*
+ * Dynamic state flags of NILFS on-memory inode (i_state)
+ */
+enum {
+	NILFS_I_NEW = 0,		/* Inode is newly created */
+	NILFS_I_DIRTY,			/* The file is dirty */
+	NILFS_I_QUEUED,			/* inode is in dirty_files list */
+	NILFS_I_BUSY,			/*
+					 * Inode is grabbed by a segment
+					 * constructor
+					 */
+	NILFS_I_COLLECTED,		/* All dirty blocks are collected */
+	NILFS_I_UPDATED,		/* The file has been written back */
+	NILFS_I_INODE_SYNC,		/* dsync is not allowed for inode */
+	NILFS_I_BMAP,			/* has bmap and btnode_cache */
+	NILFS_I_GCINODE,		/* inode for GC, on memory only */
+	NILFS_I_BTNC,			/* inode for btree node cache */
+	NILFS_I_SHADOW,			/* inode for shadowed page cache */
+};
+
+/*
+ * commit flags for nilfs_commit_super and nilfs_sync_super
+ */
+enum {
+	NILFS_SB_COMMIT = 0,	/* Commit a super block alternately */
+	NILFS_SB_COMMIT_ALL	/* Commit both super blocks */
+};
+
+/*
+ * Macros to check inode numbers
+ */
+#define NILFS_MDT_INO_BITS						\
+	(BIT(NILFS_DAT_INO) | BIT(NILFS_CPFILE_INO) |			\
+	 BIT(NILFS_SUFILE_INO) | BIT(NILFS_IFILE_INO) |			\
+	 BIT(NILFS_ATIME_INO) | BIT(NILFS_SKETCH_INO))
+
+#define NILFS_SYS_INO_BITS (BIT(NILFS_ROOT_INO) | NILFS_MDT_INO_BITS)
+
+#define NILFS_FIRST_INO(sb) (((struct the_nilfs *)sb->s_fs_info)->ns_first_ino)
+
+#define NILFS_MDT_INODE(sb, ino) \
+	((ino) < NILFS_FIRST_INO(sb) && (NILFS_MDT_INO_BITS & BIT(ino)))
+#define NILFS_VALID_INODE(sb, ino) \
+	((ino) >= NILFS_FIRST_INO(sb) || (NILFS_SYS_INO_BITS & BIT(ino)))
+
+/**
+ * struct nilfs_transaction_info: context information for synchronization
+ * @ti_magic: Magic number
+ * @ti_save: Backup of journal_info field of task_struct
+ * @ti_flags: Flags
+ * @ti_count: Nest level
+ */
+struct nilfs_transaction_info {
+	u32			ti_magic;
+	void		       *ti_save;
+				/*
+				 * This should never be used.  If it happens,
+				 * one of other filesystems has a bug.
+				 */
+	unsigned short		ti_flags;
+	unsigned short		ti_count;
+};
+
+/* ti_magic */
+#define NILFS_TI_MAGIC		0xd9e392fb
+
+/* ti_flags */
+#define NILFS_TI_DYNAMIC_ALLOC	0x0001  /* Allocated from slab */
+#define NILFS_TI_SYNC		0x0002	/*
+					 * Force to construct segment at the
+					 * end of transaction.
+					 */
+#define NILFS_TI_GC		0x0004	/* GC context */
+#define NILFS_TI_COMMIT		0x0008	/* Change happened or not */
+#define NILFS_TI_WRITER		0x0010	/* Constructor context */
+
+
+int nilfs_transaction_begin(struct super_block *,
+			    struct nilfs_transaction_info *, int);
+int nilfs_transaction_commit(struct super_block *);
+void nilfs_transaction_abort(struct super_block *);
+
+static inline void nilfs_set_transaction_flag(unsigned int flag)
+{
+	struct nilfs_transaction_info *ti = current->journal_info;
+
+	ti->ti_flags |= flag;
+}
+
+static inline int nilfs_test_transaction_flag(unsigned int flag)
+{
+	struct nilfs_transaction_info *ti = current->journal_info;
+
+	if (ti == NULL || ti->ti_magic != NILFS_TI_MAGIC)
+		return 0;
+	return !!(ti->ti_flags & flag);
+}
+
+static inline int nilfs_doing_gc(void)
+{
+	return nilfs_test_transaction_flag(NILFS_TI_GC);
+}
+
+static inline int nilfs_doing_construction(void)
+{
+	return nilfs_test_transaction_flag(NILFS_TI_WRITER);
+}
+
+/*
+ * function prototype
+ */
+#ifdef CONFIG_NILFS_POSIX_ACL
+#error "NILFS: not yet supported POSIX ACL"
+extern int nilfs_acl_chmod(struct inode *);
+extern int nilfs_init_acl(struct inode *, struct inode *);
+#else
+static inline int nilfs_acl_chmod(struct inode *inode)
+{
+	return 0;
+}
+
+static inline int nilfs_init_acl(struct inode *inode, struct inode *dir)
+{
+	if (S_ISLNK(inode->i_mode))
+		return 0;
+
+	inode->i_mode &= ~current_umask();
+	return 0;
+}
+#endif
+
+#define NILFS_ATIME_DISABLE
+
+/* Flags that should be inherited by new inodes from their parent. */
+#define NILFS_FL_INHERITED						\
+	(FS_SECRM_FL | FS_UNRM_FL | FS_COMPR_FL | FS_SYNC_FL |		\
+	 FS_IMMUTABLE_FL | FS_APPEND_FL | FS_NODUMP_FL | FS_NOATIME_FL |\
+	 FS_COMPRBLK_FL | FS_NOCOMP_FL | FS_NOTAIL_FL | FS_DIRSYNC_FL)
+
+/* Mask out flags that are inappropriate for the given type of inode. */
+static inline __u32 nilfs_mask_flags(umode_t mode, __u32 flags)
+{
+	if (S_ISDIR(mode))
+		return flags;
+	else if (S_ISREG(mode))
+		return flags & ~(FS_DIRSYNC_FL | FS_TOPDIR_FL);
+	else
+		return flags & (FS_NODUMP_FL | FS_NOATIME_FL);
+}
+
+/* dir.c */
+extern int nilfs_add_link(struct dentry *, struct inode *);
+extern ino_t nilfs_inode_by_name(struct inode *, const struct qstr *);
+extern int nilfs_make_empty(struct inode *, struct inode *);
+extern struct nilfs_dir_entry *
+nilfs_find_entry(struct inode *, const struct qstr *, struct page **);
+extern int nilfs_delete_entry(struct nilfs_dir_entry *, struct page *);
+extern int nilfs_empty_dir(struct inode *);
+extern struct nilfs_dir_entry *nilfs_dotdot(struct inode *, struct page **);
+extern void nilfs_set_link(struct inode *, struct nilfs_dir_entry *,
+			   struct page *, struct inode *);
+
+/* file.c */
+extern int nilfs_sync_file(struct file *, loff_t, loff_t, int);
+
+/* ioctl.c */
+int nilfs_fileattr_get(struct dentry *dentry, struct fileattr *m);
+int nilfs_fileattr_set(struct mnt_idmap *idmap,
+		       struct dentry *dentry, struct fileattr *fa);
+long nilfs_ioctl(struct file *, unsigned int, unsigned long);
+long nilfs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
+int nilfs_ioctl_prepare_clean_segments(struct the_nilfs *, struct nilfs_argv *,
+				       void **);
+
+/* inode.c */
+void nilfs_inode_add_blocks(struct inode *inode, int n);
+void nilfs_inode_sub_blocks(struct inode *inode, int n);
+extern struct inode *nilfs_new_inode(struct inode *, umode_t);
+extern int nilfs_get_block(struct inode *, sector_t, struct buffer_head *, int);
+extern void nilfs_set_inode_flags(struct inode *);
+extern int nilfs_read_inode_common(struct inode *, struct nilfs_inode *);
+extern void nilfs_write_inode_common(struct inode *, struct nilfs_inode *, int);
+struct inode *nilfs_ilookup(struct super_block *sb, struct nilfs_root *root,
+			    unsigned long ino);
+struct inode *nilfs_iget_locked(struct super_block *sb, struct nilfs_root *root,
+				unsigned long ino);
+struct inode *nilfs_iget(struct super_block *sb, struct nilfs_root *root,
+			 unsigned long ino);
+extern struct inode *nilfs_iget_for_gc(struct super_block *sb,
+				       unsigned long ino, __u64 cno);
+int nilfs_attach_btree_node_cache(struct inode *inode);
+void nilfs_detach_btree_node_cache(struct inode *inode);
+struct inode *nilfs_iget_for_shadow(struct inode *inode);
+extern void nilfs_update_inode(struct inode *, struct buffer_head *, int);
+extern void nilfs_truncate(struct inode *);
+extern void nilfs_evict_inode(struct inode *);
+extern int nilfs_setattr(struct mnt_idmap *, struct dentry *,
+			 struct iattr *);
+extern void nilfs_write_failed(struct address_space *mapping, loff_t to);
+int nilfs_permission(struct mnt_idmap *idmap, struct inode *inode,
+		     int mask);
+int nilfs_load_inode_block(struct inode *inode, struct buffer_head **pbh);
+extern int nilfs_inode_dirty(struct inode *);
+int nilfs_set_file_dirty(struct inode *inode, unsigned int nr_dirty);
+extern int __nilfs_mark_inode_dirty(struct inode *, int);
+extern void nilfs_dirty_inode(struct inode *, int flags);
+int nilfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
+		 __u64 start, __u64 len);
+static inline int nilfs_mark_inode_dirty(struct inode *inode)
+{
+	return __nilfs_mark_inode_dirty(inode, I_DIRTY);
+}
+static inline int nilfs_mark_inode_dirty_sync(struct inode *inode)
+{
+	return __nilfs_mark_inode_dirty(inode, I_DIRTY_SYNC);
+}
+
+/* super.c */
+extern struct inode *nilfs_alloc_inode(struct super_block *);
+
+__printf(2, 3)
+void __nilfs_msg(struct super_block *sb, const char *fmt, ...);
+extern __printf(3, 4)
+void __nilfs_error(struct super_block *sb, const char *function,
+		   const char *fmt, ...);
+
+#ifdef CONFIG_PRINTK
+
+#define nilfs_msg(sb, level, fmt, ...)					\
+	__nilfs_msg(sb, level fmt, ##__VA_ARGS__)
+#define nilfs_error(sb, fmt, ...)					\
+	__nilfs_error(sb, __func__, fmt, ##__VA_ARGS__)
+
+#else
+
+#define nilfs_msg(sb, level, fmt, ...)					\
+	do {								\
+		no_printk(level fmt, ##__VA_ARGS__);			\
+		(void)(sb);						\
+	} while (0)
+#define nilfs_error(sb, fmt, ...)					\
+	do {								\
+		no_printk(fmt, ##__VA_ARGS__);				\
+		__nilfs_error(sb, "", " ");				\
+	} while (0)
+
+#endif /* CONFIG_PRINTK */
+
+#define nilfs_crit(sb, fmt, ...)					\
+	nilfs_msg(sb, KERN_CRIT, fmt, ##__VA_ARGS__)
+#define nilfs_err(sb, fmt, ...)						\
+	nilfs_msg(sb, KERN_ERR, fmt, ##__VA_ARGS__)
+#define nilfs_warn(sb, fmt, ...)					\
+	nilfs_msg(sb, KERN_WARNING, fmt, ##__VA_ARGS__)
+#define nilfs_info(sb, fmt, ...)					\
+	nilfs_msg(sb, KERN_INFO, fmt, ##__VA_ARGS__)
+
+extern struct nilfs_super_block *
+nilfs_read_super_block(struct super_block *, u64, int, struct buffer_head **);
+extern int nilfs_store_magic_and_option(struct super_block *,
+					struct nilfs_super_block *, char *);
+extern int nilfs_check_feature_compatibility(struct super_block *,
+					     struct nilfs_super_block *);
+extern void nilfs_set_log_cursor(struct nilfs_super_block *,
+				 struct the_nilfs *);
+struct nilfs_super_block **nilfs_prepare_super(struct super_block *sb,
+					       int flip);
+int nilfs_commit_super(struct super_block *sb, int flag);
+int nilfs_cleanup_super(struct super_block *sb);
+int nilfs_resize_fs(struct super_block *sb, __u64 newsize);
+int nilfs_attach_checkpoint(struct super_block *sb, __u64 cno, int curr_mnt,
+			    struct nilfs_root **root);
+int nilfs_checkpoint_is_mounted(struct super_block *sb, __u64 cno);
+
+/* gcinode.c */
+int nilfs_gccache_submit_read_data(struct inode *, sector_t, sector_t, __u64,
+				   struct buffer_head **);
+int nilfs_gccache_submit_read_node(struct inode *, sector_t, __u64,
+				   struct buffer_head **);
+int nilfs_gccache_wait_and_mark_dirty(struct buffer_head *);
+int nilfs_init_gcinode(struct inode *inode);
+void nilfs_remove_all_gcinodes(struct the_nilfs *nilfs);
+
+/* sysfs.c */
+int __init nilfs_sysfs_init(void);
+void nilfs_sysfs_exit(void);
+int nilfs_sysfs_create_device_group(struct super_block *);
+void nilfs_sysfs_delete_device_group(struct the_nilfs *);
+int nilfs_sysfs_create_snapshot_group(struct nilfs_root *);
+void nilfs_sysfs_delete_snapshot_group(struct nilfs_root *);
+
+/*
+ * Inodes and files operations
+ */
+extern const struct file_operations nilfs_dir_operations;
+extern const struct inode_operations nilfs_file_inode_operations;
+extern const struct file_operations nilfs_file_operations;
+extern const struct address_space_operations nilfs_aops;
+extern const struct inode_operations nilfs_dir_inode_operations;
+extern const struct inode_operations nilfs_special_inode_operations;
+extern const struct inode_operations nilfs_symlink_inode_operations;
+
+/*
+ * filesystem type
+ */
+extern struct file_system_type nilfs_fs_type;
+
+
+#endif	/* _NILFS_H */
diff --git a/fs/nilfs2/page.c b/fs/nilfs2/page.c
new file mode 100644
index 0000000000..b4e54d079b
--- /dev/null
+++ b/fs/nilfs2/page.c
@@ -0,0 +1,549 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Buffer/page management specific to NILFS
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Ryusuke Konishi and Seiji Kihara.
+ */
+
+#include <linux/pagemap.h>
+#include <linux/writeback.h>
+#include <linux/swap.h>
+#include <linux/bitops.h>
+#include <linux/page-flags.h>
+#include <linux/list.h>
+#include <linux/highmem.h>
+#include <linux/pagevec.h>
+#include <linux/gfp.h>
+#include "nilfs.h"
+#include "page.h"
+#include "mdt.h"
+
+
+#define NILFS_BUFFER_INHERENT_BITS					\
+	(BIT(BH_Uptodate) | BIT(BH_Mapped) | BIT(BH_NILFS_Node) |	\
+	 BIT(BH_NILFS_Volatile) | BIT(BH_NILFS_Checked))
+
+static struct buffer_head *
+__nilfs_get_page_block(struct page *page, unsigned long block, pgoff_t index,
+		       int blkbits, unsigned long b_state)
+
+{
+	unsigned long first_block;
+	struct buffer_head *bh;
+
+	if (!page_has_buffers(page))
+		create_empty_buffers(page, 1 << blkbits, b_state);
+
+	first_block = (unsigned long)index << (PAGE_SHIFT - blkbits);
+	bh = nilfs_page_get_nth_block(page, block - first_block);
+
+	touch_buffer(bh);
+	wait_on_buffer(bh);
+	return bh;
+}
+
+struct buffer_head *nilfs_grab_buffer(struct inode *inode,
+				      struct address_space *mapping,
+				      unsigned long blkoff,
+				      unsigned long b_state)
+{
+	int blkbits = inode->i_blkbits;
+	pgoff_t index = blkoff >> (PAGE_SHIFT - blkbits);
+	struct page *page;
+	struct buffer_head *bh;
+
+	page = grab_cache_page(mapping, index);
+	if (unlikely(!page))
+		return NULL;
+
+	bh = __nilfs_get_page_block(page, blkoff, index, blkbits, b_state);
+	if (unlikely(!bh)) {
+		unlock_page(page);
+		put_page(page);
+		return NULL;
+	}
+	return bh;
+}
+
+/**
+ * nilfs_forget_buffer - discard dirty state
+ * @bh: buffer head of the buffer to be discarded
+ */
+void nilfs_forget_buffer(struct buffer_head *bh)
+{
+	struct page *page = bh->b_page;
+	const unsigned long clear_bits =
+		(BIT(BH_Uptodate) | BIT(BH_Dirty) | BIT(BH_Mapped) |
+		 BIT(BH_Async_Write) | BIT(BH_NILFS_Volatile) |
+		 BIT(BH_NILFS_Checked) | BIT(BH_NILFS_Redirected));
+
+	lock_buffer(bh);
+	set_mask_bits(&bh->b_state, clear_bits, 0);
+	if (nilfs_page_buffers_clean(page))
+		__nilfs_clear_page_dirty(page);
+
+	bh->b_blocknr = -1;
+	ClearPageUptodate(page);
+	ClearPageMappedToDisk(page);
+	unlock_buffer(bh);
+	brelse(bh);
+}
+
+/**
+ * nilfs_copy_buffer -- copy buffer data and flags
+ * @dbh: destination buffer
+ * @sbh: source buffer
+ */
+void nilfs_copy_buffer(struct buffer_head *dbh, struct buffer_head *sbh)
+{
+	void *kaddr0, *kaddr1;
+	unsigned long bits;
+	struct page *spage = sbh->b_page, *dpage = dbh->b_page;
+	struct buffer_head *bh;
+
+	kaddr0 = kmap_atomic(spage);
+	kaddr1 = kmap_atomic(dpage);
+	memcpy(kaddr1 + bh_offset(dbh), kaddr0 + bh_offset(sbh), sbh->b_size);
+	kunmap_atomic(kaddr1);
+	kunmap_atomic(kaddr0);
+
+	dbh->b_state = sbh->b_state & NILFS_BUFFER_INHERENT_BITS;
+	dbh->b_blocknr = sbh->b_blocknr;
+	dbh->b_bdev = sbh->b_bdev;
+
+	bh = dbh;
+	bits = sbh->b_state & (BIT(BH_Uptodate) | BIT(BH_Mapped));
+	while ((bh = bh->b_this_page) != dbh) {
+		lock_buffer(bh);
+		bits &= bh->b_state;
+		unlock_buffer(bh);
+	}
+	if (bits & BIT(BH_Uptodate))
+		SetPageUptodate(dpage);
+	else
+		ClearPageUptodate(dpage);
+	if (bits & BIT(BH_Mapped))
+		SetPageMappedToDisk(dpage);
+	else
+		ClearPageMappedToDisk(dpage);
+}
+
+/**
+ * nilfs_page_buffers_clean - check if a page has dirty buffers or not.
+ * @page: page to be checked
+ *
+ * nilfs_page_buffers_clean() returns zero if the page has dirty buffers.
+ * Otherwise, it returns non-zero value.
+ */
+int nilfs_page_buffers_clean(struct page *page)
+{
+	struct buffer_head *bh, *head;
+
+	bh = head = page_buffers(page);
+	do {
+		if (buffer_dirty(bh))
+			return 0;
+		bh = bh->b_this_page;
+	} while (bh != head);
+	return 1;
+}
+
+void nilfs_page_bug(struct page *page)
+{
+	struct address_space *m;
+	unsigned long ino;
+
+	if (unlikely(!page)) {
+		printk(KERN_CRIT "NILFS_PAGE_BUG(NULL)\n");
+		return;
+	}
+
+	m = page->mapping;
+	ino = m ? m->host->i_ino : 0;
+
+	printk(KERN_CRIT "NILFS_PAGE_BUG(%p): cnt=%d index#=%llu flags=0x%lx "
+	       "mapping=%p ino=%lu\n",
+	       page, page_ref_count(page),
+	       (unsigned long long)page->index, page->flags, m, ino);
+
+	if (page_has_buffers(page)) {
+		struct buffer_head *bh, *head;
+		int i = 0;
+
+		bh = head = page_buffers(page);
+		do {
+			printk(KERN_CRIT
+			       " BH[%d] %p: cnt=%d block#=%llu state=0x%lx\n",
+			       i++, bh, atomic_read(&bh->b_count),
+			       (unsigned long long)bh->b_blocknr, bh->b_state);
+			bh = bh->b_this_page;
+		} while (bh != head);
+	}
+}
+
+/**
+ * nilfs_copy_page -- copy the page with buffers
+ * @dst: destination page
+ * @src: source page
+ * @copy_dirty: flag whether to copy dirty states on the page's buffer heads.
+ *
+ * This function is for both data pages and btnode pages.  The dirty flag
+ * should be treated by caller.  The page must not be under i/o.
+ * Both src and dst page must be locked
+ */
+static void nilfs_copy_page(struct page *dst, struct page *src, int copy_dirty)
+{
+	struct buffer_head *dbh, *dbufs, *sbh;
+	unsigned long mask = NILFS_BUFFER_INHERENT_BITS;
+
+	BUG_ON(PageWriteback(dst));
+
+	sbh = page_buffers(src);
+	if (!page_has_buffers(dst))
+		create_empty_buffers(dst, sbh->b_size, 0);
+
+	if (copy_dirty)
+		mask |= BIT(BH_Dirty);
+
+	dbh = dbufs = page_buffers(dst);
+	do {
+		lock_buffer(sbh);
+		lock_buffer(dbh);
+		dbh->b_state = sbh->b_state & mask;
+		dbh->b_blocknr = sbh->b_blocknr;
+		dbh->b_bdev = sbh->b_bdev;
+		sbh = sbh->b_this_page;
+		dbh = dbh->b_this_page;
+	} while (dbh != dbufs);
+
+	copy_highpage(dst, src);
+
+	if (PageUptodate(src) && !PageUptodate(dst))
+		SetPageUptodate(dst);
+	else if (!PageUptodate(src) && PageUptodate(dst))
+		ClearPageUptodate(dst);
+	if (PageMappedToDisk(src) && !PageMappedToDisk(dst))
+		SetPageMappedToDisk(dst);
+	else if (!PageMappedToDisk(src) && PageMappedToDisk(dst))
+		ClearPageMappedToDisk(dst);
+
+	do {
+		unlock_buffer(sbh);
+		unlock_buffer(dbh);
+		sbh = sbh->b_this_page;
+		dbh = dbh->b_this_page;
+	} while (dbh != dbufs);
+}
+
+int nilfs_copy_dirty_pages(struct address_space *dmap,
+			   struct address_space *smap)
+{
+	struct folio_batch fbatch;
+	unsigned int i;
+	pgoff_t index = 0;
+	int err = 0;
+
+	folio_batch_init(&fbatch);
+repeat:
+	if (!filemap_get_folios_tag(smap, &index, (pgoff_t)-1,
+				PAGECACHE_TAG_DIRTY, &fbatch))
+		return 0;
+
+	for (i = 0; i < folio_batch_count(&fbatch); i++) {
+		struct folio *folio = fbatch.folios[i], *dfolio;
+
+		folio_lock(folio);
+		if (unlikely(!folio_test_dirty(folio)))
+			NILFS_PAGE_BUG(&folio->page, "inconsistent dirty state");
+
+		dfolio = filemap_grab_folio(dmap, folio->index);
+		if (unlikely(IS_ERR(dfolio))) {
+			/* No empty page is added to the page cache */
+			folio_unlock(folio);
+			err = PTR_ERR(dfolio);
+			break;
+		}
+		if (unlikely(!folio_buffers(folio)))
+			NILFS_PAGE_BUG(&folio->page,
+				       "found empty page in dat page cache");
+
+		nilfs_copy_page(&dfolio->page, &folio->page, 1);
+		filemap_dirty_folio(folio_mapping(dfolio), dfolio);
+
+		folio_unlock(dfolio);
+		folio_put(dfolio);
+		folio_unlock(folio);
+	}
+	folio_batch_release(&fbatch);
+	cond_resched();
+
+	if (likely(!err))
+		goto repeat;
+	return err;
+}
+
+/**
+ * nilfs_copy_back_pages -- copy back pages to original cache from shadow cache
+ * @dmap: destination page cache
+ * @smap: source page cache
+ *
+ * No pages must be added to the cache during this process.
+ * This must be ensured by the caller.
+ */
+void nilfs_copy_back_pages(struct address_space *dmap,
+			   struct address_space *smap)
+{
+	struct folio_batch fbatch;
+	unsigned int i, n;
+	pgoff_t start = 0;
+
+	folio_batch_init(&fbatch);
+repeat:
+	n = filemap_get_folios(smap, &start, ~0UL, &fbatch);
+	if (!n)
+		return;
+
+	for (i = 0; i < folio_batch_count(&fbatch); i++) {
+		struct folio *folio = fbatch.folios[i], *dfolio;
+		pgoff_t index = folio->index;
+
+		folio_lock(folio);
+		dfolio = filemap_lock_folio(dmap, index);
+		if (!IS_ERR(dfolio)) {
+			/* overwrite existing folio in the destination cache */
+			WARN_ON(folio_test_dirty(dfolio));
+			nilfs_copy_page(&dfolio->page, &folio->page, 0);
+			folio_unlock(dfolio);
+			folio_put(dfolio);
+			/* Do we not need to remove folio from smap here? */
+		} else {
+			struct folio *f;
+
+			/* move the folio to the destination cache */
+			xa_lock_irq(&smap->i_pages);
+			f = __xa_erase(&smap->i_pages, index);
+			WARN_ON(folio != f);
+			smap->nrpages--;
+			xa_unlock_irq(&smap->i_pages);
+
+			xa_lock_irq(&dmap->i_pages);
+			f = __xa_store(&dmap->i_pages, index, folio, GFP_NOFS);
+			if (unlikely(f)) {
+				/* Probably -ENOMEM */
+				folio->mapping = NULL;
+				folio_put(folio);
+			} else {
+				folio->mapping = dmap;
+				dmap->nrpages++;
+				if (folio_test_dirty(folio))
+					__xa_set_mark(&dmap->i_pages, index,
+							PAGECACHE_TAG_DIRTY);
+			}
+			xa_unlock_irq(&dmap->i_pages);
+		}
+		folio_unlock(folio);
+	}
+	folio_batch_release(&fbatch);
+	cond_resched();
+
+	goto repeat;
+}
+
+/**
+ * nilfs_clear_dirty_pages - discard dirty pages in address space
+ * @mapping: address space with dirty pages for discarding
+ * @silent: suppress [true] or print [false] warning messages
+ */
+void nilfs_clear_dirty_pages(struct address_space *mapping, bool silent)
+{
+	struct folio_batch fbatch;
+	unsigned int i;
+	pgoff_t index = 0;
+
+	folio_batch_init(&fbatch);
+
+	while (filemap_get_folios_tag(mapping, &index, (pgoff_t)-1,
+				PAGECACHE_TAG_DIRTY, &fbatch)) {
+		for (i = 0; i < folio_batch_count(&fbatch); i++) {
+			struct folio *folio = fbatch.folios[i];
+
+			folio_lock(folio);
+
+			/*
+			 * This folio may have been removed from the address
+			 * space by truncation or invalidation when the lock
+			 * was acquired.  Skip processing in that case.
+			 */
+			if (likely(folio->mapping == mapping))
+				nilfs_clear_dirty_page(&folio->page, silent);
+
+			folio_unlock(folio);
+		}
+		folio_batch_release(&fbatch);
+		cond_resched();
+	}
+}
+
+/**
+ * nilfs_clear_dirty_page - discard dirty page
+ * @page: dirty page that will be discarded
+ * @silent: suppress [true] or print [false] warning messages
+ */
+void nilfs_clear_dirty_page(struct page *page, bool silent)
+{
+	struct inode *inode = page->mapping->host;
+	struct super_block *sb = inode->i_sb;
+
+	BUG_ON(!PageLocked(page));
+
+	if (!silent)
+		nilfs_warn(sb, "discard dirty page: offset=%lld, ino=%lu",
+			   page_offset(page), inode->i_ino);
+
+	ClearPageUptodate(page);
+	ClearPageMappedToDisk(page);
+
+	if (page_has_buffers(page)) {
+		struct buffer_head *bh, *head;
+		const unsigned long clear_bits =
+			(BIT(BH_Uptodate) | BIT(BH_Dirty) | BIT(BH_Mapped) |
+			 BIT(BH_Async_Write) | BIT(BH_NILFS_Volatile) |
+			 BIT(BH_NILFS_Checked) | BIT(BH_NILFS_Redirected));
+
+		bh = head = page_buffers(page);
+		do {
+			lock_buffer(bh);
+			if (!silent)
+				nilfs_warn(sb,
+					   "discard dirty block: blocknr=%llu, size=%zu",
+					   (u64)bh->b_blocknr, bh->b_size);
+
+			set_mask_bits(&bh->b_state, clear_bits, 0);
+			unlock_buffer(bh);
+		} while (bh = bh->b_this_page, bh != head);
+	}
+
+	__nilfs_clear_page_dirty(page);
+}
+
+unsigned int nilfs_page_count_clean_buffers(struct page *page,
+					    unsigned int from, unsigned int to)
+{
+	unsigned int block_start, block_end;
+	struct buffer_head *bh, *head;
+	unsigned int nc = 0;
+
+	for (bh = head = page_buffers(page), block_start = 0;
+	     bh != head || !block_start;
+	     block_start = block_end, bh = bh->b_this_page) {
+		block_end = block_start + bh->b_size;
+		if (block_end > from && block_start < to && !buffer_dirty(bh))
+			nc++;
+	}
+	return nc;
+}
+
+/*
+ * NILFS2 needs clear_page_dirty() in the following two cases:
+ *
+ * 1) For B-tree node pages and data pages of DAT file, NILFS2 clears dirty
+ *    flag of pages when it copies back pages from shadow cache to the
+ *    original cache.
+ *
+ * 2) Some B-tree operations like insertion or deletion may dispose buffers
+ *    in dirty state, and this needs to cancel the dirty state of their pages.
+ */
+int __nilfs_clear_page_dirty(struct page *page)
+{
+	struct address_space *mapping = page->mapping;
+
+	if (mapping) {
+		xa_lock_irq(&mapping->i_pages);
+		if (test_bit(PG_dirty, &page->flags)) {
+			__xa_clear_mark(&mapping->i_pages, page_index(page),
+					     PAGECACHE_TAG_DIRTY);
+			xa_unlock_irq(&mapping->i_pages);
+			return clear_page_dirty_for_io(page);
+		}
+		xa_unlock_irq(&mapping->i_pages);
+		return 0;
+	}
+	return TestClearPageDirty(page);
+}
+
+/**
+ * nilfs_find_uncommitted_extent - find extent of uncommitted data
+ * @inode: inode
+ * @start_blk: start block offset (in)
+ * @blkoff: start offset of the found extent (out)
+ *
+ * This function searches an extent of buffers marked "delayed" which
+ * starts from a block offset equal to or larger than @start_blk.  If
+ * such an extent was found, this will store the start offset in
+ * @blkoff and return its length in blocks.  Otherwise, zero is
+ * returned.
+ */
+unsigned long nilfs_find_uncommitted_extent(struct inode *inode,
+					    sector_t start_blk,
+					    sector_t *blkoff)
+{
+	unsigned int i, nr_folios;
+	pgoff_t index;
+	unsigned long length = 0;
+	struct folio_batch fbatch;
+	struct folio *folio;
+
+	if (inode->i_mapping->nrpages == 0)
+		return 0;
+
+	index = start_blk >> (PAGE_SHIFT - inode->i_blkbits);
+
+	folio_batch_init(&fbatch);
+
+repeat:
+	nr_folios = filemap_get_folios_contig(inode->i_mapping, &index, ULONG_MAX,
+			&fbatch);
+	if (nr_folios == 0)
+		return length;
+
+	i = 0;
+	do {
+		folio = fbatch.folios[i];
+
+		folio_lock(folio);
+		if (folio_buffers(folio)) {
+			struct buffer_head *bh, *head;
+			sector_t b;
+
+			b = folio->index << (PAGE_SHIFT - inode->i_blkbits);
+			bh = head = folio_buffers(folio);
+			do {
+				if (b < start_blk)
+					continue;
+				if (buffer_delay(bh)) {
+					if (length == 0)
+						*blkoff = b;
+					length++;
+				} else if (length > 0) {
+					goto out_locked;
+				}
+			} while (++b, bh = bh->b_this_page, bh != head);
+		} else {
+			if (length > 0)
+				goto out_locked;
+		}
+		folio_unlock(folio);
+
+	} while (++i < nr_folios);
+
+	folio_batch_release(&fbatch);
+	cond_resched();
+	goto repeat;
+
+out_locked:
+	folio_unlock(folio);
+	folio_batch_release(&fbatch);
+	return length;
+}
diff --git a/fs/nilfs2/page.h b/fs/nilfs2/page.h
new file mode 100644
index 0000000000..21ddcdd4d6
--- /dev/null
+++ b/fs/nilfs2/page.h
@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Buffer/page management specific to NILFS
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Ryusuke Konishi and Seiji Kihara.
+ */
+
+#ifndef _NILFS_PAGE_H
+#define _NILFS_PAGE_H
+
+#include <linux/buffer_head.h>
+#include "nilfs.h"
+
+/*
+ * Extended buffer state bits
+ */
+enum {
+	BH_NILFS_Allocated = BH_PrivateStart,
+	BH_NILFS_Node,
+	BH_NILFS_Volatile,
+	BH_NILFS_Checked,
+	BH_NILFS_Redirected,
+};
+
+BUFFER_FNS(NILFS_Node, nilfs_node)		/* nilfs node buffers */
+BUFFER_FNS(NILFS_Volatile, nilfs_volatile)
+BUFFER_FNS(NILFS_Checked, nilfs_checked)	/* buffer is verified */
+BUFFER_FNS(NILFS_Redirected, nilfs_redirected)	/* redirected to a copy */
+
+
+int __nilfs_clear_page_dirty(struct page *);
+
+struct buffer_head *nilfs_grab_buffer(struct inode *, struct address_space *,
+				      unsigned long, unsigned long);
+void nilfs_forget_buffer(struct buffer_head *);
+void nilfs_copy_buffer(struct buffer_head *, struct buffer_head *);
+int nilfs_page_buffers_clean(struct page *);
+void nilfs_page_bug(struct page *);
+
+int nilfs_copy_dirty_pages(struct address_space *, struct address_space *);
+void nilfs_copy_back_pages(struct address_space *, struct address_space *);
+void nilfs_clear_dirty_page(struct page *, bool);
+void nilfs_clear_dirty_pages(struct address_space *, bool);
+unsigned int nilfs_page_count_clean_buffers(struct page *, unsigned int,
+					    unsigned int);
+unsigned long nilfs_find_uncommitted_extent(struct inode *inode,
+					    sector_t start_blk,
+					    sector_t *blkoff);
+
+#define NILFS_PAGE_BUG(page, m, a...) \
+	do { nilfs_page_bug(page); BUG(); } while (0)
+
+static inline struct buffer_head *
+nilfs_page_get_nth_block(struct page *page, unsigned int count)
+{
+	struct buffer_head *bh = page_buffers(page);
+
+	while (count-- > 0)
+		bh = bh->b_this_page;
+	get_bh(bh);
+	return bh;
+}
+
+#endif /* _NILFS_PAGE_H */
diff --git a/fs/nilfs2/recovery.c b/fs/nilfs2/recovery.c
new file mode 100644
index 0000000000..0955b65793
--- /dev/null
+++ b/fs/nilfs2/recovery.c
@@ -0,0 +1,950 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NILFS recovery logic
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Ryusuke Konishi.
+ */
+
+#include <linux/buffer_head.h>
+#include <linux/blkdev.h>
+#include <linux/swap.h>
+#include <linux/slab.h>
+#include <linux/crc32.h>
+#include "nilfs.h"
+#include "segment.h"
+#include "sufile.h"
+#include "page.h"
+#include "segbuf.h"
+
+/*
+ * Segment check result
+ */
+enum {
+	NILFS_SEG_VALID,
+	NILFS_SEG_NO_SUPER_ROOT,
+	NILFS_SEG_FAIL_IO,
+	NILFS_SEG_FAIL_MAGIC,
+	NILFS_SEG_FAIL_SEQ,
+	NILFS_SEG_FAIL_CHECKSUM_SUPER_ROOT,
+	NILFS_SEG_FAIL_CHECKSUM_FULL,
+	NILFS_SEG_FAIL_CONSISTENCY,
+};
+
+/* work structure for recovery */
+struct nilfs_recovery_block {
+	ino_t ino;		/*
+				 * Inode number of the file that this block
+				 * belongs to
+				 */
+	sector_t blocknr;	/* block number */
+	__u64 vblocknr;		/* virtual block number */
+	unsigned long blkoff;	/* File offset of the data block (per block) */
+	struct list_head list;
+};
+
+
+static int nilfs_warn_segment_error(struct super_block *sb, int err)
+{
+	const char *msg = NULL;
+
+	switch (err) {
+	case NILFS_SEG_FAIL_IO:
+		nilfs_err(sb, "I/O error reading segment");
+		return -EIO;
+	case NILFS_SEG_FAIL_MAGIC:
+		msg = "Magic number mismatch";
+		break;
+	case NILFS_SEG_FAIL_SEQ:
+		msg = "Sequence number mismatch";
+		break;
+	case NILFS_SEG_FAIL_CHECKSUM_SUPER_ROOT:
+		msg = "Checksum error in super root";
+		break;
+	case NILFS_SEG_FAIL_CHECKSUM_FULL:
+		msg = "Checksum error in segment payload";
+		break;
+	case NILFS_SEG_FAIL_CONSISTENCY:
+		msg = "Inconsistency found";
+		break;
+	case NILFS_SEG_NO_SUPER_ROOT:
+		msg = "No super root in the last segment";
+		break;
+	default:
+		nilfs_err(sb, "unrecognized segment error %d", err);
+		return -EINVAL;
+	}
+	nilfs_warn(sb, "invalid segment: %s", msg);
+	return -EINVAL;
+}
+
+/**
+ * nilfs_compute_checksum - compute checksum of blocks continuously
+ * @nilfs: nilfs object
+ * @bhs: buffer head of start block
+ * @sum: place to store result
+ * @offset: offset bytes in the first block
+ * @check_bytes: number of bytes to be checked
+ * @start: DBN of start block
+ * @nblock: number of blocks to be checked
+ */
+static int nilfs_compute_checksum(struct the_nilfs *nilfs,
+				  struct buffer_head *bhs, u32 *sum,
+				  unsigned long offset, u64 check_bytes,
+				  sector_t start, unsigned long nblock)
+{
+	unsigned int blocksize = nilfs->ns_blocksize;
+	unsigned long size;
+	u32 crc;
+
+	BUG_ON(offset >= blocksize);
+	check_bytes -= offset;
+	size = min_t(u64, check_bytes, blocksize - offset);
+	crc = crc32_le(nilfs->ns_crc_seed,
+		       (unsigned char *)bhs->b_data + offset, size);
+	if (--nblock > 0) {
+		do {
+			struct buffer_head *bh;
+
+			bh = __bread(nilfs->ns_bdev, ++start, blocksize);
+			if (!bh)
+				return -EIO;
+			check_bytes -= size;
+			size = min_t(u64, check_bytes, blocksize);
+			crc = crc32_le(crc, bh->b_data, size);
+			brelse(bh);
+		} while (--nblock > 0);
+	}
+	*sum = crc;
+	return 0;
+}
+
+/**
+ * nilfs_read_super_root_block - read super root block
+ * @nilfs: nilfs object
+ * @sr_block: disk block number of the super root block
+ * @pbh: address of a buffer_head pointer to return super root buffer
+ * @check: CRC check flag
+ */
+int nilfs_read_super_root_block(struct the_nilfs *nilfs, sector_t sr_block,
+				struct buffer_head **pbh, int check)
+{
+	struct buffer_head *bh_sr;
+	struct nilfs_super_root *sr;
+	u32 crc;
+	int ret;
+
+	*pbh = NULL;
+	bh_sr = __bread(nilfs->ns_bdev, sr_block, nilfs->ns_blocksize);
+	if (unlikely(!bh_sr)) {
+		ret = NILFS_SEG_FAIL_IO;
+		goto failed;
+	}
+
+	sr = (struct nilfs_super_root *)bh_sr->b_data;
+	if (check) {
+		unsigned int bytes = le16_to_cpu(sr->sr_bytes);
+
+		if (bytes == 0 || bytes > nilfs->ns_blocksize) {
+			ret = NILFS_SEG_FAIL_CHECKSUM_SUPER_ROOT;
+			goto failed_bh;
+		}
+		if (nilfs_compute_checksum(
+			    nilfs, bh_sr, &crc, sizeof(sr->sr_sum), bytes,
+			    sr_block, 1)) {
+			ret = NILFS_SEG_FAIL_IO;
+			goto failed_bh;
+		}
+		if (crc != le32_to_cpu(sr->sr_sum)) {
+			ret = NILFS_SEG_FAIL_CHECKSUM_SUPER_ROOT;
+			goto failed_bh;
+		}
+	}
+	*pbh = bh_sr;
+	return 0;
+
+ failed_bh:
+	brelse(bh_sr);
+
+ failed:
+	return nilfs_warn_segment_error(nilfs->ns_sb, ret);
+}
+
+/**
+ * nilfs_read_log_header - read summary header of the specified log
+ * @nilfs: nilfs object
+ * @start_blocknr: start block number of the log
+ * @sum: pointer to return segment summary structure
+ */
+static struct buffer_head *
+nilfs_read_log_header(struct the_nilfs *nilfs, sector_t start_blocknr,
+		      struct nilfs_segment_summary **sum)
+{
+	struct buffer_head *bh_sum;
+
+	bh_sum = __bread(nilfs->ns_bdev, start_blocknr, nilfs->ns_blocksize);
+	if (bh_sum)
+		*sum = (struct nilfs_segment_summary *)bh_sum->b_data;
+	return bh_sum;
+}
+
+/**
+ * nilfs_validate_log - verify consistency of log
+ * @nilfs: nilfs object
+ * @seg_seq: sequence number of segment
+ * @bh_sum: buffer head of summary block
+ * @sum: segment summary struct
+ */
+static int nilfs_validate_log(struct the_nilfs *nilfs, u64 seg_seq,
+			      struct buffer_head *bh_sum,
+			      struct nilfs_segment_summary *sum)
+{
+	unsigned long nblock;
+	u32 crc;
+	int ret;
+
+	ret = NILFS_SEG_FAIL_MAGIC;
+	if (le32_to_cpu(sum->ss_magic) != NILFS_SEGSUM_MAGIC)
+		goto out;
+
+	ret = NILFS_SEG_FAIL_SEQ;
+	if (le64_to_cpu(sum->ss_seq) != seg_seq)
+		goto out;
+
+	nblock = le32_to_cpu(sum->ss_nblocks);
+	ret = NILFS_SEG_FAIL_CONSISTENCY;
+	if (unlikely(nblock == 0 || nblock > nilfs->ns_blocks_per_segment))
+		/* This limits the number of blocks read in the CRC check */
+		goto out;
+
+	ret = NILFS_SEG_FAIL_IO;
+	if (nilfs_compute_checksum(nilfs, bh_sum, &crc, sizeof(sum->ss_datasum),
+				   ((u64)nblock << nilfs->ns_blocksize_bits),
+				   bh_sum->b_blocknr, nblock))
+		goto out;
+
+	ret = NILFS_SEG_FAIL_CHECKSUM_FULL;
+	if (crc != le32_to_cpu(sum->ss_datasum))
+		goto out;
+	ret = 0;
+out:
+	return ret;
+}
+
+/**
+ * nilfs_read_summary_info - read an item on summary blocks of a log
+ * @nilfs: nilfs object
+ * @pbh: the current buffer head on summary blocks [in, out]
+ * @offset: the current byte offset on summary blocks [in, out]
+ * @bytes: byte size of the item to be read
+ */
+static void *nilfs_read_summary_info(struct the_nilfs *nilfs,
+				     struct buffer_head **pbh,
+				     unsigned int *offset, unsigned int bytes)
+{
+	void *ptr;
+	sector_t blocknr;
+
+	BUG_ON((*pbh)->b_size < *offset);
+	if (bytes > (*pbh)->b_size - *offset) {
+		blocknr = (*pbh)->b_blocknr;
+		brelse(*pbh);
+		*pbh = __bread(nilfs->ns_bdev, blocknr + 1,
+			       nilfs->ns_blocksize);
+		if (unlikely(!*pbh))
+			return NULL;
+		*offset = 0;
+	}
+	ptr = (*pbh)->b_data + *offset;
+	*offset += bytes;
+	return ptr;
+}
+
+/**
+ * nilfs_skip_summary_info - skip items on summary blocks of a log
+ * @nilfs: nilfs object
+ * @pbh: the current buffer head on summary blocks [in, out]
+ * @offset: the current byte offset on summary blocks [in, out]
+ * @bytes: byte size of the item to be skipped
+ * @count: number of items to be skipped
+ */
+static void nilfs_skip_summary_info(struct the_nilfs *nilfs,
+				    struct buffer_head **pbh,
+				    unsigned int *offset, unsigned int bytes,
+				    unsigned long count)
+{
+	unsigned int rest_item_in_current_block
+		= ((*pbh)->b_size - *offset) / bytes;
+
+	if (count <= rest_item_in_current_block) {
+		*offset += bytes * count;
+	} else {
+		sector_t blocknr = (*pbh)->b_blocknr;
+		unsigned int nitem_per_block = (*pbh)->b_size / bytes;
+		unsigned int bcnt;
+
+		count -= rest_item_in_current_block;
+		bcnt = DIV_ROUND_UP(count, nitem_per_block);
+		*offset = bytes * (count - (bcnt - 1) * nitem_per_block);
+
+		brelse(*pbh);
+		*pbh = __bread(nilfs->ns_bdev, blocknr + bcnt,
+			       nilfs->ns_blocksize);
+	}
+}
+
+/**
+ * nilfs_scan_dsync_log - get block information of a log written for data sync
+ * @nilfs: nilfs object
+ * @start_blocknr: start block number of the log
+ * @sum: log summary information
+ * @head: list head to add nilfs_recovery_block struct
+ */
+static int nilfs_scan_dsync_log(struct the_nilfs *nilfs, sector_t start_blocknr,
+				struct nilfs_segment_summary *sum,
+				struct list_head *head)
+{
+	struct buffer_head *bh;
+	unsigned int offset;
+	u32 nfinfo, sumbytes;
+	sector_t blocknr;
+	ino_t ino;
+	int err = -EIO;
+
+	nfinfo = le32_to_cpu(sum->ss_nfinfo);
+	if (!nfinfo)
+		return 0;
+
+	sumbytes = le32_to_cpu(sum->ss_sumbytes);
+	blocknr = start_blocknr + DIV_ROUND_UP(sumbytes, nilfs->ns_blocksize);
+	bh = __bread(nilfs->ns_bdev, start_blocknr, nilfs->ns_blocksize);
+	if (unlikely(!bh))
+		goto out;
+
+	offset = le16_to_cpu(sum->ss_bytes);
+	for (;;) {
+		unsigned long nblocks, ndatablk, nnodeblk;
+		struct nilfs_finfo *finfo;
+
+		finfo = nilfs_read_summary_info(nilfs, &bh, &offset,
+						sizeof(*finfo));
+		if (unlikely(!finfo))
+			goto out;
+
+		ino = le64_to_cpu(finfo->fi_ino);
+		nblocks = le32_to_cpu(finfo->fi_nblocks);
+		ndatablk = le32_to_cpu(finfo->fi_ndatablk);
+		nnodeblk = nblocks - ndatablk;
+
+		while (ndatablk-- > 0) {
+			struct nilfs_recovery_block *rb;
+			struct nilfs_binfo_v *binfo;
+
+			binfo = nilfs_read_summary_info(nilfs, &bh, &offset,
+							sizeof(*binfo));
+			if (unlikely(!binfo))
+				goto out;
+
+			rb = kmalloc(sizeof(*rb), GFP_NOFS);
+			if (unlikely(!rb)) {
+				err = -ENOMEM;
+				goto out;
+			}
+			rb->ino = ino;
+			rb->blocknr = blocknr++;
+			rb->vblocknr = le64_to_cpu(binfo->bi_vblocknr);
+			rb->blkoff = le64_to_cpu(binfo->bi_blkoff);
+			/* INIT_LIST_HEAD(&rb->list); */
+			list_add_tail(&rb->list, head);
+		}
+		if (--nfinfo == 0)
+			break;
+		blocknr += nnodeblk; /* always 0 for data sync logs */
+		nilfs_skip_summary_info(nilfs, &bh, &offset, sizeof(__le64),
+					nnodeblk);
+		if (unlikely(!bh))
+			goto out;
+	}
+	err = 0;
+ out:
+	brelse(bh);   /* brelse(NULL) is just ignored */
+	return err;
+}
+
+static void dispose_recovery_list(struct list_head *head)
+{
+	while (!list_empty(head)) {
+		struct nilfs_recovery_block *rb;
+
+		rb = list_first_entry(head, struct nilfs_recovery_block, list);
+		list_del(&rb->list);
+		kfree(rb);
+	}
+}
+
+struct nilfs_segment_entry {
+	struct list_head	list;
+	__u64			segnum;
+};
+
+static int nilfs_segment_list_add(struct list_head *head, __u64 segnum)
+{
+	struct nilfs_segment_entry *ent = kmalloc(sizeof(*ent), GFP_NOFS);
+
+	if (unlikely(!ent))
+		return -ENOMEM;
+
+	ent->segnum = segnum;
+	INIT_LIST_HEAD(&ent->list);
+	list_add_tail(&ent->list, head);
+	return 0;
+}
+
+void nilfs_dispose_segment_list(struct list_head *head)
+{
+	while (!list_empty(head)) {
+		struct nilfs_segment_entry *ent;
+
+		ent = list_first_entry(head, struct nilfs_segment_entry, list);
+		list_del(&ent->list);
+		kfree(ent);
+	}
+}
+
+static int nilfs_prepare_segment_for_recovery(struct the_nilfs *nilfs,
+					      struct super_block *sb,
+					      struct nilfs_recovery_info *ri)
+{
+	struct list_head *head = &ri->ri_used_segments;
+	struct nilfs_segment_entry *ent, *n;
+	struct inode *sufile = nilfs->ns_sufile;
+	__u64 segnum[4];
+	int err;
+	int i;
+
+	segnum[0] = nilfs->ns_segnum;
+	segnum[1] = nilfs->ns_nextnum;
+	segnum[2] = ri->ri_segnum;
+	segnum[3] = ri->ri_nextnum;
+
+	/*
+	 * Releasing the next segment of the latest super root.
+	 * The next segment is invalidated by this recovery.
+	 */
+	err = nilfs_sufile_free(sufile, segnum[1]);
+	if (unlikely(err))
+		goto failed;
+
+	for (i = 1; i < 4; i++) {
+		err = nilfs_segment_list_add(head, segnum[i]);
+		if (unlikely(err))
+			goto failed;
+	}
+
+	/*
+	 * Collecting segments written after the latest super root.
+	 * These are marked dirty to avoid being reallocated in the next write.
+	 */
+	list_for_each_entry_safe(ent, n, head, list) {
+		if (ent->segnum != segnum[0]) {
+			err = nilfs_sufile_scrap(sufile, ent->segnum);
+			if (unlikely(err))
+				goto failed;
+		}
+		list_del(&ent->list);
+		kfree(ent);
+	}
+
+	/* Allocate new segments for recovery */
+	err = nilfs_sufile_alloc(sufile, &segnum[0]);
+	if (unlikely(err))
+		goto failed;
+
+	nilfs->ns_pseg_offset = 0;
+	nilfs->ns_seg_seq = ri->ri_seq + 2;
+	nilfs->ns_nextnum = nilfs->ns_segnum = segnum[0];
+
+ failed:
+	/* No need to recover sufile because it will be destroyed on error */
+	return err;
+}
+
+static int nilfs_recovery_copy_block(struct the_nilfs *nilfs,
+				     struct nilfs_recovery_block *rb,
+				     struct page *page)
+{
+	struct buffer_head *bh_org;
+	void *kaddr;
+
+	bh_org = __bread(nilfs->ns_bdev, rb->blocknr, nilfs->ns_blocksize);
+	if (unlikely(!bh_org))
+		return -EIO;
+
+	kaddr = kmap_atomic(page);
+	memcpy(kaddr + bh_offset(bh_org), bh_org->b_data, bh_org->b_size);
+	kunmap_atomic(kaddr);
+	brelse(bh_org);
+	return 0;
+}
+
+static int nilfs_recover_dsync_blocks(struct the_nilfs *nilfs,
+				      struct super_block *sb,
+				      struct nilfs_root *root,
+				      struct list_head *head,
+				      unsigned long *nr_salvaged_blocks)
+{
+	struct inode *inode;
+	struct nilfs_recovery_block *rb, *n;
+	unsigned int blocksize = nilfs->ns_blocksize;
+	struct page *page;
+	loff_t pos;
+	int err = 0, err2 = 0;
+
+	list_for_each_entry_safe(rb, n, head, list) {
+		inode = nilfs_iget(sb, root, rb->ino);
+		if (IS_ERR(inode)) {
+			err = PTR_ERR(inode);
+			inode = NULL;
+			goto failed_inode;
+		}
+
+		pos = rb->blkoff << inode->i_blkbits;
+		err = block_write_begin(inode->i_mapping, pos, blocksize,
+					&page, nilfs_get_block);
+		if (unlikely(err)) {
+			loff_t isize = inode->i_size;
+
+			if (pos + blocksize > isize)
+				nilfs_write_failed(inode->i_mapping,
+							pos + blocksize);
+			goto failed_inode;
+		}
+
+		err = nilfs_recovery_copy_block(nilfs, rb, page);
+		if (unlikely(err))
+			goto failed_page;
+
+		err = nilfs_set_file_dirty(inode, 1);
+		if (unlikely(err))
+			goto failed_page;
+
+		block_write_end(NULL, inode->i_mapping, pos, blocksize,
+				blocksize, page, NULL);
+
+		unlock_page(page);
+		put_page(page);
+
+		(*nr_salvaged_blocks)++;
+		goto next;
+
+ failed_page:
+		unlock_page(page);
+		put_page(page);
+
+ failed_inode:
+		nilfs_warn(sb,
+			   "error %d recovering data block (ino=%lu, block-offset=%llu)",
+			   err, (unsigned long)rb->ino,
+			   (unsigned long long)rb->blkoff);
+		if (!err2)
+			err2 = err;
+ next:
+		iput(inode); /* iput(NULL) is just ignored */
+		list_del_init(&rb->list);
+		kfree(rb);
+	}
+	return err2;
+}
+
+/**
+ * nilfs_do_roll_forward - salvage logical segments newer than the latest
+ * checkpoint
+ * @nilfs: nilfs object
+ * @sb: super block instance
+ * @ri: pointer to a nilfs_recovery_info
+ */
+static int nilfs_do_roll_forward(struct the_nilfs *nilfs,
+				 struct super_block *sb,
+				 struct nilfs_root *root,
+				 struct nilfs_recovery_info *ri)
+{
+	struct buffer_head *bh_sum = NULL;
+	struct nilfs_segment_summary *sum = NULL;
+	sector_t pseg_start;
+	sector_t seg_start, seg_end;  /* Starting/ending DBN of full segment */
+	unsigned long nsalvaged_blocks = 0;
+	unsigned int flags;
+	u64 seg_seq;
+	__u64 segnum, nextnum = 0;
+	int empty_seg = 0;
+	int err = 0, ret;
+	LIST_HEAD(dsync_blocks);  /* list of data blocks to be recovered */
+	enum {
+		RF_INIT_ST,
+		RF_DSYNC_ST,   /* scanning data-sync segments */
+	};
+	int state = RF_INIT_ST;
+
+	pseg_start = ri->ri_lsegs_start;
+	seg_seq = ri->ri_lsegs_start_seq;
+	segnum = nilfs_get_segnum_of_block(nilfs, pseg_start);
+	nilfs_get_segment_range(nilfs, segnum, &seg_start, &seg_end);
+
+	while (segnum != ri->ri_segnum || pseg_start <= ri->ri_pseg_start) {
+		brelse(bh_sum);
+		bh_sum = nilfs_read_log_header(nilfs, pseg_start, &sum);
+		if (!bh_sum) {
+			err = -EIO;
+			goto failed;
+		}
+
+		ret = nilfs_validate_log(nilfs, seg_seq, bh_sum, sum);
+		if (ret) {
+			if (ret == NILFS_SEG_FAIL_IO) {
+				err = -EIO;
+				goto failed;
+			}
+			goto strayed;
+		}
+
+		flags = le16_to_cpu(sum->ss_flags);
+		if (flags & NILFS_SS_SR)
+			goto confused;
+
+		/* Found a valid partial segment; do recovery actions */
+		nextnum = nilfs_get_segnum_of_block(nilfs,
+						    le64_to_cpu(sum->ss_next));
+		empty_seg = 0;
+		nilfs->ns_ctime = le64_to_cpu(sum->ss_create);
+		if (!(flags & NILFS_SS_GC))
+			nilfs->ns_nongc_ctime = nilfs->ns_ctime;
+
+		switch (state) {
+		case RF_INIT_ST:
+			if (!(flags & NILFS_SS_LOGBGN) ||
+			    !(flags & NILFS_SS_SYNDT))
+				goto try_next_pseg;
+			state = RF_DSYNC_ST;
+			fallthrough;
+		case RF_DSYNC_ST:
+			if (!(flags & NILFS_SS_SYNDT))
+				goto confused;
+
+			err = nilfs_scan_dsync_log(nilfs, pseg_start, sum,
+						   &dsync_blocks);
+			if (unlikely(err))
+				goto failed;
+			if (flags & NILFS_SS_LOGEND) {
+				err = nilfs_recover_dsync_blocks(
+					nilfs, sb, root, &dsync_blocks,
+					&nsalvaged_blocks);
+				if (unlikely(err))
+					goto failed;
+				state = RF_INIT_ST;
+			}
+			break; /* Fall through to try_next_pseg */
+		}
+
+ try_next_pseg:
+		if (pseg_start == ri->ri_lsegs_end)
+			break;
+		pseg_start += le32_to_cpu(sum->ss_nblocks);
+		if (pseg_start < seg_end)
+			continue;
+		goto feed_segment;
+
+ strayed:
+		if (pseg_start == ri->ri_lsegs_end)
+			break;
+
+ feed_segment:
+		/* Looking to the next full segment */
+		if (empty_seg++)
+			break;
+		seg_seq++;
+		segnum = nextnum;
+		nilfs_get_segment_range(nilfs, segnum, &seg_start, &seg_end);
+		pseg_start = seg_start;
+	}
+
+	if (nsalvaged_blocks) {
+		nilfs_info(sb, "salvaged %lu blocks", nsalvaged_blocks);
+		ri->ri_need_recovery = NILFS_RECOVERY_ROLLFORWARD_DONE;
+	}
+ out:
+	brelse(bh_sum);
+	dispose_recovery_list(&dsync_blocks);
+	return err;
+
+ confused:
+	err = -EINVAL;
+ failed:
+	nilfs_err(sb,
+		  "error %d roll-forwarding partial segment at blocknr = %llu",
+		  err, (unsigned long long)pseg_start);
+	goto out;
+}
+
+static void nilfs_finish_roll_forward(struct the_nilfs *nilfs,
+				      struct nilfs_recovery_info *ri)
+{
+	struct buffer_head *bh;
+	int err;
+
+	if (nilfs_get_segnum_of_block(nilfs, ri->ri_lsegs_start) !=
+	    nilfs_get_segnum_of_block(nilfs, ri->ri_super_root))
+		return;
+
+	bh = __getblk(nilfs->ns_bdev, ri->ri_lsegs_start, nilfs->ns_blocksize);
+	BUG_ON(!bh);
+	memset(bh->b_data, 0, bh->b_size);
+	set_buffer_dirty(bh);
+	err = sync_dirty_buffer(bh);
+	if (unlikely(err))
+		nilfs_warn(nilfs->ns_sb,
+			   "buffer sync write failed during post-cleaning of recovery.");
+	brelse(bh);
+}
+
+/**
+ * nilfs_salvage_orphan_logs - salvage logs written after the latest checkpoint
+ * @nilfs: nilfs object
+ * @sb: super block instance
+ * @ri: pointer to a nilfs_recovery_info struct to store search results.
+ *
+ * Return Value: On success, 0 is returned.  On error, one of the following
+ * negative error code is returned.
+ *
+ * %-EINVAL - Inconsistent filesystem state.
+ *
+ * %-EIO - I/O error
+ *
+ * %-ENOSPC - No space left on device (only in a panic state).
+ *
+ * %-ERESTARTSYS - Interrupted.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ */
+int nilfs_salvage_orphan_logs(struct the_nilfs *nilfs,
+			      struct super_block *sb,
+			      struct nilfs_recovery_info *ri)
+{
+	struct nilfs_root *root;
+	int err;
+
+	if (ri->ri_lsegs_start == 0 || ri->ri_lsegs_end == 0)
+		return 0;
+
+	err = nilfs_attach_checkpoint(sb, ri->ri_cno, true, &root);
+	if (unlikely(err)) {
+		nilfs_err(sb, "error %d loading the latest checkpoint", err);
+		return err;
+	}
+
+	err = nilfs_do_roll_forward(nilfs, sb, root, ri);
+	if (unlikely(err))
+		goto failed;
+
+	if (ri->ri_need_recovery == NILFS_RECOVERY_ROLLFORWARD_DONE) {
+		err = nilfs_prepare_segment_for_recovery(nilfs, sb, ri);
+		if (unlikely(err)) {
+			nilfs_err(sb, "error %d preparing segment for recovery",
+				  err);
+			goto failed;
+		}
+
+		err = nilfs_attach_log_writer(sb, root);
+		if (unlikely(err))
+			goto failed;
+
+		set_nilfs_discontinued(nilfs);
+		err = nilfs_construct_segment(sb);
+		nilfs_detach_log_writer(sb);
+
+		if (unlikely(err)) {
+			nilfs_err(sb, "error %d writing segment for recovery",
+				  err);
+			goto failed;
+		}
+
+		nilfs_finish_roll_forward(nilfs, ri);
+	}
+
+ failed:
+	nilfs_put_root(root);
+	return err;
+}
+
+/**
+ * nilfs_search_super_root - search the latest valid super root
+ * @nilfs: the_nilfs
+ * @ri: pointer to a nilfs_recovery_info struct to store search results.
+ *
+ * nilfs_search_super_root() looks for the latest super-root from a partial
+ * segment pointed by the superblock.  It sets up struct the_nilfs through
+ * this search. It fills nilfs_recovery_info (ri) required for recovery.
+ *
+ * Return Value: On success, 0 is returned.  On error, one of the following
+ * negative error code is returned.
+ *
+ * %-EINVAL - No valid segment found
+ *
+ * %-EIO - I/O error
+ *
+ * %-ENOMEM - Insufficient memory available.
+ */
+int nilfs_search_super_root(struct the_nilfs *nilfs,
+			    struct nilfs_recovery_info *ri)
+{
+	struct buffer_head *bh_sum = NULL;
+	struct nilfs_segment_summary *sum = NULL;
+	sector_t pseg_start, pseg_end, sr_pseg_start = 0;
+	sector_t seg_start, seg_end; /* range of full segment (block number) */
+	sector_t b, end;
+	unsigned long nblocks;
+	unsigned int flags;
+	u64 seg_seq;
+	__u64 segnum, nextnum = 0;
+	__u64 cno;
+	LIST_HEAD(segments);
+	int empty_seg = 0, scan_newer = 0;
+	int ret;
+
+	pseg_start = nilfs->ns_last_pseg;
+	seg_seq = nilfs->ns_last_seq;
+	cno = nilfs->ns_last_cno;
+	segnum = nilfs_get_segnum_of_block(nilfs, pseg_start);
+
+	/* Calculate range of segment */
+	nilfs_get_segment_range(nilfs, segnum, &seg_start, &seg_end);
+
+	/* Read ahead segment */
+	b = seg_start;
+	while (b <= seg_end)
+		__breadahead(nilfs->ns_bdev, b++, nilfs->ns_blocksize);
+
+	for (;;) {
+		brelse(bh_sum);
+		ret = NILFS_SEG_FAIL_IO;
+		bh_sum = nilfs_read_log_header(nilfs, pseg_start, &sum);
+		if (!bh_sum)
+			goto failed;
+
+		ret = nilfs_validate_log(nilfs, seg_seq, bh_sum, sum);
+		if (ret) {
+			if (ret == NILFS_SEG_FAIL_IO)
+				goto failed;
+			goto strayed;
+		}
+
+		nblocks = le32_to_cpu(sum->ss_nblocks);
+		pseg_end = pseg_start + nblocks - 1;
+		if (unlikely(pseg_end > seg_end)) {
+			ret = NILFS_SEG_FAIL_CONSISTENCY;
+			goto strayed;
+		}
+
+		/* A valid partial segment */
+		ri->ri_pseg_start = pseg_start;
+		ri->ri_seq = seg_seq;
+		ri->ri_segnum = segnum;
+		nextnum = nilfs_get_segnum_of_block(nilfs,
+						    le64_to_cpu(sum->ss_next));
+		ri->ri_nextnum = nextnum;
+		empty_seg = 0;
+
+		flags = le16_to_cpu(sum->ss_flags);
+		if (!(flags & NILFS_SS_SR) && !scan_newer) {
+			/*
+			 * This will never happen because a superblock
+			 * (last_segment) always points to a pseg with
+			 * a super root.
+			 */
+			ret = NILFS_SEG_FAIL_CONSISTENCY;
+			goto failed;
+		}
+
+		if (pseg_start == seg_start) {
+			nilfs_get_segment_range(nilfs, nextnum, &b, &end);
+			while (b <= end)
+				__breadahead(nilfs->ns_bdev, b++,
+					     nilfs->ns_blocksize);
+		}
+		if (!(flags & NILFS_SS_SR)) {
+			if (!ri->ri_lsegs_start && (flags & NILFS_SS_LOGBGN)) {
+				ri->ri_lsegs_start = pseg_start;
+				ri->ri_lsegs_start_seq = seg_seq;
+			}
+			if (flags & NILFS_SS_LOGEND)
+				ri->ri_lsegs_end = pseg_start;
+			goto try_next_pseg;
+		}
+
+		/* A valid super root was found. */
+		ri->ri_cno = cno++;
+		ri->ri_super_root = pseg_end;
+		ri->ri_lsegs_start = ri->ri_lsegs_end = 0;
+
+		nilfs_dispose_segment_list(&segments);
+		sr_pseg_start = pseg_start;
+		nilfs->ns_pseg_offset = pseg_start + nblocks - seg_start;
+		nilfs->ns_seg_seq = seg_seq;
+		nilfs->ns_segnum = segnum;
+		nilfs->ns_cno = cno;  /* nilfs->ns_cno = ri->ri_cno + 1 */
+		nilfs->ns_ctime = le64_to_cpu(sum->ss_create);
+		nilfs->ns_nextnum = nextnum;
+
+		if (scan_newer)
+			ri->ri_need_recovery = NILFS_RECOVERY_SR_UPDATED;
+		else {
+			if (nilfs->ns_mount_state & NILFS_VALID_FS)
+				goto super_root_found;
+			scan_newer = 1;
+		}
+
+ try_next_pseg:
+		/* Standing on a course, or met an inconsistent state */
+		pseg_start += nblocks;
+		if (pseg_start < seg_end)
+			continue;
+		goto feed_segment;
+
+ strayed:
+		/* Off the trail */
+		if (!scan_newer)
+			/*
+			 * This can happen if a checkpoint was written without
+			 * barriers, or as a result of an I/O failure.
+			 */
+			goto failed;
+
+ feed_segment:
+		/* Looking to the next full segment */
+		if (empty_seg++)
+			goto super_root_found; /* found a valid super root */
+
+		ret = nilfs_segment_list_add(&segments, segnum);
+		if (unlikely(ret))
+			goto failed;
+
+		seg_seq++;
+		segnum = nextnum;
+		nilfs_get_segment_range(nilfs, segnum, &seg_start, &seg_end);
+		pseg_start = seg_start;
+	}
+
+ super_root_found:
+	/* Updating pointers relating to the latest checkpoint */
+	brelse(bh_sum);
+	list_splice_tail(&segments, &ri->ri_used_segments);
+	nilfs->ns_last_pseg = sr_pseg_start;
+	nilfs->ns_last_seq = nilfs->ns_seg_seq;
+	nilfs->ns_last_cno = ri->ri_cno;
+	return 0;
+
+ failed:
+	brelse(bh_sum);
+	nilfs_dispose_segment_list(&segments);
+	return ret < 0 ? ret : nilfs_warn_segment_error(nilfs->ns_sb, ret);
+}
diff --git a/fs/nilfs2/segbuf.c b/fs/nilfs2/segbuf.c
new file mode 100644
index 0000000000..6e59dc19a7
--- /dev/null
+++ b/fs/nilfs2/segbuf.c
@@ -0,0 +1,477 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NILFS segment buffer
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Ryusuke Konishi.
+ *
+ */
+
+#include <linux/buffer_head.h>
+#include <linux/writeback.h>
+#include <linux/crc32.h>
+#include <linux/backing-dev.h>
+#include <linux/slab.h>
+#include "page.h"
+#include "segbuf.h"
+
+
+struct nilfs_write_info {
+	struct the_nilfs       *nilfs;
+	struct bio	       *bio;
+	int			start, end; /* The region to be submitted */
+	int			rest_blocks;
+	int			max_pages;
+	int			nr_vecs;
+	sector_t		blocknr;
+};
+
+static int nilfs_segbuf_write(struct nilfs_segment_buffer *segbuf,
+			      struct the_nilfs *nilfs);
+static int nilfs_segbuf_wait(struct nilfs_segment_buffer *segbuf);
+
+struct nilfs_segment_buffer *nilfs_segbuf_new(struct super_block *sb)
+{
+	struct nilfs_segment_buffer *segbuf;
+
+	segbuf = kmem_cache_alloc(nilfs_segbuf_cachep, GFP_NOFS);
+	if (unlikely(!segbuf))
+		return NULL;
+
+	segbuf->sb_super = sb;
+	INIT_LIST_HEAD(&segbuf->sb_list);
+	INIT_LIST_HEAD(&segbuf->sb_segsum_buffers);
+	INIT_LIST_HEAD(&segbuf->sb_payload_buffers);
+	segbuf->sb_super_root = NULL;
+
+	init_completion(&segbuf->sb_bio_event);
+	atomic_set(&segbuf->sb_err, 0);
+	segbuf->sb_nbio = 0;
+
+	return segbuf;
+}
+
+void nilfs_segbuf_free(struct nilfs_segment_buffer *segbuf)
+{
+	kmem_cache_free(nilfs_segbuf_cachep, segbuf);
+}
+
+void nilfs_segbuf_map(struct nilfs_segment_buffer *segbuf, __u64 segnum,
+		     unsigned long offset, struct the_nilfs *nilfs)
+{
+	segbuf->sb_segnum = segnum;
+	nilfs_get_segment_range(nilfs, segnum, &segbuf->sb_fseg_start,
+				&segbuf->sb_fseg_end);
+
+	segbuf->sb_pseg_start = segbuf->sb_fseg_start + offset;
+	segbuf->sb_rest_blocks =
+		segbuf->sb_fseg_end - segbuf->sb_pseg_start + 1;
+}
+
+/**
+ * nilfs_segbuf_map_cont - map a new log behind a given log
+ * @segbuf: new segment buffer
+ * @prev: segment buffer containing a log to be continued
+ */
+void nilfs_segbuf_map_cont(struct nilfs_segment_buffer *segbuf,
+			   struct nilfs_segment_buffer *prev)
+{
+	segbuf->sb_segnum = prev->sb_segnum;
+	segbuf->sb_fseg_start = prev->sb_fseg_start;
+	segbuf->sb_fseg_end = prev->sb_fseg_end;
+	segbuf->sb_pseg_start = prev->sb_pseg_start + prev->sb_sum.nblocks;
+	segbuf->sb_rest_blocks =
+		segbuf->sb_fseg_end - segbuf->sb_pseg_start + 1;
+}
+
+void nilfs_segbuf_set_next_segnum(struct nilfs_segment_buffer *segbuf,
+				  __u64 nextnum, struct the_nilfs *nilfs)
+{
+	segbuf->sb_nextnum = nextnum;
+	segbuf->sb_sum.next = nilfs_get_segment_start_blocknr(nilfs, nextnum);
+}
+
+int nilfs_segbuf_extend_segsum(struct nilfs_segment_buffer *segbuf)
+{
+	struct buffer_head *bh;
+
+	bh = sb_getblk(segbuf->sb_super,
+		       segbuf->sb_pseg_start + segbuf->sb_sum.nsumblk);
+	if (unlikely(!bh))
+		return -ENOMEM;
+
+	lock_buffer(bh);
+	if (!buffer_uptodate(bh)) {
+		memset(bh->b_data, 0, bh->b_size);
+		set_buffer_uptodate(bh);
+	}
+	unlock_buffer(bh);
+	nilfs_segbuf_add_segsum_buffer(segbuf, bh);
+	return 0;
+}
+
+int nilfs_segbuf_extend_payload(struct nilfs_segment_buffer *segbuf,
+				struct buffer_head **bhp)
+{
+	struct buffer_head *bh;
+
+	bh = sb_getblk(segbuf->sb_super,
+		       segbuf->sb_pseg_start + segbuf->sb_sum.nblocks);
+	if (unlikely(!bh))
+		return -ENOMEM;
+
+	nilfs_segbuf_add_payload_buffer(segbuf, bh);
+	*bhp = bh;
+	return 0;
+}
+
+int nilfs_segbuf_reset(struct nilfs_segment_buffer *segbuf, unsigned int flags,
+		       time64_t ctime, __u64 cno)
+{
+	int err;
+
+	segbuf->sb_sum.nblocks = segbuf->sb_sum.nsumblk = 0;
+	err = nilfs_segbuf_extend_segsum(segbuf);
+	if (unlikely(err))
+		return err;
+
+	segbuf->sb_sum.flags = flags;
+	segbuf->sb_sum.sumbytes = sizeof(struct nilfs_segment_summary);
+	segbuf->sb_sum.nfinfo = segbuf->sb_sum.nfileblk = 0;
+	segbuf->sb_sum.ctime = ctime;
+	segbuf->sb_sum.cno = cno;
+	return 0;
+}
+
+/*
+ * Setup segment summary
+ */
+void nilfs_segbuf_fill_in_segsum(struct nilfs_segment_buffer *segbuf)
+{
+	struct nilfs_segment_summary *raw_sum;
+	struct buffer_head *bh_sum;
+
+	bh_sum = list_entry(segbuf->sb_segsum_buffers.next,
+			    struct buffer_head, b_assoc_buffers);
+	raw_sum = (struct nilfs_segment_summary *)bh_sum->b_data;
+
+	raw_sum->ss_magic    = cpu_to_le32(NILFS_SEGSUM_MAGIC);
+	raw_sum->ss_bytes    = cpu_to_le16(sizeof(*raw_sum));
+	raw_sum->ss_flags    = cpu_to_le16(segbuf->sb_sum.flags);
+	raw_sum->ss_seq      = cpu_to_le64(segbuf->sb_sum.seg_seq);
+	raw_sum->ss_create   = cpu_to_le64(segbuf->sb_sum.ctime);
+	raw_sum->ss_next     = cpu_to_le64(segbuf->sb_sum.next);
+	raw_sum->ss_nblocks  = cpu_to_le32(segbuf->sb_sum.nblocks);
+	raw_sum->ss_nfinfo   = cpu_to_le32(segbuf->sb_sum.nfinfo);
+	raw_sum->ss_sumbytes = cpu_to_le32(segbuf->sb_sum.sumbytes);
+	raw_sum->ss_pad      = 0;
+	raw_sum->ss_cno      = cpu_to_le64(segbuf->sb_sum.cno);
+}
+
+/*
+ * CRC calculation routines
+ */
+static void
+nilfs_segbuf_fill_in_segsum_crc(struct nilfs_segment_buffer *segbuf, u32 seed)
+{
+	struct buffer_head *bh;
+	struct nilfs_segment_summary *raw_sum;
+	unsigned long size, bytes = segbuf->sb_sum.sumbytes;
+	u32 crc;
+
+	bh = list_entry(segbuf->sb_segsum_buffers.next, struct buffer_head,
+			b_assoc_buffers);
+
+	raw_sum = (struct nilfs_segment_summary *)bh->b_data;
+	size = min_t(unsigned long, bytes, bh->b_size);
+	crc = crc32_le(seed,
+		       (unsigned char *)raw_sum +
+		       sizeof(raw_sum->ss_datasum) + sizeof(raw_sum->ss_sumsum),
+		       size - (sizeof(raw_sum->ss_datasum) +
+			       sizeof(raw_sum->ss_sumsum)));
+
+	list_for_each_entry_continue(bh, &segbuf->sb_segsum_buffers,
+				     b_assoc_buffers) {
+		bytes -= size;
+		size = min_t(unsigned long, bytes, bh->b_size);
+		crc = crc32_le(crc, bh->b_data, size);
+	}
+	raw_sum->ss_sumsum = cpu_to_le32(crc);
+}
+
+static void nilfs_segbuf_fill_in_data_crc(struct nilfs_segment_buffer *segbuf,
+					  u32 seed)
+{
+	struct buffer_head *bh;
+	struct nilfs_segment_summary *raw_sum;
+	void *kaddr;
+	u32 crc;
+
+	bh = list_entry(segbuf->sb_segsum_buffers.next, struct buffer_head,
+			b_assoc_buffers);
+	raw_sum = (struct nilfs_segment_summary *)bh->b_data;
+	crc = crc32_le(seed,
+		       (unsigned char *)raw_sum + sizeof(raw_sum->ss_datasum),
+		       bh->b_size - sizeof(raw_sum->ss_datasum));
+
+	list_for_each_entry_continue(bh, &segbuf->sb_segsum_buffers,
+				     b_assoc_buffers) {
+		crc = crc32_le(crc, bh->b_data, bh->b_size);
+	}
+	list_for_each_entry(bh, &segbuf->sb_payload_buffers, b_assoc_buffers) {
+		kaddr = kmap_atomic(bh->b_page);
+		crc = crc32_le(crc, kaddr + bh_offset(bh), bh->b_size);
+		kunmap_atomic(kaddr);
+	}
+	raw_sum->ss_datasum = cpu_to_le32(crc);
+}
+
+static void
+nilfs_segbuf_fill_in_super_root_crc(struct nilfs_segment_buffer *segbuf,
+				    u32 seed)
+{
+	struct nilfs_super_root *raw_sr;
+	struct the_nilfs *nilfs = segbuf->sb_super->s_fs_info;
+	unsigned int srsize;
+	u32 crc;
+
+	raw_sr = (struct nilfs_super_root *)segbuf->sb_super_root->b_data;
+	srsize = NILFS_SR_BYTES(nilfs->ns_inode_size);
+	crc = crc32_le(seed,
+		       (unsigned char *)raw_sr + sizeof(raw_sr->sr_sum),
+		       srsize - sizeof(raw_sr->sr_sum));
+	raw_sr->sr_sum = cpu_to_le32(crc);
+}
+
+static void nilfs_release_buffers(struct list_head *list)
+{
+	struct buffer_head *bh, *n;
+
+	list_for_each_entry_safe(bh, n, list, b_assoc_buffers) {
+		list_del_init(&bh->b_assoc_buffers);
+		brelse(bh);
+	}
+}
+
+static void nilfs_segbuf_clear(struct nilfs_segment_buffer *segbuf)
+{
+	nilfs_release_buffers(&segbuf->sb_segsum_buffers);
+	nilfs_release_buffers(&segbuf->sb_payload_buffers);
+	segbuf->sb_super_root = NULL;
+}
+
+/*
+ * Iterators for segment buffers
+ */
+void nilfs_clear_logs(struct list_head *logs)
+{
+	struct nilfs_segment_buffer *segbuf;
+
+	list_for_each_entry(segbuf, logs, sb_list)
+		nilfs_segbuf_clear(segbuf);
+}
+
+void nilfs_truncate_logs(struct list_head *logs,
+			 struct nilfs_segment_buffer *last)
+{
+	struct nilfs_segment_buffer *n, *segbuf;
+
+	segbuf = list_prepare_entry(last, logs, sb_list);
+	list_for_each_entry_safe_continue(segbuf, n, logs, sb_list) {
+		list_del_init(&segbuf->sb_list);
+		nilfs_segbuf_clear(segbuf);
+		nilfs_segbuf_free(segbuf);
+	}
+}
+
+int nilfs_write_logs(struct list_head *logs, struct the_nilfs *nilfs)
+{
+	struct nilfs_segment_buffer *segbuf;
+	int ret = 0;
+
+	list_for_each_entry(segbuf, logs, sb_list) {
+		ret = nilfs_segbuf_write(segbuf, nilfs);
+		if (ret)
+			break;
+	}
+	return ret;
+}
+
+int nilfs_wait_on_logs(struct list_head *logs)
+{
+	struct nilfs_segment_buffer *segbuf;
+	int err, ret = 0;
+
+	list_for_each_entry(segbuf, logs, sb_list) {
+		err = nilfs_segbuf_wait(segbuf);
+		if (err && !ret)
+			ret = err;
+	}
+	return ret;
+}
+
+/**
+ * nilfs_add_checksums_on_logs - add checksums on the logs
+ * @logs: list of segment buffers storing target logs
+ * @seed: checksum seed value
+ */
+void nilfs_add_checksums_on_logs(struct list_head *logs, u32 seed)
+{
+	struct nilfs_segment_buffer *segbuf;
+
+	list_for_each_entry(segbuf, logs, sb_list) {
+		if (segbuf->sb_super_root)
+			nilfs_segbuf_fill_in_super_root_crc(segbuf, seed);
+		nilfs_segbuf_fill_in_segsum_crc(segbuf, seed);
+		nilfs_segbuf_fill_in_data_crc(segbuf, seed);
+	}
+}
+
+/*
+ * BIO operations
+ */
+static void nilfs_end_bio_write(struct bio *bio)
+{
+	struct nilfs_segment_buffer *segbuf = bio->bi_private;
+
+	if (bio->bi_status)
+		atomic_inc(&segbuf->sb_err);
+
+	bio_put(bio);
+	complete(&segbuf->sb_bio_event);
+}
+
+static int nilfs_segbuf_submit_bio(struct nilfs_segment_buffer *segbuf,
+				   struct nilfs_write_info *wi)
+{
+	struct bio *bio = wi->bio;
+
+	bio->bi_end_io = nilfs_end_bio_write;
+	bio->bi_private = segbuf;
+	submit_bio(bio);
+	segbuf->sb_nbio++;
+
+	wi->bio = NULL;
+	wi->rest_blocks -= wi->end - wi->start;
+	wi->nr_vecs = min(wi->max_pages, wi->rest_blocks);
+	wi->start = wi->end;
+	return 0;
+}
+
+static void nilfs_segbuf_prepare_write(struct nilfs_segment_buffer *segbuf,
+				       struct nilfs_write_info *wi)
+{
+	wi->bio = NULL;
+	wi->rest_blocks = segbuf->sb_sum.nblocks;
+	wi->max_pages = BIO_MAX_VECS;
+	wi->nr_vecs = min(wi->max_pages, wi->rest_blocks);
+	wi->start = wi->end = 0;
+	wi->blocknr = segbuf->sb_pseg_start;
+}
+
+static int nilfs_segbuf_submit_bh(struct nilfs_segment_buffer *segbuf,
+				  struct nilfs_write_info *wi,
+				  struct buffer_head *bh)
+{
+	int len, err;
+
+	BUG_ON(wi->nr_vecs <= 0);
+ repeat:
+	if (!wi->bio) {
+		wi->bio = bio_alloc(wi->nilfs->ns_bdev, wi->nr_vecs,
+				    REQ_OP_WRITE, GFP_NOIO);
+		wi->bio->bi_iter.bi_sector = (wi->blocknr + wi->end) <<
+			(wi->nilfs->ns_blocksize_bits - 9);
+	}
+
+	len = bio_add_page(wi->bio, bh->b_page, bh->b_size, bh_offset(bh));
+	if (len == bh->b_size) {
+		wi->end++;
+		return 0;
+	}
+	/* bio is FULL */
+	err = nilfs_segbuf_submit_bio(segbuf, wi);
+	/* never submit current bh */
+	if (likely(!err))
+		goto repeat;
+	return err;
+}
+
+/**
+ * nilfs_segbuf_write - submit write requests of a log
+ * @segbuf: buffer storing a log to be written
+ * @nilfs: nilfs object
+ *
+ * Return Value: On Success, 0 is returned. On Error, one of the following
+ * negative error code is returned.
+ *
+ * %-EIO - I/O error
+ *
+ * %-ENOMEM - Insufficient memory available.
+ */
+static int nilfs_segbuf_write(struct nilfs_segment_buffer *segbuf,
+			      struct the_nilfs *nilfs)
+{
+	struct nilfs_write_info wi;
+	struct buffer_head *bh;
+	int res = 0;
+
+	wi.nilfs = nilfs;
+	nilfs_segbuf_prepare_write(segbuf, &wi);
+
+	list_for_each_entry(bh, &segbuf->sb_segsum_buffers, b_assoc_buffers) {
+		res = nilfs_segbuf_submit_bh(segbuf, &wi, bh);
+		if (unlikely(res))
+			goto failed_bio;
+	}
+
+	list_for_each_entry(bh, &segbuf->sb_payload_buffers, b_assoc_buffers) {
+		res = nilfs_segbuf_submit_bh(segbuf, &wi, bh);
+		if (unlikely(res))
+			goto failed_bio;
+	}
+
+	if (wi.bio) {
+		/*
+		 * Last BIO is always sent through the following
+		 * submission.
+		 */
+		wi.bio->bi_opf |= REQ_SYNC;
+		res = nilfs_segbuf_submit_bio(segbuf, &wi);
+	}
+
+ failed_bio:
+	return res;
+}
+
+/**
+ * nilfs_segbuf_wait - wait for completion of requested BIOs
+ * @segbuf: segment buffer
+ *
+ * Return Value: On Success, 0 is returned. On Error, one of the following
+ * negative error code is returned.
+ *
+ * %-EIO - I/O error
+ */
+static int nilfs_segbuf_wait(struct nilfs_segment_buffer *segbuf)
+{
+	int err = 0;
+
+	if (!segbuf->sb_nbio)
+		return 0;
+
+	do {
+		wait_for_completion(&segbuf->sb_bio_event);
+	} while (--segbuf->sb_nbio > 0);
+
+	if (unlikely(atomic_read(&segbuf->sb_err) > 0)) {
+		nilfs_err(segbuf->sb_super,
+			  "I/O error writing log (start-blocknr=%llu, block-count=%lu) in segment %llu",
+			  (unsigned long long)segbuf->sb_pseg_start,
+			  segbuf->sb_sum.nblocks,
+			  (unsigned long long)segbuf->sb_segnum);
+		err = -EIO;
+	}
+	return err;
+}
diff --git a/fs/nilfs2/segbuf.h b/fs/nilfs2/segbuf.h
new file mode 100644
index 0000000000..e20091eded
--- /dev/null
+++ b/fs/nilfs2/segbuf.h
@@ -0,0 +1,172 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * NILFS Segment buffer prototypes and definitions
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Ryusuke Konishi.
+ *
+ */
+#ifndef _NILFS_SEGBUF_H
+#define _NILFS_SEGBUF_H
+
+#include <linux/fs.h>
+#include <linux/buffer_head.h>
+#include <linux/bio.h>
+#include <linux/completion.h>
+
+/**
+ * struct nilfs_segsum_info - On-memory segment summary
+ * @flags: Flags
+ * @nfinfo: Number of file information structures
+ * @nblocks: Number of blocks included in the partial segment
+ * @nsumblk: Number of summary blocks
+ * @sumbytes: Byte count of segment summary
+ * @nfileblk: Total number of file blocks
+ * @seg_seq: Segment sequence number
+ * @cno: Checkpoint number
+ * @ctime: Creation time
+ * @next: Block number of the next full segment
+ */
+struct nilfs_segsum_info {
+	unsigned int		flags;
+	unsigned long		nfinfo;
+	unsigned long		nblocks;
+	unsigned long		nsumblk;
+	unsigned long		sumbytes;
+	unsigned long		nfileblk;
+	u64			seg_seq;
+	__u64			cno;
+	time64_t		ctime;
+	sector_t		next;
+};
+
+/**
+ * struct nilfs_segment_buffer - Segment buffer
+ * @sb_super: back pointer to a superblock struct
+ * @sb_list: List head to chain this structure
+ * @sb_sum: On-memory segment summary
+ * @sb_segnum: Index number of the full segment
+ * @sb_nextnum: Index number of the next full segment
+ * @sb_fseg_start: Start block number of the full segment
+ * @sb_fseg_end: End block number of the full segment
+ * @sb_pseg_start: Disk block number of partial segment
+ * @sb_rest_blocks: Number of residual blocks in the current segment
+ * @sb_segsum_buffers: List of buffers for segment summaries
+ * @sb_payload_buffers: List of buffers for segment payload
+ * @sb_super_root: Pointer to buffer storing a super root block (if exists)
+ * @sb_nbio: Number of flying bio requests
+ * @sb_err: I/O error status
+ * @sb_bio_event: Completion event of log writing
+ */
+struct nilfs_segment_buffer {
+	struct super_block     *sb_super;
+	struct list_head	sb_list;
+
+	/* Segment information */
+	struct nilfs_segsum_info sb_sum;
+	__u64			sb_segnum;
+	__u64			sb_nextnum;
+	sector_t		sb_fseg_start, sb_fseg_end;
+	sector_t		sb_pseg_start;
+	unsigned int		sb_rest_blocks;
+
+	/* Buffers */
+	struct list_head	sb_segsum_buffers;
+	struct list_head	sb_payload_buffers; /* including super root */
+	struct buffer_head     *sb_super_root;
+
+	/* io status */
+	int			sb_nbio;
+	atomic_t		sb_err;
+	struct completion	sb_bio_event;
+};
+
+#define NILFS_LIST_SEGBUF(head)  \
+	list_entry((head), struct nilfs_segment_buffer, sb_list)
+#define NILFS_NEXT_SEGBUF(segbuf)  NILFS_LIST_SEGBUF((segbuf)->sb_list.next)
+#define NILFS_PREV_SEGBUF(segbuf)  NILFS_LIST_SEGBUF((segbuf)->sb_list.prev)
+#define NILFS_LAST_SEGBUF(head)    NILFS_LIST_SEGBUF((head)->prev)
+#define NILFS_FIRST_SEGBUF(head)   NILFS_LIST_SEGBUF((head)->next)
+#define NILFS_SEGBUF_IS_LAST(segbuf, head)  ((segbuf)->sb_list.next == (head))
+
+#define nilfs_for_each_segbuf_before(s, t, h) \
+	for ((s) = NILFS_FIRST_SEGBUF(h); (s) != (t); \
+	     (s) = NILFS_NEXT_SEGBUF(s))
+
+#define NILFS_SEGBUF_FIRST_BH(head)  \
+	(list_entry((head)->next, struct buffer_head, b_assoc_buffers))
+#define NILFS_SEGBUF_NEXT_BH(bh)  \
+	(list_entry((bh)->b_assoc_buffers.next, struct buffer_head, \
+		    b_assoc_buffers))
+#define NILFS_SEGBUF_BH_IS_LAST(bh, head)  ((bh)->b_assoc_buffers.next == head)
+
+extern struct kmem_cache *nilfs_segbuf_cachep;
+
+struct nilfs_segment_buffer *nilfs_segbuf_new(struct super_block *);
+void nilfs_segbuf_free(struct nilfs_segment_buffer *);
+void nilfs_segbuf_map(struct nilfs_segment_buffer *, __u64, unsigned long,
+		      struct the_nilfs *);
+void nilfs_segbuf_map_cont(struct nilfs_segment_buffer *segbuf,
+			   struct nilfs_segment_buffer *prev);
+void nilfs_segbuf_set_next_segnum(struct nilfs_segment_buffer *, __u64,
+				  struct the_nilfs *);
+int nilfs_segbuf_reset(struct nilfs_segment_buffer *, unsigned int, time64_t,
+		       __u64);
+int nilfs_segbuf_extend_segsum(struct nilfs_segment_buffer *);
+int nilfs_segbuf_extend_payload(struct nilfs_segment_buffer *,
+				struct buffer_head **);
+void nilfs_segbuf_fill_in_segsum(struct nilfs_segment_buffer *);
+
+static inline int nilfs_segbuf_simplex(struct nilfs_segment_buffer *segbuf)
+{
+	unsigned int flags = segbuf->sb_sum.flags;
+
+	return (flags & (NILFS_SS_LOGBGN | NILFS_SS_LOGEND)) ==
+		(NILFS_SS_LOGBGN | NILFS_SS_LOGEND);
+}
+
+static inline int nilfs_segbuf_empty(struct nilfs_segment_buffer *segbuf)
+{
+	return segbuf->sb_sum.nblocks == segbuf->sb_sum.nsumblk;
+}
+
+static inline void
+nilfs_segbuf_add_segsum_buffer(struct nilfs_segment_buffer *segbuf,
+			       struct buffer_head *bh)
+{
+	list_add_tail(&bh->b_assoc_buffers, &segbuf->sb_segsum_buffers);
+	segbuf->sb_sum.nblocks++;
+	segbuf->sb_sum.nsumblk++;
+}
+
+static inline void
+nilfs_segbuf_add_payload_buffer(struct nilfs_segment_buffer *segbuf,
+				struct buffer_head *bh)
+{
+	list_add_tail(&bh->b_assoc_buffers, &segbuf->sb_payload_buffers);
+	segbuf->sb_sum.nblocks++;
+}
+
+static inline void
+nilfs_segbuf_add_file_buffer(struct nilfs_segment_buffer *segbuf,
+			     struct buffer_head *bh)
+{
+	get_bh(bh);
+	nilfs_segbuf_add_payload_buffer(segbuf, bh);
+	segbuf->sb_sum.nfileblk++;
+}
+
+void nilfs_clear_logs(struct list_head *logs);
+void nilfs_truncate_logs(struct list_head *logs,
+			 struct nilfs_segment_buffer *last);
+int nilfs_write_logs(struct list_head *logs, struct the_nilfs *nilfs);
+int nilfs_wait_on_logs(struct list_head *logs);
+void nilfs_add_checksums_on_logs(struct list_head *logs, u32 seed);
+
+static inline void nilfs_destroy_logs(struct list_head *logs)
+{
+	nilfs_truncate_logs(logs, NULL);
+}
+
+#endif /* _NILFS_SEGBUF_H */
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
new file mode 100644
index 0000000000..7ec1687975
--- /dev/null
+++ b/fs/nilfs2/segment.c
@@ -0,0 +1,2867 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NILFS segment constructor.
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Ryusuke Konishi.
+ *
+ */
+
+#include <linux/pagemap.h>
+#include <linux/buffer_head.h>
+#include <linux/writeback.h>
+#include <linux/bitops.h>
+#include <linux/bio.h>
+#include <linux/completion.h>
+#include <linux/blkdev.h>
+#include <linux/backing-dev.h>
+#include <linux/freezer.h>
+#include <linux/kthread.h>
+#include <linux/crc32.h>
+#include <linux/pagevec.h>
+#include <linux/slab.h>
+#include <linux/sched/signal.h>
+
+#include "nilfs.h"
+#include "btnode.h"
+#include "page.h"
+#include "segment.h"
+#include "sufile.h"
+#include "cpfile.h"
+#include "ifile.h"
+#include "segbuf.h"
+
+
+/*
+ * Segment constructor
+ */
+#define SC_N_INODEVEC	16   /* Size of locally allocated inode vector */
+
+#define SC_MAX_SEGDELTA 64   /*
+			      * Upper limit of the number of segments
+			      * appended in collection retry loop
+			      */
+
+/* Construction mode */
+enum {
+	SC_LSEG_SR = 1,	/* Make a logical segment having a super root */
+	SC_LSEG_DSYNC,	/*
+			 * Flush data blocks of a given file and make
+			 * a logical segment without a super root.
+			 */
+	SC_FLUSH_FILE,	/*
+			 * Flush data files, leads to segment writes without
+			 * creating a checkpoint.
+			 */
+	SC_FLUSH_DAT,	/*
+			 * Flush DAT file.  This also creates segments
+			 * without a checkpoint.
+			 */
+};
+
+/* Stage numbers of dirty block collection */
+enum {
+	NILFS_ST_INIT = 0,
+	NILFS_ST_GC,		/* Collecting dirty blocks for GC */
+	NILFS_ST_FILE,
+	NILFS_ST_IFILE,
+	NILFS_ST_CPFILE,
+	NILFS_ST_SUFILE,
+	NILFS_ST_DAT,
+	NILFS_ST_SR,		/* Super root */
+	NILFS_ST_DSYNC,		/* Data sync blocks */
+	NILFS_ST_DONE,
+};
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/nilfs2.h>
+
+/*
+ * nilfs_sc_cstage_inc(), nilfs_sc_cstage_set(), nilfs_sc_cstage_get() are
+ * wrapper functions of stage count (nilfs_sc_info->sc_stage.scnt). Users of
+ * the variable must use them because transition of stage count must involve
+ * trace events (trace_nilfs2_collection_stage_transition).
+ *
+ * nilfs_sc_cstage_get() isn't required for the above purpose because it doesn't
+ * produce tracepoint events. It is provided just for making the intention
+ * clear.
+ */
+static inline void nilfs_sc_cstage_inc(struct nilfs_sc_info *sci)
+{
+	sci->sc_stage.scnt++;
+	trace_nilfs2_collection_stage_transition(sci);
+}
+
+static inline void nilfs_sc_cstage_set(struct nilfs_sc_info *sci, int next_scnt)
+{
+	sci->sc_stage.scnt = next_scnt;
+	trace_nilfs2_collection_stage_transition(sci);
+}
+
+static inline int nilfs_sc_cstage_get(struct nilfs_sc_info *sci)
+{
+	return sci->sc_stage.scnt;
+}
+
+/* State flags of collection */
+#define NILFS_CF_NODE		0x0001	/* Collecting node blocks */
+#define NILFS_CF_IFILE_STARTED	0x0002	/* IFILE stage has started */
+#define NILFS_CF_SUFREED	0x0004	/* segment usages has been freed */
+#define NILFS_CF_HISTORY_MASK	(NILFS_CF_IFILE_STARTED | NILFS_CF_SUFREED)
+
+/* Operations depending on the construction mode and file type */
+struct nilfs_sc_operations {
+	int (*collect_data)(struct nilfs_sc_info *, struct buffer_head *,
+			    struct inode *);
+	int (*collect_node)(struct nilfs_sc_info *, struct buffer_head *,
+			    struct inode *);
+	int (*collect_bmap)(struct nilfs_sc_info *, struct buffer_head *,
+			    struct inode *);
+	void (*write_data_binfo)(struct nilfs_sc_info *,
+				 struct nilfs_segsum_pointer *,
+				 union nilfs_binfo *);
+	void (*write_node_binfo)(struct nilfs_sc_info *,
+				 struct nilfs_segsum_pointer *,
+				 union nilfs_binfo *);
+};
+
+/*
+ * Other definitions
+ */
+static void nilfs_segctor_start_timer(struct nilfs_sc_info *);
+static void nilfs_segctor_do_flush(struct nilfs_sc_info *, int);
+static void nilfs_segctor_do_immediate_flush(struct nilfs_sc_info *);
+static void nilfs_dispose_list(struct the_nilfs *, struct list_head *, int);
+
+#define nilfs_cnt32_ge(a, b)   \
+	(typecheck(__u32, a) && typecheck(__u32, b) && \
+	 ((__s32)(a) - (__s32)(b) >= 0))
+
+static int nilfs_prepare_segment_lock(struct super_block *sb,
+				      struct nilfs_transaction_info *ti)
+{
+	struct nilfs_transaction_info *cur_ti = current->journal_info;
+	void *save = NULL;
+
+	if (cur_ti) {
+		if (cur_ti->ti_magic == NILFS_TI_MAGIC)
+			return ++cur_ti->ti_count;
+
+		/*
+		 * If journal_info field is occupied by other FS,
+		 * it is saved and will be restored on
+		 * nilfs_transaction_commit().
+		 */
+		nilfs_warn(sb, "journal info from a different FS");
+		save = current->journal_info;
+	}
+	if (!ti) {
+		ti = kmem_cache_alloc(nilfs_transaction_cachep, GFP_NOFS);
+		if (!ti)
+			return -ENOMEM;
+		ti->ti_flags = NILFS_TI_DYNAMIC_ALLOC;
+	} else {
+		ti->ti_flags = 0;
+	}
+	ti->ti_count = 0;
+	ti->ti_save = save;
+	ti->ti_magic = NILFS_TI_MAGIC;
+	current->journal_info = ti;
+	return 0;
+}
+
+/**
+ * nilfs_transaction_begin - start indivisible file operations.
+ * @sb: super block
+ * @ti: nilfs_transaction_info
+ * @vacancy_check: flags for vacancy rate checks
+ *
+ * nilfs_transaction_begin() acquires a reader/writer semaphore, called
+ * the segment semaphore, to make a segment construction and write tasks
+ * exclusive.  The function is used with nilfs_transaction_commit() in pairs.
+ * The region enclosed by these two functions can be nested.  To avoid a
+ * deadlock, the semaphore is only acquired or released in the outermost call.
+ *
+ * This function allocates a nilfs_transaction_info struct to keep context
+ * information on it.  It is initialized and hooked onto the current task in
+ * the outermost call.  If a pre-allocated struct is given to @ti, it is used
+ * instead; otherwise a new struct is assigned from a slab.
+ *
+ * When @vacancy_check flag is set, this function will check the amount of
+ * free space, and will wait for the GC to reclaim disk space if low capacity.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error code is returned.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ *
+ * %-ENOSPC - No space left on device
+ */
+int nilfs_transaction_begin(struct super_block *sb,
+			    struct nilfs_transaction_info *ti,
+			    int vacancy_check)
+{
+	struct the_nilfs *nilfs;
+	int ret = nilfs_prepare_segment_lock(sb, ti);
+	struct nilfs_transaction_info *trace_ti;
+
+	if (unlikely(ret < 0))
+		return ret;
+	if (ret > 0) {
+		trace_ti = current->journal_info;
+
+		trace_nilfs2_transaction_transition(sb, trace_ti,
+				    trace_ti->ti_count, trace_ti->ti_flags,
+				    TRACE_NILFS2_TRANSACTION_BEGIN);
+		return 0;
+	}
+
+	sb_start_intwrite(sb);
+
+	nilfs = sb->s_fs_info;
+	down_read(&nilfs->ns_segctor_sem);
+	if (vacancy_check && nilfs_near_disk_full(nilfs)) {
+		up_read(&nilfs->ns_segctor_sem);
+		ret = -ENOSPC;
+		goto failed;
+	}
+
+	trace_ti = current->journal_info;
+	trace_nilfs2_transaction_transition(sb, trace_ti, trace_ti->ti_count,
+					    trace_ti->ti_flags,
+					    TRACE_NILFS2_TRANSACTION_BEGIN);
+	return 0;
+
+ failed:
+	ti = current->journal_info;
+	current->journal_info = ti->ti_save;
+	if (ti->ti_flags & NILFS_TI_DYNAMIC_ALLOC)
+		kmem_cache_free(nilfs_transaction_cachep, ti);
+	sb_end_intwrite(sb);
+	return ret;
+}
+
+/**
+ * nilfs_transaction_commit - commit indivisible file operations.
+ * @sb: super block
+ *
+ * nilfs_transaction_commit() releases the read semaphore which is
+ * acquired by nilfs_transaction_begin(). This is only performed
+ * in outermost call of this function.  If a commit flag is set,
+ * nilfs_transaction_commit() sets a timer to start the segment
+ * constructor.  If a sync flag is set, it starts construction
+ * directly.
+ */
+int nilfs_transaction_commit(struct super_block *sb)
+{
+	struct nilfs_transaction_info *ti = current->journal_info;
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	int err = 0;
+
+	BUG_ON(ti == NULL || ti->ti_magic != NILFS_TI_MAGIC);
+	ti->ti_flags |= NILFS_TI_COMMIT;
+	if (ti->ti_count > 0) {
+		ti->ti_count--;
+		trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
+			    ti->ti_flags, TRACE_NILFS2_TRANSACTION_COMMIT);
+		return 0;
+	}
+	if (nilfs->ns_writer) {
+		struct nilfs_sc_info *sci = nilfs->ns_writer;
+
+		if (ti->ti_flags & NILFS_TI_COMMIT)
+			nilfs_segctor_start_timer(sci);
+		if (atomic_read(&nilfs->ns_ndirtyblks) > sci->sc_watermark)
+			nilfs_segctor_do_flush(sci, 0);
+	}
+	up_read(&nilfs->ns_segctor_sem);
+	trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
+			    ti->ti_flags, TRACE_NILFS2_TRANSACTION_COMMIT);
+
+	current->journal_info = ti->ti_save;
+
+	if (ti->ti_flags & NILFS_TI_SYNC)
+		err = nilfs_construct_segment(sb);
+	if (ti->ti_flags & NILFS_TI_DYNAMIC_ALLOC)
+		kmem_cache_free(nilfs_transaction_cachep, ti);
+	sb_end_intwrite(sb);
+	return err;
+}
+
+void nilfs_transaction_abort(struct super_block *sb)
+{
+	struct nilfs_transaction_info *ti = current->journal_info;
+	struct the_nilfs *nilfs = sb->s_fs_info;
+
+	BUG_ON(ti == NULL || ti->ti_magic != NILFS_TI_MAGIC);
+	if (ti->ti_count > 0) {
+		ti->ti_count--;
+		trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
+			    ti->ti_flags, TRACE_NILFS2_TRANSACTION_ABORT);
+		return;
+	}
+	up_read(&nilfs->ns_segctor_sem);
+
+	trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
+		    ti->ti_flags, TRACE_NILFS2_TRANSACTION_ABORT);
+
+	current->journal_info = ti->ti_save;
+	if (ti->ti_flags & NILFS_TI_DYNAMIC_ALLOC)
+		kmem_cache_free(nilfs_transaction_cachep, ti);
+	sb_end_intwrite(sb);
+}
+
+void nilfs_relax_pressure_in_lock(struct super_block *sb)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct nilfs_sc_info *sci = nilfs->ns_writer;
+
+	if (sb_rdonly(sb) || unlikely(!sci) || !sci->sc_flush_request)
+		return;
+
+	set_bit(NILFS_SC_PRIOR_FLUSH, &sci->sc_flags);
+	up_read(&nilfs->ns_segctor_sem);
+
+	down_write(&nilfs->ns_segctor_sem);
+	if (sci->sc_flush_request &&
+	    test_bit(NILFS_SC_PRIOR_FLUSH, &sci->sc_flags)) {
+		struct nilfs_transaction_info *ti = current->journal_info;
+
+		ti->ti_flags |= NILFS_TI_WRITER;
+		nilfs_segctor_do_immediate_flush(sci);
+		ti->ti_flags &= ~NILFS_TI_WRITER;
+	}
+	downgrade_write(&nilfs->ns_segctor_sem);
+}
+
+static void nilfs_transaction_lock(struct super_block *sb,
+				   struct nilfs_transaction_info *ti,
+				   int gcflag)
+{
+	struct nilfs_transaction_info *cur_ti = current->journal_info;
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct nilfs_sc_info *sci = nilfs->ns_writer;
+
+	WARN_ON(cur_ti);
+	ti->ti_flags = NILFS_TI_WRITER;
+	ti->ti_count = 0;
+	ti->ti_save = cur_ti;
+	ti->ti_magic = NILFS_TI_MAGIC;
+	current->journal_info = ti;
+
+	for (;;) {
+		trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
+			    ti->ti_flags, TRACE_NILFS2_TRANSACTION_TRYLOCK);
+
+		down_write(&nilfs->ns_segctor_sem);
+		if (!test_bit(NILFS_SC_PRIOR_FLUSH, &sci->sc_flags))
+			break;
+
+		nilfs_segctor_do_immediate_flush(sci);
+
+		up_write(&nilfs->ns_segctor_sem);
+		cond_resched();
+	}
+	if (gcflag)
+		ti->ti_flags |= NILFS_TI_GC;
+
+	trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
+			    ti->ti_flags, TRACE_NILFS2_TRANSACTION_LOCK);
+}
+
+static void nilfs_transaction_unlock(struct super_block *sb)
+{
+	struct nilfs_transaction_info *ti = current->journal_info;
+	struct the_nilfs *nilfs = sb->s_fs_info;
+
+	BUG_ON(ti == NULL || ti->ti_magic != NILFS_TI_MAGIC);
+	BUG_ON(ti->ti_count > 0);
+
+	up_write(&nilfs->ns_segctor_sem);
+	current->journal_info = ti->ti_save;
+
+	trace_nilfs2_transaction_transition(sb, ti, ti->ti_count,
+			    ti->ti_flags, TRACE_NILFS2_TRANSACTION_UNLOCK);
+}
+
+static void *nilfs_segctor_map_segsum_entry(struct nilfs_sc_info *sci,
+					    struct nilfs_segsum_pointer *ssp,
+					    unsigned int bytes)
+{
+	struct nilfs_segment_buffer *segbuf = sci->sc_curseg;
+	unsigned int blocksize = sci->sc_super->s_blocksize;
+	void *p;
+
+	if (unlikely(ssp->offset + bytes > blocksize)) {
+		ssp->offset = 0;
+		BUG_ON(NILFS_SEGBUF_BH_IS_LAST(ssp->bh,
+					       &segbuf->sb_segsum_buffers));
+		ssp->bh = NILFS_SEGBUF_NEXT_BH(ssp->bh);
+	}
+	p = ssp->bh->b_data + ssp->offset;
+	ssp->offset += bytes;
+	return p;
+}
+
+/**
+ * nilfs_segctor_reset_segment_buffer - reset the current segment buffer
+ * @sci: nilfs_sc_info
+ */
+static int nilfs_segctor_reset_segment_buffer(struct nilfs_sc_info *sci)
+{
+	struct nilfs_segment_buffer *segbuf = sci->sc_curseg;
+	struct buffer_head *sumbh;
+	unsigned int sumbytes;
+	unsigned int flags = 0;
+	int err;
+
+	if (nilfs_doing_gc())
+		flags = NILFS_SS_GC;
+	err = nilfs_segbuf_reset(segbuf, flags, sci->sc_seg_ctime, sci->sc_cno);
+	if (unlikely(err))
+		return err;
+
+	sumbh = NILFS_SEGBUF_FIRST_BH(&segbuf->sb_segsum_buffers);
+	sumbytes = segbuf->sb_sum.sumbytes;
+	sci->sc_finfo_ptr.bh = sumbh;  sci->sc_finfo_ptr.offset = sumbytes;
+	sci->sc_binfo_ptr.bh = sumbh;  sci->sc_binfo_ptr.offset = sumbytes;
+	sci->sc_blk_cnt = sci->sc_datablk_cnt = 0;
+	return 0;
+}
+
+/**
+ * nilfs_segctor_zeropad_segsum - zero pad the rest of the segment summary area
+ * @sci: segment constructor object
+ *
+ * nilfs_segctor_zeropad_segsum() zero-fills unallocated space at the end of
+ * the current segment summary block.
+ */
+static void nilfs_segctor_zeropad_segsum(struct nilfs_sc_info *sci)
+{
+	struct nilfs_segsum_pointer *ssp;
+
+	ssp = sci->sc_blk_cnt > 0 ? &sci->sc_binfo_ptr : &sci->sc_finfo_ptr;
+	if (ssp->offset < ssp->bh->b_size)
+		memset(ssp->bh->b_data + ssp->offset, 0,
+		       ssp->bh->b_size - ssp->offset);
+}
+
+static int nilfs_segctor_feed_segment(struct nilfs_sc_info *sci)
+{
+	sci->sc_nblk_this_inc += sci->sc_curseg->sb_sum.nblocks;
+	if (NILFS_SEGBUF_IS_LAST(sci->sc_curseg, &sci->sc_segbufs))
+		return -E2BIG; /*
+				* The current segment is filled up
+				* (internal code)
+				*/
+	nilfs_segctor_zeropad_segsum(sci);
+	sci->sc_curseg = NILFS_NEXT_SEGBUF(sci->sc_curseg);
+	return nilfs_segctor_reset_segment_buffer(sci);
+}
+
+static int nilfs_segctor_add_super_root(struct nilfs_sc_info *sci)
+{
+	struct nilfs_segment_buffer *segbuf = sci->sc_curseg;
+	int err;
+
+	if (segbuf->sb_sum.nblocks >= segbuf->sb_rest_blocks) {
+		err = nilfs_segctor_feed_segment(sci);
+		if (err)
+			return err;
+		segbuf = sci->sc_curseg;
+	}
+	err = nilfs_segbuf_extend_payload(segbuf, &segbuf->sb_super_root);
+	if (likely(!err))
+		segbuf->sb_sum.flags |= NILFS_SS_SR;
+	return err;
+}
+
+/*
+ * Functions for making segment summary and payloads
+ */
+static int nilfs_segctor_segsum_block_required(
+	struct nilfs_sc_info *sci, const struct nilfs_segsum_pointer *ssp,
+	unsigned int binfo_size)
+{
+	unsigned int blocksize = sci->sc_super->s_blocksize;
+	/* Size of finfo and binfo is enough small against blocksize */
+
+	return ssp->offset + binfo_size +
+		(!sci->sc_blk_cnt ? sizeof(struct nilfs_finfo) : 0) >
+		blocksize;
+}
+
+static void nilfs_segctor_begin_finfo(struct nilfs_sc_info *sci,
+				      struct inode *inode)
+{
+	sci->sc_curseg->sb_sum.nfinfo++;
+	sci->sc_binfo_ptr = sci->sc_finfo_ptr;
+	nilfs_segctor_map_segsum_entry(
+		sci, &sci->sc_binfo_ptr, sizeof(struct nilfs_finfo));
+
+	if (NILFS_I(inode)->i_root &&
+	    !test_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags))
+		set_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags);
+	/* skip finfo */
+}
+
+static void nilfs_segctor_end_finfo(struct nilfs_sc_info *sci,
+				    struct inode *inode)
+{
+	struct nilfs_finfo *finfo;
+	struct nilfs_inode_info *ii;
+	struct nilfs_segment_buffer *segbuf;
+	__u64 cno;
+
+	if (sci->sc_blk_cnt == 0)
+		return;
+
+	ii = NILFS_I(inode);
+
+	if (test_bit(NILFS_I_GCINODE, &ii->i_state))
+		cno = ii->i_cno;
+	else if (NILFS_ROOT_METADATA_FILE(inode->i_ino))
+		cno = 0;
+	else
+		cno = sci->sc_cno;
+
+	finfo = nilfs_segctor_map_segsum_entry(sci, &sci->sc_finfo_ptr,
+						 sizeof(*finfo));
+	finfo->fi_ino = cpu_to_le64(inode->i_ino);
+	finfo->fi_nblocks = cpu_to_le32(sci->sc_blk_cnt);
+	finfo->fi_ndatablk = cpu_to_le32(sci->sc_datablk_cnt);
+	finfo->fi_cno = cpu_to_le64(cno);
+
+	segbuf = sci->sc_curseg;
+	segbuf->sb_sum.sumbytes = sci->sc_binfo_ptr.offset +
+		sci->sc_super->s_blocksize * (segbuf->sb_sum.nsumblk - 1);
+	sci->sc_finfo_ptr = sci->sc_binfo_ptr;
+	sci->sc_blk_cnt = sci->sc_datablk_cnt = 0;
+}
+
+static int nilfs_segctor_add_file_block(struct nilfs_sc_info *sci,
+					struct buffer_head *bh,
+					struct inode *inode,
+					unsigned int binfo_size)
+{
+	struct nilfs_segment_buffer *segbuf;
+	int required, err = 0;
+
+ retry:
+	segbuf = sci->sc_curseg;
+	required = nilfs_segctor_segsum_block_required(
+		sci, &sci->sc_binfo_ptr, binfo_size);
+	if (segbuf->sb_sum.nblocks + required + 1 > segbuf->sb_rest_blocks) {
+		nilfs_segctor_end_finfo(sci, inode);
+		err = nilfs_segctor_feed_segment(sci);
+		if (err)
+			return err;
+		goto retry;
+	}
+	if (unlikely(required)) {
+		nilfs_segctor_zeropad_segsum(sci);
+		err = nilfs_segbuf_extend_segsum(segbuf);
+		if (unlikely(err))
+			goto failed;
+	}
+	if (sci->sc_blk_cnt == 0)
+		nilfs_segctor_begin_finfo(sci, inode);
+
+	nilfs_segctor_map_segsum_entry(sci, &sci->sc_binfo_ptr, binfo_size);
+	/* Substitution to vblocknr is delayed until update_blocknr() */
+	nilfs_segbuf_add_file_buffer(segbuf, bh);
+	sci->sc_blk_cnt++;
+ failed:
+	return err;
+}
+
+/*
+ * Callback functions that enumerate, mark, and collect dirty blocks
+ */
+static int nilfs_collect_file_data(struct nilfs_sc_info *sci,
+				   struct buffer_head *bh, struct inode *inode)
+{
+	int err;
+
+	err = nilfs_bmap_propagate(NILFS_I(inode)->i_bmap, bh);
+	if (err < 0)
+		return err;
+
+	err = nilfs_segctor_add_file_block(sci, bh, inode,
+					   sizeof(struct nilfs_binfo_v));
+	if (!err)
+		sci->sc_datablk_cnt++;
+	return err;
+}
+
+static int nilfs_collect_file_node(struct nilfs_sc_info *sci,
+				   struct buffer_head *bh,
+				   struct inode *inode)
+{
+	return nilfs_bmap_propagate(NILFS_I(inode)->i_bmap, bh);
+}
+
+static int nilfs_collect_file_bmap(struct nilfs_sc_info *sci,
+				   struct buffer_head *bh,
+				   struct inode *inode)
+{
+	WARN_ON(!buffer_dirty(bh));
+	return nilfs_segctor_add_file_block(sci, bh, inode, sizeof(__le64));
+}
+
+static void nilfs_write_file_data_binfo(struct nilfs_sc_info *sci,
+					struct nilfs_segsum_pointer *ssp,
+					union nilfs_binfo *binfo)
+{
+	struct nilfs_binfo_v *binfo_v = nilfs_segctor_map_segsum_entry(
+		sci, ssp, sizeof(*binfo_v));
+	*binfo_v = binfo->bi_v;
+}
+
+static void nilfs_write_file_node_binfo(struct nilfs_sc_info *sci,
+					struct nilfs_segsum_pointer *ssp,
+					union nilfs_binfo *binfo)
+{
+	__le64 *vblocknr = nilfs_segctor_map_segsum_entry(
+		sci, ssp, sizeof(*vblocknr));
+	*vblocknr = binfo->bi_v.bi_vblocknr;
+}
+
+static const struct nilfs_sc_operations nilfs_sc_file_ops = {
+	.collect_data = nilfs_collect_file_data,
+	.collect_node = nilfs_collect_file_node,
+	.collect_bmap = nilfs_collect_file_bmap,
+	.write_data_binfo = nilfs_write_file_data_binfo,
+	.write_node_binfo = nilfs_write_file_node_binfo,
+};
+
+static int nilfs_collect_dat_data(struct nilfs_sc_info *sci,
+				  struct buffer_head *bh, struct inode *inode)
+{
+	int err;
+
+	err = nilfs_bmap_propagate(NILFS_I(inode)->i_bmap, bh);
+	if (err < 0)
+		return err;
+
+	err = nilfs_segctor_add_file_block(sci, bh, inode, sizeof(__le64));
+	if (!err)
+		sci->sc_datablk_cnt++;
+	return err;
+}
+
+static int nilfs_collect_dat_bmap(struct nilfs_sc_info *sci,
+				  struct buffer_head *bh, struct inode *inode)
+{
+	WARN_ON(!buffer_dirty(bh));
+	return nilfs_segctor_add_file_block(sci, bh, inode,
+					    sizeof(struct nilfs_binfo_dat));
+}
+
+static void nilfs_write_dat_data_binfo(struct nilfs_sc_info *sci,
+				       struct nilfs_segsum_pointer *ssp,
+				       union nilfs_binfo *binfo)
+{
+	__le64 *blkoff = nilfs_segctor_map_segsum_entry(sci, ssp,
+							  sizeof(*blkoff));
+	*blkoff = binfo->bi_dat.bi_blkoff;
+}
+
+static void nilfs_write_dat_node_binfo(struct nilfs_sc_info *sci,
+				       struct nilfs_segsum_pointer *ssp,
+				       union nilfs_binfo *binfo)
+{
+	struct nilfs_binfo_dat *binfo_dat =
+		nilfs_segctor_map_segsum_entry(sci, ssp, sizeof(*binfo_dat));
+	*binfo_dat = binfo->bi_dat;
+}
+
+static const struct nilfs_sc_operations nilfs_sc_dat_ops = {
+	.collect_data = nilfs_collect_dat_data,
+	.collect_node = nilfs_collect_file_node,
+	.collect_bmap = nilfs_collect_dat_bmap,
+	.write_data_binfo = nilfs_write_dat_data_binfo,
+	.write_node_binfo = nilfs_write_dat_node_binfo,
+};
+
+static const struct nilfs_sc_operations nilfs_sc_dsync_ops = {
+	.collect_data = nilfs_collect_file_data,
+	.collect_node = NULL,
+	.collect_bmap = NULL,
+	.write_data_binfo = nilfs_write_file_data_binfo,
+	.write_node_binfo = NULL,
+};
+
+static size_t nilfs_lookup_dirty_data_buffers(struct inode *inode,
+					      struct list_head *listp,
+					      size_t nlimit,
+					      loff_t start, loff_t end)
+{
+	struct address_space *mapping = inode->i_mapping;
+	struct folio_batch fbatch;
+	pgoff_t index = 0, last = ULONG_MAX;
+	size_t ndirties = 0;
+	int i;
+
+	if (unlikely(start != 0 || end != LLONG_MAX)) {
+		/*
+		 * A valid range is given for sync-ing data pages. The
+		 * range is rounded to per-page; extra dirty buffers
+		 * may be included if blocksize < pagesize.
+		 */
+		index = start >> PAGE_SHIFT;
+		last = end >> PAGE_SHIFT;
+	}
+	folio_batch_init(&fbatch);
+ repeat:
+	if (unlikely(index > last) ||
+	      !filemap_get_folios_tag(mapping, &index, last,
+		      PAGECACHE_TAG_DIRTY, &fbatch))
+		return ndirties;
+
+	for (i = 0; i < folio_batch_count(&fbatch); i++) {
+		struct buffer_head *bh, *head;
+		struct folio *folio = fbatch.folios[i];
+
+		folio_lock(folio);
+		if (unlikely(folio->mapping != mapping)) {
+			/* Exclude folios removed from the address space */
+			folio_unlock(folio);
+			continue;
+		}
+		head = folio_buffers(folio);
+		if (!head) {
+			create_empty_buffers(&folio->page, i_blocksize(inode), 0);
+			head = folio_buffers(folio);
+		}
+		folio_unlock(folio);
+
+		bh = head;
+		do {
+			if (!buffer_dirty(bh) || buffer_async_write(bh))
+				continue;
+			get_bh(bh);
+			list_add_tail(&bh->b_assoc_buffers, listp);
+			ndirties++;
+			if (unlikely(ndirties >= nlimit)) {
+				folio_batch_release(&fbatch);
+				cond_resched();
+				return ndirties;
+			}
+		} while (bh = bh->b_this_page, bh != head);
+	}
+	folio_batch_release(&fbatch);
+	cond_resched();
+	goto repeat;
+}
+
+static void nilfs_lookup_dirty_node_buffers(struct inode *inode,
+					    struct list_head *listp)
+{
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+	struct inode *btnc_inode = ii->i_assoc_inode;
+	struct folio_batch fbatch;
+	struct buffer_head *bh, *head;
+	unsigned int i;
+	pgoff_t index = 0;
+
+	if (!btnc_inode)
+		return;
+	folio_batch_init(&fbatch);
+
+	while (filemap_get_folios_tag(btnc_inode->i_mapping, &index,
+				(pgoff_t)-1, PAGECACHE_TAG_DIRTY, &fbatch)) {
+		for (i = 0; i < folio_batch_count(&fbatch); i++) {
+			bh = head = folio_buffers(fbatch.folios[i]);
+			do {
+				if (buffer_dirty(bh) &&
+						!buffer_async_write(bh)) {
+					get_bh(bh);
+					list_add_tail(&bh->b_assoc_buffers,
+						      listp);
+				}
+				bh = bh->b_this_page;
+			} while (bh != head);
+		}
+		folio_batch_release(&fbatch);
+		cond_resched();
+	}
+}
+
+static void nilfs_dispose_list(struct the_nilfs *nilfs,
+			       struct list_head *head, int force)
+{
+	struct nilfs_inode_info *ii, *n;
+	struct nilfs_inode_info *ivec[SC_N_INODEVEC], **pii;
+	unsigned int nv = 0;
+
+	while (!list_empty(head)) {
+		spin_lock(&nilfs->ns_inode_lock);
+		list_for_each_entry_safe(ii, n, head, i_dirty) {
+			list_del_init(&ii->i_dirty);
+			if (force) {
+				if (unlikely(ii->i_bh)) {
+					brelse(ii->i_bh);
+					ii->i_bh = NULL;
+				}
+			} else if (test_bit(NILFS_I_DIRTY, &ii->i_state)) {
+				set_bit(NILFS_I_QUEUED, &ii->i_state);
+				list_add_tail(&ii->i_dirty,
+					      &nilfs->ns_dirty_files);
+				continue;
+			}
+			ivec[nv++] = ii;
+			if (nv == SC_N_INODEVEC)
+				break;
+		}
+		spin_unlock(&nilfs->ns_inode_lock);
+
+		for (pii = ivec; nv > 0; pii++, nv--)
+			iput(&(*pii)->vfs_inode);
+	}
+}
+
+static void nilfs_iput_work_func(struct work_struct *work)
+{
+	struct nilfs_sc_info *sci = container_of(work, struct nilfs_sc_info,
+						 sc_iput_work);
+	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
+
+	nilfs_dispose_list(nilfs, &sci->sc_iput_queue, 0);
+}
+
+static int nilfs_test_metadata_dirty(struct the_nilfs *nilfs,
+				     struct nilfs_root *root)
+{
+	int ret = 0;
+
+	if (nilfs_mdt_fetch_dirty(root->ifile))
+		ret++;
+	if (nilfs_mdt_fetch_dirty(nilfs->ns_cpfile))
+		ret++;
+	if (nilfs_mdt_fetch_dirty(nilfs->ns_sufile))
+		ret++;
+	if ((ret || nilfs_doing_gc()) && nilfs_mdt_fetch_dirty(nilfs->ns_dat))
+		ret++;
+	return ret;
+}
+
+static int nilfs_segctor_clean(struct nilfs_sc_info *sci)
+{
+	return list_empty(&sci->sc_dirty_files) &&
+		!test_bit(NILFS_SC_DIRTY, &sci->sc_flags) &&
+		sci->sc_nfreesegs == 0 &&
+		(!nilfs_doing_gc() || list_empty(&sci->sc_gc_inodes));
+}
+
+static int nilfs_segctor_confirm(struct nilfs_sc_info *sci)
+{
+	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
+	int ret = 0;
+
+	if (nilfs_test_metadata_dirty(nilfs, sci->sc_root))
+		set_bit(NILFS_SC_DIRTY, &sci->sc_flags);
+
+	spin_lock(&nilfs->ns_inode_lock);
+	if (list_empty(&nilfs->ns_dirty_files) && nilfs_segctor_clean(sci))
+		ret++;
+
+	spin_unlock(&nilfs->ns_inode_lock);
+	return ret;
+}
+
+static void nilfs_segctor_clear_metadata_dirty(struct nilfs_sc_info *sci)
+{
+	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
+
+	nilfs_mdt_clear_dirty(sci->sc_root->ifile);
+	nilfs_mdt_clear_dirty(nilfs->ns_cpfile);
+	nilfs_mdt_clear_dirty(nilfs->ns_sufile);
+	nilfs_mdt_clear_dirty(nilfs->ns_dat);
+}
+
+static int nilfs_segctor_create_checkpoint(struct nilfs_sc_info *sci)
+{
+	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
+	struct buffer_head *bh_cp;
+	struct nilfs_checkpoint *raw_cp;
+	int err;
+
+	/* XXX: this interface will be changed */
+	err = nilfs_cpfile_get_checkpoint(nilfs->ns_cpfile, nilfs->ns_cno, 1,
+					  &raw_cp, &bh_cp);
+	if (likely(!err)) {
+		/*
+		 * The following code is duplicated with cpfile.  But, it is
+		 * needed to collect the checkpoint even if it was not newly
+		 * created.
+		 */
+		mark_buffer_dirty(bh_cp);
+		nilfs_mdt_mark_dirty(nilfs->ns_cpfile);
+		nilfs_cpfile_put_checkpoint(
+			nilfs->ns_cpfile, nilfs->ns_cno, bh_cp);
+	} else if (err == -EINVAL || err == -ENOENT) {
+		nilfs_error(sci->sc_super,
+			    "checkpoint creation failed due to metadata corruption.");
+		err = -EIO;
+	}
+	return err;
+}
+
+static int nilfs_segctor_fill_in_checkpoint(struct nilfs_sc_info *sci)
+{
+	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
+	struct buffer_head *bh_cp;
+	struct nilfs_checkpoint *raw_cp;
+	int err;
+
+	err = nilfs_cpfile_get_checkpoint(nilfs->ns_cpfile, nilfs->ns_cno, 0,
+					  &raw_cp, &bh_cp);
+	if (unlikely(err)) {
+		if (err == -EINVAL || err == -ENOENT) {
+			nilfs_error(sci->sc_super,
+				    "checkpoint finalization failed due to metadata corruption.");
+			err = -EIO;
+		}
+		goto failed_ibh;
+	}
+	raw_cp->cp_snapshot_list.ssl_next = 0;
+	raw_cp->cp_snapshot_list.ssl_prev = 0;
+	raw_cp->cp_inodes_count =
+		cpu_to_le64(atomic64_read(&sci->sc_root->inodes_count));
+	raw_cp->cp_blocks_count =
+		cpu_to_le64(atomic64_read(&sci->sc_root->blocks_count));
+	raw_cp->cp_nblk_inc =
+		cpu_to_le64(sci->sc_nblk_inc + sci->sc_nblk_this_inc);
+	raw_cp->cp_create = cpu_to_le64(sci->sc_seg_ctime);
+	raw_cp->cp_cno = cpu_to_le64(nilfs->ns_cno);
+
+	if (test_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags))
+		nilfs_checkpoint_clear_minor(raw_cp);
+	else
+		nilfs_checkpoint_set_minor(raw_cp);
+
+	nilfs_write_inode_common(sci->sc_root->ifile,
+				 &raw_cp->cp_ifile_inode, 1);
+	nilfs_cpfile_put_checkpoint(nilfs->ns_cpfile, nilfs->ns_cno, bh_cp);
+	return 0;
+
+ failed_ibh:
+	return err;
+}
+
+static void nilfs_fill_in_file_bmap(struct inode *ifile,
+				    struct nilfs_inode_info *ii)
+
+{
+	struct buffer_head *ibh;
+	struct nilfs_inode *raw_inode;
+
+	if (test_bit(NILFS_I_BMAP, &ii->i_state)) {
+		ibh = ii->i_bh;
+		BUG_ON(!ibh);
+		raw_inode = nilfs_ifile_map_inode(ifile, ii->vfs_inode.i_ino,
+						  ibh);
+		nilfs_bmap_write(ii->i_bmap, raw_inode);
+		nilfs_ifile_unmap_inode(ifile, ii->vfs_inode.i_ino, ibh);
+	}
+}
+
+static void nilfs_segctor_fill_in_file_bmap(struct nilfs_sc_info *sci)
+{
+	struct nilfs_inode_info *ii;
+
+	list_for_each_entry(ii, &sci->sc_dirty_files, i_dirty) {
+		nilfs_fill_in_file_bmap(sci->sc_root->ifile, ii);
+		set_bit(NILFS_I_COLLECTED, &ii->i_state);
+	}
+}
+
+static void nilfs_segctor_fill_in_super_root(struct nilfs_sc_info *sci,
+					     struct the_nilfs *nilfs)
+{
+	struct buffer_head *bh_sr;
+	struct nilfs_super_root *raw_sr;
+	unsigned int isz, srsz;
+
+	bh_sr = NILFS_LAST_SEGBUF(&sci->sc_segbufs)->sb_super_root;
+
+	lock_buffer(bh_sr);
+	raw_sr = (struct nilfs_super_root *)bh_sr->b_data;
+	isz = nilfs->ns_inode_size;
+	srsz = NILFS_SR_BYTES(isz);
+
+	raw_sr->sr_sum = 0;  /* Ensure initialization within this update */
+	raw_sr->sr_bytes = cpu_to_le16(srsz);
+	raw_sr->sr_nongc_ctime
+		= cpu_to_le64(nilfs_doing_gc() ?
+			      nilfs->ns_nongc_ctime : sci->sc_seg_ctime);
+	raw_sr->sr_flags = 0;
+
+	nilfs_write_inode_common(nilfs->ns_dat, (void *)raw_sr +
+				 NILFS_SR_DAT_OFFSET(isz), 1);
+	nilfs_write_inode_common(nilfs->ns_cpfile, (void *)raw_sr +
+				 NILFS_SR_CPFILE_OFFSET(isz), 1);
+	nilfs_write_inode_common(nilfs->ns_sufile, (void *)raw_sr +
+				 NILFS_SR_SUFILE_OFFSET(isz), 1);
+	memset((void *)raw_sr + srsz, 0, nilfs->ns_blocksize - srsz);
+	set_buffer_uptodate(bh_sr);
+	unlock_buffer(bh_sr);
+}
+
+static void nilfs_redirty_inodes(struct list_head *head)
+{
+	struct nilfs_inode_info *ii;
+
+	list_for_each_entry(ii, head, i_dirty) {
+		if (test_bit(NILFS_I_COLLECTED, &ii->i_state))
+			clear_bit(NILFS_I_COLLECTED, &ii->i_state);
+	}
+}
+
+static void nilfs_drop_collected_inodes(struct list_head *head)
+{
+	struct nilfs_inode_info *ii;
+
+	list_for_each_entry(ii, head, i_dirty) {
+		if (!test_and_clear_bit(NILFS_I_COLLECTED, &ii->i_state))
+			continue;
+
+		clear_bit(NILFS_I_INODE_SYNC, &ii->i_state);
+		set_bit(NILFS_I_UPDATED, &ii->i_state);
+	}
+}
+
+static int nilfs_segctor_apply_buffers(struct nilfs_sc_info *sci,
+				       struct inode *inode,
+				       struct list_head *listp,
+				       int (*collect)(struct nilfs_sc_info *,
+						      struct buffer_head *,
+						      struct inode *))
+{
+	struct buffer_head *bh, *n;
+	int err = 0;
+
+	if (collect) {
+		list_for_each_entry_safe(bh, n, listp, b_assoc_buffers) {
+			list_del_init(&bh->b_assoc_buffers);
+			err = collect(sci, bh, inode);
+			brelse(bh);
+			if (unlikely(err))
+				goto dispose_buffers;
+		}
+		return 0;
+	}
+
+ dispose_buffers:
+	while (!list_empty(listp)) {
+		bh = list_first_entry(listp, struct buffer_head,
+				      b_assoc_buffers);
+		list_del_init(&bh->b_assoc_buffers);
+		brelse(bh);
+	}
+	return err;
+}
+
+static size_t nilfs_segctor_buffer_rest(struct nilfs_sc_info *sci)
+{
+	/* Remaining number of blocks within segment buffer */
+	return sci->sc_segbuf_nblocks -
+		(sci->sc_nblk_this_inc + sci->sc_curseg->sb_sum.nblocks);
+}
+
+static int nilfs_segctor_scan_file(struct nilfs_sc_info *sci,
+				   struct inode *inode,
+				   const struct nilfs_sc_operations *sc_ops)
+{
+	LIST_HEAD(data_buffers);
+	LIST_HEAD(node_buffers);
+	int err;
+
+	if (!(sci->sc_stage.flags & NILFS_CF_NODE)) {
+		size_t n, rest = nilfs_segctor_buffer_rest(sci);
+
+		n = nilfs_lookup_dirty_data_buffers(
+			inode, &data_buffers, rest + 1, 0, LLONG_MAX);
+		if (n > rest) {
+			err = nilfs_segctor_apply_buffers(
+				sci, inode, &data_buffers,
+				sc_ops->collect_data);
+			BUG_ON(!err); /* always receive -E2BIG or true error */
+			goto break_or_fail;
+		}
+	}
+	nilfs_lookup_dirty_node_buffers(inode, &node_buffers);
+
+	if (!(sci->sc_stage.flags & NILFS_CF_NODE)) {
+		err = nilfs_segctor_apply_buffers(
+			sci, inode, &data_buffers, sc_ops->collect_data);
+		if (unlikely(err)) {
+			/* dispose node list */
+			nilfs_segctor_apply_buffers(
+				sci, inode, &node_buffers, NULL);
+			goto break_or_fail;
+		}
+		sci->sc_stage.flags |= NILFS_CF_NODE;
+	}
+	/* Collect node */
+	err = nilfs_segctor_apply_buffers(
+		sci, inode, &node_buffers, sc_ops->collect_node);
+	if (unlikely(err))
+		goto break_or_fail;
+
+	nilfs_bmap_lookup_dirty_buffers(NILFS_I(inode)->i_bmap, &node_buffers);
+	err = nilfs_segctor_apply_buffers(
+		sci, inode, &node_buffers, sc_ops->collect_bmap);
+	if (unlikely(err))
+		goto break_or_fail;
+
+	nilfs_segctor_end_finfo(sci, inode);
+	sci->sc_stage.flags &= ~NILFS_CF_NODE;
+
+ break_or_fail:
+	return err;
+}
+
+static int nilfs_segctor_scan_file_dsync(struct nilfs_sc_info *sci,
+					 struct inode *inode)
+{
+	LIST_HEAD(data_buffers);
+	size_t n, rest = nilfs_segctor_buffer_rest(sci);
+	int err;
+
+	n = nilfs_lookup_dirty_data_buffers(inode, &data_buffers, rest + 1,
+					    sci->sc_dsync_start,
+					    sci->sc_dsync_end);
+
+	err = nilfs_segctor_apply_buffers(sci, inode, &data_buffers,
+					  nilfs_collect_file_data);
+	if (!err) {
+		nilfs_segctor_end_finfo(sci, inode);
+		BUG_ON(n > rest);
+		/* always receive -E2BIG or true error if n > rest */
+	}
+	return err;
+}
+
+static int nilfs_segctor_collect_blocks(struct nilfs_sc_info *sci, int mode)
+{
+	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
+	struct list_head *head;
+	struct nilfs_inode_info *ii;
+	size_t ndone;
+	int err = 0;
+
+	switch (nilfs_sc_cstage_get(sci)) {
+	case NILFS_ST_INIT:
+		/* Pre-processes */
+		sci->sc_stage.flags = 0;
+
+		if (!test_bit(NILFS_SC_UNCLOSED, &sci->sc_flags)) {
+			sci->sc_nblk_inc = 0;
+			sci->sc_curseg->sb_sum.flags = NILFS_SS_LOGBGN;
+			if (mode == SC_LSEG_DSYNC) {
+				nilfs_sc_cstage_set(sci, NILFS_ST_DSYNC);
+				goto dsync_mode;
+			}
+		}
+
+		sci->sc_stage.dirty_file_ptr = NULL;
+		sci->sc_stage.gc_inode_ptr = NULL;
+		if (mode == SC_FLUSH_DAT) {
+			nilfs_sc_cstage_set(sci, NILFS_ST_DAT);
+			goto dat_stage;
+		}
+		nilfs_sc_cstage_inc(sci);
+		fallthrough;
+	case NILFS_ST_GC:
+		if (nilfs_doing_gc()) {
+			head = &sci->sc_gc_inodes;
+			ii = list_prepare_entry(sci->sc_stage.gc_inode_ptr,
+						head, i_dirty);
+			list_for_each_entry_continue(ii, head, i_dirty) {
+				err = nilfs_segctor_scan_file(
+					sci, &ii->vfs_inode,
+					&nilfs_sc_file_ops);
+				if (unlikely(err)) {
+					sci->sc_stage.gc_inode_ptr = list_entry(
+						ii->i_dirty.prev,
+						struct nilfs_inode_info,
+						i_dirty);
+					goto break_or_fail;
+				}
+				set_bit(NILFS_I_COLLECTED, &ii->i_state);
+			}
+			sci->sc_stage.gc_inode_ptr = NULL;
+		}
+		nilfs_sc_cstage_inc(sci);
+		fallthrough;
+	case NILFS_ST_FILE:
+		head = &sci->sc_dirty_files;
+		ii = list_prepare_entry(sci->sc_stage.dirty_file_ptr, head,
+					i_dirty);
+		list_for_each_entry_continue(ii, head, i_dirty) {
+			clear_bit(NILFS_I_DIRTY, &ii->i_state);
+
+			err = nilfs_segctor_scan_file(sci, &ii->vfs_inode,
+						      &nilfs_sc_file_ops);
+			if (unlikely(err)) {
+				sci->sc_stage.dirty_file_ptr =
+					list_entry(ii->i_dirty.prev,
+						   struct nilfs_inode_info,
+						   i_dirty);
+				goto break_or_fail;
+			}
+			/* sci->sc_stage.dirty_file_ptr = NILFS_I(inode); */
+			/* XXX: required ? */
+		}
+		sci->sc_stage.dirty_file_ptr = NULL;
+		if (mode == SC_FLUSH_FILE) {
+			nilfs_sc_cstage_set(sci, NILFS_ST_DONE);
+			return 0;
+		}
+		nilfs_sc_cstage_inc(sci);
+		sci->sc_stage.flags |= NILFS_CF_IFILE_STARTED;
+		fallthrough;
+	case NILFS_ST_IFILE:
+		err = nilfs_segctor_scan_file(sci, sci->sc_root->ifile,
+					      &nilfs_sc_file_ops);
+		if (unlikely(err))
+			break;
+		nilfs_sc_cstage_inc(sci);
+		/* Creating a checkpoint */
+		err = nilfs_segctor_create_checkpoint(sci);
+		if (unlikely(err))
+			break;
+		fallthrough;
+	case NILFS_ST_CPFILE:
+		err = nilfs_segctor_scan_file(sci, nilfs->ns_cpfile,
+					      &nilfs_sc_file_ops);
+		if (unlikely(err))
+			break;
+		nilfs_sc_cstage_inc(sci);
+		fallthrough;
+	case NILFS_ST_SUFILE:
+		err = nilfs_sufile_freev(nilfs->ns_sufile, sci->sc_freesegs,
+					 sci->sc_nfreesegs, &ndone);
+		if (unlikely(err)) {
+			nilfs_sufile_cancel_freev(nilfs->ns_sufile,
+						  sci->sc_freesegs, ndone,
+						  NULL);
+			break;
+		}
+		sci->sc_stage.flags |= NILFS_CF_SUFREED;
+
+		err = nilfs_segctor_scan_file(sci, nilfs->ns_sufile,
+					      &nilfs_sc_file_ops);
+		if (unlikely(err))
+			break;
+		nilfs_sc_cstage_inc(sci);
+		fallthrough;
+	case NILFS_ST_DAT:
+ dat_stage:
+		err = nilfs_segctor_scan_file(sci, nilfs->ns_dat,
+					      &nilfs_sc_dat_ops);
+		if (unlikely(err))
+			break;
+		if (mode == SC_FLUSH_DAT) {
+			nilfs_sc_cstage_set(sci, NILFS_ST_DONE);
+			return 0;
+		}
+		nilfs_sc_cstage_inc(sci);
+		fallthrough;
+	case NILFS_ST_SR:
+		if (mode == SC_LSEG_SR) {
+			/* Appending a super root */
+			err = nilfs_segctor_add_super_root(sci);
+			if (unlikely(err))
+				break;
+		}
+		/* End of a logical segment */
+		sci->sc_curseg->sb_sum.flags |= NILFS_SS_LOGEND;
+		nilfs_sc_cstage_set(sci, NILFS_ST_DONE);
+		return 0;
+	case NILFS_ST_DSYNC:
+ dsync_mode:
+		sci->sc_curseg->sb_sum.flags |= NILFS_SS_SYNDT;
+		ii = sci->sc_dsync_inode;
+		if (!test_bit(NILFS_I_BUSY, &ii->i_state))
+			break;
+
+		err = nilfs_segctor_scan_file_dsync(sci, &ii->vfs_inode);
+		if (unlikely(err))
+			break;
+		sci->sc_curseg->sb_sum.flags |= NILFS_SS_LOGEND;
+		nilfs_sc_cstage_set(sci, NILFS_ST_DONE);
+		return 0;
+	case NILFS_ST_DONE:
+		return 0;
+	default:
+		BUG();
+	}
+
+ break_or_fail:
+	return err;
+}
+
+/**
+ * nilfs_segctor_begin_construction - setup segment buffer to make a new log
+ * @sci: nilfs_sc_info
+ * @nilfs: nilfs object
+ */
+static int nilfs_segctor_begin_construction(struct nilfs_sc_info *sci,
+					    struct the_nilfs *nilfs)
+{
+	struct nilfs_segment_buffer *segbuf, *prev;
+	__u64 nextnum;
+	int err, alloc = 0;
+
+	segbuf = nilfs_segbuf_new(sci->sc_super);
+	if (unlikely(!segbuf))
+		return -ENOMEM;
+
+	if (list_empty(&sci->sc_write_logs)) {
+		nilfs_segbuf_map(segbuf, nilfs->ns_segnum,
+				 nilfs->ns_pseg_offset, nilfs);
+		if (segbuf->sb_rest_blocks < NILFS_PSEG_MIN_BLOCKS) {
+			nilfs_shift_to_next_segment(nilfs);
+			nilfs_segbuf_map(segbuf, nilfs->ns_segnum, 0, nilfs);
+		}
+
+		segbuf->sb_sum.seg_seq = nilfs->ns_seg_seq;
+		nextnum = nilfs->ns_nextnum;
+
+		if (nilfs->ns_segnum == nilfs->ns_nextnum)
+			/* Start from the head of a new full segment */
+			alloc++;
+	} else {
+		/* Continue logs */
+		prev = NILFS_LAST_SEGBUF(&sci->sc_write_logs);
+		nilfs_segbuf_map_cont(segbuf, prev);
+		segbuf->sb_sum.seg_seq = prev->sb_sum.seg_seq;
+		nextnum = prev->sb_nextnum;
+
+		if (segbuf->sb_rest_blocks < NILFS_PSEG_MIN_BLOCKS) {
+			nilfs_segbuf_map(segbuf, prev->sb_nextnum, 0, nilfs);
+			segbuf->sb_sum.seg_seq++;
+			alloc++;
+		}
+	}
+
+	err = nilfs_sufile_mark_dirty(nilfs->ns_sufile, segbuf->sb_segnum);
+	if (err)
+		goto failed;
+
+	if (alloc) {
+		err = nilfs_sufile_alloc(nilfs->ns_sufile, &nextnum);
+		if (err)
+			goto failed;
+	}
+	nilfs_segbuf_set_next_segnum(segbuf, nextnum, nilfs);
+
+	BUG_ON(!list_empty(&sci->sc_segbufs));
+	list_add_tail(&segbuf->sb_list, &sci->sc_segbufs);
+	sci->sc_segbuf_nblocks = segbuf->sb_rest_blocks;
+	return 0;
+
+ failed:
+	nilfs_segbuf_free(segbuf);
+	return err;
+}
+
+static int nilfs_segctor_extend_segments(struct nilfs_sc_info *sci,
+					 struct the_nilfs *nilfs, int nadd)
+{
+	struct nilfs_segment_buffer *segbuf, *prev;
+	struct inode *sufile = nilfs->ns_sufile;
+	__u64 nextnextnum;
+	LIST_HEAD(list);
+	int err, ret, i;
+
+	prev = NILFS_LAST_SEGBUF(&sci->sc_segbufs);
+	/*
+	 * Since the segment specified with nextnum might be allocated during
+	 * the previous construction, the buffer including its segusage may
+	 * not be dirty.  The following call ensures that the buffer is dirty
+	 * and will pin the buffer on memory until the sufile is written.
+	 */
+	err = nilfs_sufile_mark_dirty(sufile, prev->sb_nextnum);
+	if (unlikely(err))
+		return err;
+
+	for (i = 0; i < nadd; i++) {
+		/* extend segment info */
+		err = -ENOMEM;
+		segbuf = nilfs_segbuf_new(sci->sc_super);
+		if (unlikely(!segbuf))
+			goto failed;
+
+		/* map this buffer to region of segment on-disk */
+		nilfs_segbuf_map(segbuf, prev->sb_nextnum, 0, nilfs);
+		sci->sc_segbuf_nblocks += segbuf->sb_rest_blocks;
+
+		/* allocate the next next full segment */
+		err = nilfs_sufile_alloc(sufile, &nextnextnum);
+		if (unlikely(err))
+			goto failed_segbuf;
+
+		segbuf->sb_sum.seg_seq = prev->sb_sum.seg_seq + 1;
+		nilfs_segbuf_set_next_segnum(segbuf, nextnextnum, nilfs);
+
+		list_add_tail(&segbuf->sb_list, &list);
+		prev = segbuf;
+	}
+	list_splice_tail(&list, &sci->sc_segbufs);
+	return 0;
+
+ failed_segbuf:
+	nilfs_segbuf_free(segbuf);
+ failed:
+	list_for_each_entry(segbuf, &list, sb_list) {
+		ret = nilfs_sufile_free(sufile, segbuf->sb_nextnum);
+		WARN_ON(ret); /* never fails */
+	}
+	nilfs_destroy_logs(&list);
+	return err;
+}
+
+static void nilfs_free_incomplete_logs(struct list_head *logs,
+				       struct the_nilfs *nilfs)
+{
+	struct nilfs_segment_buffer *segbuf, *prev;
+	struct inode *sufile = nilfs->ns_sufile;
+	int ret;
+
+	segbuf = NILFS_FIRST_SEGBUF(logs);
+	if (nilfs->ns_nextnum != segbuf->sb_nextnum) {
+		ret = nilfs_sufile_free(sufile, segbuf->sb_nextnum);
+		WARN_ON(ret); /* never fails */
+	}
+	if (atomic_read(&segbuf->sb_err)) {
+		/* Case 1: The first segment failed */
+		if (segbuf->sb_pseg_start != segbuf->sb_fseg_start)
+			/*
+			 * Case 1a:  Partial segment appended into an existing
+			 * segment
+			 */
+			nilfs_terminate_segment(nilfs, segbuf->sb_fseg_start,
+						segbuf->sb_fseg_end);
+		else /* Case 1b:  New full segment */
+			set_nilfs_discontinued(nilfs);
+	}
+
+	prev = segbuf;
+	list_for_each_entry_continue(segbuf, logs, sb_list) {
+		if (prev->sb_nextnum != segbuf->sb_nextnum) {
+			ret = nilfs_sufile_free(sufile, segbuf->sb_nextnum);
+			WARN_ON(ret); /* never fails */
+		}
+		if (atomic_read(&segbuf->sb_err) &&
+		    segbuf->sb_segnum != nilfs->ns_nextnum)
+			/* Case 2: extended segment (!= next) failed */
+			nilfs_sufile_set_error(sufile, segbuf->sb_segnum);
+		prev = segbuf;
+	}
+}
+
+static void nilfs_segctor_update_segusage(struct nilfs_sc_info *sci,
+					  struct inode *sufile)
+{
+	struct nilfs_segment_buffer *segbuf;
+	unsigned long live_blocks;
+	int ret;
+
+	list_for_each_entry(segbuf, &sci->sc_segbufs, sb_list) {
+		live_blocks = segbuf->sb_sum.nblocks +
+			(segbuf->sb_pseg_start - segbuf->sb_fseg_start);
+		ret = nilfs_sufile_set_segment_usage(sufile, segbuf->sb_segnum,
+						     live_blocks,
+						     sci->sc_seg_ctime);
+		WARN_ON(ret); /* always succeed because the segusage is dirty */
+	}
+}
+
+static void nilfs_cancel_segusage(struct list_head *logs, struct inode *sufile)
+{
+	struct nilfs_segment_buffer *segbuf;
+	int ret;
+
+	segbuf = NILFS_FIRST_SEGBUF(logs);
+	ret = nilfs_sufile_set_segment_usage(sufile, segbuf->sb_segnum,
+					     segbuf->sb_pseg_start -
+					     segbuf->sb_fseg_start, 0);
+	WARN_ON(ret); /* always succeed because the segusage is dirty */
+
+	list_for_each_entry_continue(segbuf, logs, sb_list) {
+		ret = nilfs_sufile_set_segment_usage(sufile, segbuf->sb_segnum,
+						     0, 0);
+		WARN_ON(ret); /* always succeed */
+	}
+}
+
+static void nilfs_segctor_truncate_segments(struct nilfs_sc_info *sci,
+					    struct nilfs_segment_buffer *last,
+					    struct inode *sufile)
+{
+	struct nilfs_segment_buffer *segbuf = last;
+	int ret;
+
+	list_for_each_entry_continue(segbuf, &sci->sc_segbufs, sb_list) {
+		sci->sc_segbuf_nblocks -= segbuf->sb_rest_blocks;
+		ret = nilfs_sufile_free(sufile, segbuf->sb_nextnum);
+		WARN_ON(ret);
+	}
+	nilfs_truncate_logs(&sci->sc_segbufs, last);
+}
+
+
+static int nilfs_segctor_collect(struct nilfs_sc_info *sci,
+				 struct the_nilfs *nilfs, int mode)
+{
+	struct nilfs_cstage prev_stage = sci->sc_stage;
+	int err, nadd = 1;
+
+	/* Collection retry loop */
+	for (;;) {
+		sci->sc_nblk_this_inc = 0;
+		sci->sc_curseg = NILFS_FIRST_SEGBUF(&sci->sc_segbufs);
+
+		err = nilfs_segctor_reset_segment_buffer(sci);
+		if (unlikely(err))
+			goto failed;
+
+		err = nilfs_segctor_collect_blocks(sci, mode);
+		sci->sc_nblk_this_inc += sci->sc_curseg->sb_sum.nblocks;
+		if (!err)
+			break;
+
+		if (unlikely(err != -E2BIG))
+			goto failed;
+
+		/* The current segment is filled up */
+		if (mode != SC_LSEG_SR ||
+		    nilfs_sc_cstage_get(sci) < NILFS_ST_CPFILE)
+			break;
+
+		nilfs_clear_logs(&sci->sc_segbufs);
+
+		if (sci->sc_stage.flags & NILFS_CF_SUFREED) {
+			err = nilfs_sufile_cancel_freev(nilfs->ns_sufile,
+							sci->sc_freesegs,
+							sci->sc_nfreesegs,
+							NULL);
+			WARN_ON(err); /* do not happen */
+			sci->sc_stage.flags &= ~NILFS_CF_SUFREED;
+		}
+
+		err = nilfs_segctor_extend_segments(sci, nilfs, nadd);
+		if (unlikely(err))
+			return err;
+
+		nadd = min_t(int, nadd << 1, SC_MAX_SEGDELTA);
+		sci->sc_stage = prev_stage;
+	}
+	nilfs_segctor_zeropad_segsum(sci);
+	nilfs_segctor_truncate_segments(sci, sci->sc_curseg, nilfs->ns_sufile);
+	return 0;
+
+ failed:
+	return err;
+}
+
+static void nilfs_list_replace_buffer(struct buffer_head *old_bh,
+				      struct buffer_head *new_bh)
+{
+	BUG_ON(!list_empty(&new_bh->b_assoc_buffers));
+
+	list_replace_init(&old_bh->b_assoc_buffers, &new_bh->b_assoc_buffers);
+	/* The caller must release old_bh */
+}
+
+static int
+nilfs_segctor_update_payload_blocknr(struct nilfs_sc_info *sci,
+				     struct nilfs_segment_buffer *segbuf,
+				     int mode)
+{
+	struct inode *inode = NULL;
+	sector_t blocknr;
+	unsigned long nfinfo = segbuf->sb_sum.nfinfo;
+	unsigned long nblocks = 0, ndatablk = 0;
+	const struct nilfs_sc_operations *sc_op = NULL;
+	struct nilfs_segsum_pointer ssp;
+	struct nilfs_finfo *finfo = NULL;
+	union nilfs_binfo binfo;
+	struct buffer_head *bh, *bh_org;
+	ino_t ino = 0;
+	int err = 0;
+
+	if (!nfinfo)
+		goto out;
+
+	blocknr = segbuf->sb_pseg_start + segbuf->sb_sum.nsumblk;
+	ssp.bh = NILFS_SEGBUF_FIRST_BH(&segbuf->sb_segsum_buffers);
+	ssp.offset = sizeof(struct nilfs_segment_summary);
+
+	list_for_each_entry(bh, &segbuf->sb_payload_buffers, b_assoc_buffers) {
+		if (bh == segbuf->sb_super_root)
+			break;
+		if (!finfo) {
+			finfo =	nilfs_segctor_map_segsum_entry(
+				sci, &ssp, sizeof(*finfo));
+			ino = le64_to_cpu(finfo->fi_ino);
+			nblocks = le32_to_cpu(finfo->fi_nblocks);
+			ndatablk = le32_to_cpu(finfo->fi_ndatablk);
+
+			inode = bh->b_folio->mapping->host;
+
+			if (mode == SC_LSEG_DSYNC)
+				sc_op = &nilfs_sc_dsync_ops;
+			else if (ino == NILFS_DAT_INO)
+				sc_op = &nilfs_sc_dat_ops;
+			else /* file blocks */
+				sc_op = &nilfs_sc_file_ops;
+		}
+		bh_org = bh;
+		get_bh(bh_org);
+		err = nilfs_bmap_assign(NILFS_I(inode)->i_bmap, &bh, blocknr,
+					&binfo);
+		if (bh != bh_org)
+			nilfs_list_replace_buffer(bh_org, bh);
+		brelse(bh_org);
+		if (unlikely(err))
+			goto failed_bmap;
+
+		if (ndatablk > 0)
+			sc_op->write_data_binfo(sci, &ssp, &binfo);
+		else
+			sc_op->write_node_binfo(sci, &ssp, &binfo);
+
+		blocknr++;
+		if (--nblocks == 0) {
+			finfo = NULL;
+			if (--nfinfo == 0)
+				break;
+		} else if (ndatablk > 0)
+			ndatablk--;
+	}
+ out:
+	return 0;
+
+ failed_bmap:
+	return err;
+}
+
+static int nilfs_segctor_assign(struct nilfs_sc_info *sci, int mode)
+{
+	struct nilfs_segment_buffer *segbuf;
+	int err;
+
+	list_for_each_entry(segbuf, &sci->sc_segbufs, sb_list) {
+		err = nilfs_segctor_update_payload_blocknr(sci, segbuf, mode);
+		if (unlikely(err))
+			return err;
+		nilfs_segbuf_fill_in_segsum(segbuf);
+	}
+	return 0;
+}
+
+static void nilfs_begin_page_io(struct page *page)
+{
+	if (!page || PageWriteback(page))
+		/*
+		 * For split b-tree node pages, this function may be called
+		 * twice.  We ignore the 2nd or later calls by this check.
+		 */
+		return;
+
+	lock_page(page);
+	clear_page_dirty_for_io(page);
+	set_page_writeback(page);
+	unlock_page(page);
+}
+
+static void nilfs_segctor_prepare_write(struct nilfs_sc_info *sci)
+{
+	struct nilfs_segment_buffer *segbuf;
+	struct page *bd_page = NULL, *fs_page = NULL;
+
+	list_for_each_entry(segbuf, &sci->sc_segbufs, sb_list) {
+		struct buffer_head *bh;
+
+		list_for_each_entry(bh, &segbuf->sb_segsum_buffers,
+				    b_assoc_buffers) {
+			if (bh->b_page != bd_page) {
+				if (bd_page) {
+					lock_page(bd_page);
+					clear_page_dirty_for_io(bd_page);
+					set_page_writeback(bd_page);
+					unlock_page(bd_page);
+				}
+				bd_page = bh->b_page;
+			}
+		}
+
+		list_for_each_entry(bh, &segbuf->sb_payload_buffers,
+				    b_assoc_buffers) {
+			set_buffer_async_write(bh);
+			if (bh == segbuf->sb_super_root) {
+				if (bh->b_page != bd_page) {
+					lock_page(bd_page);
+					clear_page_dirty_for_io(bd_page);
+					set_page_writeback(bd_page);
+					unlock_page(bd_page);
+					bd_page = bh->b_page;
+				}
+				break;
+			}
+			if (bh->b_page != fs_page) {
+				nilfs_begin_page_io(fs_page);
+				fs_page = bh->b_page;
+			}
+		}
+	}
+	if (bd_page) {
+		lock_page(bd_page);
+		clear_page_dirty_for_io(bd_page);
+		set_page_writeback(bd_page);
+		unlock_page(bd_page);
+	}
+	nilfs_begin_page_io(fs_page);
+}
+
+static int nilfs_segctor_write(struct nilfs_sc_info *sci,
+			       struct the_nilfs *nilfs)
+{
+	int ret;
+
+	ret = nilfs_write_logs(&sci->sc_segbufs, nilfs);
+	list_splice_tail_init(&sci->sc_segbufs, &sci->sc_write_logs);
+	return ret;
+}
+
+static void nilfs_end_page_io(struct page *page, int err)
+{
+	if (!page)
+		return;
+
+	if (buffer_nilfs_node(page_buffers(page)) && !PageWriteback(page)) {
+		/*
+		 * For b-tree node pages, this function may be called twice
+		 * or more because they might be split in a segment.
+		 */
+		if (PageDirty(page)) {
+			/*
+			 * For pages holding split b-tree node buffers, dirty
+			 * flag on the buffers may be cleared discretely.
+			 * In that case, the page is once redirtied for
+			 * remaining buffers, and it must be cancelled if
+			 * all the buffers get cleaned later.
+			 */
+			lock_page(page);
+			if (nilfs_page_buffers_clean(page))
+				__nilfs_clear_page_dirty(page);
+			unlock_page(page);
+		}
+		return;
+	}
+
+	if (!err) {
+		if (!nilfs_page_buffers_clean(page))
+			__set_page_dirty_nobuffers(page);
+		ClearPageError(page);
+	} else {
+		__set_page_dirty_nobuffers(page);
+		SetPageError(page);
+	}
+
+	end_page_writeback(page);
+}
+
+static void nilfs_abort_logs(struct list_head *logs, int err)
+{
+	struct nilfs_segment_buffer *segbuf;
+	struct page *bd_page = NULL, *fs_page = NULL;
+	struct buffer_head *bh;
+
+	if (list_empty(logs))
+		return;
+
+	list_for_each_entry(segbuf, logs, sb_list) {
+		list_for_each_entry(bh, &segbuf->sb_segsum_buffers,
+				    b_assoc_buffers) {
+			clear_buffer_uptodate(bh);
+			if (bh->b_page != bd_page) {
+				if (bd_page)
+					end_page_writeback(bd_page);
+				bd_page = bh->b_page;
+			}
+		}
+
+		list_for_each_entry(bh, &segbuf->sb_payload_buffers,
+				    b_assoc_buffers) {
+			clear_buffer_async_write(bh);
+			if (bh == segbuf->sb_super_root) {
+				clear_buffer_uptodate(bh);
+				if (bh->b_page != bd_page) {
+					end_page_writeback(bd_page);
+					bd_page = bh->b_page;
+				}
+				break;
+			}
+			if (bh->b_page != fs_page) {
+				nilfs_end_page_io(fs_page, err);
+				fs_page = bh->b_page;
+			}
+		}
+	}
+	if (bd_page)
+		end_page_writeback(bd_page);
+
+	nilfs_end_page_io(fs_page, err);
+}
+
+static void nilfs_segctor_abort_construction(struct nilfs_sc_info *sci,
+					     struct the_nilfs *nilfs, int err)
+{
+	LIST_HEAD(logs);
+	int ret;
+
+	list_splice_tail_init(&sci->sc_write_logs, &logs);
+	ret = nilfs_wait_on_logs(&logs);
+	nilfs_abort_logs(&logs, ret ? : err);
+
+	list_splice_tail_init(&sci->sc_segbufs, &logs);
+	nilfs_cancel_segusage(&logs, nilfs->ns_sufile);
+	nilfs_free_incomplete_logs(&logs, nilfs);
+
+	if (sci->sc_stage.flags & NILFS_CF_SUFREED) {
+		ret = nilfs_sufile_cancel_freev(nilfs->ns_sufile,
+						sci->sc_freesegs,
+						sci->sc_nfreesegs,
+						NULL);
+		WARN_ON(ret); /* do not happen */
+	}
+
+	nilfs_destroy_logs(&logs);
+}
+
+static void nilfs_set_next_segment(struct the_nilfs *nilfs,
+				   struct nilfs_segment_buffer *segbuf)
+{
+	nilfs->ns_segnum = segbuf->sb_segnum;
+	nilfs->ns_nextnum = segbuf->sb_nextnum;
+	nilfs->ns_pseg_offset = segbuf->sb_pseg_start - segbuf->sb_fseg_start
+		+ segbuf->sb_sum.nblocks;
+	nilfs->ns_seg_seq = segbuf->sb_sum.seg_seq;
+	nilfs->ns_ctime = segbuf->sb_sum.ctime;
+}
+
+static void nilfs_segctor_complete_write(struct nilfs_sc_info *sci)
+{
+	struct nilfs_segment_buffer *segbuf;
+	struct page *bd_page = NULL, *fs_page = NULL;
+	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
+	int update_sr = false;
+
+	list_for_each_entry(segbuf, &sci->sc_write_logs, sb_list) {
+		struct buffer_head *bh;
+
+		list_for_each_entry(bh, &segbuf->sb_segsum_buffers,
+				    b_assoc_buffers) {
+			set_buffer_uptodate(bh);
+			clear_buffer_dirty(bh);
+			if (bh->b_page != bd_page) {
+				if (bd_page)
+					end_page_writeback(bd_page);
+				bd_page = bh->b_page;
+			}
+		}
+		/*
+		 * We assume that the buffers which belong to the same page
+		 * continue over the buffer list.
+		 * Under this assumption, the last BHs of pages is
+		 * identifiable by the discontinuity of bh->b_page
+		 * (page != fs_page).
+		 *
+		 * For B-tree node blocks, however, this assumption is not
+		 * guaranteed.  The cleanup code of B-tree node pages needs
+		 * special care.
+		 */
+		list_for_each_entry(bh, &segbuf->sb_payload_buffers,
+				    b_assoc_buffers) {
+			const unsigned long set_bits = BIT(BH_Uptodate);
+			const unsigned long clear_bits =
+				(BIT(BH_Dirty) | BIT(BH_Async_Write) |
+				 BIT(BH_Delay) | BIT(BH_NILFS_Volatile) |
+				 BIT(BH_NILFS_Redirected));
+
+			set_mask_bits(&bh->b_state, clear_bits, set_bits);
+			if (bh == segbuf->sb_super_root) {
+				if (bh->b_page != bd_page) {
+					end_page_writeback(bd_page);
+					bd_page = bh->b_page;
+				}
+				update_sr = true;
+				break;
+			}
+			if (bh->b_page != fs_page) {
+				nilfs_end_page_io(fs_page, 0);
+				fs_page = bh->b_page;
+			}
+		}
+
+		if (!nilfs_segbuf_simplex(segbuf)) {
+			if (segbuf->sb_sum.flags & NILFS_SS_LOGBGN) {
+				set_bit(NILFS_SC_UNCLOSED, &sci->sc_flags);
+				sci->sc_lseg_stime = jiffies;
+			}
+			if (segbuf->sb_sum.flags & NILFS_SS_LOGEND)
+				clear_bit(NILFS_SC_UNCLOSED, &sci->sc_flags);
+		}
+	}
+	/*
+	 * Since pages may continue over multiple segment buffers,
+	 * end of the last page must be checked outside of the loop.
+	 */
+	if (bd_page)
+		end_page_writeback(bd_page);
+
+	nilfs_end_page_io(fs_page, 0);
+
+	nilfs_drop_collected_inodes(&sci->sc_dirty_files);
+
+	if (nilfs_doing_gc())
+		nilfs_drop_collected_inodes(&sci->sc_gc_inodes);
+	else
+		nilfs->ns_nongc_ctime = sci->sc_seg_ctime;
+
+	sci->sc_nblk_inc += sci->sc_nblk_this_inc;
+
+	segbuf = NILFS_LAST_SEGBUF(&sci->sc_write_logs);
+	nilfs_set_next_segment(nilfs, segbuf);
+
+	if (update_sr) {
+		nilfs->ns_flushed_device = 0;
+		nilfs_set_last_segment(nilfs, segbuf->sb_pseg_start,
+				       segbuf->sb_sum.seg_seq, nilfs->ns_cno++);
+
+		clear_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags);
+		clear_bit(NILFS_SC_DIRTY, &sci->sc_flags);
+		set_bit(NILFS_SC_SUPER_ROOT, &sci->sc_flags);
+		nilfs_segctor_clear_metadata_dirty(sci);
+	} else
+		clear_bit(NILFS_SC_SUPER_ROOT, &sci->sc_flags);
+}
+
+static int nilfs_segctor_wait(struct nilfs_sc_info *sci)
+{
+	int ret;
+
+	ret = nilfs_wait_on_logs(&sci->sc_write_logs);
+	if (!ret) {
+		nilfs_segctor_complete_write(sci);
+		nilfs_destroy_logs(&sci->sc_write_logs);
+	}
+	return ret;
+}
+
+static int nilfs_segctor_collect_dirty_files(struct nilfs_sc_info *sci,
+					     struct the_nilfs *nilfs)
+{
+	struct nilfs_inode_info *ii, *n;
+	struct inode *ifile = sci->sc_root->ifile;
+
+	spin_lock(&nilfs->ns_inode_lock);
+ retry:
+	list_for_each_entry_safe(ii, n, &nilfs->ns_dirty_files, i_dirty) {
+		if (!ii->i_bh) {
+			struct buffer_head *ibh;
+			int err;
+
+			spin_unlock(&nilfs->ns_inode_lock);
+			err = nilfs_ifile_get_inode_block(
+				ifile, ii->vfs_inode.i_ino, &ibh);
+			if (unlikely(err)) {
+				nilfs_warn(sci->sc_super,
+					   "log writer: error %d getting inode block (ino=%lu)",
+					   err, ii->vfs_inode.i_ino);
+				return err;
+			}
+			spin_lock(&nilfs->ns_inode_lock);
+			if (likely(!ii->i_bh))
+				ii->i_bh = ibh;
+			else
+				brelse(ibh);
+			goto retry;
+		}
+
+		// Always redirty the buffer to avoid race condition
+		mark_buffer_dirty(ii->i_bh);
+		nilfs_mdt_mark_dirty(ifile);
+
+		clear_bit(NILFS_I_QUEUED, &ii->i_state);
+		set_bit(NILFS_I_BUSY, &ii->i_state);
+		list_move_tail(&ii->i_dirty, &sci->sc_dirty_files);
+	}
+	spin_unlock(&nilfs->ns_inode_lock);
+
+	return 0;
+}
+
+static void nilfs_segctor_drop_written_files(struct nilfs_sc_info *sci,
+					     struct the_nilfs *nilfs)
+{
+	struct nilfs_inode_info *ii, *n;
+	int during_mount = !(sci->sc_super->s_flags & SB_ACTIVE);
+	int defer_iput = false;
+
+	spin_lock(&nilfs->ns_inode_lock);
+	list_for_each_entry_safe(ii, n, &sci->sc_dirty_files, i_dirty) {
+		if (!test_and_clear_bit(NILFS_I_UPDATED, &ii->i_state) ||
+		    test_bit(NILFS_I_DIRTY, &ii->i_state))
+			continue;
+
+		clear_bit(NILFS_I_BUSY, &ii->i_state);
+		brelse(ii->i_bh);
+		ii->i_bh = NULL;
+		list_del_init(&ii->i_dirty);
+		if (!ii->vfs_inode.i_nlink || during_mount) {
+			/*
+			 * Defer calling iput() to avoid deadlocks if
+			 * i_nlink == 0 or mount is not yet finished.
+			 */
+			list_add_tail(&ii->i_dirty, &sci->sc_iput_queue);
+			defer_iput = true;
+		} else {
+			spin_unlock(&nilfs->ns_inode_lock);
+			iput(&ii->vfs_inode);
+			spin_lock(&nilfs->ns_inode_lock);
+		}
+	}
+	spin_unlock(&nilfs->ns_inode_lock);
+
+	if (defer_iput)
+		schedule_work(&sci->sc_iput_work);
+}
+
+/*
+ * Main procedure of segment constructor
+ */
+static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
+{
+	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
+	int err;
+
+	if (sb_rdonly(sci->sc_super))
+		return -EROFS;
+
+	nilfs_sc_cstage_set(sci, NILFS_ST_INIT);
+	sci->sc_cno = nilfs->ns_cno;
+
+	err = nilfs_segctor_collect_dirty_files(sci, nilfs);
+	if (unlikely(err))
+		goto out;
+
+	if (nilfs_test_metadata_dirty(nilfs, sci->sc_root))
+		set_bit(NILFS_SC_DIRTY, &sci->sc_flags);
+
+	if (nilfs_segctor_clean(sci))
+		goto out;
+
+	do {
+		sci->sc_stage.flags &= ~NILFS_CF_HISTORY_MASK;
+
+		err = nilfs_segctor_begin_construction(sci, nilfs);
+		if (unlikely(err))
+			goto out;
+
+		/* Update time stamp */
+		sci->sc_seg_ctime = ktime_get_real_seconds();
+
+		err = nilfs_segctor_collect(sci, nilfs, mode);
+		if (unlikely(err))
+			goto failed;
+
+		/* Avoid empty segment */
+		if (nilfs_sc_cstage_get(sci) == NILFS_ST_DONE &&
+		    nilfs_segbuf_empty(sci->sc_curseg)) {
+			nilfs_segctor_abort_construction(sci, nilfs, 1);
+			goto out;
+		}
+
+		err = nilfs_segctor_assign(sci, mode);
+		if (unlikely(err))
+			goto failed;
+
+		if (sci->sc_stage.flags & NILFS_CF_IFILE_STARTED)
+			nilfs_segctor_fill_in_file_bmap(sci);
+
+		if (mode == SC_LSEG_SR &&
+		    nilfs_sc_cstage_get(sci) >= NILFS_ST_CPFILE) {
+			err = nilfs_segctor_fill_in_checkpoint(sci);
+			if (unlikely(err))
+				goto failed_to_write;
+
+			nilfs_segctor_fill_in_super_root(sci, nilfs);
+		}
+		nilfs_segctor_update_segusage(sci, nilfs->ns_sufile);
+
+		/* Write partial segments */
+		nilfs_segctor_prepare_write(sci);
+
+		nilfs_add_checksums_on_logs(&sci->sc_segbufs,
+					    nilfs->ns_crc_seed);
+
+		err = nilfs_segctor_write(sci, nilfs);
+		if (unlikely(err))
+			goto failed_to_write;
+
+		if (nilfs_sc_cstage_get(sci) == NILFS_ST_DONE ||
+		    nilfs->ns_blocksize_bits != PAGE_SHIFT) {
+			/*
+			 * At this point, we avoid double buffering
+			 * for blocksize < pagesize because page dirty
+			 * flag is turned off during write and dirty
+			 * buffers are not properly collected for
+			 * pages crossing over segments.
+			 */
+			err = nilfs_segctor_wait(sci);
+			if (err)
+				goto failed_to_write;
+		}
+	} while (nilfs_sc_cstage_get(sci) != NILFS_ST_DONE);
+
+ out:
+	nilfs_segctor_drop_written_files(sci, nilfs);
+	return err;
+
+ failed_to_write:
+	if (sci->sc_stage.flags & NILFS_CF_IFILE_STARTED)
+		nilfs_redirty_inodes(&sci->sc_dirty_files);
+
+ failed:
+	if (nilfs_doing_gc())
+		nilfs_redirty_inodes(&sci->sc_gc_inodes);
+	nilfs_segctor_abort_construction(sci, nilfs, err);
+	goto out;
+}
+
+/**
+ * nilfs_segctor_start_timer - set timer of background write
+ * @sci: nilfs_sc_info
+ *
+ * If the timer has already been set, it ignores the new request.
+ * This function MUST be called within a section locking the segment
+ * semaphore.
+ */
+static void nilfs_segctor_start_timer(struct nilfs_sc_info *sci)
+{
+	spin_lock(&sci->sc_state_lock);
+	if (!(sci->sc_state & NILFS_SEGCTOR_COMMIT)) {
+		sci->sc_timer.expires = jiffies + sci->sc_interval;
+		add_timer(&sci->sc_timer);
+		sci->sc_state |= NILFS_SEGCTOR_COMMIT;
+	}
+	spin_unlock(&sci->sc_state_lock);
+}
+
+static void nilfs_segctor_do_flush(struct nilfs_sc_info *sci, int bn)
+{
+	spin_lock(&sci->sc_state_lock);
+	if (!(sci->sc_flush_request & BIT(bn))) {
+		unsigned long prev_req = sci->sc_flush_request;
+
+		sci->sc_flush_request |= BIT(bn);
+		if (!prev_req)
+			wake_up(&sci->sc_wait_daemon);
+	}
+	spin_unlock(&sci->sc_state_lock);
+}
+
+/**
+ * nilfs_flush_segment - trigger a segment construction for resource control
+ * @sb: super block
+ * @ino: inode number of the file to be flushed out.
+ */
+void nilfs_flush_segment(struct super_block *sb, ino_t ino)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct nilfs_sc_info *sci = nilfs->ns_writer;
+
+	if (!sci || nilfs_doing_construction())
+		return;
+	nilfs_segctor_do_flush(sci, NILFS_MDT_INODE(sb, ino) ? ino : 0);
+					/* assign bit 0 to data files */
+}
+
+struct nilfs_segctor_wait_request {
+	wait_queue_entry_t	wq;
+	__u32		seq;
+	int		err;
+	atomic_t	done;
+};
+
+static int nilfs_segctor_sync(struct nilfs_sc_info *sci)
+{
+	struct nilfs_segctor_wait_request wait_req;
+	int err = 0;
+
+	spin_lock(&sci->sc_state_lock);
+	init_wait(&wait_req.wq);
+	wait_req.err = 0;
+	atomic_set(&wait_req.done, 0);
+	wait_req.seq = ++sci->sc_seq_request;
+	spin_unlock(&sci->sc_state_lock);
+
+	init_waitqueue_entry(&wait_req.wq, current);
+	add_wait_queue(&sci->sc_wait_request, &wait_req.wq);
+	set_current_state(TASK_INTERRUPTIBLE);
+	wake_up(&sci->sc_wait_daemon);
+
+	for (;;) {
+		if (atomic_read(&wait_req.done)) {
+			err = wait_req.err;
+			break;
+		}
+		if (!signal_pending(current)) {
+			schedule();
+			continue;
+		}
+		err = -ERESTARTSYS;
+		break;
+	}
+	finish_wait(&sci->sc_wait_request, &wait_req.wq);
+	return err;
+}
+
+static void nilfs_segctor_wakeup(struct nilfs_sc_info *sci, int err)
+{
+	struct nilfs_segctor_wait_request *wrq, *n;
+	unsigned long flags;
+
+	spin_lock_irqsave(&sci->sc_wait_request.lock, flags);
+	list_for_each_entry_safe(wrq, n, &sci->sc_wait_request.head, wq.entry) {
+		if (!atomic_read(&wrq->done) &&
+		    nilfs_cnt32_ge(sci->sc_seq_done, wrq->seq)) {
+			wrq->err = err;
+			atomic_set(&wrq->done, 1);
+		}
+		if (atomic_read(&wrq->done)) {
+			wrq->wq.func(&wrq->wq,
+				     TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE,
+				     0, NULL);
+		}
+	}
+	spin_unlock_irqrestore(&sci->sc_wait_request.lock, flags);
+}
+
+/**
+ * nilfs_construct_segment - construct a logical segment
+ * @sb: super block
+ *
+ * Return Value: On success, 0 is returned. On errors, one of the following
+ * negative error code is returned.
+ *
+ * %-EROFS - Read only filesystem.
+ *
+ * %-EIO - I/O error
+ *
+ * %-ENOSPC - No space left on device (only in a panic state).
+ *
+ * %-ERESTARTSYS - Interrupted.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ */
+int nilfs_construct_segment(struct super_block *sb)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct nilfs_sc_info *sci = nilfs->ns_writer;
+	struct nilfs_transaction_info *ti;
+
+	if (sb_rdonly(sb) || unlikely(!sci))
+		return -EROFS;
+
+	/* A call inside transactions causes a deadlock. */
+	BUG_ON((ti = current->journal_info) && ti->ti_magic == NILFS_TI_MAGIC);
+
+	return nilfs_segctor_sync(sci);
+}
+
+/**
+ * nilfs_construct_dsync_segment - construct a data-only logical segment
+ * @sb: super block
+ * @inode: inode whose data blocks should be written out
+ * @start: start byte offset
+ * @end: end byte offset (inclusive)
+ *
+ * Return Value: On success, 0 is returned. On errors, one of the following
+ * negative error code is returned.
+ *
+ * %-EROFS - Read only filesystem.
+ *
+ * %-EIO - I/O error
+ *
+ * %-ENOSPC - No space left on device (only in a panic state).
+ *
+ * %-ERESTARTSYS - Interrupted.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ */
+int nilfs_construct_dsync_segment(struct super_block *sb, struct inode *inode,
+				  loff_t start, loff_t end)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct nilfs_sc_info *sci = nilfs->ns_writer;
+	struct nilfs_inode_info *ii;
+	struct nilfs_transaction_info ti;
+	int err = 0;
+
+	if (sb_rdonly(sb) || unlikely(!sci))
+		return -EROFS;
+
+	nilfs_transaction_lock(sb, &ti, 0);
+
+	ii = NILFS_I(inode);
+	if (test_bit(NILFS_I_INODE_SYNC, &ii->i_state) ||
+	    nilfs_test_opt(nilfs, STRICT_ORDER) ||
+	    test_bit(NILFS_SC_UNCLOSED, &sci->sc_flags) ||
+	    nilfs_discontinued(nilfs)) {
+		nilfs_transaction_unlock(sb);
+		err = nilfs_segctor_sync(sci);
+		return err;
+	}
+
+	spin_lock(&nilfs->ns_inode_lock);
+	if (!test_bit(NILFS_I_QUEUED, &ii->i_state) &&
+	    !test_bit(NILFS_I_BUSY, &ii->i_state)) {
+		spin_unlock(&nilfs->ns_inode_lock);
+		nilfs_transaction_unlock(sb);
+		return 0;
+	}
+	spin_unlock(&nilfs->ns_inode_lock);
+	sci->sc_dsync_inode = ii;
+	sci->sc_dsync_start = start;
+	sci->sc_dsync_end = end;
+
+	err = nilfs_segctor_do_construct(sci, SC_LSEG_DSYNC);
+	if (!err)
+		nilfs->ns_flushed_device = 0;
+
+	nilfs_transaction_unlock(sb);
+	return err;
+}
+
+#define FLUSH_FILE_BIT	(0x1) /* data file only */
+#define FLUSH_DAT_BIT	BIT(NILFS_DAT_INO) /* DAT only */
+
+/**
+ * nilfs_segctor_accept - record accepted sequence count of log-write requests
+ * @sci: segment constructor object
+ */
+static void nilfs_segctor_accept(struct nilfs_sc_info *sci)
+{
+	spin_lock(&sci->sc_state_lock);
+	sci->sc_seq_accepted = sci->sc_seq_request;
+	spin_unlock(&sci->sc_state_lock);
+	del_timer_sync(&sci->sc_timer);
+}
+
+/**
+ * nilfs_segctor_notify - notify the result of request to caller threads
+ * @sci: segment constructor object
+ * @mode: mode of log forming
+ * @err: error code to be notified
+ */
+static void nilfs_segctor_notify(struct nilfs_sc_info *sci, int mode, int err)
+{
+	/* Clear requests (even when the construction failed) */
+	spin_lock(&sci->sc_state_lock);
+
+	if (mode == SC_LSEG_SR) {
+		sci->sc_state &= ~NILFS_SEGCTOR_COMMIT;
+		sci->sc_seq_done = sci->sc_seq_accepted;
+		nilfs_segctor_wakeup(sci, err);
+		sci->sc_flush_request = 0;
+	} else {
+		if (mode == SC_FLUSH_FILE)
+			sci->sc_flush_request &= ~FLUSH_FILE_BIT;
+		else if (mode == SC_FLUSH_DAT)
+			sci->sc_flush_request &= ~FLUSH_DAT_BIT;
+
+		/* re-enable timer if checkpoint creation was not done */
+		if ((sci->sc_state & NILFS_SEGCTOR_COMMIT) &&
+		    time_before(jiffies, sci->sc_timer.expires))
+			add_timer(&sci->sc_timer);
+	}
+	spin_unlock(&sci->sc_state_lock);
+}
+
+/**
+ * nilfs_segctor_construct - form logs and write them to disk
+ * @sci: segment constructor object
+ * @mode: mode of log forming
+ */
+static int nilfs_segctor_construct(struct nilfs_sc_info *sci, int mode)
+{
+	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
+	struct nilfs_super_block **sbp;
+	int err = 0;
+
+	nilfs_segctor_accept(sci);
+
+	if (nilfs_discontinued(nilfs))
+		mode = SC_LSEG_SR;
+	if (!nilfs_segctor_confirm(sci))
+		err = nilfs_segctor_do_construct(sci, mode);
+
+	if (likely(!err)) {
+		if (mode != SC_FLUSH_DAT)
+			atomic_set(&nilfs->ns_ndirtyblks, 0);
+		if (test_bit(NILFS_SC_SUPER_ROOT, &sci->sc_flags) &&
+		    nilfs_discontinued(nilfs)) {
+			down_write(&nilfs->ns_sem);
+			err = -EIO;
+			sbp = nilfs_prepare_super(sci->sc_super,
+						  nilfs_sb_will_flip(nilfs));
+			if (likely(sbp)) {
+				nilfs_set_log_cursor(sbp[0], nilfs);
+				err = nilfs_commit_super(sci->sc_super,
+							 NILFS_SB_COMMIT);
+			}
+			up_write(&nilfs->ns_sem);
+		}
+	}
+
+	nilfs_segctor_notify(sci, mode, err);
+	return err;
+}
+
+static void nilfs_construction_timeout(struct timer_list *t)
+{
+	struct nilfs_sc_info *sci = from_timer(sci, t, sc_timer);
+
+	wake_up_process(sci->sc_timer_task);
+}
+
+static void
+nilfs_remove_written_gcinodes(struct the_nilfs *nilfs, struct list_head *head)
+{
+	struct nilfs_inode_info *ii, *n;
+
+	list_for_each_entry_safe(ii, n, head, i_dirty) {
+		if (!test_bit(NILFS_I_UPDATED, &ii->i_state))
+			continue;
+		list_del_init(&ii->i_dirty);
+		truncate_inode_pages(&ii->vfs_inode.i_data, 0);
+		nilfs_btnode_cache_clear(ii->i_assoc_inode->i_mapping);
+		iput(&ii->vfs_inode);
+	}
+}
+
+int nilfs_clean_segments(struct super_block *sb, struct nilfs_argv *argv,
+			 void **kbufs)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct nilfs_sc_info *sci = nilfs->ns_writer;
+	struct nilfs_transaction_info ti;
+	int err;
+
+	if (unlikely(!sci))
+		return -EROFS;
+
+	nilfs_transaction_lock(sb, &ti, 1);
+
+	err = nilfs_mdt_save_to_shadow_map(nilfs->ns_dat);
+	if (unlikely(err))
+		goto out_unlock;
+
+	err = nilfs_ioctl_prepare_clean_segments(nilfs, argv, kbufs);
+	if (unlikely(err)) {
+		nilfs_mdt_restore_from_shadow_map(nilfs->ns_dat);
+		goto out_unlock;
+	}
+
+	sci->sc_freesegs = kbufs[4];
+	sci->sc_nfreesegs = argv[4].v_nmembs;
+	list_splice_tail_init(&nilfs->ns_gc_inodes, &sci->sc_gc_inodes);
+
+	for (;;) {
+		err = nilfs_segctor_construct(sci, SC_LSEG_SR);
+		nilfs_remove_written_gcinodes(nilfs, &sci->sc_gc_inodes);
+
+		if (likely(!err))
+			break;
+
+		nilfs_warn(sb, "error %d cleaning segments", err);
+		set_current_state(TASK_INTERRUPTIBLE);
+		schedule_timeout(sci->sc_interval);
+	}
+	if (nilfs_test_opt(nilfs, DISCARD)) {
+		int ret = nilfs_discard_segments(nilfs, sci->sc_freesegs,
+						 sci->sc_nfreesegs);
+		if (ret) {
+			nilfs_warn(sb,
+				   "error %d on discard request, turning discards off for the device",
+				   ret);
+			nilfs_clear_opt(nilfs, DISCARD);
+		}
+	}
+
+ out_unlock:
+	sci->sc_freesegs = NULL;
+	sci->sc_nfreesegs = 0;
+	nilfs_mdt_clear_shadow_map(nilfs->ns_dat);
+	nilfs_transaction_unlock(sb);
+	return err;
+}
+
+static void nilfs_segctor_thread_construct(struct nilfs_sc_info *sci, int mode)
+{
+	struct nilfs_transaction_info ti;
+
+	nilfs_transaction_lock(sci->sc_super, &ti, 0);
+	nilfs_segctor_construct(sci, mode);
+
+	/*
+	 * Unclosed segment should be retried.  We do this using sc_timer.
+	 * Timeout of sc_timer will invoke complete construction which leads
+	 * to close the current logical segment.
+	 */
+	if (test_bit(NILFS_SC_UNCLOSED, &sci->sc_flags))
+		nilfs_segctor_start_timer(sci);
+
+	nilfs_transaction_unlock(sci->sc_super);
+}
+
+static void nilfs_segctor_do_immediate_flush(struct nilfs_sc_info *sci)
+{
+	int mode = 0;
+
+	spin_lock(&sci->sc_state_lock);
+	mode = (sci->sc_flush_request & FLUSH_DAT_BIT) ?
+		SC_FLUSH_DAT : SC_FLUSH_FILE;
+	spin_unlock(&sci->sc_state_lock);
+
+	if (mode) {
+		nilfs_segctor_do_construct(sci, mode);
+
+		spin_lock(&sci->sc_state_lock);
+		sci->sc_flush_request &= (mode == SC_FLUSH_FILE) ?
+			~FLUSH_FILE_BIT : ~FLUSH_DAT_BIT;
+		spin_unlock(&sci->sc_state_lock);
+	}
+	clear_bit(NILFS_SC_PRIOR_FLUSH, &sci->sc_flags);
+}
+
+static int nilfs_segctor_flush_mode(struct nilfs_sc_info *sci)
+{
+	if (!test_bit(NILFS_SC_UNCLOSED, &sci->sc_flags) ||
+	    time_before(jiffies, sci->sc_lseg_stime + sci->sc_mjcp_freq)) {
+		if (!(sci->sc_flush_request & ~FLUSH_FILE_BIT))
+			return SC_FLUSH_FILE;
+		else if (!(sci->sc_flush_request & ~FLUSH_DAT_BIT))
+			return SC_FLUSH_DAT;
+	}
+	return SC_LSEG_SR;
+}
+
+/**
+ * nilfs_segctor_thread - main loop of the segment constructor thread.
+ * @arg: pointer to a struct nilfs_sc_info.
+ *
+ * nilfs_segctor_thread() initializes a timer and serves as a daemon
+ * to execute segment constructions.
+ */
+static int nilfs_segctor_thread(void *arg)
+{
+	struct nilfs_sc_info *sci = (struct nilfs_sc_info *)arg;
+	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
+	int timeout = 0;
+
+	sci->sc_timer_task = current;
+
+	/* start sync. */
+	sci->sc_task = current;
+	wake_up(&sci->sc_wait_task); /* for nilfs_segctor_start_thread() */
+	nilfs_info(sci->sc_super,
+		   "segctord starting. Construction interval = %lu seconds, CP frequency < %lu seconds",
+		   sci->sc_interval / HZ, sci->sc_mjcp_freq / HZ);
+
+	spin_lock(&sci->sc_state_lock);
+ loop:
+	for (;;) {
+		int mode;
+
+		if (sci->sc_state & NILFS_SEGCTOR_QUIT)
+			goto end_thread;
+
+		if (timeout || sci->sc_seq_request != sci->sc_seq_done)
+			mode = SC_LSEG_SR;
+		else if (sci->sc_flush_request)
+			mode = nilfs_segctor_flush_mode(sci);
+		else
+			break;
+
+		spin_unlock(&sci->sc_state_lock);
+		nilfs_segctor_thread_construct(sci, mode);
+		spin_lock(&sci->sc_state_lock);
+		timeout = 0;
+	}
+
+
+	if (freezing(current)) {
+		spin_unlock(&sci->sc_state_lock);
+		try_to_freeze();
+		spin_lock(&sci->sc_state_lock);
+	} else {
+		DEFINE_WAIT(wait);
+		int should_sleep = 1;
+
+		prepare_to_wait(&sci->sc_wait_daemon, &wait,
+				TASK_INTERRUPTIBLE);
+
+		if (sci->sc_seq_request != sci->sc_seq_done)
+			should_sleep = 0;
+		else if (sci->sc_flush_request)
+			should_sleep = 0;
+		else if (sci->sc_state & NILFS_SEGCTOR_COMMIT)
+			should_sleep = time_before(jiffies,
+					sci->sc_timer.expires);
+
+		if (should_sleep) {
+			spin_unlock(&sci->sc_state_lock);
+			schedule();
+			spin_lock(&sci->sc_state_lock);
+		}
+		finish_wait(&sci->sc_wait_daemon, &wait);
+		timeout = ((sci->sc_state & NILFS_SEGCTOR_COMMIT) &&
+			   time_after_eq(jiffies, sci->sc_timer.expires));
+
+		if (nilfs_sb_dirty(nilfs) && nilfs_sb_need_update(nilfs))
+			set_nilfs_discontinued(nilfs);
+	}
+	goto loop;
+
+ end_thread:
+	/* end sync. */
+	sci->sc_task = NULL;
+	wake_up(&sci->sc_wait_task); /* for nilfs_segctor_kill_thread() */
+	spin_unlock(&sci->sc_state_lock);
+	return 0;
+}
+
+static int nilfs_segctor_start_thread(struct nilfs_sc_info *sci)
+{
+	struct task_struct *t;
+
+	t = kthread_run(nilfs_segctor_thread, sci, "segctord");
+	if (IS_ERR(t)) {
+		int err = PTR_ERR(t);
+
+		nilfs_err(sci->sc_super, "error %d creating segctord thread",
+			  err);
+		return err;
+	}
+	wait_event(sci->sc_wait_task, sci->sc_task != NULL);
+	return 0;
+}
+
+static void nilfs_segctor_kill_thread(struct nilfs_sc_info *sci)
+	__acquires(&sci->sc_state_lock)
+	__releases(&sci->sc_state_lock)
+{
+	sci->sc_state |= NILFS_SEGCTOR_QUIT;
+
+	while (sci->sc_task) {
+		wake_up(&sci->sc_wait_daemon);
+		spin_unlock(&sci->sc_state_lock);
+		wait_event(sci->sc_wait_task, sci->sc_task == NULL);
+		spin_lock(&sci->sc_state_lock);
+	}
+}
+
+/*
+ * Setup & clean-up functions
+ */
+static struct nilfs_sc_info *nilfs_segctor_new(struct super_block *sb,
+					       struct nilfs_root *root)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct nilfs_sc_info *sci;
+
+	sci = kzalloc(sizeof(*sci), GFP_KERNEL);
+	if (!sci)
+		return NULL;
+
+	sci->sc_super = sb;
+
+	nilfs_get_root(root);
+	sci->sc_root = root;
+
+	init_waitqueue_head(&sci->sc_wait_request);
+	init_waitqueue_head(&sci->sc_wait_daemon);
+	init_waitqueue_head(&sci->sc_wait_task);
+	spin_lock_init(&sci->sc_state_lock);
+	INIT_LIST_HEAD(&sci->sc_dirty_files);
+	INIT_LIST_HEAD(&sci->sc_segbufs);
+	INIT_LIST_HEAD(&sci->sc_write_logs);
+	INIT_LIST_HEAD(&sci->sc_gc_inodes);
+	INIT_LIST_HEAD(&sci->sc_iput_queue);
+	INIT_WORK(&sci->sc_iput_work, nilfs_iput_work_func);
+	timer_setup(&sci->sc_timer, nilfs_construction_timeout, 0);
+
+	sci->sc_interval = HZ * NILFS_SC_DEFAULT_TIMEOUT;
+	sci->sc_mjcp_freq = HZ * NILFS_SC_DEFAULT_SR_FREQ;
+	sci->sc_watermark = NILFS_SC_DEFAULT_WATERMARK;
+
+	if (nilfs->ns_interval)
+		sci->sc_interval = HZ * nilfs->ns_interval;
+	if (nilfs->ns_watermark)
+		sci->sc_watermark = nilfs->ns_watermark;
+	return sci;
+}
+
+static void nilfs_segctor_write_out(struct nilfs_sc_info *sci)
+{
+	int ret, retrycount = NILFS_SC_CLEANUP_RETRY;
+
+	/*
+	 * The segctord thread was stopped and its timer was removed.
+	 * But some tasks remain.
+	 */
+	do {
+		struct nilfs_transaction_info ti;
+
+		nilfs_transaction_lock(sci->sc_super, &ti, 0);
+		ret = nilfs_segctor_construct(sci, SC_LSEG_SR);
+		nilfs_transaction_unlock(sci->sc_super);
+
+		flush_work(&sci->sc_iput_work);
+
+	} while (ret && ret != -EROFS && retrycount-- > 0);
+}
+
+/**
+ * nilfs_segctor_destroy - destroy the segment constructor.
+ * @sci: nilfs_sc_info
+ *
+ * nilfs_segctor_destroy() kills the segctord thread and frees
+ * the nilfs_sc_info struct.
+ * Caller must hold the segment semaphore.
+ */
+static void nilfs_segctor_destroy(struct nilfs_sc_info *sci)
+{
+	struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
+	int flag;
+
+	up_write(&nilfs->ns_segctor_sem);
+
+	spin_lock(&sci->sc_state_lock);
+	nilfs_segctor_kill_thread(sci);
+	flag = ((sci->sc_state & NILFS_SEGCTOR_COMMIT) || sci->sc_flush_request
+		|| sci->sc_seq_request != sci->sc_seq_done);
+	spin_unlock(&sci->sc_state_lock);
+
+	if (flush_work(&sci->sc_iput_work))
+		flag = true;
+
+	if (flag || !nilfs_segctor_confirm(sci))
+		nilfs_segctor_write_out(sci);
+
+	if (!list_empty(&sci->sc_dirty_files)) {
+		nilfs_warn(sci->sc_super,
+			   "disposed unprocessed dirty file(s) when stopping log writer");
+		nilfs_dispose_list(nilfs, &sci->sc_dirty_files, 1);
+	}
+
+	if (!list_empty(&sci->sc_iput_queue)) {
+		nilfs_warn(sci->sc_super,
+			   "disposed unprocessed inode(s) in iput queue when stopping log writer");
+		nilfs_dispose_list(nilfs, &sci->sc_iput_queue, 1);
+	}
+
+	WARN_ON(!list_empty(&sci->sc_segbufs));
+	WARN_ON(!list_empty(&sci->sc_write_logs));
+
+	nilfs_put_root(sci->sc_root);
+
+	down_write(&nilfs->ns_segctor_sem);
+
+	timer_shutdown_sync(&sci->sc_timer);
+	kfree(sci);
+}
+
+/**
+ * nilfs_attach_log_writer - attach log writer
+ * @sb: super block instance
+ * @root: root object of the current filesystem tree
+ *
+ * This allocates a log writer object, initializes it, and starts the
+ * log writer.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error code is returned.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ */
+int nilfs_attach_log_writer(struct super_block *sb, struct nilfs_root *root)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	int err;
+
+	if (nilfs->ns_writer) {
+		/*
+		 * This happens if the filesystem is made read-only by
+		 * __nilfs_error or nilfs_remount and then remounted
+		 * read/write.  In these cases, reuse the existing
+		 * writer.
+		 */
+		return 0;
+	}
+
+	nilfs->ns_writer = nilfs_segctor_new(sb, root);
+	if (!nilfs->ns_writer)
+		return -ENOMEM;
+
+	inode_attach_wb(nilfs->ns_bdev->bd_inode, NULL);
+
+	err = nilfs_segctor_start_thread(nilfs->ns_writer);
+	if (unlikely(err))
+		nilfs_detach_log_writer(sb);
+
+	return err;
+}
+
+/**
+ * nilfs_detach_log_writer - destroy log writer
+ * @sb: super block instance
+ *
+ * This kills log writer daemon, frees the log writer object, and
+ * destroys list of dirty files.
+ */
+void nilfs_detach_log_writer(struct super_block *sb)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	LIST_HEAD(garbage_list);
+
+	down_write(&nilfs->ns_segctor_sem);
+	if (nilfs->ns_writer) {
+		nilfs_segctor_destroy(nilfs->ns_writer);
+		nilfs->ns_writer = NULL;
+	}
+	set_nilfs_purging(nilfs);
+
+	/* Force to free the list of dirty files */
+	spin_lock(&nilfs->ns_inode_lock);
+	if (!list_empty(&nilfs->ns_dirty_files)) {
+		list_splice_init(&nilfs->ns_dirty_files, &garbage_list);
+		nilfs_warn(sb,
+			   "disposed unprocessed dirty file(s) when detaching log writer");
+	}
+	spin_unlock(&nilfs->ns_inode_lock);
+	up_write(&nilfs->ns_segctor_sem);
+
+	nilfs_dispose_list(nilfs, &garbage_list, 1);
+	clear_nilfs_purging(nilfs);
+}
diff --git a/fs/nilfs2/segment.h b/fs/nilfs2/segment.h
new file mode 100644
index 0000000000..1060f72ebf
--- /dev/null
+++ b/fs/nilfs2/segment.h
@@ -0,0 +1,249 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * NILFS Segment constructor prototypes and definitions
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Ryusuke Konishi.
+ *
+ */
+#ifndef _NILFS_SEGMENT_H
+#define _NILFS_SEGMENT_H
+
+#include <linux/types.h>
+#include <linux/fs.h>
+#include <linux/buffer_head.h>
+#include <linux/workqueue.h>
+#include "nilfs.h"
+
+struct nilfs_root;
+
+/**
+ * struct nilfs_recovery_info - Recovery information
+ * @ri_need_recovery: Recovery status
+ * @ri_super_root: Block number of the last super root
+ * @ri_ri_cno: Number of the last checkpoint
+ * @ri_lsegs_start: Region for roll-forwarding (start block number)
+ * @ri_lsegs_end: Region for roll-forwarding (end block number)
+ * @ri_lseg_start_seq: Sequence value of the segment at ri_lsegs_start
+ * @ri_used_segments: List of segments to be mark active
+ * @ri_pseg_start: Block number of the last partial segment
+ * @ri_seq: Sequence number on the last partial segment
+ * @ri_segnum: Segment number on the last partial segment
+ * @ri_nextnum: Next segment number on the last partial segment
+ */
+struct nilfs_recovery_info {
+	int			ri_need_recovery;
+	sector_t		ri_super_root;
+	__u64			ri_cno;
+
+	sector_t		ri_lsegs_start;
+	sector_t		ri_lsegs_end;
+	u64			ri_lsegs_start_seq;
+	struct list_head	ri_used_segments;
+	sector_t		ri_pseg_start;
+	u64			ri_seq;
+	__u64			ri_segnum;
+	__u64			ri_nextnum;
+};
+
+/* ri_need_recovery */
+#define NILFS_RECOVERY_SR_UPDATED	 1  /* The super root was updated */
+#define NILFS_RECOVERY_ROLLFORWARD_DONE	 2  /* Rollforward was carried out */
+
+/**
+ * struct nilfs_cstage - Context of collection stage
+ * @scnt: Stage count, must be accessed via wrappers:
+ *        nilfs_sc_cstage_inc(), nilfs_sc_cstage_set(), nilfs_sc_cstage_get()
+ * @flags: State flags
+ * @dirty_file_ptr: Pointer on dirty_files list, or inode of a target file
+ * @gc_inode_ptr: Pointer on the list of gc-inodes
+ */
+struct nilfs_cstage {
+	int			scnt;
+	unsigned int		flags;
+	struct nilfs_inode_info *dirty_file_ptr;
+	struct nilfs_inode_info *gc_inode_ptr;
+};
+
+struct nilfs_segment_buffer;
+
+struct nilfs_segsum_pointer {
+	struct buffer_head     *bh;
+	unsigned int		offset; /* offset in bytes */
+};
+
+/**
+ * struct nilfs_sc_info - Segment constructor information
+ * @sc_super: Back pointer to super_block struct
+ * @sc_root: root object of the current filesystem tree
+ * @sc_nblk_inc: Block count of current generation
+ * @sc_dirty_files: List of files to be written
+ * @sc_gc_inodes: List of GC inodes having blocks to be written
+ * @sc_iput_queue: list of inodes for which iput should be done
+ * @sc_iput_work: work struct to defer iput call
+ * @sc_freesegs: array of segment numbers to be freed
+ * @sc_nfreesegs: number of segments on @sc_freesegs
+ * @sc_dsync_inode: inode whose data pages are written for a sync operation
+ * @sc_dsync_start: start byte offset of data pages
+ * @sc_dsync_end: end byte offset of data pages (inclusive)
+ * @sc_segbufs: List of segment buffers
+ * @sc_write_logs: List of segment buffers to hold logs under writing
+ * @sc_segbuf_nblocks: Number of available blocks in segment buffers.
+ * @sc_curseg: Current segment buffer
+ * @sc_stage: Collection stage
+ * @sc_finfo_ptr: pointer to the current finfo struct in the segment summary
+ * @sc_binfo_ptr: pointer to the current binfo struct in the segment summary
+ * @sc_blk_cnt:	Block count of a file
+ * @sc_datablk_cnt: Data block count of a file
+ * @sc_nblk_this_inc: Number of blocks included in the current logical segment
+ * @sc_seg_ctime: Creation time
+ * @sc_cno: checkpoint number of current log
+ * @sc_flags: Internal flags
+ * @sc_state_lock: spinlock for sc_state and so on
+ * @sc_state: Segctord state flags
+ * @sc_flush_request: inode bitmap of metadata files to be flushed
+ * @sc_wait_request: Client request queue
+ * @sc_wait_daemon: Daemon wait queue
+ * @sc_wait_task: Start/end wait queue to control segctord task
+ * @sc_seq_request: Request counter
+ * @sc_seq_accept: Accepted request count
+ * @sc_seq_done: Completion counter
+ * @sc_sync: Request of explicit sync operation
+ * @sc_interval: Timeout value of background construction
+ * @sc_mjcp_freq: Frequency of creating checkpoints
+ * @sc_lseg_stime: Start time of the latest logical segment
+ * @sc_watermark: Watermark for the number of dirty buffers
+ * @sc_timer: Timer for segctord
+ * @sc_task: current thread of segctord
+ */
+struct nilfs_sc_info {
+	struct super_block     *sc_super;
+	struct nilfs_root      *sc_root;
+
+	unsigned long		sc_nblk_inc;
+
+	struct list_head	sc_dirty_files;
+	struct list_head	sc_gc_inodes;
+	struct list_head	sc_iput_queue;
+	struct work_struct	sc_iput_work;
+
+	__u64		       *sc_freesegs;
+	size_t			sc_nfreesegs;
+
+	struct nilfs_inode_info *sc_dsync_inode;
+	loff_t			sc_dsync_start;
+	loff_t			sc_dsync_end;
+
+	/* Segment buffers */
+	struct list_head	sc_segbufs;
+	struct list_head	sc_write_logs;
+	unsigned long		sc_segbuf_nblocks;
+	struct nilfs_segment_buffer *sc_curseg;
+
+	struct nilfs_cstage	sc_stage;
+
+	struct nilfs_segsum_pointer sc_finfo_ptr;
+	struct nilfs_segsum_pointer sc_binfo_ptr;
+	unsigned long		sc_blk_cnt;
+	unsigned long		sc_datablk_cnt;
+	unsigned long		sc_nblk_this_inc;
+	time64_t		sc_seg_ctime;
+	__u64			sc_cno;
+	unsigned long		sc_flags;
+
+	spinlock_t		sc_state_lock;
+	unsigned long		sc_state;
+	unsigned long		sc_flush_request;
+
+	wait_queue_head_t	sc_wait_request;
+	wait_queue_head_t	sc_wait_daemon;
+	wait_queue_head_t	sc_wait_task;
+
+	__u32			sc_seq_request;
+	__u32			sc_seq_accepted;
+	__u32			sc_seq_done;
+
+	int			sc_sync;
+	unsigned long		sc_interval;
+	unsigned long		sc_mjcp_freq;
+	unsigned long		sc_lseg_stime;	/* in 1/HZ seconds */
+	unsigned long		sc_watermark;
+
+	struct timer_list	sc_timer;
+	struct task_struct     *sc_timer_task;
+	struct task_struct     *sc_task;
+};
+
+/* sc_flags */
+enum {
+	NILFS_SC_DIRTY,		/* One or more dirty meta-data blocks exist */
+	NILFS_SC_UNCLOSED,	/* Logical segment is not closed */
+	NILFS_SC_SUPER_ROOT,	/* The latest segment has a super root */
+	NILFS_SC_PRIOR_FLUSH,	/*
+				 * Requesting immediate flush without making a
+				 * checkpoint
+				 */
+	NILFS_SC_HAVE_DELTA,	/*
+				 * Next checkpoint will have update of files
+				 * other than DAT, cpfile, sufile, or files
+				 * moved by GC.
+				 */
+};
+
+/* sc_state */
+#define NILFS_SEGCTOR_QUIT	    0x0001  /* segctord is being destroyed */
+#define NILFS_SEGCTOR_COMMIT	    0x0004  /* committed transaction exists */
+
+/*
+ * Constant parameters
+ */
+#define NILFS_SC_CLEANUP_RETRY	    3  /*
+					* Retry count of construction when
+					* destroying segctord
+					*/
+
+/*
+ * Default values of timeout, in seconds.
+ */
+#define NILFS_SC_DEFAULT_TIMEOUT    5   /*
+					 * Timeout value of dirty blocks.
+					 * It triggers construction of a
+					 * logical segment with a super root.
+					 */
+#define NILFS_SC_DEFAULT_SR_FREQ    30  /*
+					 * Maximum frequency of super root
+					 * creation
+					 */
+
+/*
+ * The default threshold amount of data, in block counts.
+ */
+#define NILFS_SC_DEFAULT_WATERMARK  3600
+
+/* super.c */
+extern struct kmem_cache *nilfs_transaction_cachep;
+
+/* segment.c */
+extern void nilfs_relax_pressure_in_lock(struct super_block *);
+
+extern int nilfs_construct_segment(struct super_block *);
+extern int nilfs_construct_dsync_segment(struct super_block *, struct inode *,
+					 loff_t, loff_t);
+extern void nilfs_flush_segment(struct super_block *, ino_t);
+extern int nilfs_clean_segments(struct super_block *, struct nilfs_argv *,
+				void **);
+
+int nilfs_attach_log_writer(struct super_block *sb, struct nilfs_root *root);
+void nilfs_detach_log_writer(struct super_block *sb);
+
+/* recovery.c */
+extern int nilfs_read_super_root_block(struct the_nilfs *, sector_t,
+				       struct buffer_head **, int);
+extern int nilfs_search_super_root(struct the_nilfs *,
+				   struct nilfs_recovery_info *);
+int nilfs_salvage_orphan_logs(struct the_nilfs *nilfs, struct super_block *sb,
+			      struct nilfs_recovery_info *ri);
+extern void nilfs_dispose_segment_list(struct list_head *);
+
+#endif /* _NILFS_SEGMENT_H */
diff --git a/fs/nilfs2/sufile.c b/fs/nilfs2/sufile.c
new file mode 100644
index 0000000000..58ca7c9363
--- /dev/null
+++ b/fs/nilfs2/sufile.c
@@ -0,0 +1,1260 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NILFS segment usage file.
+ *
+ * Copyright (C) 2006-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Koji Sato.
+ * Revised by Ryusuke Konishi.
+ */
+
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/string.h>
+#include <linux/buffer_head.h>
+#include <linux/errno.h>
+#include "mdt.h"
+#include "sufile.h"
+
+#include <trace/events/nilfs2.h>
+
+/**
+ * struct nilfs_sufile_info - on-memory private data of sufile
+ * @mi: on-memory private data of metadata file
+ * @ncleansegs: number of clean segments
+ * @allocmin: lower limit of allocatable segment range
+ * @allocmax: upper limit of allocatable segment range
+ */
+struct nilfs_sufile_info {
+	struct nilfs_mdt_info mi;
+	unsigned long ncleansegs;/* number of clean segments */
+	__u64 allocmin;		/* lower limit of allocatable segment range */
+	__u64 allocmax;		/* upper limit of allocatable segment range */
+};
+
+static inline struct nilfs_sufile_info *NILFS_SUI(struct inode *sufile)
+{
+	return (struct nilfs_sufile_info *)NILFS_MDT(sufile);
+}
+
+static inline unsigned long
+nilfs_sufile_segment_usages_per_block(const struct inode *sufile)
+{
+	return NILFS_MDT(sufile)->mi_entries_per_block;
+}
+
+static unsigned long
+nilfs_sufile_get_blkoff(const struct inode *sufile, __u64 segnum)
+{
+	__u64 t = segnum + NILFS_MDT(sufile)->mi_first_entry_offset;
+
+	do_div(t, nilfs_sufile_segment_usages_per_block(sufile));
+	return (unsigned long)t;
+}
+
+static unsigned long
+nilfs_sufile_get_offset(const struct inode *sufile, __u64 segnum)
+{
+	__u64 t = segnum + NILFS_MDT(sufile)->mi_first_entry_offset;
+
+	return do_div(t, nilfs_sufile_segment_usages_per_block(sufile));
+}
+
+static unsigned long
+nilfs_sufile_segment_usages_in_block(const struct inode *sufile, __u64 curr,
+				     __u64 max)
+{
+	return min_t(unsigned long,
+		     nilfs_sufile_segment_usages_per_block(sufile) -
+		     nilfs_sufile_get_offset(sufile, curr),
+		     max - curr + 1);
+}
+
+static struct nilfs_segment_usage *
+nilfs_sufile_block_get_segment_usage(const struct inode *sufile, __u64 segnum,
+				     struct buffer_head *bh, void *kaddr)
+{
+	return kaddr + bh_offset(bh) +
+		nilfs_sufile_get_offset(sufile, segnum) *
+		NILFS_MDT(sufile)->mi_entry_size;
+}
+
+static inline int nilfs_sufile_get_header_block(struct inode *sufile,
+						struct buffer_head **bhp)
+{
+	return nilfs_mdt_get_block(sufile, 0, 0, NULL, bhp);
+}
+
+static inline int
+nilfs_sufile_get_segment_usage_block(struct inode *sufile, __u64 segnum,
+				     int create, struct buffer_head **bhp)
+{
+	return nilfs_mdt_get_block(sufile,
+				   nilfs_sufile_get_blkoff(sufile, segnum),
+				   create, NULL, bhp);
+}
+
+static int nilfs_sufile_delete_segment_usage_block(struct inode *sufile,
+						   __u64 segnum)
+{
+	return nilfs_mdt_delete_block(sufile,
+				      nilfs_sufile_get_blkoff(sufile, segnum));
+}
+
+static void nilfs_sufile_mod_counter(struct buffer_head *header_bh,
+				     u64 ncleanadd, u64 ndirtyadd)
+{
+	struct nilfs_sufile_header *header;
+	void *kaddr;
+
+	kaddr = kmap_atomic(header_bh->b_page);
+	header = kaddr + bh_offset(header_bh);
+	le64_add_cpu(&header->sh_ncleansegs, ncleanadd);
+	le64_add_cpu(&header->sh_ndirtysegs, ndirtyadd);
+	kunmap_atomic(kaddr);
+
+	mark_buffer_dirty(header_bh);
+}
+
+/**
+ * nilfs_sufile_get_ncleansegs - return the number of clean segments
+ * @sufile: inode of segment usage file
+ */
+unsigned long nilfs_sufile_get_ncleansegs(struct inode *sufile)
+{
+	return NILFS_SUI(sufile)->ncleansegs;
+}
+
+/**
+ * nilfs_sufile_updatev - modify multiple segment usages at a time
+ * @sufile: inode of segment usage file
+ * @segnumv: array of segment numbers
+ * @nsegs: size of @segnumv array
+ * @create: creation flag
+ * @ndone: place to store number of modified segments on @segnumv
+ * @dofunc: primitive operation for the update
+ *
+ * Description: nilfs_sufile_updatev() repeatedly calls @dofunc
+ * against the given array of segments.  The @dofunc is called with
+ * buffers of a header block and the sufile block in which the target
+ * segment usage entry is contained.  If @ndone is given, the number
+ * of successfully modified segments from the head is stored in the
+ * place @ndone points to.
+ *
+ * Return Value: On success, zero is returned.  On error, one of the
+ * following negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-ENOENT - Given segment usage is in hole block (may be returned if
+ *            @create is zero)
+ *
+ * %-EINVAL - Invalid segment usage number
+ */
+int nilfs_sufile_updatev(struct inode *sufile, __u64 *segnumv, size_t nsegs,
+			 int create, size_t *ndone,
+			 void (*dofunc)(struct inode *, __u64,
+					struct buffer_head *,
+					struct buffer_head *))
+{
+	struct buffer_head *header_bh, *bh;
+	unsigned long blkoff, prev_blkoff;
+	__u64 *seg;
+	size_t nerr = 0, n = 0;
+	int ret = 0;
+
+	if (unlikely(nsegs == 0))
+		goto out;
+
+	down_write(&NILFS_MDT(sufile)->mi_sem);
+	for (seg = segnumv; seg < segnumv + nsegs; seg++) {
+		if (unlikely(*seg >= nilfs_sufile_get_nsegments(sufile))) {
+			nilfs_warn(sufile->i_sb,
+				   "%s: invalid segment number: %llu",
+				   __func__, (unsigned long long)*seg);
+			nerr++;
+		}
+	}
+	if (nerr > 0) {
+		ret = -EINVAL;
+		goto out_sem;
+	}
+
+	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
+	if (ret < 0)
+		goto out_sem;
+
+	seg = segnumv;
+	blkoff = nilfs_sufile_get_blkoff(sufile, *seg);
+	ret = nilfs_mdt_get_block(sufile, blkoff, create, NULL, &bh);
+	if (ret < 0)
+		goto out_header;
+
+	for (;;) {
+		dofunc(sufile, *seg, header_bh, bh);
+
+		if (++seg >= segnumv + nsegs)
+			break;
+		prev_blkoff = blkoff;
+		blkoff = nilfs_sufile_get_blkoff(sufile, *seg);
+		if (blkoff == prev_blkoff)
+			continue;
+
+		/* get different block */
+		brelse(bh);
+		ret = nilfs_mdt_get_block(sufile, blkoff, create, NULL, &bh);
+		if (unlikely(ret < 0))
+			goto out_header;
+	}
+	brelse(bh);
+
+ out_header:
+	n = seg - segnumv;
+	brelse(header_bh);
+ out_sem:
+	up_write(&NILFS_MDT(sufile)->mi_sem);
+ out:
+	if (ndone)
+		*ndone = n;
+	return ret;
+}
+
+int nilfs_sufile_update(struct inode *sufile, __u64 segnum, int create,
+			void (*dofunc)(struct inode *, __u64,
+				       struct buffer_head *,
+				       struct buffer_head *))
+{
+	struct buffer_head *header_bh, *bh;
+	int ret;
+
+	if (unlikely(segnum >= nilfs_sufile_get_nsegments(sufile))) {
+		nilfs_warn(sufile->i_sb, "%s: invalid segment number: %llu",
+			   __func__, (unsigned long long)segnum);
+		return -EINVAL;
+	}
+	down_write(&NILFS_MDT(sufile)->mi_sem);
+
+	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
+	if (ret < 0)
+		goto out_sem;
+
+	ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, create, &bh);
+	if (!ret) {
+		dofunc(sufile, segnum, header_bh, bh);
+		brelse(bh);
+	}
+	brelse(header_bh);
+
+ out_sem:
+	up_write(&NILFS_MDT(sufile)->mi_sem);
+	return ret;
+}
+
+/**
+ * nilfs_sufile_set_alloc_range - limit range of segment to be allocated
+ * @sufile: inode of segment usage file
+ * @start: minimum segment number of allocatable region (inclusive)
+ * @end: maximum segment number of allocatable region (inclusive)
+ *
+ * Return Value: On success, 0 is returned.  On error, one of the
+ * following negative error codes is returned.
+ *
+ * %-ERANGE - invalid segment region
+ */
+int nilfs_sufile_set_alloc_range(struct inode *sufile, __u64 start, __u64 end)
+{
+	struct nilfs_sufile_info *sui = NILFS_SUI(sufile);
+	__u64 nsegs;
+	int ret = -ERANGE;
+
+	down_write(&NILFS_MDT(sufile)->mi_sem);
+	nsegs = nilfs_sufile_get_nsegments(sufile);
+
+	if (start <= end && end < nsegs) {
+		sui->allocmin = start;
+		sui->allocmax = end;
+		ret = 0;
+	}
+	up_write(&NILFS_MDT(sufile)->mi_sem);
+	return ret;
+}
+
+/**
+ * nilfs_sufile_alloc - allocate a segment
+ * @sufile: inode of segment usage file
+ * @segnump: pointer to segment number
+ *
+ * Description: nilfs_sufile_alloc() allocates a clean segment.
+ *
+ * Return Value: On success, 0 is returned and the segment number of the
+ * allocated segment is stored in the place pointed by @segnump. On error, one
+ * of the following negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-ENOSPC - No clean segment left.
+ */
+int nilfs_sufile_alloc(struct inode *sufile, __u64 *segnump)
+{
+	struct buffer_head *header_bh, *su_bh;
+	struct nilfs_sufile_header *header;
+	struct nilfs_segment_usage *su;
+	struct nilfs_sufile_info *sui = NILFS_SUI(sufile);
+	size_t susz = NILFS_MDT(sufile)->mi_entry_size;
+	__u64 segnum, maxsegnum, last_alloc;
+	void *kaddr;
+	unsigned long nsegments, nsus, cnt;
+	int ret, j;
+
+	down_write(&NILFS_MDT(sufile)->mi_sem);
+
+	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
+	if (ret < 0)
+		goto out_sem;
+	kaddr = kmap_atomic(header_bh->b_page);
+	header = kaddr + bh_offset(header_bh);
+	last_alloc = le64_to_cpu(header->sh_last_alloc);
+	kunmap_atomic(kaddr);
+
+	nsegments = nilfs_sufile_get_nsegments(sufile);
+	maxsegnum = sui->allocmax;
+	segnum = last_alloc + 1;
+	if (segnum < sui->allocmin || segnum > sui->allocmax)
+		segnum = sui->allocmin;
+
+	for (cnt = 0; cnt < nsegments; cnt += nsus) {
+		if (segnum > maxsegnum) {
+			if (cnt < sui->allocmax - sui->allocmin + 1) {
+				/*
+				 * wrap around in the limited region.
+				 * if allocation started from
+				 * sui->allocmin, this never happens.
+				 */
+				segnum = sui->allocmin;
+				maxsegnum = last_alloc;
+			} else if (segnum > sui->allocmin &&
+				   sui->allocmax + 1 < nsegments) {
+				segnum = sui->allocmax + 1;
+				maxsegnum = nsegments - 1;
+			} else if (sui->allocmin > 0)  {
+				segnum = 0;
+				maxsegnum = sui->allocmin - 1;
+			} else {
+				break; /* never happens */
+			}
+		}
+		trace_nilfs2_segment_usage_check(sufile, segnum, cnt);
+		ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 1,
+							   &su_bh);
+		if (ret < 0)
+			goto out_header;
+		kaddr = kmap_atomic(su_bh->b_page);
+		su = nilfs_sufile_block_get_segment_usage(
+			sufile, segnum, su_bh, kaddr);
+
+		nsus = nilfs_sufile_segment_usages_in_block(
+			sufile, segnum, maxsegnum);
+		for (j = 0; j < nsus; j++, su = (void *)su + susz, segnum++) {
+			if (!nilfs_segment_usage_clean(su))
+				continue;
+			/* found a clean segment */
+			nilfs_segment_usage_set_dirty(su);
+			kunmap_atomic(kaddr);
+
+			kaddr = kmap_atomic(header_bh->b_page);
+			header = kaddr + bh_offset(header_bh);
+			le64_add_cpu(&header->sh_ncleansegs, -1);
+			le64_add_cpu(&header->sh_ndirtysegs, 1);
+			header->sh_last_alloc = cpu_to_le64(segnum);
+			kunmap_atomic(kaddr);
+
+			sui->ncleansegs--;
+			mark_buffer_dirty(header_bh);
+			mark_buffer_dirty(su_bh);
+			nilfs_mdt_mark_dirty(sufile);
+			brelse(su_bh);
+			*segnump = segnum;
+
+			trace_nilfs2_segment_usage_allocated(sufile, segnum);
+
+			goto out_header;
+		}
+
+		kunmap_atomic(kaddr);
+		brelse(su_bh);
+	}
+
+	/* no segments left */
+	ret = -ENOSPC;
+
+ out_header:
+	brelse(header_bh);
+
+ out_sem:
+	up_write(&NILFS_MDT(sufile)->mi_sem);
+	return ret;
+}
+
+void nilfs_sufile_do_cancel_free(struct inode *sufile, __u64 segnum,
+				 struct buffer_head *header_bh,
+				 struct buffer_head *su_bh)
+{
+	struct nilfs_segment_usage *su;
+	void *kaddr;
+
+	kaddr = kmap_atomic(su_bh->b_page);
+	su = nilfs_sufile_block_get_segment_usage(sufile, segnum, su_bh, kaddr);
+	if (unlikely(!nilfs_segment_usage_clean(su))) {
+		nilfs_warn(sufile->i_sb, "%s: segment %llu must be clean",
+			   __func__, (unsigned long long)segnum);
+		kunmap_atomic(kaddr);
+		return;
+	}
+	nilfs_segment_usage_set_dirty(su);
+	kunmap_atomic(kaddr);
+
+	nilfs_sufile_mod_counter(header_bh, -1, 1);
+	NILFS_SUI(sufile)->ncleansegs--;
+
+	mark_buffer_dirty(su_bh);
+	nilfs_mdt_mark_dirty(sufile);
+}
+
+void nilfs_sufile_do_scrap(struct inode *sufile, __u64 segnum,
+			   struct buffer_head *header_bh,
+			   struct buffer_head *su_bh)
+{
+	struct nilfs_segment_usage *su;
+	void *kaddr;
+	int clean, dirty;
+
+	kaddr = kmap_atomic(su_bh->b_page);
+	su = nilfs_sufile_block_get_segment_usage(sufile, segnum, su_bh, kaddr);
+	if (su->su_flags == cpu_to_le32(BIT(NILFS_SEGMENT_USAGE_DIRTY)) &&
+	    su->su_nblocks == cpu_to_le32(0)) {
+		kunmap_atomic(kaddr);
+		return;
+	}
+	clean = nilfs_segment_usage_clean(su);
+	dirty = nilfs_segment_usage_dirty(su);
+
+	/* make the segment garbage */
+	su->su_lastmod = cpu_to_le64(0);
+	su->su_nblocks = cpu_to_le32(0);
+	su->su_flags = cpu_to_le32(BIT(NILFS_SEGMENT_USAGE_DIRTY));
+	kunmap_atomic(kaddr);
+
+	nilfs_sufile_mod_counter(header_bh, clean ? (u64)-1 : 0, dirty ? 0 : 1);
+	NILFS_SUI(sufile)->ncleansegs -= clean;
+
+	mark_buffer_dirty(su_bh);
+	nilfs_mdt_mark_dirty(sufile);
+}
+
+void nilfs_sufile_do_free(struct inode *sufile, __u64 segnum,
+			  struct buffer_head *header_bh,
+			  struct buffer_head *su_bh)
+{
+	struct nilfs_segment_usage *su;
+	void *kaddr;
+	int sudirty;
+
+	kaddr = kmap_atomic(su_bh->b_page);
+	su = nilfs_sufile_block_get_segment_usage(sufile, segnum, su_bh, kaddr);
+	if (nilfs_segment_usage_clean(su)) {
+		nilfs_warn(sufile->i_sb, "%s: segment %llu is already clean",
+			   __func__, (unsigned long long)segnum);
+		kunmap_atomic(kaddr);
+		return;
+	}
+	WARN_ON(nilfs_segment_usage_error(su));
+	WARN_ON(!nilfs_segment_usage_dirty(su));
+
+	sudirty = nilfs_segment_usage_dirty(su);
+	nilfs_segment_usage_set_clean(su);
+	kunmap_atomic(kaddr);
+	mark_buffer_dirty(su_bh);
+
+	nilfs_sufile_mod_counter(header_bh, 1, sudirty ? (u64)-1 : 0);
+	NILFS_SUI(sufile)->ncleansegs++;
+
+	nilfs_mdt_mark_dirty(sufile);
+
+	trace_nilfs2_segment_usage_freed(sufile, segnum);
+}
+
+/**
+ * nilfs_sufile_mark_dirty - mark the buffer having a segment usage dirty
+ * @sufile: inode of segment usage file
+ * @segnum: segment number
+ */
+int nilfs_sufile_mark_dirty(struct inode *sufile, __u64 segnum)
+{
+	struct buffer_head *bh;
+	void *kaddr;
+	struct nilfs_segment_usage *su;
+	int ret;
+
+	down_write(&NILFS_MDT(sufile)->mi_sem);
+	ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0, &bh);
+	if (ret)
+		goto out_sem;
+
+	kaddr = kmap_atomic(bh->b_page);
+	su = nilfs_sufile_block_get_segment_usage(sufile, segnum, bh, kaddr);
+	if (unlikely(nilfs_segment_usage_error(su))) {
+		struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
+
+		kunmap_atomic(kaddr);
+		brelse(bh);
+		if (nilfs_segment_is_active(nilfs, segnum)) {
+			nilfs_error(sufile->i_sb,
+				    "active segment %llu is erroneous",
+				    (unsigned long long)segnum);
+		} else {
+			/*
+			 * Segments marked erroneous are never allocated by
+			 * nilfs_sufile_alloc(); only active segments, ie,
+			 * the segments indexed by ns_segnum or ns_nextnum,
+			 * can be erroneous here.
+			 */
+			WARN_ON_ONCE(1);
+		}
+		ret = -EIO;
+	} else {
+		nilfs_segment_usage_set_dirty(su);
+		kunmap_atomic(kaddr);
+		mark_buffer_dirty(bh);
+		nilfs_mdt_mark_dirty(sufile);
+		brelse(bh);
+	}
+out_sem:
+	up_write(&NILFS_MDT(sufile)->mi_sem);
+	return ret;
+}
+
+/**
+ * nilfs_sufile_set_segment_usage - set usage of a segment
+ * @sufile: inode of segment usage file
+ * @segnum: segment number
+ * @nblocks: number of live blocks in the segment
+ * @modtime: modification time (option)
+ */
+int nilfs_sufile_set_segment_usage(struct inode *sufile, __u64 segnum,
+				   unsigned long nblocks, time64_t modtime)
+{
+	struct buffer_head *bh;
+	struct nilfs_segment_usage *su;
+	void *kaddr;
+	int ret;
+
+	down_write(&NILFS_MDT(sufile)->mi_sem);
+	ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0, &bh);
+	if (ret < 0)
+		goto out_sem;
+
+	kaddr = kmap_atomic(bh->b_page);
+	su = nilfs_sufile_block_get_segment_usage(sufile, segnum, bh, kaddr);
+	if (modtime) {
+		/*
+		 * Check segusage error and set su_lastmod only when updating
+		 * this entry with a valid timestamp, not for cancellation.
+		 */
+		WARN_ON_ONCE(nilfs_segment_usage_error(su));
+		su->su_lastmod = cpu_to_le64(modtime);
+	}
+	su->su_nblocks = cpu_to_le32(nblocks);
+	kunmap_atomic(kaddr);
+
+	mark_buffer_dirty(bh);
+	nilfs_mdt_mark_dirty(sufile);
+	brelse(bh);
+
+ out_sem:
+	up_write(&NILFS_MDT(sufile)->mi_sem);
+	return ret;
+}
+
+/**
+ * nilfs_sufile_get_stat - get segment usage statistics
+ * @sufile: inode of segment usage file
+ * @sustat: pointer to a structure of segment usage statistics
+ *
+ * Description: nilfs_sufile_get_stat() returns information about segment
+ * usage.
+ *
+ * Return Value: On success, 0 is returned, and segment usage information is
+ * stored in the place pointed by @sustat. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ */
+int nilfs_sufile_get_stat(struct inode *sufile, struct nilfs_sustat *sustat)
+{
+	struct buffer_head *header_bh;
+	struct nilfs_sufile_header *header;
+	struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
+	void *kaddr;
+	int ret;
+
+	down_read(&NILFS_MDT(sufile)->mi_sem);
+
+	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
+	if (ret < 0)
+		goto out_sem;
+
+	kaddr = kmap_atomic(header_bh->b_page);
+	header = kaddr + bh_offset(header_bh);
+	sustat->ss_nsegs = nilfs_sufile_get_nsegments(sufile);
+	sustat->ss_ncleansegs = le64_to_cpu(header->sh_ncleansegs);
+	sustat->ss_ndirtysegs = le64_to_cpu(header->sh_ndirtysegs);
+	sustat->ss_ctime = nilfs->ns_ctime;
+	sustat->ss_nongc_ctime = nilfs->ns_nongc_ctime;
+	spin_lock(&nilfs->ns_last_segment_lock);
+	sustat->ss_prot_seq = nilfs->ns_prot_seq;
+	spin_unlock(&nilfs->ns_last_segment_lock);
+	kunmap_atomic(kaddr);
+	brelse(header_bh);
+
+ out_sem:
+	up_read(&NILFS_MDT(sufile)->mi_sem);
+	return ret;
+}
+
+void nilfs_sufile_do_set_error(struct inode *sufile, __u64 segnum,
+			       struct buffer_head *header_bh,
+			       struct buffer_head *su_bh)
+{
+	struct nilfs_segment_usage *su;
+	void *kaddr;
+	int suclean;
+
+	kaddr = kmap_atomic(su_bh->b_page);
+	su = nilfs_sufile_block_get_segment_usage(sufile, segnum, su_bh, kaddr);
+	if (nilfs_segment_usage_error(su)) {
+		kunmap_atomic(kaddr);
+		return;
+	}
+	suclean = nilfs_segment_usage_clean(su);
+	nilfs_segment_usage_set_error(su);
+	kunmap_atomic(kaddr);
+
+	if (suclean) {
+		nilfs_sufile_mod_counter(header_bh, -1, 0);
+		NILFS_SUI(sufile)->ncleansegs--;
+	}
+	mark_buffer_dirty(su_bh);
+	nilfs_mdt_mark_dirty(sufile);
+}
+
+/**
+ * nilfs_sufile_truncate_range - truncate range of segment array
+ * @sufile: inode of segment usage file
+ * @start: start segment number (inclusive)
+ * @end: end segment number (inclusive)
+ *
+ * Return Value: On success, 0 is returned.  On error, one of the
+ * following negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-EINVAL - Invalid number of segments specified
+ *
+ * %-EBUSY - Dirty or active segments are present in the range
+ */
+static int nilfs_sufile_truncate_range(struct inode *sufile,
+				       __u64 start, __u64 end)
+{
+	struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
+	struct buffer_head *header_bh;
+	struct buffer_head *su_bh;
+	struct nilfs_segment_usage *su, *su2;
+	size_t susz = NILFS_MDT(sufile)->mi_entry_size;
+	unsigned long segusages_per_block;
+	unsigned long nsegs, ncleaned;
+	__u64 segnum;
+	void *kaddr;
+	ssize_t n, nc;
+	int ret;
+	int j;
+
+	nsegs = nilfs_sufile_get_nsegments(sufile);
+
+	ret = -EINVAL;
+	if (start > end || start >= nsegs)
+		goto out;
+
+	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
+	if (ret < 0)
+		goto out;
+
+	segusages_per_block = nilfs_sufile_segment_usages_per_block(sufile);
+	ncleaned = 0;
+
+	for (segnum = start; segnum <= end; segnum += n) {
+		n = min_t(unsigned long,
+			  segusages_per_block -
+				  nilfs_sufile_get_offset(sufile, segnum),
+			  end - segnum + 1);
+		ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0,
+							   &su_bh);
+		if (ret < 0) {
+			if (ret != -ENOENT)
+				goto out_header;
+			/* hole */
+			continue;
+		}
+		kaddr = kmap_atomic(su_bh->b_page);
+		su = nilfs_sufile_block_get_segment_usage(
+			sufile, segnum, su_bh, kaddr);
+		su2 = su;
+		for (j = 0; j < n; j++, su = (void *)su + susz) {
+			if ((le32_to_cpu(su->su_flags) &
+			     ~BIT(NILFS_SEGMENT_USAGE_ERROR)) ||
+			    nilfs_segment_is_active(nilfs, segnum + j)) {
+				ret = -EBUSY;
+				kunmap_atomic(kaddr);
+				brelse(su_bh);
+				goto out_header;
+			}
+		}
+		nc = 0;
+		for (su = su2, j = 0; j < n; j++, su = (void *)su + susz) {
+			if (nilfs_segment_usage_error(su)) {
+				nilfs_segment_usage_set_clean(su);
+				nc++;
+			}
+		}
+		kunmap_atomic(kaddr);
+		if (nc > 0) {
+			mark_buffer_dirty(su_bh);
+			ncleaned += nc;
+		}
+		brelse(su_bh);
+
+		if (n == segusages_per_block) {
+			/* make hole */
+			nilfs_sufile_delete_segment_usage_block(sufile, segnum);
+		}
+	}
+	ret = 0;
+
+out_header:
+	if (ncleaned > 0) {
+		NILFS_SUI(sufile)->ncleansegs += ncleaned;
+		nilfs_sufile_mod_counter(header_bh, ncleaned, 0);
+		nilfs_mdt_mark_dirty(sufile);
+	}
+	brelse(header_bh);
+out:
+	return ret;
+}
+
+/**
+ * nilfs_sufile_resize - resize segment array
+ * @sufile: inode of segment usage file
+ * @newnsegs: new number of segments
+ *
+ * Return Value: On success, 0 is returned.  On error, one of the
+ * following negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-ENOSPC - Enough free space is not left for shrinking
+ *
+ * %-EBUSY - Dirty or active segments exist in the region to be truncated
+ */
+int nilfs_sufile_resize(struct inode *sufile, __u64 newnsegs)
+{
+	struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
+	struct buffer_head *header_bh;
+	struct nilfs_sufile_header *header;
+	struct nilfs_sufile_info *sui = NILFS_SUI(sufile);
+	void *kaddr;
+	unsigned long nsegs, nrsvsegs;
+	int ret = 0;
+
+	down_write(&NILFS_MDT(sufile)->mi_sem);
+
+	nsegs = nilfs_sufile_get_nsegments(sufile);
+	if (nsegs == newnsegs)
+		goto out;
+
+	ret = -ENOSPC;
+	nrsvsegs = nilfs_nrsvsegs(nilfs, newnsegs);
+	if (newnsegs < nsegs && nsegs - newnsegs + nrsvsegs > sui->ncleansegs)
+		goto out;
+
+	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
+	if (ret < 0)
+		goto out;
+
+	if (newnsegs > nsegs) {
+		sui->ncleansegs += newnsegs - nsegs;
+	} else /* newnsegs < nsegs */ {
+		ret = nilfs_sufile_truncate_range(sufile, newnsegs, nsegs - 1);
+		if (ret < 0)
+			goto out_header;
+
+		sui->ncleansegs -= nsegs - newnsegs;
+
+		/*
+		 * If the sufile is successfully truncated, immediately adjust
+		 * the segment allocation space while locking the semaphore
+		 * "mi_sem" so that nilfs_sufile_alloc() never allocates
+		 * segments in the truncated space.
+		 */
+		sui->allocmax = newnsegs - 1;
+		sui->allocmin = 0;
+	}
+
+	kaddr = kmap_atomic(header_bh->b_page);
+	header = kaddr + bh_offset(header_bh);
+	header->sh_ncleansegs = cpu_to_le64(sui->ncleansegs);
+	kunmap_atomic(kaddr);
+
+	mark_buffer_dirty(header_bh);
+	nilfs_mdt_mark_dirty(sufile);
+	nilfs_set_nsegments(nilfs, newnsegs);
+
+out_header:
+	brelse(header_bh);
+out:
+	up_write(&NILFS_MDT(sufile)->mi_sem);
+	return ret;
+}
+
+/**
+ * nilfs_sufile_get_suinfo -
+ * @sufile: inode of segment usage file
+ * @segnum: segment number to start looking
+ * @buf: array of suinfo
+ * @sisz: byte size of suinfo
+ * @nsi: size of suinfo array
+ *
+ * Description:
+ *
+ * Return Value: On success, 0 is returned and .... On error, one of the
+ * following negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ */
+ssize_t nilfs_sufile_get_suinfo(struct inode *sufile, __u64 segnum, void *buf,
+				unsigned int sisz, size_t nsi)
+{
+	struct buffer_head *su_bh;
+	struct nilfs_segment_usage *su;
+	struct nilfs_suinfo *si = buf;
+	size_t susz = NILFS_MDT(sufile)->mi_entry_size;
+	struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
+	void *kaddr;
+	unsigned long nsegs, segusages_per_block;
+	ssize_t n;
+	int ret, i, j;
+
+	down_read(&NILFS_MDT(sufile)->mi_sem);
+
+	segusages_per_block = nilfs_sufile_segment_usages_per_block(sufile);
+	nsegs = min_t(unsigned long,
+		      nilfs_sufile_get_nsegments(sufile) - segnum,
+		      nsi);
+	for (i = 0; i < nsegs; i += n, segnum += n) {
+		n = min_t(unsigned long,
+			  segusages_per_block -
+				  nilfs_sufile_get_offset(sufile, segnum),
+			  nsegs - i);
+		ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0,
+							   &su_bh);
+		if (ret < 0) {
+			if (ret != -ENOENT)
+				goto out;
+			/* hole */
+			memset(si, 0, sisz * n);
+			si = (void *)si + sisz * n;
+			continue;
+		}
+
+		kaddr = kmap_atomic(su_bh->b_page);
+		su = nilfs_sufile_block_get_segment_usage(
+			sufile, segnum, su_bh, kaddr);
+		for (j = 0; j < n;
+		     j++, su = (void *)su + susz, si = (void *)si + sisz) {
+			si->sui_lastmod = le64_to_cpu(su->su_lastmod);
+			si->sui_nblocks = le32_to_cpu(su->su_nblocks);
+			si->sui_flags = le32_to_cpu(su->su_flags) &
+				~BIT(NILFS_SEGMENT_USAGE_ACTIVE);
+			if (nilfs_segment_is_active(nilfs, segnum + j))
+				si->sui_flags |=
+					BIT(NILFS_SEGMENT_USAGE_ACTIVE);
+		}
+		kunmap_atomic(kaddr);
+		brelse(su_bh);
+	}
+	ret = nsegs;
+
+ out:
+	up_read(&NILFS_MDT(sufile)->mi_sem);
+	return ret;
+}
+
+/**
+ * nilfs_sufile_set_suinfo - sets segment usage info
+ * @sufile: inode of segment usage file
+ * @buf: array of suinfo_update
+ * @supsz: byte size of suinfo_update
+ * @nsup: size of suinfo_update array
+ *
+ * Description: Takes an array of nilfs_suinfo_update structs and updates
+ * segment usage accordingly. Only the fields indicated by the sup_flags
+ * are updated.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the
+ * following negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-EINVAL - Invalid values in input (segment number, flags or nblocks)
+ */
+ssize_t nilfs_sufile_set_suinfo(struct inode *sufile, void *buf,
+				unsigned int supsz, size_t nsup)
+{
+	struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
+	struct buffer_head *header_bh, *bh;
+	struct nilfs_suinfo_update *sup, *supend = buf + supsz * nsup;
+	struct nilfs_segment_usage *su;
+	void *kaddr;
+	unsigned long blkoff, prev_blkoff;
+	int cleansi, cleansu, dirtysi, dirtysu;
+	long ncleaned = 0, ndirtied = 0;
+	int ret = 0;
+
+	if (unlikely(nsup == 0))
+		return ret;
+
+	for (sup = buf; sup < supend; sup = (void *)sup + supsz) {
+		if (sup->sup_segnum >= nilfs->ns_nsegments
+			|| (sup->sup_flags &
+				(~0UL << __NR_NILFS_SUINFO_UPDATE_FIELDS))
+			|| (nilfs_suinfo_update_nblocks(sup) &&
+				sup->sup_sui.sui_nblocks >
+				nilfs->ns_blocks_per_segment))
+			return -EINVAL;
+	}
+
+	down_write(&NILFS_MDT(sufile)->mi_sem);
+
+	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
+	if (ret < 0)
+		goto out_sem;
+
+	sup = buf;
+	blkoff = nilfs_sufile_get_blkoff(sufile, sup->sup_segnum);
+	ret = nilfs_mdt_get_block(sufile, blkoff, 1, NULL, &bh);
+	if (ret < 0)
+		goto out_header;
+
+	for (;;) {
+		kaddr = kmap_atomic(bh->b_page);
+		su = nilfs_sufile_block_get_segment_usage(
+			sufile, sup->sup_segnum, bh, kaddr);
+
+		if (nilfs_suinfo_update_lastmod(sup))
+			su->su_lastmod = cpu_to_le64(sup->sup_sui.sui_lastmod);
+
+		if (nilfs_suinfo_update_nblocks(sup))
+			su->su_nblocks = cpu_to_le32(sup->sup_sui.sui_nblocks);
+
+		if (nilfs_suinfo_update_flags(sup)) {
+			/*
+			 * Active flag is a virtual flag projected by running
+			 * nilfs kernel code - drop it not to write it to
+			 * disk.
+			 */
+			sup->sup_sui.sui_flags &=
+					~BIT(NILFS_SEGMENT_USAGE_ACTIVE);
+
+			cleansi = nilfs_suinfo_clean(&sup->sup_sui);
+			cleansu = nilfs_segment_usage_clean(su);
+			dirtysi = nilfs_suinfo_dirty(&sup->sup_sui);
+			dirtysu = nilfs_segment_usage_dirty(su);
+
+			if (cleansi && !cleansu)
+				++ncleaned;
+			else if (!cleansi && cleansu)
+				--ncleaned;
+
+			if (dirtysi && !dirtysu)
+				++ndirtied;
+			else if (!dirtysi && dirtysu)
+				--ndirtied;
+
+			su->su_flags = cpu_to_le32(sup->sup_sui.sui_flags);
+		}
+
+		kunmap_atomic(kaddr);
+
+		sup = (void *)sup + supsz;
+		if (sup >= supend)
+			break;
+
+		prev_blkoff = blkoff;
+		blkoff = nilfs_sufile_get_blkoff(sufile, sup->sup_segnum);
+		if (blkoff == prev_blkoff)
+			continue;
+
+		/* get different block */
+		mark_buffer_dirty(bh);
+		put_bh(bh);
+		ret = nilfs_mdt_get_block(sufile, blkoff, 1, NULL, &bh);
+		if (unlikely(ret < 0))
+			goto out_mark;
+	}
+	mark_buffer_dirty(bh);
+	put_bh(bh);
+
+ out_mark:
+	if (ncleaned || ndirtied) {
+		nilfs_sufile_mod_counter(header_bh, (u64)ncleaned,
+				(u64)ndirtied);
+		NILFS_SUI(sufile)->ncleansegs += ncleaned;
+	}
+	nilfs_mdt_mark_dirty(sufile);
+ out_header:
+	put_bh(header_bh);
+ out_sem:
+	up_write(&NILFS_MDT(sufile)->mi_sem);
+	return ret;
+}
+
+/**
+ * nilfs_sufile_trim_fs() - trim ioctl handle function
+ * @sufile: inode of segment usage file
+ * @range: fstrim_range structure
+ *
+ * start:	First Byte to trim
+ * len:		number of Bytes to trim from start
+ * minlen:	minimum extent length in Bytes
+ *
+ * Decription: nilfs_sufile_trim_fs goes through all segments containing bytes
+ * from start to start+len. start is rounded up to the next block boundary
+ * and start+len is rounded down. For each clean segment blkdev_issue_discard
+ * function is invoked.
+ *
+ * Return Value: On success, 0 is returned or negative error code, otherwise.
+ */
+int nilfs_sufile_trim_fs(struct inode *sufile, struct fstrim_range *range)
+{
+	struct the_nilfs *nilfs = sufile->i_sb->s_fs_info;
+	struct buffer_head *su_bh;
+	struct nilfs_segment_usage *su;
+	void *kaddr;
+	size_t n, i, susz = NILFS_MDT(sufile)->mi_entry_size;
+	sector_t seg_start, seg_end, start_block, end_block;
+	sector_t start = 0, nblocks = 0;
+	u64 segnum, segnum_end, minlen, len, max_blocks, ndiscarded = 0;
+	int ret = 0;
+	unsigned int sects_per_block;
+
+	sects_per_block = (1 << nilfs->ns_blocksize_bits) /
+			bdev_logical_block_size(nilfs->ns_bdev);
+	len = range->len >> nilfs->ns_blocksize_bits;
+	minlen = range->minlen >> nilfs->ns_blocksize_bits;
+	max_blocks = ((u64)nilfs->ns_nsegments * nilfs->ns_blocks_per_segment);
+
+	if (!len || range->start >= max_blocks << nilfs->ns_blocksize_bits)
+		return -EINVAL;
+
+	start_block = (range->start + nilfs->ns_blocksize - 1) >>
+			nilfs->ns_blocksize_bits;
+
+	/*
+	 * range->len can be very large (actually, it is set to
+	 * ULLONG_MAX by default) - truncate upper end of the range
+	 * carefully so as not to overflow.
+	 */
+	if (max_blocks - start_block < len)
+		end_block = max_blocks - 1;
+	else
+		end_block = start_block + len - 1;
+
+	segnum = nilfs_get_segnum_of_block(nilfs, start_block);
+	segnum_end = nilfs_get_segnum_of_block(nilfs, end_block);
+
+	down_read(&NILFS_MDT(sufile)->mi_sem);
+
+	while (segnum <= segnum_end) {
+		n = nilfs_sufile_segment_usages_in_block(sufile, segnum,
+				segnum_end);
+
+		ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 0,
+							   &su_bh);
+		if (ret < 0) {
+			if (ret != -ENOENT)
+				goto out_sem;
+			/* hole */
+			segnum += n;
+			continue;
+		}
+
+		kaddr = kmap_atomic(su_bh->b_page);
+		su = nilfs_sufile_block_get_segment_usage(sufile, segnum,
+				su_bh, kaddr);
+		for (i = 0; i < n; ++i, ++segnum, su = (void *)su + susz) {
+			if (!nilfs_segment_usage_clean(su))
+				continue;
+
+			nilfs_get_segment_range(nilfs, segnum, &seg_start,
+						&seg_end);
+
+			if (!nblocks) {
+				/* start new extent */
+				start = seg_start;
+				nblocks = seg_end - seg_start + 1;
+				continue;
+			}
+
+			if (start + nblocks == seg_start) {
+				/* add to previous extent */
+				nblocks += seg_end - seg_start + 1;
+				continue;
+			}
+
+			/* discard previous extent */
+			if (start < start_block) {
+				nblocks -= start_block - start;
+				start = start_block;
+			}
+
+			if (nblocks >= minlen) {
+				kunmap_atomic(kaddr);
+
+				ret = blkdev_issue_discard(nilfs->ns_bdev,
+						start * sects_per_block,
+						nblocks * sects_per_block,
+						GFP_NOFS);
+				if (ret < 0) {
+					put_bh(su_bh);
+					goto out_sem;
+				}
+
+				ndiscarded += nblocks;
+				kaddr = kmap_atomic(su_bh->b_page);
+				su = nilfs_sufile_block_get_segment_usage(
+					sufile, segnum, su_bh, kaddr);
+			}
+
+			/* start new extent */
+			start = seg_start;
+			nblocks = seg_end - seg_start + 1;
+		}
+		kunmap_atomic(kaddr);
+		put_bh(su_bh);
+	}
+
+
+	if (nblocks) {
+		/* discard last extent */
+		if (start < start_block) {
+			nblocks -= start_block - start;
+			start = start_block;
+		}
+		if (start + nblocks > end_block + 1)
+			nblocks = end_block - start + 1;
+
+		if (nblocks >= minlen) {
+			ret = blkdev_issue_discard(nilfs->ns_bdev,
+					start * sects_per_block,
+					nblocks * sects_per_block,
+					GFP_NOFS);
+			if (!ret)
+				ndiscarded += nblocks;
+		}
+	}
+
+out_sem:
+	up_read(&NILFS_MDT(sufile)->mi_sem);
+
+	range->len = ndiscarded << nilfs->ns_blocksize_bits;
+	return ret;
+}
+
+/**
+ * nilfs_sufile_read - read or get sufile inode
+ * @sb: super block instance
+ * @susize: size of a segment usage entry
+ * @raw_inode: on-disk sufile inode
+ * @inodep: buffer to store the inode
+ */
+int nilfs_sufile_read(struct super_block *sb, size_t susize,
+		      struct nilfs_inode *raw_inode, struct inode **inodep)
+{
+	struct inode *sufile;
+	struct nilfs_sufile_info *sui;
+	struct buffer_head *header_bh;
+	struct nilfs_sufile_header *header;
+	void *kaddr;
+	int err;
+
+	if (susize > sb->s_blocksize) {
+		nilfs_err(sb, "too large segment usage size: %zu bytes",
+			  susize);
+		return -EINVAL;
+	} else if (susize < NILFS_MIN_SEGMENT_USAGE_SIZE) {
+		nilfs_err(sb, "too small segment usage size: %zu bytes",
+			  susize);
+		return -EINVAL;
+	}
+
+	sufile = nilfs_iget_locked(sb, NULL, NILFS_SUFILE_INO);
+	if (unlikely(!sufile))
+		return -ENOMEM;
+	if (!(sufile->i_state & I_NEW))
+		goto out;
+
+	err = nilfs_mdt_init(sufile, NILFS_MDT_GFP, sizeof(*sui));
+	if (err)
+		goto failed;
+
+	nilfs_mdt_set_entry_size(sufile, susize,
+				 sizeof(struct nilfs_sufile_header));
+
+	err = nilfs_read_inode_common(sufile, raw_inode);
+	if (err)
+		goto failed;
+
+	err = nilfs_sufile_get_header_block(sufile, &header_bh);
+	if (err)
+		goto failed;
+
+	sui = NILFS_SUI(sufile);
+	kaddr = kmap_atomic(header_bh->b_page);
+	header = kaddr + bh_offset(header_bh);
+	sui->ncleansegs = le64_to_cpu(header->sh_ncleansegs);
+	kunmap_atomic(kaddr);
+	brelse(header_bh);
+
+	sui->allocmax = nilfs_sufile_get_nsegments(sufile) - 1;
+	sui->allocmin = 0;
+
+	unlock_new_inode(sufile);
+ out:
+	*inodep = sufile;
+	return 0;
+ failed:
+	iget_failed(sufile);
+	return err;
+}
diff --git a/fs/nilfs2/sufile.h b/fs/nilfs2/sufile.h
new file mode 100644
index 0000000000..8e8a1a5a04
--- /dev/null
+++ b/fs/nilfs2/sufile.h
@@ -0,0 +1,132 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * NILFS segment usage file.
+ *
+ * Copyright (C) 2006-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Koji Sato.
+ */
+
+#ifndef _NILFS_SUFILE_H
+#define _NILFS_SUFILE_H
+
+#include <linux/fs.h>
+#include <linux/buffer_head.h>
+#include "mdt.h"
+
+
+static inline unsigned long nilfs_sufile_get_nsegments(struct inode *sufile)
+{
+	return ((struct the_nilfs *)sufile->i_sb->s_fs_info)->ns_nsegments;
+}
+
+unsigned long nilfs_sufile_get_ncleansegs(struct inode *sufile);
+
+int nilfs_sufile_set_alloc_range(struct inode *sufile, __u64 start, __u64 end);
+int nilfs_sufile_alloc(struct inode *, __u64 *);
+int nilfs_sufile_mark_dirty(struct inode *sufile, __u64 segnum);
+int nilfs_sufile_set_segment_usage(struct inode *sufile, __u64 segnum,
+				   unsigned long nblocks, time64_t modtime);
+int nilfs_sufile_get_stat(struct inode *, struct nilfs_sustat *);
+ssize_t nilfs_sufile_get_suinfo(struct inode *, __u64, void *, unsigned int,
+				size_t);
+ssize_t nilfs_sufile_set_suinfo(struct inode *, void *, unsigned int, size_t);
+
+int nilfs_sufile_updatev(struct inode *, __u64 *, size_t, int, size_t *,
+			 void (*dofunc)(struct inode *, __u64,
+					struct buffer_head *,
+					struct buffer_head *));
+int nilfs_sufile_update(struct inode *, __u64, int,
+			void (*dofunc)(struct inode *, __u64,
+				       struct buffer_head *,
+				       struct buffer_head *));
+void nilfs_sufile_do_scrap(struct inode *, __u64, struct buffer_head *,
+			   struct buffer_head *);
+void nilfs_sufile_do_free(struct inode *, __u64, struct buffer_head *,
+			  struct buffer_head *);
+void nilfs_sufile_do_cancel_free(struct inode *, __u64, struct buffer_head *,
+				 struct buffer_head *);
+void nilfs_sufile_do_set_error(struct inode *, __u64, struct buffer_head *,
+			       struct buffer_head *);
+
+int nilfs_sufile_resize(struct inode *sufile, __u64 newnsegs);
+int nilfs_sufile_read(struct super_block *sb, size_t susize,
+		      struct nilfs_inode *raw_inode, struct inode **inodep);
+int nilfs_sufile_trim_fs(struct inode *sufile, struct fstrim_range *range);
+
+/**
+ * nilfs_sufile_scrap - make a segment garbage
+ * @sufile: inode of segment usage file
+ * @segnum: segment number to be freed
+ */
+static inline int nilfs_sufile_scrap(struct inode *sufile, __u64 segnum)
+{
+	return nilfs_sufile_update(sufile, segnum, 1, nilfs_sufile_do_scrap);
+}
+
+/**
+ * nilfs_sufile_free - free segment
+ * @sufile: inode of segment usage file
+ * @segnum: segment number to be freed
+ */
+static inline int nilfs_sufile_free(struct inode *sufile, __u64 segnum)
+{
+	return nilfs_sufile_update(sufile, segnum, 0, nilfs_sufile_do_free);
+}
+
+/**
+ * nilfs_sufile_freev - free segments
+ * @sufile: inode of segment usage file
+ * @segnumv: array of segment numbers
+ * @nsegs: size of @segnumv array
+ * @ndone: place to store the number of freed segments
+ */
+static inline int nilfs_sufile_freev(struct inode *sufile, __u64 *segnumv,
+				     size_t nsegs, size_t *ndone)
+{
+	return nilfs_sufile_updatev(sufile, segnumv, nsegs, 0, ndone,
+				    nilfs_sufile_do_free);
+}
+
+/**
+ * nilfs_sufile_cancel_freev - reallocate freeing segments
+ * @sufile: inode of segment usage file
+ * @segnumv: array of segment numbers
+ * @nsegs: size of @segnumv array
+ * @ndone: place to store the number of cancelled segments
+ *
+ * Return Value: On success, 0 is returned. On error, a negative error codes
+ * is returned.
+ */
+static inline int nilfs_sufile_cancel_freev(struct inode *sufile,
+					    __u64 *segnumv, size_t nsegs,
+					    size_t *ndone)
+{
+	return nilfs_sufile_updatev(sufile, segnumv, nsegs, 0, ndone,
+				    nilfs_sufile_do_cancel_free);
+}
+
+/**
+ * nilfs_sufile_set_error - mark a segment as erroneous
+ * @sufile: inode of segment usage file
+ * @segnum: segment number
+ *
+ * Description: nilfs_sufile_set_error() marks the segment specified by
+ * @segnum as erroneous. The error segment will never be used again.
+ *
+ * Return Value: On success, 0 is returned. On error, one of the following
+ * negative error codes is returned.
+ *
+ * %-EIO - I/O error.
+ *
+ * %-ENOMEM - Insufficient amount of memory available.
+ *
+ * %-EINVAL - Invalid segment usage number.
+ */
+static inline int nilfs_sufile_set_error(struct inode *sufile, __u64 segnum)
+{
+	return nilfs_sufile_update(sufile, segnum, 0,
+				   nilfs_sufile_do_set_error);
+}
+
+#endif	/* _NILFS_SUFILE_H */
diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
new file mode 100644
index 0000000000..a5d1fa4e75
--- /dev/null
+++ b/fs/nilfs2/super.c
@@ -0,0 +1,1477 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * NILFS module and super block management.
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Ryusuke Konishi.
+ */
+/*
+ *  linux/fs/ext2/super.c
+ *
+ * Copyright (C) 1992, 1993, 1994, 1995
+ * Remy Card (card@masi.ibp.fr)
+ * Laboratoire MASI - Institut Blaise Pascal
+ * Universite Pierre et Marie Curie (Paris VI)
+ *
+ *  from
+ *
+ *  linux/fs/minix/inode.c
+ *
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ *
+ *  Big-endian to little-endian byte-swapping/bitmaps by
+ *        David S. Miller (davem@caip.rutgers.edu), 1995
+ */
+
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/blkdev.h>
+#include <linux/parser.h>
+#include <linux/crc32.h>
+#include <linux/vfs.h>
+#include <linux/writeback.h>
+#include <linux/seq_file.h>
+#include <linux/mount.h>
+#include <linux/fs_context.h>
+#include "nilfs.h"
+#include "export.h"
+#include "mdt.h"
+#include "alloc.h"
+#include "btree.h"
+#include "btnode.h"
+#include "page.h"
+#include "cpfile.h"
+#include "sufile.h" /* nilfs_sufile_resize(), nilfs_sufile_set_alloc_range() */
+#include "ifile.h"
+#include "dat.h"
+#include "segment.h"
+#include "segbuf.h"
+
+MODULE_AUTHOR("NTT Corp.");
+MODULE_DESCRIPTION("A New Implementation of the Log-structured Filesystem "
+		   "(NILFS)");
+MODULE_LICENSE("GPL");
+
+static struct kmem_cache *nilfs_inode_cachep;
+struct kmem_cache *nilfs_transaction_cachep;
+struct kmem_cache *nilfs_segbuf_cachep;
+struct kmem_cache *nilfs_btree_path_cache;
+
+static int nilfs_setup_super(struct super_block *sb, int is_mount);
+static int nilfs_remount(struct super_block *sb, int *flags, char *data);
+
+void __nilfs_msg(struct super_block *sb, const char *fmt, ...)
+{
+	struct va_format vaf;
+	va_list args;
+	int level;
+
+	va_start(args, fmt);
+
+	level = printk_get_level(fmt);
+	vaf.fmt = printk_skip_level(fmt);
+	vaf.va = &args;
+
+	if (sb)
+		printk("%c%cNILFS (%s): %pV\n",
+		       KERN_SOH_ASCII, level, sb->s_id, &vaf);
+	else
+		printk("%c%cNILFS: %pV\n",
+		       KERN_SOH_ASCII, level, &vaf);
+
+	va_end(args);
+}
+
+static void nilfs_set_error(struct super_block *sb)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct nilfs_super_block **sbp;
+
+	down_write(&nilfs->ns_sem);
+	if (!(nilfs->ns_mount_state & NILFS_ERROR_FS)) {
+		nilfs->ns_mount_state |= NILFS_ERROR_FS;
+		sbp = nilfs_prepare_super(sb, 0);
+		if (likely(sbp)) {
+			sbp[0]->s_state |= cpu_to_le16(NILFS_ERROR_FS);
+			if (sbp[1])
+				sbp[1]->s_state |= cpu_to_le16(NILFS_ERROR_FS);
+			nilfs_commit_super(sb, NILFS_SB_COMMIT_ALL);
+		}
+	}
+	up_write(&nilfs->ns_sem);
+}
+
+/**
+ * __nilfs_error() - report failure condition on a filesystem
+ *
+ * __nilfs_error() sets an ERROR_FS flag on the superblock as well as
+ * reporting an error message.  This function should be called when
+ * NILFS detects incoherences or defects of meta data on disk.
+ *
+ * This implements the body of nilfs_error() macro.  Normally,
+ * nilfs_error() should be used.  As for sustainable errors such as a
+ * single-shot I/O error, nilfs_err() should be used instead.
+ *
+ * Callers should not add a trailing newline since this will do it.
+ */
+void __nilfs_error(struct super_block *sb, const char *function,
+		   const char *fmt, ...)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct va_format vaf;
+	va_list args;
+
+	va_start(args, fmt);
+
+	vaf.fmt = fmt;
+	vaf.va = &args;
+
+	printk(KERN_CRIT "NILFS error (device %s): %s: %pV\n",
+	       sb->s_id, function, &vaf);
+
+	va_end(args);
+
+	if (!sb_rdonly(sb)) {
+		nilfs_set_error(sb);
+
+		if (nilfs_test_opt(nilfs, ERRORS_RO)) {
+			printk(KERN_CRIT "Remounting filesystem read-only\n");
+			sb->s_flags |= SB_RDONLY;
+		}
+	}
+
+	if (nilfs_test_opt(nilfs, ERRORS_PANIC))
+		panic("NILFS (device %s): panic forced after error\n",
+		      sb->s_id);
+}
+
+struct inode *nilfs_alloc_inode(struct super_block *sb)
+{
+	struct nilfs_inode_info *ii;
+
+	ii = alloc_inode_sb(sb, nilfs_inode_cachep, GFP_NOFS);
+	if (!ii)
+		return NULL;
+	ii->i_bh = NULL;
+	ii->i_state = 0;
+	ii->i_cno = 0;
+	ii->i_assoc_inode = NULL;
+	ii->i_bmap = &ii->i_bmap_data;
+	return &ii->vfs_inode;
+}
+
+static void nilfs_free_inode(struct inode *inode)
+{
+	if (nilfs_is_metadata_file_inode(inode))
+		nilfs_mdt_destroy(inode);
+
+	kmem_cache_free(nilfs_inode_cachep, NILFS_I(inode));
+}
+
+static int nilfs_sync_super(struct super_block *sb, int flag)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	int err;
+
+ retry:
+	set_buffer_dirty(nilfs->ns_sbh[0]);
+	if (nilfs_test_opt(nilfs, BARRIER)) {
+		err = __sync_dirty_buffer(nilfs->ns_sbh[0],
+					  REQ_SYNC | REQ_PREFLUSH | REQ_FUA);
+	} else {
+		err = sync_dirty_buffer(nilfs->ns_sbh[0]);
+	}
+
+	if (unlikely(err)) {
+		nilfs_err(sb, "unable to write superblock: err=%d", err);
+		if (err == -EIO && nilfs->ns_sbh[1]) {
+			/*
+			 * sbp[0] points to newer log than sbp[1],
+			 * so copy sbp[0] to sbp[1] to take over sbp[0].
+			 */
+			memcpy(nilfs->ns_sbp[1], nilfs->ns_sbp[0],
+			       nilfs->ns_sbsize);
+			nilfs_fall_back_super_block(nilfs);
+			goto retry;
+		}
+	} else {
+		struct nilfs_super_block *sbp = nilfs->ns_sbp[0];
+
+		nilfs->ns_sbwcount++;
+
+		/*
+		 * The latest segment becomes trailable from the position
+		 * written in superblock.
+		 */
+		clear_nilfs_discontinued(nilfs);
+
+		/* update GC protection for recent segments */
+		if (nilfs->ns_sbh[1]) {
+			if (flag == NILFS_SB_COMMIT_ALL) {
+				set_buffer_dirty(nilfs->ns_sbh[1]);
+				if (sync_dirty_buffer(nilfs->ns_sbh[1]) < 0)
+					goto out;
+			}
+			if (le64_to_cpu(nilfs->ns_sbp[1]->s_last_cno) <
+			    le64_to_cpu(nilfs->ns_sbp[0]->s_last_cno))
+				sbp = nilfs->ns_sbp[1];
+		}
+
+		spin_lock(&nilfs->ns_last_segment_lock);
+		nilfs->ns_prot_seq = le64_to_cpu(sbp->s_last_seq);
+		spin_unlock(&nilfs->ns_last_segment_lock);
+	}
+ out:
+	return err;
+}
+
+void nilfs_set_log_cursor(struct nilfs_super_block *sbp,
+			  struct the_nilfs *nilfs)
+{
+	sector_t nfreeblocks;
+
+	/* nilfs->ns_sem must be locked by the caller. */
+	nilfs_count_free_blocks(nilfs, &nfreeblocks);
+	sbp->s_free_blocks_count = cpu_to_le64(nfreeblocks);
+
+	spin_lock(&nilfs->ns_last_segment_lock);
+	sbp->s_last_seq = cpu_to_le64(nilfs->ns_last_seq);
+	sbp->s_last_pseg = cpu_to_le64(nilfs->ns_last_pseg);
+	sbp->s_last_cno = cpu_to_le64(nilfs->ns_last_cno);
+	spin_unlock(&nilfs->ns_last_segment_lock);
+}
+
+struct nilfs_super_block **nilfs_prepare_super(struct super_block *sb,
+					       int flip)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct nilfs_super_block **sbp = nilfs->ns_sbp;
+
+	/* nilfs->ns_sem must be locked by the caller. */
+	if (sbp[0]->s_magic != cpu_to_le16(NILFS_SUPER_MAGIC)) {
+		if (sbp[1] &&
+		    sbp[1]->s_magic == cpu_to_le16(NILFS_SUPER_MAGIC)) {
+			memcpy(sbp[0], sbp[1], nilfs->ns_sbsize);
+		} else {
+			nilfs_crit(sb, "superblock broke");
+			return NULL;
+		}
+	} else if (sbp[1] &&
+		   sbp[1]->s_magic != cpu_to_le16(NILFS_SUPER_MAGIC)) {
+		memcpy(sbp[1], sbp[0], nilfs->ns_sbsize);
+	}
+
+	if (flip && sbp[1])
+		nilfs_swap_super_block(nilfs);
+
+	return sbp;
+}
+
+int nilfs_commit_super(struct super_block *sb, int flag)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct nilfs_super_block **sbp = nilfs->ns_sbp;
+	time64_t t;
+
+	/* nilfs->ns_sem must be locked by the caller. */
+	t = ktime_get_real_seconds();
+	nilfs->ns_sbwtime = t;
+	sbp[0]->s_wtime = cpu_to_le64(t);
+	sbp[0]->s_sum = 0;
+	sbp[0]->s_sum = cpu_to_le32(crc32_le(nilfs->ns_crc_seed,
+					     (unsigned char *)sbp[0],
+					     nilfs->ns_sbsize));
+	if (flag == NILFS_SB_COMMIT_ALL && sbp[1]) {
+		sbp[1]->s_wtime = sbp[0]->s_wtime;
+		sbp[1]->s_sum = 0;
+		sbp[1]->s_sum = cpu_to_le32(crc32_le(nilfs->ns_crc_seed,
+					    (unsigned char *)sbp[1],
+					    nilfs->ns_sbsize));
+	}
+	clear_nilfs_sb_dirty(nilfs);
+	nilfs->ns_flushed_device = 1;
+	/* make sure store to ns_flushed_device cannot be reordered */
+	smp_wmb();
+	return nilfs_sync_super(sb, flag);
+}
+
+/**
+ * nilfs_cleanup_super() - write filesystem state for cleanup
+ * @sb: super block instance to be unmounted or degraded to read-only
+ *
+ * This function restores state flags in the on-disk super block.
+ * This will set "clean" flag (i.e. NILFS_VALID_FS) unless the
+ * filesystem was not clean previously.
+ */
+int nilfs_cleanup_super(struct super_block *sb)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct nilfs_super_block **sbp;
+	int flag = NILFS_SB_COMMIT;
+	int ret = -EIO;
+
+	sbp = nilfs_prepare_super(sb, 0);
+	if (sbp) {
+		sbp[0]->s_state = cpu_to_le16(nilfs->ns_mount_state);
+		nilfs_set_log_cursor(sbp[0], nilfs);
+		if (sbp[1] && sbp[0]->s_last_cno == sbp[1]->s_last_cno) {
+			/*
+			 * make the "clean" flag also to the opposite
+			 * super block if both super blocks point to
+			 * the same checkpoint.
+			 */
+			sbp[1]->s_state = sbp[0]->s_state;
+			flag = NILFS_SB_COMMIT_ALL;
+		}
+		ret = nilfs_commit_super(sb, flag);
+	}
+	return ret;
+}
+
+/**
+ * nilfs_move_2nd_super - relocate secondary super block
+ * @sb: super block instance
+ * @sb2off: new offset of the secondary super block (in bytes)
+ */
+static int nilfs_move_2nd_super(struct super_block *sb, loff_t sb2off)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct buffer_head *nsbh;
+	struct nilfs_super_block *nsbp;
+	sector_t blocknr, newblocknr;
+	unsigned long offset;
+	int sb2i;  /* array index of the secondary superblock */
+	int ret = 0;
+
+	/* nilfs->ns_sem must be locked by the caller. */
+	if (nilfs->ns_sbh[1] &&
+	    nilfs->ns_sbh[1]->b_blocknr > nilfs->ns_first_data_block) {
+		sb2i = 1;
+		blocknr = nilfs->ns_sbh[1]->b_blocknr;
+	} else if (nilfs->ns_sbh[0]->b_blocknr > nilfs->ns_first_data_block) {
+		sb2i = 0;
+		blocknr = nilfs->ns_sbh[0]->b_blocknr;
+	} else {
+		sb2i = -1;
+		blocknr = 0;
+	}
+	if (sb2i >= 0 && (u64)blocknr << nilfs->ns_blocksize_bits == sb2off)
+		goto out;  /* super block location is unchanged */
+
+	/* Get new super block buffer */
+	newblocknr = sb2off >> nilfs->ns_blocksize_bits;
+	offset = sb2off & (nilfs->ns_blocksize - 1);
+	nsbh = sb_getblk(sb, newblocknr);
+	if (!nsbh) {
+		nilfs_warn(sb,
+			   "unable to move secondary superblock to block %llu",
+			   (unsigned long long)newblocknr);
+		ret = -EIO;
+		goto out;
+	}
+	nsbp = (void *)nsbh->b_data + offset;
+
+	lock_buffer(nsbh);
+	if (sb2i >= 0) {
+		/*
+		 * The position of the second superblock only changes by 4KiB,
+		 * which is larger than the maximum superblock data size
+		 * (= 1KiB), so there is no need to use memmove() to allow
+		 * overlap between source and destination.
+		 */
+		memcpy(nsbp, nilfs->ns_sbp[sb2i], nilfs->ns_sbsize);
+
+		/*
+		 * Zero fill after copy to avoid overwriting in case of move
+		 * within the same block.
+		 */
+		memset(nsbh->b_data, 0, offset);
+		memset((void *)nsbp + nilfs->ns_sbsize, 0,
+		       nsbh->b_size - offset - nilfs->ns_sbsize);
+	} else {
+		memset(nsbh->b_data, 0, nsbh->b_size);
+	}
+	set_buffer_uptodate(nsbh);
+	unlock_buffer(nsbh);
+
+	if (sb2i >= 0) {
+		brelse(nilfs->ns_sbh[sb2i]);
+		nilfs->ns_sbh[sb2i] = nsbh;
+		nilfs->ns_sbp[sb2i] = nsbp;
+	} else if (nilfs->ns_sbh[0]->b_blocknr < nilfs->ns_first_data_block) {
+		/* secondary super block will be restored to index 1 */
+		nilfs->ns_sbh[1] = nsbh;
+		nilfs->ns_sbp[1] = nsbp;
+	} else {
+		brelse(nsbh);
+	}
+out:
+	return ret;
+}
+
+/**
+ * nilfs_resize_fs - resize the filesystem
+ * @sb: super block instance
+ * @newsize: new size of the filesystem (in bytes)
+ */
+int nilfs_resize_fs(struct super_block *sb, __u64 newsize)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct nilfs_super_block **sbp;
+	__u64 devsize, newnsegs;
+	loff_t sb2off;
+	int ret;
+
+	ret = -ERANGE;
+	devsize = bdev_nr_bytes(sb->s_bdev);
+	if (newsize > devsize)
+		goto out;
+
+	/*
+	 * Prevent underflow in second superblock position calculation.
+	 * The exact minimum size check is done in nilfs_sufile_resize().
+	 */
+	if (newsize < 4096) {
+		ret = -ENOSPC;
+		goto out;
+	}
+
+	/*
+	 * Write lock is required to protect some functions depending
+	 * on the number of segments, the number of reserved segments,
+	 * and so forth.
+	 */
+	down_write(&nilfs->ns_segctor_sem);
+
+	sb2off = NILFS_SB2_OFFSET_BYTES(newsize);
+	newnsegs = sb2off >> nilfs->ns_blocksize_bits;
+	do_div(newnsegs, nilfs->ns_blocks_per_segment);
+
+	ret = nilfs_sufile_resize(nilfs->ns_sufile, newnsegs);
+	up_write(&nilfs->ns_segctor_sem);
+	if (ret < 0)
+		goto out;
+
+	ret = nilfs_construct_segment(sb);
+	if (ret < 0)
+		goto out;
+
+	down_write(&nilfs->ns_sem);
+	nilfs_move_2nd_super(sb, sb2off);
+	ret = -EIO;
+	sbp = nilfs_prepare_super(sb, 0);
+	if (likely(sbp)) {
+		nilfs_set_log_cursor(sbp[0], nilfs);
+		/*
+		 * Drop NILFS_RESIZE_FS flag for compatibility with
+		 * mount-time resize which may be implemented in a
+		 * future release.
+		 */
+		sbp[0]->s_state = cpu_to_le16(le16_to_cpu(sbp[0]->s_state) &
+					      ~NILFS_RESIZE_FS);
+		sbp[0]->s_dev_size = cpu_to_le64(newsize);
+		sbp[0]->s_nsegments = cpu_to_le64(nilfs->ns_nsegments);
+		if (sbp[1])
+			memcpy(sbp[1], sbp[0], nilfs->ns_sbsize);
+		ret = nilfs_commit_super(sb, NILFS_SB_COMMIT_ALL);
+	}
+	up_write(&nilfs->ns_sem);
+
+	/*
+	 * Reset the range of allocatable segments last.  This order
+	 * is important in the case of expansion because the secondary
+	 * superblock must be protected from log write until migration
+	 * completes.
+	 */
+	if (!ret)
+		nilfs_sufile_set_alloc_range(nilfs->ns_sufile, 0, newnsegs - 1);
+out:
+	return ret;
+}
+
+static void nilfs_put_super(struct super_block *sb)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+
+	nilfs_detach_log_writer(sb);
+
+	if (!sb_rdonly(sb)) {
+		down_write(&nilfs->ns_sem);
+		nilfs_cleanup_super(sb);
+		up_write(&nilfs->ns_sem);
+	}
+
+	nilfs_sysfs_delete_device_group(nilfs);
+	iput(nilfs->ns_sufile);
+	iput(nilfs->ns_cpfile);
+	iput(nilfs->ns_dat);
+
+	destroy_nilfs(nilfs);
+	sb->s_fs_info = NULL;
+}
+
+static int nilfs_sync_fs(struct super_block *sb, int wait)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct nilfs_super_block **sbp;
+	int err = 0;
+
+	/* This function is called when super block should be written back */
+	if (wait)
+		err = nilfs_construct_segment(sb);
+
+	down_write(&nilfs->ns_sem);
+	if (nilfs_sb_dirty(nilfs)) {
+		sbp = nilfs_prepare_super(sb, nilfs_sb_will_flip(nilfs));
+		if (likely(sbp)) {
+			nilfs_set_log_cursor(sbp[0], nilfs);
+			nilfs_commit_super(sb, NILFS_SB_COMMIT);
+		}
+	}
+	up_write(&nilfs->ns_sem);
+
+	if (!err)
+		err = nilfs_flush_device(nilfs);
+
+	return err;
+}
+
+int nilfs_attach_checkpoint(struct super_block *sb, __u64 cno, int curr_mnt,
+			    struct nilfs_root **rootp)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct nilfs_root *root;
+	struct nilfs_checkpoint *raw_cp;
+	struct buffer_head *bh_cp;
+	int err = -ENOMEM;
+
+	root = nilfs_find_or_create_root(
+		nilfs, curr_mnt ? NILFS_CPTREE_CURRENT_CNO : cno);
+	if (!root)
+		return err;
+
+	if (root->ifile)
+		goto reuse; /* already attached checkpoint */
+
+	down_read(&nilfs->ns_segctor_sem);
+	err = nilfs_cpfile_get_checkpoint(nilfs->ns_cpfile, cno, 0, &raw_cp,
+					  &bh_cp);
+	up_read(&nilfs->ns_segctor_sem);
+	if (unlikely(err)) {
+		if (err == -ENOENT || err == -EINVAL) {
+			nilfs_err(sb,
+				  "Invalid checkpoint (checkpoint number=%llu)",
+				  (unsigned long long)cno);
+			err = -EINVAL;
+		}
+		goto failed;
+	}
+
+	err = nilfs_ifile_read(sb, root, nilfs->ns_inode_size,
+			       &raw_cp->cp_ifile_inode, &root->ifile);
+	if (err)
+		goto failed_bh;
+
+	atomic64_set(&root->inodes_count,
+			le64_to_cpu(raw_cp->cp_inodes_count));
+	atomic64_set(&root->blocks_count,
+			le64_to_cpu(raw_cp->cp_blocks_count));
+
+	nilfs_cpfile_put_checkpoint(nilfs->ns_cpfile, cno, bh_cp);
+
+ reuse:
+	*rootp = root;
+	return 0;
+
+ failed_bh:
+	nilfs_cpfile_put_checkpoint(nilfs->ns_cpfile, cno, bh_cp);
+ failed:
+	nilfs_put_root(root);
+
+	return err;
+}
+
+static int nilfs_freeze(struct super_block *sb)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	int err;
+
+	if (sb_rdonly(sb))
+		return 0;
+
+	/* Mark super block clean */
+	down_write(&nilfs->ns_sem);
+	err = nilfs_cleanup_super(sb);
+	up_write(&nilfs->ns_sem);
+	return err;
+}
+
+static int nilfs_unfreeze(struct super_block *sb)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+
+	if (sb_rdonly(sb))
+		return 0;
+
+	down_write(&nilfs->ns_sem);
+	nilfs_setup_super(sb, false);
+	up_write(&nilfs->ns_sem);
+	return 0;
+}
+
+static int nilfs_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+	struct super_block *sb = dentry->d_sb;
+	struct nilfs_root *root = NILFS_I(d_inode(dentry))->i_root;
+	struct the_nilfs *nilfs = root->nilfs;
+	u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
+	unsigned long long blocks;
+	unsigned long overhead;
+	unsigned long nrsvblocks;
+	sector_t nfreeblocks;
+	u64 nmaxinodes, nfreeinodes;
+	int err;
+
+	/*
+	 * Compute all of the segment blocks
+	 *
+	 * The blocks before first segment and after last segment
+	 * are excluded.
+	 */
+	blocks = nilfs->ns_blocks_per_segment * nilfs->ns_nsegments
+		- nilfs->ns_first_data_block;
+	nrsvblocks = nilfs->ns_nrsvsegs * nilfs->ns_blocks_per_segment;
+
+	/*
+	 * Compute the overhead
+	 *
+	 * When distributing meta data blocks outside segment structure,
+	 * We must count them as the overhead.
+	 */
+	overhead = 0;
+
+	err = nilfs_count_free_blocks(nilfs, &nfreeblocks);
+	if (unlikely(err))
+		return err;
+
+	err = nilfs_ifile_count_free_inodes(root->ifile,
+					    &nmaxinodes, &nfreeinodes);
+	if (unlikely(err)) {
+		nilfs_warn(sb, "failed to count free inodes: err=%d", err);
+		if (err == -ERANGE) {
+			/*
+			 * If nilfs_palloc_count_max_entries() returns
+			 * -ERANGE error code then we simply treat
+			 * curent inodes count as maximum possible and
+			 * zero as free inodes value.
+			 */
+			nmaxinodes = atomic64_read(&root->inodes_count);
+			nfreeinodes = 0;
+			err = 0;
+		} else
+			return err;
+	}
+
+	buf->f_type = NILFS_SUPER_MAGIC;
+	buf->f_bsize = sb->s_blocksize;
+	buf->f_blocks = blocks - overhead;
+	buf->f_bfree = nfreeblocks;
+	buf->f_bavail = (buf->f_bfree >= nrsvblocks) ?
+		(buf->f_bfree - nrsvblocks) : 0;
+	buf->f_files = nmaxinodes;
+	buf->f_ffree = nfreeinodes;
+	buf->f_namelen = NILFS_NAME_LEN;
+	buf->f_fsid = u64_to_fsid(id);
+
+	return 0;
+}
+
+static int nilfs_show_options(struct seq_file *seq, struct dentry *dentry)
+{
+	struct super_block *sb = dentry->d_sb;
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct nilfs_root *root = NILFS_I(d_inode(dentry))->i_root;
+
+	if (!nilfs_test_opt(nilfs, BARRIER))
+		seq_puts(seq, ",nobarrier");
+	if (root->cno != NILFS_CPTREE_CURRENT_CNO)
+		seq_printf(seq, ",cp=%llu", (unsigned long long)root->cno);
+	if (nilfs_test_opt(nilfs, ERRORS_PANIC))
+		seq_puts(seq, ",errors=panic");
+	if (nilfs_test_opt(nilfs, ERRORS_CONT))
+		seq_puts(seq, ",errors=continue");
+	if (nilfs_test_opt(nilfs, STRICT_ORDER))
+		seq_puts(seq, ",order=strict");
+	if (nilfs_test_opt(nilfs, NORECOVERY))
+		seq_puts(seq, ",norecovery");
+	if (nilfs_test_opt(nilfs, DISCARD))
+		seq_puts(seq, ",discard");
+
+	return 0;
+}
+
+static const struct super_operations nilfs_sops = {
+	.alloc_inode    = nilfs_alloc_inode,
+	.free_inode     = nilfs_free_inode,
+	.dirty_inode    = nilfs_dirty_inode,
+	.evict_inode    = nilfs_evict_inode,
+	.put_super      = nilfs_put_super,
+	.sync_fs        = nilfs_sync_fs,
+	.freeze_fs	= nilfs_freeze,
+	.unfreeze_fs	= nilfs_unfreeze,
+	.statfs         = nilfs_statfs,
+	.remount_fs     = nilfs_remount,
+	.show_options = nilfs_show_options
+};
+
+enum {
+	Opt_err_cont, Opt_err_panic, Opt_err_ro,
+	Opt_barrier, Opt_nobarrier, Opt_snapshot, Opt_order, Opt_norecovery,
+	Opt_discard, Opt_nodiscard, Opt_err,
+};
+
+static match_table_t tokens = {
+	{Opt_err_cont, "errors=continue"},
+	{Opt_err_panic, "errors=panic"},
+	{Opt_err_ro, "errors=remount-ro"},
+	{Opt_barrier, "barrier"},
+	{Opt_nobarrier, "nobarrier"},
+	{Opt_snapshot, "cp=%u"},
+	{Opt_order, "order=%s"},
+	{Opt_norecovery, "norecovery"},
+	{Opt_discard, "discard"},
+	{Opt_nodiscard, "nodiscard"},
+	{Opt_err, NULL}
+};
+
+static int parse_options(char *options, struct super_block *sb, int is_remount)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	char *p;
+	substring_t args[MAX_OPT_ARGS];
+
+	if (!options)
+		return 1;
+
+	while ((p = strsep(&options, ",")) != NULL) {
+		int token;
+
+		if (!*p)
+			continue;
+
+		token = match_token(p, tokens, args);
+		switch (token) {
+		case Opt_barrier:
+			nilfs_set_opt(nilfs, BARRIER);
+			break;
+		case Opt_nobarrier:
+			nilfs_clear_opt(nilfs, BARRIER);
+			break;
+		case Opt_order:
+			if (strcmp(args[0].from, "relaxed") == 0)
+				/* Ordered data semantics */
+				nilfs_clear_opt(nilfs, STRICT_ORDER);
+			else if (strcmp(args[0].from, "strict") == 0)
+				/* Strict in-order semantics */
+				nilfs_set_opt(nilfs, STRICT_ORDER);
+			else
+				return 0;
+			break;
+		case Opt_err_panic:
+			nilfs_write_opt(nilfs, ERROR_MODE, ERRORS_PANIC);
+			break;
+		case Opt_err_ro:
+			nilfs_write_opt(nilfs, ERROR_MODE, ERRORS_RO);
+			break;
+		case Opt_err_cont:
+			nilfs_write_opt(nilfs, ERROR_MODE, ERRORS_CONT);
+			break;
+		case Opt_snapshot:
+			if (is_remount) {
+				nilfs_err(sb,
+					  "\"%s\" option is invalid for remount",
+					  p);
+				return 0;
+			}
+			break;
+		case Opt_norecovery:
+			nilfs_set_opt(nilfs, NORECOVERY);
+			break;
+		case Opt_discard:
+			nilfs_set_opt(nilfs, DISCARD);
+			break;
+		case Opt_nodiscard:
+			nilfs_clear_opt(nilfs, DISCARD);
+			break;
+		default:
+			nilfs_err(sb, "unrecognized mount option \"%s\"", p);
+			return 0;
+		}
+	}
+	return 1;
+}
+
+static inline void
+nilfs_set_default_options(struct super_block *sb,
+			  struct nilfs_super_block *sbp)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+
+	nilfs->ns_mount_opt =
+		NILFS_MOUNT_ERRORS_RO | NILFS_MOUNT_BARRIER;
+}
+
+static int nilfs_setup_super(struct super_block *sb, int is_mount)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct nilfs_super_block **sbp;
+	int max_mnt_count;
+	int mnt_count;
+
+	/* nilfs->ns_sem must be locked by the caller. */
+	sbp = nilfs_prepare_super(sb, 0);
+	if (!sbp)
+		return -EIO;
+
+	if (!is_mount)
+		goto skip_mount_setup;
+
+	max_mnt_count = le16_to_cpu(sbp[0]->s_max_mnt_count);
+	mnt_count = le16_to_cpu(sbp[0]->s_mnt_count);
+
+	if (nilfs->ns_mount_state & NILFS_ERROR_FS) {
+		nilfs_warn(sb, "mounting fs with errors");
+#if 0
+	} else if (max_mnt_count >= 0 && mnt_count >= max_mnt_count) {
+		nilfs_warn(sb, "maximal mount count reached");
+#endif
+	}
+	if (!max_mnt_count)
+		sbp[0]->s_max_mnt_count = cpu_to_le16(NILFS_DFL_MAX_MNT_COUNT);
+
+	sbp[0]->s_mnt_count = cpu_to_le16(mnt_count + 1);
+	sbp[0]->s_mtime = cpu_to_le64(ktime_get_real_seconds());
+
+skip_mount_setup:
+	sbp[0]->s_state =
+		cpu_to_le16(le16_to_cpu(sbp[0]->s_state) & ~NILFS_VALID_FS);
+	/* synchronize sbp[1] with sbp[0] */
+	if (sbp[1])
+		memcpy(sbp[1], sbp[0], nilfs->ns_sbsize);
+	return nilfs_commit_super(sb, NILFS_SB_COMMIT_ALL);
+}
+
+struct nilfs_super_block *nilfs_read_super_block(struct super_block *sb,
+						 u64 pos, int blocksize,
+						 struct buffer_head **pbh)
+{
+	unsigned long long sb_index = pos;
+	unsigned long offset;
+
+	offset = do_div(sb_index, blocksize);
+	*pbh = sb_bread(sb, sb_index);
+	if (!*pbh)
+		return NULL;
+	return (struct nilfs_super_block *)((char *)(*pbh)->b_data + offset);
+}
+
+int nilfs_store_magic_and_option(struct super_block *sb,
+				 struct nilfs_super_block *sbp,
+				 char *data)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+
+	sb->s_magic = le16_to_cpu(sbp->s_magic);
+
+	/* FS independent flags */
+#ifdef NILFS_ATIME_DISABLE
+	sb->s_flags |= SB_NOATIME;
+#endif
+
+	nilfs_set_default_options(sb, sbp);
+
+	nilfs->ns_resuid = le16_to_cpu(sbp->s_def_resuid);
+	nilfs->ns_resgid = le16_to_cpu(sbp->s_def_resgid);
+	nilfs->ns_interval = le32_to_cpu(sbp->s_c_interval);
+	nilfs->ns_watermark = le32_to_cpu(sbp->s_c_block_max);
+
+	return !parse_options(data, sb, 0) ? -EINVAL : 0;
+}
+
+int nilfs_check_feature_compatibility(struct super_block *sb,
+				      struct nilfs_super_block *sbp)
+{
+	__u64 features;
+
+	features = le64_to_cpu(sbp->s_feature_incompat) &
+		~NILFS_FEATURE_INCOMPAT_SUPP;
+	if (features) {
+		nilfs_err(sb,
+			  "couldn't mount because of unsupported optional features (%llx)",
+			  (unsigned long long)features);
+		return -EINVAL;
+	}
+	features = le64_to_cpu(sbp->s_feature_compat_ro) &
+		~NILFS_FEATURE_COMPAT_RO_SUPP;
+	if (!sb_rdonly(sb) && features) {
+		nilfs_err(sb,
+			  "couldn't mount RDWR because of unsupported optional features (%llx)",
+			  (unsigned long long)features);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int nilfs_get_root_dentry(struct super_block *sb,
+				 struct nilfs_root *root,
+				 struct dentry **root_dentry)
+{
+	struct inode *inode;
+	struct dentry *dentry;
+	int ret = 0;
+
+	inode = nilfs_iget(sb, root, NILFS_ROOT_INO);
+	if (IS_ERR(inode)) {
+		ret = PTR_ERR(inode);
+		nilfs_err(sb, "error %d getting root inode", ret);
+		goto out;
+	}
+	if (!S_ISDIR(inode->i_mode) || !inode->i_blocks || !inode->i_size) {
+		iput(inode);
+		nilfs_err(sb, "corrupt root inode");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (root->cno == NILFS_CPTREE_CURRENT_CNO) {
+		dentry = d_find_alias(inode);
+		if (!dentry) {
+			dentry = d_make_root(inode);
+			if (!dentry) {
+				ret = -ENOMEM;
+				goto failed_dentry;
+			}
+		} else {
+			iput(inode);
+		}
+	} else {
+		dentry = d_obtain_root(inode);
+		if (IS_ERR(dentry)) {
+			ret = PTR_ERR(dentry);
+			goto failed_dentry;
+		}
+	}
+	*root_dentry = dentry;
+ out:
+	return ret;
+
+ failed_dentry:
+	nilfs_err(sb, "error %d getting root dentry", ret);
+	goto out;
+}
+
+static int nilfs_attach_snapshot(struct super_block *s, __u64 cno,
+				 struct dentry **root_dentry)
+{
+	struct the_nilfs *nilfs = s->s_fs_info;
+	struct nilfs_root *root;
+	int ret;
+
+	mutex_lock(&nilfs->ns_snapshot_mount_mutex);
+
+	down_read(&nilfs->ns_segctor_sem);
+	ret = nilfs_cpfile_is_snapshot(nilfs->ns_cpfile, cno);
+	up_read(&nilfs->ns_segctor_sem);
+	if (ret < 0) {
+		ret = (ret == -ENOENT) ? -EINVAL : ret;
+		goto out;
+	} else if (!ret) {
+		nilfs_err(s,
+			  "The specified checkpoint is not a snapshot (checkpoint number=%llu)",
+			  (unsigned long long)cno);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	ret = nilfs_attach_checkpoint(s, cno, false, &root);
+	if (ret) {
+		nilfs_err(s,
+			  "error %d while loading snapshot (checkpoint number=%llu)",
+			  ret, (unsigned long long)cno);
+		goto out;
+	}
+	ret = nilfs_get_root_dentry(s, root, root_dentry);
+	nilfs_put_root(root);
+ out:
+	mutex_unlock(&nilfs->ns_snapshot_mount_mutex);
+	return ret;
+}
+
+/**
+ * nilfs_tree_is_busy() - try to shrink dentries of a checkpoint
+ * @root_dentry: root dentry of the tree to be shrunk
+ *
+ * This function returns true if the tree was in-use.
+ */
+static bool nilfs_tree_is_busy(struct dentry *root_dentry)
+{
+	shrink_dcache_parent(root_dentry);
+	return d_count(root_dentry) > 1;
+}
+
+int nilfs_checkpoint_is_mounted(struct super_block *sb, __u64 cno)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	struct nilfs_root *root;
+	struct inode *inode;
+	struct dentry *dentry;
+	int ret;
+
+	if (cno > nilfs->ns_cno)
+		return false;
+
+	if (cno >= nilfs_last_cno(nilfs))
+		return true;	/* protect recent checkpoints */
+
+	ret = false;
+	root = nilfs_lookup_root(nilfs, cno);
+	if (root) {
+		inode = nilfs_ilookup(sb, root, NILFS_ROOT_INO);
+		if (inode) {
+			dentry = d_find_alias(inode);
+			if (dentry) {
+				ret = nilfs_tree_is_busy(dentry);
+				dput(dentry);
+			}
+			iput(inode);
+		}
+		nilfs_put_root(root);
+	}
+	return ret;
+}
+
+/**
+ * nilfs_fill_super() - initialize a super block instance
+ * @sb: super_block
+ * @data: mount options
+ * @silent: silent mode flag
+ *
+ * This function is called exclusively by nilfs->ns_mount_mutex.
+ * So, the recovery process is protected from other simultaneous mounts.
+ */
+static int
+nilfs_fill_super(struct super_block *sb, void *data, int silent)
+{
+	struct the_nilfs *nilfs;
+	struct nilfs_root *fsroot;
+	__u64 cno;
+	int err;
+
+	nilfs = alloc_nilfs(sb);
+	if (!nilfs)
+		return -ENOMEM;
+
+	sb->s_fs_info = nilfs;
+
+	err = init_nilfs(nilfs, sb, (char *)data);
+	if (err)
+		goto failed_nilfs;
+
+	sb->s_op = &nilfs_sops;
+	sb->s_export_op = &nilfs_export_ops;
+	sb->s_root = NULL;
+	sb->s_time_gran = 1;
+	sb->s_max_links = NILFS_LINK_MAX;
+
+	sb->s_bdi = bdi_get(sb->s_bdev->bd_disk->bdi);
+
+	err = load_nilfs(nilfs, sb);
+	if (err)
+		goto failed_nilfs;
+
+	cno = nilfs_last_cno(nilfs);
+	err = nilfs_attach_checkpoint(sb, cno, true, &fsroot);
+	if (err) {
+		nilfs_err(sb,
+			  "error %d while loading last checkpoint (checkpoint number=%llu)",
+			  err, (unsigned long long)cno);
+		goto failed_unload;
+	}
+
+	if (!sb_rdonly(sb)) {
+		err = nilfs_attach_log_writer(sb, fsroot);
+		if (err)
+			goto failed_checkpoint;
+	}
+
+	err = nilfs_get_root_dentry(sb, fsroot, &sb->s_root);
+	if (err)
+		goto failed_segctor;
+
+	nilfs_put_root(fsroot);
+
+	if (!sb_rdonly(sb)) {
+		down_write(&nilfs->ns_sem);
+		nilfs_setup_super(sb, true);
+		up_write(&nilfs->ns_sem);
+	}
+
+	return 0;
+
+ failed_segctor:
+	nilfs_detach_log_writer(sb);
+
+ failed_checkpoint:
+	nilfs_put_root(fsroot);
+
+ failed_unload:
+	nilfs_sysfs_delete_device_group(nilfs);
+	iput(nilfs->ns_sufile);
+	iput(nilfs->ns_cpfile);
+	iput(nilfs->ns_dat);
+
+ failed_nilfs:
+	destroy_nilfs(nilfs);
+	return err;
+}
+
+static int nilfs_remount(struct super_block *sb, int *flags, char *data)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	unsigned long old_sb_flags;
+	unsigned long old_mount_opt;
+	int err;
+
+	sync_filesystem(sb);
+	old_sb_flags = sb->s_flags;
+	old_mount_opt = nilfs->ns_mount_opt;
+
+	if (!parse_options(data, sb, 1)) {
+		err = -EINVAL;
+		goto restore_opts;
+	}
+	sb->s_flags = (sb->s_flags & ~SB_POSIXACL);
+
+	err = -EINVAL;
+
+	if (!nilfs_valid_fs(nilfs)) {
+		nilfs_warn(sb,
+			   "couldn't remount because the filesystem is in an incomplete recovery state");
+		goto restore_opts;
+	}
+
+	if ((bool)(*flags & SB_RDONLY) == sb_rdonly(sb))
+		goto out;
+	if (*flags & SB_RDONLY) {
+		sb->s_flags |= SB_RDONLY;
+
+		/*
+		 * Remounting a valid RW partition RDONLY, so set
+		 * the RDONLY flag and then mark the partition as valid again.
+		 */
+		down_write(&nilfs->ns_sem);
+		nilfs_cleanup_super(sb);
+		up_write(&nilfs->ns_sem);
+	} else {
+		__u64 features;
+		struct nilfs_root *root;
+
+		/*
+		 * Mounting a RDONLY partition read-write, so reread and
+		 * store the current valid flag.  (It may have been changed
+		 * by fsck since we originally mounted the partition.)
+		 */
+		down_read(&nilfs->ns_sem);
+		features = le64_to_cpu(nilfs->ns_sbp[0]->s_feature_compat_ro) &
+			~NILFS_FEATURE_COMPAT_RO_SUPP;
+		up_read(&nilfs->ns_sem);
+		if (features) {
+			nilfs_warn(sb,
+				   "couldn't remount RDWR because of unsupported optional features (%llx)",
+				   (unsigned long long)features);
+			err = -EROFS;
+			goto restore_opts;
+		}
+
+		sb->s_flags &= ~SB_RDONLY;
+
+		root = NILFS_I(d_inode(sb->s_root))->i_root;
+		err = nilfs_attach_log_writer(sb, root);
+		if (err)
+			goto restore_opts;
+
+		down_write(&nilfs->ns_sem);
+		nilfs_setup_super(sb, true);
+		up_write(&nilfs->ns_sem);
+	}
+ out:
+	return 0;
+
+ restore_opts:
+	sb->s_flags = old_sb_flags;
+	nilfs->ns_mount_opt = old_mount_opt;
+	return err;
+}
+
+struct nilfs_super_data {
+	__u64 cno;
+	int flags;
+};
+
+static int nilfs_parse_snapshot_option(const char *option,
+				       const substring_t *arg,
+				       struct nilfs_super_data *sd)
+{
+	unsigned long long val;
+	const char *msg = NULL;
+	int err;
+
+	if (!(sd->flags & SB_RDONLY)) {
+		msg = "read-only option is not specified";
+		goto parse_error;
+	}
+
+	err = kstrtoull(arg->from, 0, &val);
+	if (err) {
+		if (err == -ERANGE)
+			msg = "too large checkpoint number";
+		else
+			msg = "malformed argument";
+		goto parse_error;
+	} else if (val == 0) {
+		msg = "invalid checkpoint number 0";
+		goto parse_error;
+	}
+	sd->cno = val;
+	return 0;
+
+parse_error:
+	nilfs_err(NULL, "invalid option \"%s\": %s", option, msg);
+	return 1;
+}
+
+/**
+ * nilfs_identify - pre-read mount options needed to identify mount instance
+ * @data: mount options
+ * @sd: nilfs_super_data
+ */
+static int nilfs_identify(char *data, struct nilfs_super_data *sd)
+{
+	char *p, *options = data;
+	substring_t args[MAX_OPT_ARGS];
+	int token;
+	int ret = 0;
+
+	do {
+		p = strsep(&options, ",");
+		if (p != NULL && *p) {
+			token = match_token(p, tokens, args);
+			if (token == Opt_snapshot)
+				ret = nilfs_parse_snapshot_option(p, &args[0],
+								  sd);
+		}
+		if (!options)
+			break;
+		BUG_ON(options == data);
+		*(options - 1) = ',';
+	} while (!ret);
+	return ret;
+}
+
+static int nilfs_set_bdev_super(struct super_block *s, void *data)
+{
+	s->s_dev = *(dev_t *)data;
+	return 0;
+}
+
+static int nilfs_test_bdev_super(struct super_block *s, void *data)
+{
+	return !(s->s_iflags & SB_I_RETIRED) && s->s_dev == *(dev_t *)data;
+}
+
+static struct dentry *
+nilfs_mount(struct file_system_type *fs_type, int flags,
+	     const char *dev_name, void *data)
+{
+	struct nilfs_super_data sd = { .flags = flags };
+	struct super_block *s;
+	dev_t dev;
+	int err;
+
+	if (nilfs_identify(data, &sd))
+		return ERR_PTR(-EINVAL);
+
+	err = lookup_bdev(dev_name, &dev);
+	if (err)
+		return ERR_PTR(err);
+
+	s = sget(fs_type, nilfs_test_bdev_super, nilfs_set_bdev_super, flags,
+		 &dev);
+	if (IS_ERR(s))
+		return ERR_CAST(s);
+
+	if (!s->s_root) {
+		/*
+		 * We drop s_umount here because we need to open the bdev and
+		 * bdev->open_mutex ranks above s_umount (blkdev_put() ->
+		 * __invalidate_device()). It is safe because we have active sb
+		 * reference and SB_BORN is not set yet.
+		 */
+		up_write(&s->s_umount);
+		err = setup_bdev_super(s, flags, NULL);
+		down_write(&s->s_umount);
+		if (!err)
+			err = nilfs_fill_super(s, data,
+					       flags & SB_SILENT ? 1 : 0);
+		if (err)
+			goto failed_super;
+
+		s->s_flags |= SB_ACTIVE;
+	} else if (!sd.cno) {
+		if (nilfs_tree_is_busy(s->s_root)) {
+			if ((flags ^ s->s_flags) & SB_RDONLY) {
+				nilfs_err(s,
+					  "the device already has a %s mount.",
+					  sb_rdonly(s) ? "read-only" : "read/write");
+				err = -EBUSY;
+				goto failed_super;
+			}
+		} else {
+			/*
+			 * Try remount to setup mount states if the current
+			 * tree is not mounted and only snapshots use this sb.
+			 */
+			err = nilfs_remount(s, &flags, data);
+			if (err)
+				goto failed_super;
+		}
+	}
+
+	if (sd.cno) {
+		struct dentry *root_dentry;
+
+		err = nilfs_attach_snapshot(s, sd.cno, &root_dentry);
+		if (err)
+			goto failed_super;
+		return root_dentry;
+	}
+
+	return dget(s->s_root);
+
+ failed_super:
+	deactivate_locked_super(s);
+	return ERR_PTR(err);
+}
+
+struct file_system_type nilfs_fs_type = {
+	.owner    = THIS_MODULE,
+	.name     = "nilfs2",
+	.mount    = nilfs_mount,
+	.kill_sb  = kill_block_super,
+	.fs_flags = FS_REQUIRES_DEV,
+};
+MODULE_ALIAS_FS("nilfs2");
+
+static void nilfs_inode_init_once(void *obj)
+{
+	struct nilfs_inode_info *ii = obj;
+
+	INIT_LIST_HEAD(&ii->i_dirty);
+#ifdef CONFIG_NILFS_XATTR
+	init_rwsem(&ii->xattr_sem);
+#endif
+	inode_init_once(&ii->vfs_inode);
+}
+
+static void nilfs_segbuf_init_once(void *obj)
+{
+	memset(obj, 0, sizeof(struct nilfs_segment_buffer));
+}
+
+static void nilfs_destroy_cachep(void)
+{
+	/*
+	 * Make sure all delayed rcu free inodes are flushed before we
+	 * destroy cache.
+	 */
+	rcu_barrier();
+
+	kmem_cache_destroy(nilfs_inode_cachep);
+	kmem_cache_destroy(nilfs_transaction_cachep);
+	kmem_cache_destroy(nilfs_segbuf_cachep);
+	kmem_cache_destroy(nilfs_btree_path_cache);
+}
+
+static int __init nilfs_init_cachep(void)
+{
+	nilfs_inode_cachep = kmem_cache_create("nilfs2_inode_cache",
+			sizeof(struct nilfs_inode_info), 0,
+			SLAB_RECLAIM_ACCOUNT|SLAB_ACCOUNT,
+			nilfs_inode_init_once);
+	if (!nilfs_inode_cachep)
+		goto fail;
+
+	nilfs_transaction_cachep = kmem_cache_create("nilfs2_transaction_cache",
+			sizeof(struct nilfs_transaction_info), 0,
+			SLAB_RECLAIM_ACCOUNT, NULL);
+	if (!nilfs_transaction_cachep)
+		goto fail;
+
+	nilfs_segbuf_cachep = kmem_cache_create("nilfs2_segbuf_cache",
+			sizeof(struct nilfs_segment_buffer), 0,
+			SLAB_RECLAIM_ACCOUNT, nilfs_segbuf_init_once);
+	if (!nilfs_segbuf_cachep)
+		goto fail;
+
+	nilfs_btree_path_cache = kmem_cache_create("nilfs2_btree_path_cache",
+			sizeof(struct nilfs_btree_path) * NILFS_BTREE_LEVEL_MAX,
+			0, 0, NULL);
+	if (!nilfs_btree_path_cache)
+		goto fail;
+
+	return 0;
+
+fail:
+	nilfs_destroy_cachep();
+	return -ENOMEM;
+}
+
+static int __init init_nilfs_fs(void)
+{
+	int err;
+
+	err = nilfs_init_cachep();
+	if (err)
+		goto fail;
+
+	err = nilfs_sysfs_init();
+	if (err)
+		goto free_cachep;
+
+	err = register_filesystem(&nilfs_fs_type);
+	if (err)
+		goto deinit_sysfs_entry;
+
+	printk(KERN_INFO "NILFS version 2 loaded\n");
+	return 0;
+
+deinit_sysfs_entry:
+	nilfs_sysfs_exit();
+free_cachep:
+	nilfs_destroy_cachep();
+fail:
+	return err;
+}
+
+static void __exit exit_nilfs_fs(void)
+{
+	nilfs_destroy_cachep();
+	nilfs_sysfs_exit();
+	unregister_filesystem(&nilfs_fs_type);
+}
+
+module_init(init_nilfs_fs)
+module_exit(exit_nilfs_fs)
diff --git a/fs/nilfs2/sysfs.c b/fs/nilfs2/sysfs.c
new file mode 100644
index 0000000000..379d22e28e
--- /dev/null
+++ b/fs/nilfs2/sysfs.c
@@ -0,0 +1,1117 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Sysfs support implementation.
+ *
+ * Copyright (C) 2005-2014 Nippon Telegraph and Telephone Corporation.
+ * Copyright (C) 2014 HGST, Inc., a Western Digital Company.
+ *
+ * Written by Vyacheslav Dubeyko <Vyacheslav.Dubeyko@hgst.com>
+ */
+
+#include <linux/kobject.h>
+
+#include "nilfs.h"
+#include "mdt.h"
+#include "sufile.h"
+#include "cpfile.h"
+#include "sysfs.h"
+
+/* /sys/fs/<nilfs>/ */
+static struct kset *nilfs_kset;
+
+#define NILFS_DEV_INT_GROUP_OPS(name, parent_name) \
+static ssize_t nilfs_##name##_attr_show(struct kobject *kobj, \
+					struct attribute *attr, char *buf) \
+{ \
+	struct the_nilfs *nilfs = container_of(kobj->parent, \
+						struct the_nilfs, \
+						ns_##parent_name##_kobj); \
+	struct nilfs_##name##_attr *a = container_of(attr, \
+						struct nilfs_##name##_attr, \
+						attr); \
+	return a->show ? a->show(a, nilfs, buf) : 0; \
+} \
+static ssize_t nilfs_##name##_attr_store(struct kobject *kobj, \
+					 struct attribute *attr, \
+					 const char *buf, size_t len) \
+{ \
+	struct the_nilfs *nilfs = container_of(kobj->parent, \
+						struct the_nilfs, \
+						ns_##parent_name##_kobj); \
+	struct nilfs_##name##_attr *a = container_of(attr, \
+						struct nilfs_##name##_attr, \
+						attr); \
+	return a->store ? a->store(a, nilfs, buf, len) : 0; \
+} \
+static const struct sysfs_ops nilfs_##name##_attr_ops = { \
+	.show	= nilfs_##name##_attr_show, \
+	.store	= nilfs_##name##_attr_store, \
+}
+
+#define NILFS_DEV_INT_GROUP_TYPE(name, parent_name) \
+static void nilfs_##name##_attr_release(struct kobject *kobj) \
+{ \
+	struct nilfs_sysfs_##parent_name##_subgroups *subgroups = container_of(kobj, \
+						struct nilfs_sysfs_##parent_name##_subgroups, \
+						sg_##name##_kobj); \
+	complete(&subgroups->sg_##name##_kobj_unregister); \
+} \
+static struct kobj_type nilfs_##name##_ktype = { \
+	.default_groups	= nilfs_##name##_groups, \
+	.sysfs_ops	= &nilfs_##name##_attr_ops, \
+	.release	= nilfs_##name##_attr_release, \
+}
+
+#define NILFS_DEV_INT_GROUP_FNS(name, parent_name) \
+static int nilfs_sysfs_create_##name##_group(struct the_nilfs *nilfs) \
+{ \
+	struct kobject *parent; \
+	struct kobject *kobj; \
+	struct completion *kobj_unregister; \
+	struct nilfs_sysfs_##parent_name##_subgroups *subgroups; \
+	int err; \
+	subgroups = nilfs->ns_##parent_name##_subgroups; \
+	kobj = &subgroups->sg_##name##_kobj; \
+	kobj_unregister = &subgroups->sg_##name##_kobj_unregister; \
+	parent = &nilfs->ns_##parent_name##_kobj; \
+	kobj->kset = nilfs_kset; \
+	init_completion(kobj_unregister); \
+	err = kobject_init_and_add(kobj, &nilfs_##name##_ktype, parent, \
+				    #name); \
+	if (err) \
+		kobject_put(kobj); \
+	return err; \
+} \
+static void nilfs_sysfs_delete_##name##_group(struct the_nilfs *nilfs) \
+{ \
+	kobject_put(&nilfs->ns_##parent_name##_subgroups->sg_##name##_kobj); \
+}
+
+/************************************************************************
+ *                        NILFS snapshot attrs                          *
+ ************************************************************************/
+
+static ssize_t
+nilfs_snapshot_inodes_count_show(struct nilfs_snapshot_attr *attr,
+				 struct nilfs_root *root, char *buf)
+{
+	return sysfs_emit(buf, "%llu\n",
+			(unsigned long long)atomic64_read(&root->inodes_count));
+}
+
+static ssize_t
+nilfs_snapshot_blocks_count_show(struct nilfs_snapshot_attr *attr,
+				 struct nilfs_root *root, char *buf)
+{
+	return sysfs_emit(buf, "%llu\n",
+			(unsigned long long)atomic64_read(&root->blocks_count));
+}
+
+static const char snapshot_readme_str[] =
+	"The group contains details about mounted snapshot.\n\n"
+	"(1) inodes_count\n\tshow number of inodes for snapshot.\n\n"
+	"(2) blocks_count\n\tshow number of blocks for snapshot.\n\n";
+
+static ssize_t
+nilfs_snapshot_README_show(struct nilfs_snapshot_attr *attr,
+			    struct nilfs_root *root, char *buf)
+{
+	return sysfs_emit(buf, snapshot_readme_str);
+}
+
+NILFS_SNAPSHOT_RO_ATTR(inodes_count);
+NILFS_SNAPSHOT_RO_ATTR(blocks_count);
+NILFS_SNAPSHOT_RO_ATTR(README);
+
+static struct attribute *nilfs_snapshot_attrs[] = {
+	NILFS_SNAPSHOT_ATTR_LIST(inodes_count),
+	NILFS_SNAPSHOT_ATTR_LIST(blocks_count),
+	NILFS_SNAPSHOT_ATTR_LIST(README),
+	NULL,
+};
+ATTRIBUTE_GROUPS(nilfs_snapshot);
+
+static ssize_t nilfs_snapshot_attr_show(struct kobject *kobj,
+					struct attribute *attr, char *buf)
+{
+	struct nilfs_root *root =
+			container_of(kobj, struct nilfs_root, snapshot_kobj);
+	struct nilfs_snapshot_attr *a =
+			container_of(attr, struct nilfs_snapshot_attr, attr);
+
+	return a->show ? a->show(a, root, buf) : 0;
+}
+
+static ssize_t nilfs_snapshot_attr_store(struct kobject *kobj,
+					 struct attribute *attr,
+					 const char *buf, size_t len)
+{
+	struct nilfs_root *root =
+			container_of(kobj, struct nilfs_root, snapshot_kobj);
+	struct nilfs_snapshot_attr *a =
+			container_of(attr, struct nilfs_snapshot_attr, attr);
+
+	return a->store ? a->store(a, root, buf, len) : 0;
+}
+
+static void nilfs_snapshot_attr_release(struct kobject *kobj)
+{
+	struct nilfs_root *root = container_of(kobj, struct nilfs_root,
+						snapshot_kobj);
+	complete(&root->snapshot_kobj_unregister);
+}
+
+static const struct sysfs_ops nilfs_snapshot_attr_ops = {
+	.show	= nilfs_snapshot_attr_show,
+	.store	= nilfs_snapshot_attr_store,
+};
+
+static struct kobj_type nilfs_snapshot_ktype = {
+	.default_groups	= nilfs_snapshot_groups,
+	.sysfs_ops	= &nilfs_snapshot_attr_ops,
+	.release	= nilfs_snapshot_attr_release,
+};
+
+int nilfs_sysfs_create_snapshot_group(struct nilfs_root *root)
+{
+	struct the_nilfs *nilfs;
+	struct kobject *parent;
+	int err;
+
+	nilfs = root->nilfs;
+	parent = &nilfs->ns_dev_subgroups->sg_mounted_snapshots_kobj;
+	root->snapshot_kobj.kset = nilfs_kset;
+	init_completion(&root->snapshot_kobj_unregister);
+
+	if (root->cno == NILFS_CPTREE_CURRENT_CNO) {
+		err = kobject_init_and_add(&root->snapshot_kobj,
+					    &nilfs_snapshot_ktype,
+					    &nilfs->ns_dev_kobj,
+					    "current_checkpoint");
+	} else {
+		err = kobject_init_and_add(&root->snapshot_kobj,
+					    &nilfs_snapshot_ktype,
+					    parent,
+					    "%llu", root->cno);
+	}
+
+	if (err)
+		kobject_put(&root->snapshot_kobj);
+
+	return err;
+}
+
+void nilfs_sysfs_delete_snapshot_group(struct nilfs_root *root)
+{
+	kobject_put(&root->snapshot_kobj);
+}
+
+/************************************************************************
+ *                    NILFS mounted snapshots attrs                     *
+ ************************************************************************/
+
+static const char mounted_snapshots_readme_str[] =
+	"The mounted_snapshots group contains group for\n"
+	"every mounted snapshot.\n";
+
+static ssize_t
+nilfs_mounted_snapshots_README_show(struct nilfs_mounted_snapshots_attr *attr,
+				    struct the_nilfs *nilfs, char *buf)
+{
+	return sysfs_emit(buf, mounted_snapshots_readme_str);
+}
+
+NILFS_MOUNTED_SNAPSHOTS_RO_ATTR(README);
+
+static struct attribute *nilfs_mounted_snapshots_attrs[] = {
+	NILFS_MOUNTED_SNAPSHOTS_ATTR_LIST(README),
+	NULL,
+};
+ATTRIBUTE_GROUPS(nilfs_mounted_snapshots);
+
+NILFS_DEV_INT_GROUP_OPS(mounted_snapshots, dev);
+NILFS_DEV_INT_GROUP_TYPE(mounted_snapshots, dev);
+NILFS_DEV_INT_GROUP_FNS(mounted_snapshots, dev);
+
+/************************************************************************
+ *                      NILFS checkpoints attrs                         *
+ ************************************************************************/
+
+static ssize_t
+nilfs_checkpoints_checkpoints_number_show(struct nilfs_checkpoints_attr *attr,
+					    struct the_nilfs *nilfs,
+					    char *buf)
+{
+	__u64 ncheckpoints;
+	struct nilfs_cpstat cpstat;
+	int err;
+
+	down_read(&nilfs->ns_segctor_sem);
+	err = nilfs_cpfile_get_stat(nilfs->ns_cpfile, &cpstat);
+	up_read(&nilfs->ns_segctor_sem);
+	if (err < 0) {
+		nilfs_err(nilfs->ns_sb, "unable to get checkpoint stat: err=%d",
+			  err);
+		return err;
+	}
+
+	ncheckpoints = cpstat.cs_ncps;
+
+	return sysfs_emit(buf, "%llu\n", ncheckpoints);
+}
+
+static ssize_t
+nilfs_checkpoints_snapshots_number_show(struct nilfs_checkpoints_attr *attr,
+					struct the_nilfs *nilfs,
+					char *buf)
+{
+	__u64 nsnapshots;
+	struct nilfs_cpstat cpstat;
+	int err;
+
+	down_read(&nilfs->ns_segctor_sem);
+	err = nilfs_cpfile_get_stat(nilfs->ns_cpfile, &cpstat);
+	up_read(&nilfs->ns_segctor_sem);
+	if (err < 0) {
+		nilfs_err(nilfs->ns_sb, "unable to get checkpoint stat: err=%d",
+			  err);
+		return err;
+	}
+
+	nsnapshots = cpstat.cs_nsss;
+
+	return sysfs_emit(buf, "%llu\n", nsnapshots);
+}
+
+static ssize_t
+nilfs_checkpoints_last_seg_checkpoint_show(struct nilfs_checkpoints_attr *attr,
+					    struct the_nilfs *nilfs,
+					    char *buf)
+{
+	__u64 last_cno;
+
+	spin_lock(&nilfs->ns_last_segment_lock);
+	last_cno = nilfs->ns_last_cno;
+	spin_unlock(&nilfs->ns_last_segment_lock);
+
+	return sysfs_emit(buf, "%llu\n", last_cno);
+}
+
+static ssize_t
+nilfs_checkpoints_next_checkpoint_show(struct nilfs_checkpoints_attr *attr,
+					struct the_nilfs *nilfs,
+					char *buf)
+{
+	__u64 cno;
+
+	down_read(&nilfs->ns_segctor_sem);
+	cno = nilfs->ns_cno;
+	up_read(&nilfs->ns_segctor_sem);
+
+	return sysfs_emit(buf, "%llu\n", cno);
+}
+
+static const char checkpoints_readme_str[] =
+	"The checkpoints group contains attributes that describe\n"
+	"details about volume's checkpoints.\n\n"
+	"(1) checkpoints_number\n\tshow number of checkpoints on volume.\n\n"
+	"(2) snapshots_number\n\tshow number of snapshots on volume.\n\n"
+	"(3) last_seg_checkpoint\n"
+	"\tshow checkpoint number of the latest segment.\n\n"
+	"(4) next_checkpoint\n\tshow next checkpoint number.\n\n";
+
+static ssize_t
+nilfs_checkpoints_README_show(struct nilfs_checkpoints_attr *attr,
+				struct the_nilfs *nilfs, char *buf)
+{
+	return sysfs_emit(buf, checkpoints_readme_str);
+}
+
+NILFS_CHECKPOINTS_RO_ATTR(checkpoints_number);
+NILFS_CHECKPOINTS_RO_ATTR(snapshots_number);
+NILFS_CHECKPOINTS_RO_ATTR(last_seg_checkpoint);
+NILFS_CHECKPOINTS_RO_ATTR(next_checkpoint);
+NILFS_CHECKPOINTS_RO_ATTR(README);
+
+static struct attribute *nilfs_checkpoints_attrs[] = {
+	NILFS_CHECKPOINTS_ATTR_LIST(checkpoints_number),
+	NILFS_CHECKPOINTS_ATTR_LIST(snapshots_number),
+	NILFS_CHECKPOINTS_ATTR_LIST(last_seg_checkpoint),
+	NILFS_CHECKPOINTS_ATTR_LIST(next_checkpoint),
+	NILFS_CHECKPOINTS_ATTR_LIST(README),
+	NULL,
+};
+ATTRIBUTE_GROUPS(nilfs_checkpoints);
+
+NILFS_DEV_INT_GROUP_OPS(checkpoints, dev);
+NILFS_DEV_INT_GROUP_TYPE(checkpoints, dev);
+NILFS_DEV_INT_GROUP_FNS(checkpoints, dev);
+
+/************************************************************************
+ *                        NILFS segments attrs                          *
+ ************************************************************************/
+
+static ssize_t
+nilfs_segments_segments_number_show(struct nilfs_segments_attr *attr,
+				     struct the_nilfs *nilfs,
+				     char *buf)
+{
+	return sysfs_emit(buf, "%lu\n", nilfs->ns_nsegments);
+}
+
+static ssize_t
+nilfs_segments_blocks_per_segment_show(struct nilfs_segments_attr *attr,
+					struct the_nilfs *nilfs,
+					char *buf)
+{
+	return sysfs_emit(buf, "%lu\n", nilfs->ns_blocks_per_segment);
+}
+
+static ssize_t
+nilfs_segments_clean_segments_show(struct nilfs_segments_attr *attr,
+				    struct the_nilfs *nilfs,
+				    char *buf)
+{
+	unsigned long ncleansegs;
+
+	down_read(&NILFS_MDT(nilfs->ns_dat)->mi_sem);
+	ncleansegs = nilfs_sufile_get_ncleansegs(nilfs->ns_sufile);
+	up_read(&NILFS_MDT(nilfs->ns_dat)->mi_sem);
+
+	return sysfs_emit(buf, "%lu\n", ncleansegs);
+}
+
+static ssize_t
+nilfs_segments_dirty_segments_show(struct nilfs_segments_attr *attr,
+				    struct the_nilfs *nilfs,
+				    char *buf)
+{
+	struct nilfs_sustat sustat;
+	int err;
+
+	down_read(&nilfs->ns_segctor_sem);
+	err = nilfs_sufile_get_stat(nilfs->ns_sufile, &sustat);
+	up_read(&nilfs->ns_segctor_sem);
+	if (err < 0) {
+		nilfs_err(nilfs->ns_sb, "unable to get segment stat: err=%d",
+			  err);
+		return err;
+	}
+
+	return sysfs_emit(buf, "%llu\n", sustat.ss_ndirtysegs);
+}
+
+static const char segments_readme_str[] =
+	"The segments group contains attributes that describe\n"
+	"details about volume's segments.\n\n"
+	"(1) segments_number\n\tshow number of segments on volume.\n\n"
+	"(2) blocks_per_segment\n\tshow number of blocks in segment.\n\n"
+	"(3) clean_segments\n\tshow count of clean segments.\n\n"
+	"(4) dirty_segments\n\tshow count of dirty segments.\n\n";
+
+static ssize_t
+nilfs_segments_README_show(struct nilfs_segments_attr *attr,
+			    struct the_nilfs *nilfs,
+			    char *buf)
+{
+	return sysfs_emit(buf, segments_readme_str);
+}
+
+NILFS_SEGMENTS_RO_ATTR(segments_number);
+NILFS_SEGMENTS_RO_ATTR(blocks_per_segment);
+NILFS_SEGMENTS_RO_ATTR(clean_segments);
+NILFS_SEGMENTS_RO_ATTR(dirty_segments);
+NILFS_SEGMENTS_RO_ATTR(README);
+
+static struct attribute *nilfs_segments_attrs[] = {
+	NILFS_SEGMENTS_ATTR_LIST(segments_number),
+	NILFS_SEGMENTS_ATTR_LIST(blocks_per_segment),
+	NILFS_SEGMENTS_ATTR_LIST(clean_segments),
+	NILFS_SEGMENTS_ATTR_LIST(dirty_segments),
+	NILFS_SEGMENTS_ATTR_LIST(README),
+	NULL,
+};
+ATTRIBUTE_GROUPS(nilfs_segments);
+
+NILFS_DEV_INT_GROUP_OPS(segments, dev);
+NILFS_DEV_INT_GROUP_TYPE(segments, dev);
+NILFS_DEV_INT_GROUP_FNS(segments, dev);
+
+/************************************************************************
+ *                        NILFS segctor attrs                           *
+ ************************************************************************/
+
+static ssize_t
+nilfs_segctor_last_pseg_block_show(struct nilfs_segctor_attr *attr,
+				    struct the_nilfs *nilfs,
+				    char *buf)
+{
+	sector_t last_pseg;
+
+	spin_lock(&nilfs->ns_last_segment_lock);
+	last_pseg = nilfs->ns_last_pseg;
+	spin_unlock(&nilfs->ns_last_segment_lock);
+
+	return sysfs_emit(buf, "%llu\n",
+			(unsigned long long)last_pseg);
+}
+
+static ssize_t
+nilfs_segctor_last_seg_sequence_show(struct nilfs_segctor_attr *attr,
+					struct the_nilfs *nilfs,
+					char *buf)
+{
+	u64 last_seq;
+
+	spin_lock(&nilfs->ns_last_segment_lock);
+	last_seq = nilfs->ns_last_seq;
+	spin_unlock(&nilfs->ns_last_segment_lock);
+
+	return sysfs_emit(buf, "%llu\n", last_seq);
+}
+
+static ssize_t
+nilfs_segctor_last_seg_checkpoint_show(struct nilfs_segctor_attr *attr,
+					struct the_nilfs *nilfs,
+					char *buf)
+{
+	__u64 last_cno;
+
+	spin_lock(&nilfs->ns_last_segment_lock);
+	last_cno = nilfs->ns_last_cno;
+	spin_unlock(&nilfs->ns_last_segment_lock);
+
+	return sysfs_emit(buf, "%llu\n", last_cno);
+}
+
+static ssize_t
+nilfs_segctor_current_seg_sequence_show(struct nilfs_segctor_attr *attr,
+					struct the_nilfs *nilfs,
+					char *buf)
+{
+	u64 seg_seq;
+
+	down_read(&nilfs->ns_segctor_sem);
+	seg_seq = nilfs->ns_seg_seq;
+	up_read(&nilfs->ns_segctor_sem);
+
+	return sysfs_emit(buf, "%llu\n", seg_seq);
+}
+
+static ssize_t
+nilfs_segctor_current_last_full_seg_show(struct nilfs_segctor_attr *attr,
+					 struct the_nilfs *nilfs,
+					 char *buf)
+{
+	__u64 segnum;
+
+	down_read(&nilfs->ns_segctor_sem);
+	segnum = nilfs->ns_segnum;
+	up_read(&nilfs->ns_segctor_sem);
+
+	return sysfs_emit(buf, "%llu\n", segnum);
+}
+
+static ssize_t
+nilfs_segctor_next_full_seg_show(struct nilfs_segctor_attr *attr,
+				 struct the_nilfs *nilfs,
+				 char *buf)
+{
+	__u64 nextnum;
+
+	down_read(&nilfs->ns_segctor_sem);
+	nextnum = nilfs->ns_nextnum;
+	up_read(&nilfs->ns_segctor_sem);
+
+	return sysfs_emit(buf, "%llu\n", nextnum);
+}
+
+static ssize_t
+nilfs_segctor_next_pseg_offset_show(struct nilfs_segctor_attr *attr,
+					struct the_nilfs *nilfs,
+					char *buf)
+{
+	unsigned long pseg_offset;
+
+	down_read(&nilfs->ns_segctor_sem);
+	pseg_offset = nilfs->ns_pseg_offset;
+	up_read(&nilfs->ns_segctor_sem);
+
+	return sysfs_emit(buf, "%lu\n", pseg_offset);
+}
+
+static ssize_t
+nilfs_segctor_next_checkpoint_show(struct nilfs_segctor_attr *attr,
+					struct the_nilfs *nilfs,
+					char *buf)
+{
+	__u64 cno;
+
+	down_read(&nilfs->ns_segctor_sem);
+	cno = nilfs->ns_cno;
+	up_read(&nilfs->ns_segctor_sem);
+
+	return sysfs_emit(buf, "%llu\n", cno);
+}
+
+static ssize_t
+nilfs_segctor_last_seg_write_time_show(struct nilfs_segctor_attr *attr,
+					struct the_nilfs *nilfs,
+					char *buf)
+{
+	time64_t ctime;
+
+	down_read(&nilfs->ns_segctor_sem);
+	ctime = nilfs->ns_ctime;
+	up_read(&nilfs->ns_segctor_sem);
+
+	return sysfs_emit(buf, "%ptTs\n", &ctime);
+}
+
+static ssize_t
+nilfs_segctor_last_seg_write_time_secs_show(struct nilfs_segctor_attr *attr,
+					    struct the_nilfs *nilfs,
+					    char *buf)
+{
+	time64_t ctime;
+
+	down_read(&nilfs->ns_segctor_sem);
+	ctime = nilfs->ns_ctime;
+	up_read(&nilfs->ns_segctor_sem);
+
+	return sysfs_emit(buf, "%llu\n", ctime);
+}
+
+static ssize_t
+nilfs_segctor_last_nongc_write_time_show(struct nilfs_segctor_attr *attr,
+					 struct the_nilfs *nilfs,
+					 char *buf)
+{
+	time64_t nongc_ctime;
+
+	down_read(&nilfs->ns_segctor_sem);
+	nongc_ctime = nilfs->ns_nongc_ctime;
+	up_read(&nilfs->ns_segctor_sem);
+
+	return sysfs_emit(buf, "%ptTs\n", &nongc_ctime);
+}
+
+static ssize_t
+nilfs_segctor_last_nongc_write_time_secs_show(struct nilfs_segctor_attr *attr,
+						struct the_nilfs *nilfs,
+						char *buf)
+{
+	time64_t nongc_ctime;
+
+	down_read(&nilfs->ns_segctor_sem);
+	nongc_ctime = nilfs->ns_nongc_ctime;
+	up_read(&nilfs->ns_segctor_sem);
+
+	return sysfs_emit(buf, "%llu\n", nongc_ctime);
+}
+
+static ssize_t
+nilfs_segctor_dirty_data_blocks_count_show(struct nilfs_segctor_attr *attr,
+					    struct the_nilfs *nilfs,
+					    char *buf)
+{
+	u32 ndirtyblks;
+
+	down_read(&nilfs->ns_segctor_sem);
+	ndirtyblks = atomic_read(&nilfs->ns_ndirtyblks);
+	up_read(&nilfs->ns_segctor_sem);
+
+	return sysfs_emit(buf, "%u\n", ndirtyblks);
+}
+
+static const char segctor_readme_str[] =
+	"The segctor group contains attributes that describe\n"
+	"segctor thread activity details.\n\n"
+	"(1) last_pseg_block\n"
+	"\tshow start block number of the latest segment.\n\n"
+	"(2) last_seg_sequence\n"
+	"\tshow sequence value of the latest segment.\n\n"
+	"(3) last_seg_checkpoint\n"
+	"\tshow checkpoint number of the latest segment.\n\n"
+	"(4) current_seg_sequence\n\tshow segment sequence counter.\n\n"
+	"(5) current_last_full_seg\n"
+	"\tshow index number of the latest full segment.\n\n"
+	"(6) next_full_seg\n"
+	"\tshow index number of the full segment index to be used next.\n\n"
+	"(7) next_pseg_offset\n"
+	"\tshow offset of next partial segment in the current full segment.\n\n"
+	"(8) next_checkpoint\n\tshow next checkpoint number.\n\n"
+	"(9) last_seg_write_time\n"
+	"\tshow write time of the last segment in human-readable format.\n\n"
+	"(10) last_seg_write_time_secs\n"
+	"\tshow write time of the last segment in seconds.\n\n"
+	"(11) last_nongc_write_time\n"
+	"\tshow write time of the last segment not for cleaner operation "
+	"in human-readable format.\n\n"
+	"(12) last_nongc_write_time_secs\n"
+	"\tshow write time of the last segment not for cleaner operation "
+	"in seconds.\n\n"
+	"(13) dirty_data_blocks_count\n"
+	"\tshow number of dirty data blocks.\n\n";
+
+static ssize_t
+nilfs_segctor_README_show(struct nilfs_segctor_attr *attr,
+			  struct the_nilfs *nilfs, char *buf)
+{
+	return sysfs_emit(buf, segctor_readme_str);
+}
+
+NILFS_SEGCTOR_RO_ATTR(last_pseg_block);
+NILFS_SEGCTOR_RO_ATTR(last_seg_sequence);
+NILFS_SEGCTOR_RO_ATTR(last_seg_checkpoint);
+NILFS_SEGCTOR_RO_ATTR(current_seg_sequence);
+NILFS_SEGCTOR_RO_ATTR(current_last_full_seg);
+NILFS_SEGCTOR_RO_ATTR(next_full_seg);
+NILFS_SEGCTOR_RO_ATTR(next_pseg_offset);
+NILFS_SEGCTOR_RO_ATTR(next_checkpoint);
+NILFS_SEGCTOR_RO_ATTR(last_seg_write_time);
+NILFS_SEGCTOR_RO_ATTR(last_seg_write_time_secs);
+NILFS_SEGCTOR_RO_ATTR(last_nongc_write_time);
+NILFS_SEGCTOR_RO_ATTR(last_nongc_write_time_secs);
+NILFS_SEGCTOR_RO_ATTR(dirty_data_blocks_count);
+NILFS_SEGCTOR_RO_ATTR(README);
+
+static struct attribute *nilfs_segctor_attrs[] = {
+	NILFS_SEGCTOR_ATTR_LIST(last_pseg_block),
+	NILFS_SEGCTOR_ATTR_LIST(last_seg_sequence),
+	NILFS_SEGCTOR_ATTR_LIST(last_seg_checkpoint),
+	NILFS_SEGCTOR_ATTR_LIST(current_seg_sequence),
+	NILFS_SEGCTOR_ATTR_LIST(current_last_full_seg),
+	NILFS_SEGCTOR_ATTR_LIST(next_full_seg),
+	NILFS_SEGCTOR_ATTR_LIST(next_pseg_offset),
+	NILFS_SEGCTOR_ATTR_LIST(next_checkpoint),
+	NILFS_SEGCTOR_ATTR_LIST(last_seg_write_time),
+	NILFS_SEGCTOR_ATTR_LIST(last_seg_write_time_secs),
+	NILFS_SEGCTOR_ATTR_LIST(last_nongc_write_time),
+	NILFS_SEGCTOR_ATTR_LIST(last_nongc_write_time_secs),
+	NILFS_SEGCTOR_ATTR_LIST(dirty_data_blocks_count),
+	NILFS_SEGCTOR_ATTR_LIST(README),
+	NULL,
+};
+ATTRIBUTE_GROUPS(nilfs_segctor);
+
+NILFS_DEV_INT_GROUP_OPS(segctor, dev);
+NILFS_DEV_INT_GROUP_TYPE(segctor, dev);
+NILFS_DEV_INT_GROUP_FNS(segctor, dev);
+
+/************************************************************************
+ *                        NILFS superblock attrs                        *
+ ************************************************************************/
+
+static ssize_t
+nilfs_superblock_sb_write_time_show(struct nilfs_superblock_attr *attr,
+				     struct the_nilfs *nilfs,
+				     char *buf)
+{
+	time64_t sbwtime;
+
+	down_read(&nilfs->ns_sem);
+	sbwtime = nilfs->ns_sbwtime;
+	up_read(&nilfs->ns_sem);
+
+	return sysfs_emit(buf, "%ptTs\n", &sbwtime);
+}
+
+static ssize_t
+nilfs_superblock_sb_write_time_secs_show(struct nilfs_superblock_attr *attr,
+					 struct the_nilfs *nilfs,
+					 char *buf)
+{
+	time64_t sbwtime;
+
+	down_read(&nilfs->ns_sem);
+	sbwtime = nilfs->ns_sbwtime;
+	up_read(&nilfs->ns_sem);
+
+	return sysfs_emit(buf, "%llu\n", sbwtime);
+}
+
+static ssize_t
+nilfs_superblock_sb_write_count_show(struct nilfs_superblock_attr *attr,
+				      struct the_nilfs *nilfs,
+				      char *buf)
+{
+	unsigned int sbwcount;
+
+	down_read(&nilfs->ns_sem);
+	sbwcount = nilfs->ns_sbwcount;
+	up_read(&nilfs->ns_sem);
+
+	return sysfs_emit(buf, "%u\n", sbwcount);
+}
+
+static ssize_t
+nilfs_superblock_sb_update_frequency_show(struct nilfs_superblock_attr *attr,
+					    struct the_nilfs *nilfs,
+					    char *buf)
+{
+	unsigned int sb_update_freq;
+
+	down_read(&nilfs->ns_sem);
+	sb_update_freq = nilfs->ns_sb_update_freq;
+	up_read(&nilfs->ns_sem);
+
+	return sysfs_emit(buf, "%u\n", sb_update_freq);
+}
+
+static ssize_t
+nilfs_superblock_sb_update_frequency_store(struct nilfs_superblock_attr *attr,
+					    struct the_nilfs *nilfs,
+					    const char *buf, size_t count)
+{
+	unsigned int val;
+	int err;
+
+	err = kstrtouint(skip_spaces(buf), 0, &val);
+	if (err) {
+		nilfs_err(nilfs->ns_sb, "unable to convert string: err=%d",
+			  err);
+		return err;
+	}
+
+	if (val < NILFS_SB_FREQ) {
+		val = NILFS_SB_FREQ;
+		nilfs_warn(nilfs->ns_sb,
+			   "superblock update frequency cannot be lesser than 10 seconds");
+	}
+
+	down_write(&nilfs->ns_sem);
+	nilfs->ns_sb_update_freq = val;
+	up_write(&nilfs->ns_sem);
+
+	return count;
+}
+
+static const char sb_readme_str[] =
+	"The superblock group contains attributes that describe\n"
+	"superblock's details.\n\n"
+	"(1) sb_write_time\n\tshow previous write time of super block "
+	"in human-readable format.\n\n"
+	"(2) sb_write_time_secs\n\tshow previous write time of super block "
+	"in seconds.\n\n"
+	"(3) sb_write_count\n\tshow write count of super block.\n\n"
+	"(4) sb_update_frequency\n"
+	"\tshow/set interval of periodical update of superblock (in seconds).\n\n"
+	"\tYou can set preferable frequency of superblock update by command:\n\n"
+	"\t'echo <val> > /sys/fs/<nilfs>/<dev>/superblock/sb_update_frequency'\n";
+
+static ssize_t
+nilfs_superblock_README_show(struct nilfs_superblock_attr *attr,
+				struct the_nilfs *nilfs, char *buf)
+{
+	return sysfs_emit(buf, sb_readme_str);
+}
+
+NILFS_SUPERBLOCK_RO_ATTR(sb_write_time);
+NILFS_SUPERBLOCK_RO_ATTR(sb_write_time_secs);
+NILFS_SUPERBLOCK_RO_ATTR(sb_write_count);
+NILFS_SUPERBLOCK_RW_ATTR(sb_update_frequency);
+NILFS_SUPERBLOCK_RO_ATTR(README);
+
+static struct attribute *nilfs_superblock_attrs[] = {
+	NILFS_SUPERBLOCK_ATTR_LIST(sb_write_time),
+	NILFS_SUPERBLOCK_ATTR_LIST(sb_write_time_secs),
+	NILFS_SUPERBLOCK_ATTR_LIST(sb_write_count),
+	NILFS_SUPERBLOCK_ATTR_LIST(sb_update_frequency),
+	NILFS_SUPERBLOCK_ATTR_LIST(README),
+	NULL,
+};
+ATTRIBUTE_GROUPS(nilfs_superblock);
+
+NILFS_DEV_INT_GROUP_OPS(superblock, dev);
+NILFS_DEV_INT_GROUP_TYPE(superblock, dev);
+NILFS_DEV_INT_GROUP_FNS(superblock, dev);
+
+/************************************************************************
+ *                        NILFS device attrs                            *
+ ************************************************************************/
+
+static
+ssize_t nilfs_dev_revision_show(struct nilfs_dev_attr *attr,
+				struct the_nilfs *nilfs,
+				char *buf)
+{
+	struct nilfs_super_block **sbp = nilfs->ns_sbp;
+	u32 major = le32_to_cpu(sbp[0]->s_rev_level);
+	u16 minor = le16_to_cpu(sbp[0]->s_minor_rev_level);
+
+	return sysfs_emit(buf, "%d.%d\n", major, minor);
+}
+
+static
+ssize_t nilfs_dev_blocksize_show(struct nilfs_dev_attr *attr,
+				 struct the_nilfs *nilfs,
+				 char *buf)
+{
+	return sysfs_emit(buf, "%u\n", nilfs->ns_blocksize);
+}
+
+static
+ssize_t nilfs_dev_device_size_show(struct nilfs_dev_attr *attr,
+				    struct the_nilfs *nilfs,
+				    char *buf)
+{
+	struct nilfs_super_block **sbp = nilfs->ns_sbp;
+	u64 dev_size = le64_to_cpu(sbp[0]->s_dev_size);
+
+	return sysfs_emit(buf, "%llu\n", dev_size);
+}
+
+static
+ssize_t nilfs_dev_free_blocks_show(struct nilfs_dev_attr *attr,
+				   struct the_nilfs *nilfs,
+				   char *buf)
+{
+	sector_t free_blocks = 0;
+
+	nilfs_count_free_blocks(nilfs, &free_blocks);
+	return sysfs_emit(buf, "%llu\n",
+			(unsigned long long)free_blocks);
+}
+
+static
+ssize_t nilfs_dev_uuid_show(struct nilfs_dev_attr *attr,
+			    struct the_nilfs *nilfs,
+			    char *buf)
+{
+	struct nilfs_super_block **sbp = nilfs->ns_sbp;
+
+	return sysfs_emit(buf, "%pUb\n", sbp[0]->s_uuid);
+}
+
+static
+ssize_t nilfs_dev_volume_name_show(struct nilfs_dev_attr *attr,
+				    struct the_nilfs *nilfs,
+				    char *buf)
+{
+	struct nilfs_super_block **sbp = nilfs->ns_sbp;
+
+	return scnprintf(buf, sizeof(sbp[0]->s_volume_name), "%s\n",
+			 sbp[0]->s_volume_name);
+}
+
+static const char dev_readme_str[] =
+	"The <device> group contains attributes that describe file system\n"
+	"partition's details.\n\n"
+	"(1) revision\n\tshow NILFS file system revision.\n\n"
+	"(2) blocksize\n\tshow volume block size in bytes.\n\n"
+	"(3) device_size\n\tshow volume size in bytes.\n\n"
+	"(4) free_blocks\n\tshow count of free blocks on volume.\n\n"
+	"(5) uuid\n\tshow volume's UUID.\n\n"
+	"(6) volume_name\n\tshow volume's name.\n\n";
+
+static ssize_t nilfs_dev_README_show(struct nilfs_dev_attr *attr,
+				     struct the_nilfs *nilfs,
+				     char *buf)
+{
+	return sysfs_emit(buf, dev_readme_str);
+}
+
+NILFS_DEV_RO_ATTR(revision);
+NILFS_DEV_RO_ATTR(blocksize);
+NILFS_DEV_RO_ATTR(device_size);
+NILFS_DEV_RO_ATTR(free_blocks);
+NILFS_DEV_RO_ATTR(uuid);
+NILFS_DEV_RO_ATTR(volume_name);
+NILFS_DEV_RO_ATTR(README);
+
+static struct attribute *nilfs_dev_attrs[] = {
+	NILFS_DEV_ATTR_LIST(revision),
+	NILFS_DEV_ATTR_LIST(blocksize),
+	NILFS_DEV_ATTR_LIST(device_size),
+	NILFS_DEV_ATTR_LIST(free_blocks),
+	NILFS_DEV_ATTR_LIST(uuid),
+	NILFS_DEV_ATTR_LIST(volume_name),
+	NILFS_DEV_ATTR_LIST(README),
+	NULL,
+};
+ATTRIBUTE_GROUPS(nilfs_dev);
+
+static ssize_t nilfs_dev_attr_show(struct kobject *kobj,
+				    struct attribute *attr, char *buf)
+{
+	struct the_nilfs *nilfs = container_of(kobj, struct the_nilfs,
+						ns_dev_kobj);
+	struct nilfs_dev_attr *a = container_of(attr, struct nilfs_dev_attr,
+						attr);
+
+	return a->show ? a->show(a, nilfs, buf) : 0;
+}
+
+static ssize_t nilfs_dev_attr_store(struct kobject *kobj,
+				    struct attribute *attr,
+				    const char *buf, size_t len)
+{
+	struct the_nilfs *nilfs = container_of(kobj, struct the_nilfs,
+						ns_dev_kobj);
+	struct nilfs_dev_attr *a = container_of(attr, struct nilfs_dev_attr,
+						attr);
+
+	return a->store ? a->store(a, nilfs, buf, len) : 0;
+}
+
+static void nilfs_dev_attr_release(struct kobject *kobj)
+{
+	struct the_nilfs *nilfs = container_of(kobj, struct the_nilfs,
+						ns_dev_kobj);
+	complete(&nilfs->ns_dev_kobj_unregister);
+}
+
+static const struct sysfs_ops nilfs_dev_attr_ops = {
+	.show	= nilfs_dev_attr_show,
+	.store	= nilfs_dev_attr_store,
+};
+
+static struct kobj_type nilfs_dev_ktype = {
+	.default_groups	= nilfs_dev_groups,
+	.sysfs_ops	= &nilfs_dev_attr_ops,
+	.release	= nilfs_dev_attr_release,
+};
+
+int nilfs_sysfs_create_device_group(struct super_block *sb)
+{
+	struct the_nilfs *nilfs = sb->s_fs_info;
+	size_t devgrp_size = sizeof(struct nilfs_sysfs_dev_subgroups);
+	int err;
+
+	nilfs->ns_dev_subgroups = kzalloc(devgrp_size, GFP_KERNEL);
+	if (unlikely(!nilfs->ns_dev_subgroups)) {
+		err = -ENOMEM;
+		nilfs_err(sb, "unable to allocate memory for device group");
+		goto failed_create_device_group;
+	}
+
+	nilfs->ns_dev_kobj.kset = nilfs_kset;
+	init_completion(&nilfs->ns_dev_kobj_unregister);
+	err = kobject_init_and_add(&nilfs->ns_dev_kobj, &nilfs_dev_ktype, NULL,
+				    "%s", sb->s_id);
+	if (err)
+		goto cleanup_dev_kobject;
+
+	err = nilfs_sysfs_create_mounted_snapshots_group(nilfs);
+	if (err)
+		goto cleanup_dev_kobject;
+
+	err = nilfs_sysfs_create_checkpoints_group(nilfs);
+	if (err)
+		goto delete_mounted_snapshots_group;
+
+	err = nilfs_sysfs_create_segments_group(nilfs);
+	if (err)
+		goto delete_checkpoints_group;
+
+	err = nilfs_sysfs_create_superblock_group(nilfs);
+	if (err)
+		goto delete_segments_group;
+
+	err = nilfs_sysfs_create_segctor_group(nilfs);
+	if (err)
+		goto delete_superblock_group;
+
+	return 0;
+
+delete_superblock_group:
+	nilfs_sysfs_delete_superblock_group(nilfs);
+
+delete_segments_group:
+	nilfs_sysfs_delete_segments_group(nilfs);
+
+delete_checkpoints_group:
+	nilfs_sysfs_delete_checkpoints_group(nilfs);
+
+delete_mounted_snapshots_group:
+	nilfs_sysfs_delete_mounted_snapshots_group(nilfs);
+
+cleanup_dev_kobject:
+	kobject_put(&nilfs->ns_dev_kobj);
+	kfree(nilfs->ns_dev_subgroups);
+
+failed_create_device_group:
+	return err;
+}
+
+void nilfs_sysfs_delete_device_group(struct the_nilfs *nilfs)
+{
+	nilfs_sysfs_delete_mounted_snapshots_group(nilfs);
+	nilfs_sysfs_delete_checkpoints_group(nilfs);
+	nilfs_sysfs_delete_segments_group(nilfs);
+	nilfs_sysfs_delete_superblock_group(nilfs);
+	nilfs_sysfs_delete_segctor_group(nilfs);
+	kobject_del(&nilfs->ns_dev_kobj);
+	kobject_put(&nilfs->ns_dev_kobj);
+	kfree(nilfs->ns_dev_subgroups);
+}
+
+/************************************************************************
+ *                        NILFS feature attrs                           *
+ ************************************************************************/
+
+static ssize_t nilfs_feature_revision_show(struct kobject *kobj,
+					    struct attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%d.%d\n",
+			NILFS_CURRENT_REV, NILFS_MINOR_REV);
+}
+
+static const char features_readme_str[] =
+	"The features group contains attributes that describe NILFS file\n"
+	"system driver features.\n\n"
+	"(1) revision\n\tshow current revision of NILFS file system driver.\n";
+
+static ssize_t nilfs_feature_README_show(struct kobject *kobj,
+					 struct attribute *attr,
+					 char *buf)
+{
+	return sysfs_emit(buf, features_readme_str);
+}
+
+NILFS_FEATURE_RO_ATTR(revision);
+NILFS_FEATURE_RO_ATTR(README);
+
+static struct attribute *nilfs_feature_attrs[] = {
+	NILFS_FEATURE_ATTR_LIST(revision),
+	NILFS_FEATURE_ATTR_LIST(README),
+	NULL,
+};
+
+static const struct attribute_group nilfs_feature_attr_group = {
+	.name = "features",
+	.attrs = nilfs_feature_attrs,
+};
+
+int __init nilfs_sysfs_init(void)
+{
+	int err;
+
+	nilfs_kset = kset_create_and_add(NILFS_ROOT_GROUP_NAME, NULL, fs_kobj);
+	if (!nilfs_kset) {
+		err = -ENOMEM;
+		nilfs_err(NULL, "unable to create sysfs entry: err=%d", err);
+		goto failed_sysfs_init;
+	}
+
+	err = sysfs_create_group(&nilfs_kset->kobj, &nilfs_feature_attr_group);
+	if (unlikely(err)) {
+		nilfs_err(NULL, "unable to create feature group: err=%d", err);
+		goto cleanup_sysfs_init;
+	}
+
+	return 0;
+
+cleanup_sysfs_init:
+	kset_unregister(nilfs_kset);
+
+failed_sysfs_init:
+	return err;
+}
+
+void nilfs_sysfs_exit(void)
+{
+	sysfs_remove_group(&nilfs_kset->kobj, &nilfs_feature_attr_group);
+	kset_unregister(nilfs_kset);
+}
diff --git a/fs/nilfs2/sysfs.h b/fs/nilfs2/sysfs.h
new file mode 100644
index 0000000000..78a87a0169
--- /dev/null
+++ b/fs/nilfs2/sysfs.h
@@ -0,0 +1,167 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Sysfs support declarations.
+ *
+ * Copyright (C) 2005-2014 Nippon Telegraph and Telephone Corporation.
+ * Copyright (C) 2014 HGST, Inc., a Western Digital Company.
+ *
+ * Written by Vyacheslav Dubeyko <Vyacheslav.Dubeyko@hgst.com>
+ */
+
+#ifndef _NILFS_SYSFS_H
+#define _NILFS_SYSFS_H
+
+#include <linux/sysfs.h>
+
+#define NILFS_ROOT_GROUP_NAME	"nilfs2"
+
+/*
+ * struct nilfs_sysfs_dev_subgroups - device subgroup kernel objects
+ * @sg_superblock_kobj: /sys/fs/<nilfs>/<device>/superblock
+ * @sg_superblock_kobj_unregister: completion state
+ * @sg_segctor_kobj: /sys/fs/<nilfs>/<device>/segctor
+ * @sg_segctor_kobj_unregister: completion state
+ * @sg_mounted_snapshots_kobj: /sys/fs/<nilfs>/<device>/mounted_snapshots
+ * @sg_mounted_snapshots_kobj_unregister: completion state
+ * @sg_checkpoints_kobj: /sys/fs/<nilfs>/<device>/checkpoints
+ * @sg_checkpoints_kobj_unregister: completion state
+ * @sg_segments_kobj: /sys/fs/<nilfs>/<device>/segments
+ * @sg_segments_kobj_unregister: completion state
+ */
+struct nilfs_sysfs_dev_subgroups {
+	/* /sys/fs/<nilfs>/<device>/superblock */
+	struct kobject sg_superblock_kobj;
+	struct completion sg_superblock_kobj_unregister;
+
+	/* /sys/fs/<nilfs>/<device>/segctor */
+	struct kobject sg_segctor_kobj;
+	struct completion sg_segctor_kobj_unregister;
+
+	/* /sys/fs/<nilfs>/<device>/mounted_snapshots */
+	struct kobject sg_mounted_snapshots_kobj;
+	struct completion sg_mounted_snapshots_kobj_unregister;
+
+	/* /sys/fs/<nilfs>/<device>/checkpoints */
+	struct kobject sg_checkpoints_kobj;
+	struct completion sg_checkpoints_kobj_unregister;
+
+	/* /sys/fs/<nilfs>/<device>/segments */
+	struct kobject sg_segments_kobj;
+	struct completion sg_segments_kobj_unregister;
+};
+
+#define NILFS_COMMON_ATTR_STRUCT(name) \
+struct nilfs_##name##_attr { \
+	struct attribute attr; \
+	ssize_t (*show)(struct kobject *, struct attribute *, \
+			char *); \
+	ssize_t (*store)(struct kobject *, struct attribute *, \
+			 const char *, size_t); \
+}
+
+NILFS_COMMON_ATTR_STRUCT(feature);
+
+#define NILFS_DEV_ATTR_STRUCT(name) \
+struct nilfs_##name##_attr { \
+	struct attribute attr; \
+	ssize_t (*show)(struct nilfs_##name##_attr *, struct the_nilfs *, \
+			char *); \
+	ssize_t (*store)(struct nilfs_##name##_attr *, struct the_nilfs *, \
+			 const char *, size_t); \
+}
+
+NILFS_DEV_ATTR_STRUCT(dev);
+NILFS_DEV_ATTR_STRUCT(segments);
+NILFS_DEV_ATTR_STRUCT(mounted_snapshots);
+NILFS_DEV_ATTR_STRUCT(checkpoints);
+NILFS_DEV_ATTR_STRUCT(superblock);
+NILFS_DEV_ATTR_STRUCT(segctor);
+
+#define NILFS_CP_ATTR_STRUCT(name) \
+struct nilfs_##name##_attr { \
+	struct attribute attr; \
+	ssize_t (*show)(struct nilfs_##name##_attr *, struct nilfs_root *, \
+			char *); \
+	ssize_t (*store)(struct nilfs_##name##_attr *, struct nilfs_root *, \
+			 const char *, size_t); \
+}
+
+NILFS_CP_ATTR_STRUCT(snapshot);
+
+#define NILFS_ATTR(type, name, mode, show, store) \
+	static struct nilfs_##type##_attr nilfs_##type##_attr_##name = \
+		__ATTR(name, mode, show, store)
+
+#define NILFS_INFO_ATTR(type, name) \
+	NILFS_ATTR(type, name, 0444, NULL, NULL)
+#define NILFS_RO_ATTR(type, name) \
+	NILFS_ATTR(type, name, 0444, nilfs_##type##_##name##_show, NULL)
+#define NILFS_RW_ATTR(type, name) \
+	NILFS_ATTR(type, name, 0644, \
+		    nilfs_##type##_##name##_show, \
+		    nilfs_##type##_##name##_store)
+
+#define NILFS_FEATURE_INFO_ATTR(name) \
+	NILFS_INFO_ATTR(feature, name)
+#define NILFS_FEATURE_RO_ATTR(name) \
+	NILFS_RO_ATTR(feature, name)
+#define NILFS_FEATURE_RW_ATTR(name) \
+	NILFS_RW_ATTR(feature, name)
+
+#define NILFS_DEV_INFO_ATTR(name) \
+	NILFS_INFO_ATTR(dev, name)
+#define NILFS_DEV_RO_ATTR(name) \
+	NILFS_RO_ATTR(dev, name)
+#define NILFS_DEV_RW_ATTR(name) \
+	NILFS_RW_ATTR(dev, name)
+
+#define NILFS_SEGMENTS_RO_ATTR(name) \
+	NILFS_RO_ATTR(segments, name)
+#define NILFS_SEGMENTS_RW_ATTR(name) \
+	NILFS_RW_ATTR(segs_info, name)
+
+#define NILFS_MOUNTED_SNAPSHOTS_RO_ATTR(name) \
+	NILFS_RO_ATTR(mounted_snapshots, name)
+
+#define NILFS_CHECKPOINTS_RO_ATTR(name) \
+	NILFS_RO_ATTR(checkpoints, name)
+#define NILFS_CHECKPOINTS_RW_ATTR(name) \
+	NILFS_RW_ATTR(checkpoints, name)
+
+#define NILFS_SNAPSHOT_INFO_ATTR(name) \
+	NILFS_INFO_ATTR(snapshot, name)
+#define NILFS_SNAPSHOT_RO_ATTR(name) \
+	NILFS_RO_ATTR(snapshot, name)
+#define NILFS_SNAPSHOT_RW_ATTR(name) \
+	NILFS_RW_ATTR(snapshot, name)
+
+#define NILFS_SUPERBLOCK_RO_ATTR(name) \
+	NILFS_RO_ATTR(superblock, name)
+#define NILFS_SUPERBLOCK_RW_ATTR(name) \
+	NILFS_RW_ATTR(superblock, name)
+
+#define NILFS_SEGCTOR_INFO_ATTR(name) \
+	NILFS_INFO_ATTR(segctor, name)
+#define NILFS_SEGCTOR_RO_ATTR(name) \
+	NILFS_RO_ATTR(segctor, name)
+#define NILFS_SEGCTOR_RW_ATTR(name) \
+	NILFS_RW_ATTR(segctor, name)
+
+#define NILFS_FEATURE_ATTR_LIST(name) \
+	(&nilfs_feature_attr_##name.attr)
+#define NILFS_DEV_ATTR_LIST(name) \
+	(&nilfs_dev_attr_##name.attr)
+#define NILFS_SEGMENTS_ATTR_LIST(name) \
+	(&nilfs_segments_attr_##name.attr)
+#define NILFS_MOUNTED_SNAPSHOTS_ATTR_LIST(name) \
+	(&nilfs_mounted_snapshots_attr_##name.attr)
+#define NILFS_CHECKPOINTS_ATTR_LIST(name) \
+	(&nilfs_checkpoints_attr_##name.attr)
+#define NILFS_SNAPSHOT_ATTR_LIST(name) \
+	(&nilfs_snapshot_attr_##name.attr)
+#define NILFS_SUPERBLOCK_ATTR_LIST(name) \
+	(&nilfs_superblock_attr_##name.attr)
+#define NILFS_SEGCTOR_ATTR_LIST(name) \
+	(&nilfs_segctor_attr_##name.attr)
+
+#endif /* _NILFS_SYSFS_H */
diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
new file mode 100644
index 0000000000..71400496ed
--- /dev/null
+++ b/fs/nilfs2/the_nilfs.c
@@ -0,0 +1,914 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * the_nilfs shared structure.
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Ryusuke Konishi.
+ *
+ */
+
+#include <linux/buffer_head.h>
+#include <linux/slab.h>
+#include <linux/blkdev.h>
+#include <linux/backing-dev.h>
+#include <linux/random.h>
+#include <linux/log2.h>
+#include <linux/crc32.h>
+#include "nilfs.h"
+#include "segment.h"
+#include "alloc.h"
+#include "cpfile.h"
+#include "sufile.h"
+#include "dat.h"
+#include "segbuf.h"
+
+
+static int nilfs_valid_sb(struct nilfs_super_block *sbp);
+
+void nilfs_set_last_segment(struct the_nilfs *nilfs,
+			    sector_t start_blocknr, u64 seq, __u64 cno)
+{
+	spin_lock(&nilfs->ns_last_segment_lock);
+	nilfs->ns_last_pseg = start_blocknr;
+	nilfs->ns_last_seq = seq;
+	nilfs->ns_last_cno = cno;
+
+	if (!nilfs_sb_dirty(nilfs)) {
+		if (nilfs->ns_prev_seq == nilfs->ns_last_seq)
+			goto stay_cursor;
+
+		set_nilfs_sb_dirty(nilfs);
+	}
+	nilfs->ns_prev_seq = nilfs->ns_last_seq;
+
+ stay_cursor:
+	spin_unlock(&nilfs->ns_last_segment_lock);
+}
+
+/**
+ * alloc_nilfs - allocate a nilfs object
+ * @sb: super block instance
+ *
+ * Return Value: On success, pointer to the_nilfs is returned.
+ * On error, NULL is returned.
+ */
+struct the_nilfs *alloc_nilfs(struct super_block *sb)
+{
+	struct the_nilfs *nilfs;
+
+	nilfs = kzalloc(sizeof(*nilfs), GFP_KERNEL);
+	if (!nilfs)
+		return NULL;
+
+	nilfs->ns_sb = sb;
+	nilfs->ns_bdev = sb->s_bdev;
+	atomic_set(&nilfs->ns_ndirtyblks, 0);
+	init_rwsem(&nilfs->ns_sem);
+	mutex_init(&nilfs->ns_snapshot_mount_mutex);
+	INIT_LIST_HEAD(&nilfs->ns_dirty_files);
+	INIT_LIST_HEAD(&nilfs->ns_gc_inodes);
+	spin_lock_init(&nilfs->ns_inode_lock);
+	spin_lock_init(&nilfs->ns_next_gen_lock);
+	spin_lock_init(&nilfs->ns_last_segment_lock);
+	nilfs->ns_cptree = RB_ROOT;
+	spin_lock_init(&nilfs->ns_cptree_lock);
+	init_rwsem(&nilfs->ns_segctor_sem);
+	nilfs->ns_sb_update_freq = NILFS_SB_FREQ;
+
+	return nilfs;
+}
+
+/**
+ * destroy_nilfs - destroy nilfs object
+ * @nilfs: nilfs object to be released
+ */
+void destroy_nilfs(struct the_nilfs *nilfs)
+{
+	might_sleep();
+	if (nilfs_init(nilfs)) {
+		brelse(nilfs->ns_sbh[0]);
+		brelse(nilfs->ns_sbh[1]);
+	}
+	kfree(nilfs);
+}
+
+static int nilfs_load_super_root(struct the_nilfs *nilfs,
+				 struct super_block *sb, sector_t sr_block)
+{
+	struct buffer_head *bh_sr;
+	struct nilfs_super_root *raw_sr;
+	struct nilfs_super_block **sbp = nilfs->ns_sbp;
+	struct nilfs_inode *rawi;
+	unsigned int dat_entry_size, segment_usage_size, checkpoint_size;
+	unsigned int inode_size;
+	int err;
+
+	err = nilfs_read_super_root_block(nilfs, sr_block, &bh_sr, 1);
+	if (unlikely(err))
+		return err;
+
+	down_read(&nilfs->ns_sem);
+	dat_entry_size = le16_to_cpu(sbp[0]->s_dat_entry_size);
+	checkpoint_size = le16_to_cpu(sbp[0]->s_checkpoint_size);
+	segment_usage_size = le16_to_cpu(sbp[0]->s_segment_usage_size);
+	up_read(&nilfs->ns_sem);
+
+	inode_size = nilfs->ns_inode_size;
+
+	rawi = (void *)bh_sr->b_data + NILFS_SR_DAT_OFFSET(inode_size);
+	err = nilfs_dat_read(sb, dat_entry_size, rawi, &nilfs->ns_dat);
+	if (err)
+		goto failed;
+
+	rawi = (void *)bh_sr->b_data + NILFS_SR_CPFILE_OFFSET(inode_size);
+	err = nilfs_cpfile_read(sb, checkpoint_size, rawi, &nilfs->ns_cpfile);
+	if (err)
+		goto failed_dat;
+
+	rawi = (void *)bh_sr->b_data + NILFS_SR_SUFILE_OFFSET(inode_size);
+	err = nilfs_sufile_read(sb, segment_usage_size, rawi,
+				&nilfs->ns_sufile);
+	if (err)
+		goto failed_cpfile;
+
+	raw_sr = (struct nilfs_super_root *)bh_sr->b_data;
+	nilfs->ns_nongc_ctime = le64_to_cpu(raw_sr->sr_nongc_ctime);
+
+ failed:
+	brelse(bh_sr);
+	return err;
+
+ failed_cpfile:
+	iput(nilfs->ns_cpfile);
+
+ failed_dat:
+	iput(nilfs->ns_dat);
+	goto failed;
+}
+
+static void nilfs_init_recovery_info(struct nilfs_recovery_info *ri)
+{
+	memset(ri, 0, sizeof(*ri));
+	INIT_LIST_HEAD(&ri->ri_used_segments);
+}
+
+static void nilfs_clear_recovery_info(struct nilfs_recovery_info *ri)
+{
+	nilfs_dispose_segment_list(&ri->ri_used_segments);
+}
+
+/**
+ * nilfs_store_log_cursor - load log cursor from a super block
+ * @nilfs: nilfs object
+ * @sbp: buffer storing super block to be read
+ *
+ * nilfs_store_log_cursor() reads the last position of the log
+ * containing a super root from a given super block, and initializes
+ * relevant information on the nilfs object preparatory for log
+ * scanning and recovery.
+ */
+static int nilfs_store_log_cursor(struct the_nilfs *nilfs,
+				  struct nilfs_super_block *sbp)
+{
+	int ret = 0;
+
+	nilfs->ns_last_pseg = le64_to_cpu(sbp->s_last_pseg);
+	nilfs->ns_last_cno = le64_to_cpu(sbp->s_last_cno);
+	nilfs->ns_last_seq = le64_to_cpu(sbp->s_last_seq);
+
+	nilfs->ns_prev_seq = nilfs->ns_last_seq;
+	nilfs->ns_seg_seq = nilfs->ns_last_seq;
+	nilfs->ns_segnum =
+		nilfs_get_segnum_of_block(nilfs, nilfs->ns_last_pseg);
+	nilfs->ns_cno = nilfs->ns_last_cno + 1;
+	if (nilfs->ns_segnum >= nilfs->ns_nsegments) {
+		nilfs_err(nilfs->ns_sb,
+			  "pointed segment number is out of range: segnum=%llu, nsegments=%lu",
+			  (unsigned long long)nilfs->ns_segnum,
+			  nilfs->ns_nsegments);
+		ret = -EINVAL;
+	}
+	return ret;
+}
+
+/**
+ * nilfs_get_blocksize - get block size from raw superblock data
+ * @sb: super block instance
+ * @sbp: superblock raw data buffer
+ * @blocksize: place to store block size
+ *
+ * nilfs_get_blocksize() calculates the block size from the block size
+ * exponent information written in @sbp and stores it in @blocksize,
+ * or aborts with an error message if it's too large.
+ *
+ * Return Value: On success, 0 is returned. If the block size is too
+ * large, -EINVAL is returned.
+ */
+static int nilfs_get_blocksize(struct super_block *sb,
+			       struct nilfs_super_block *sbp, int *blocksize)
+{
+	unsigned int shift_bits = le32_to_cpu(sbp->s_log_block_size);
+
+	if (unlikely(shift_bits >
+		     ilog2(NILFS_MAX_BLOCK_SIZE) - BLOCK_SIZE_BITS)) {
+		nilfs_err(sb, "too large filesystem blocksize: 2 ^ %u KiB",
+			  shift_bits);
+		return -EINVAL;
+	}
+	*blocksize = BLOCK_SIZE << shift_bits;
+	return 0;
+}
+
+/**
+ * load_nilfs - load and recover the nilfs
+ * @nilfs: the_nilfs structure to be released
+ * @sb: super block instance used to recover past segment
+ *
+ * load_nilfs() searches and load the latest super root,
+ * attaches the last segment, and does recovery if needed.
+ * The caller must call this exclusively for simultaneous mounts.
+ */
+int load_nilfs(struct the_nilfs *nilfs, struct super_block *sb)
+{
+	struct nilfs_recovery_info ri;
+	unsigned int s_flags = sb->s_flags;
+	int really_read_only = bdev_read_only(nilfs->ns_bdev);
+	int valid_fs = nilfs_valid_fs(nilfs);
+	int err;
+
+	if (!valid_fs) {
+		nilfs_warn(sb, "mounting unchecked fs");
+		if (s_flags & SB_RDONLY) {
+			nilfs_info(sb,
+				   "recovery required for readonly filesystem");
+			nilfs_info(sb,
+				   "write access will be enabled during recovery");
+		}
+	}
+
+	nilfs_init_recovery_info(&ri);
+
+	err = nilfs_search_super_root(nilfs, &ri);
+	if (unlikely(err)) {
+		struct nilfs_super_block **sbp = nilfs->ns_sbp;
+		int blocksize;
+
+		if (err != -EINVAL)
+			goto scan_error;
+
+		if (!nilfs_valid_sb(sbp[1])) {
+			nilfs_warn(sb,
+				   "unable to fall back to spare super block");
+			goto scan_error;
+		}
+		nilfs_info(sb, "trying rollback from an earlier position");
+
+		/*
+		 * restore super block with its spare and reconfigure
+		 * relevant states of the nilfs object.
+		 */
+		memcpy(sbp[0], sbp[1], nilfs->ns_sbsize);
+		nilfs->ns_crc_seed = le32_to_cpu(sbp[0]->s_crc_seed);
+		nilfs->ns_sbwtime = le64_to_cpu(sbp[0]->s_wtime);
+
+		/* verify consistency between two super blocks */
+		err = nilfs_get_blocksize(sb, sbp[0], &blocksize);
+		if (err)
+			goto scan_error;
+
+		if (blocksize != nilfs->ns_blocksize) {
+			nilfs_warn(sb,
+				   "blocksize differs between two super blocks (%d != %d)",
+				   blocksize, nilfs->ns_blocksize);
+			err = -EINVAL;
+			goto scan_error;
+		}
+
+		err = nilfs_store_log_cursor(nilfs, sbp[0]);
+		if (err)
+			goto scan_error;
+
+		/* drop clean flag to allow roll-forward and recovery */
+		nilfs->ns_mount_state &= ~NILFS_VALID_FS;
+		valid_fs = 0;
+
+		err = nilfs_search_super_root(nilfs, &ri);
+		if (err)
+			goto scan_error;
+	}
+
+	err = nilfs_load_super_root(nilfs, sb, ri.ri_super_root);
+	if (unlikely(err)) {
+		nilfs_err(sb, "error %d while loading super root", err);
+		goto failed;
+	}
+
+	err = nilfs_sysfs_create_device_group(sb);
+	if (unlikely(err))
+		goto sysfs_error;
+
+	if (valid_fs)
+		goto skip_recovery;
+
+	if (s_flags & SB_RDONLY) {
+		__u64 features;
+
+		if (nilfs_test_opt(nilfs, NORECOVERY)) {
+			nilfs_info(sb,
+				   "norecovery option specified, skipping roll-forward recovery");
+			goto skip_recovery;
+		}
+		features = le64_to_cpu(nilfs->ns_sbp[0]->s_feature_compat_ro) &
+			~NILFS_FEATURE_COMPAT_RO_SUPP;
+		if (features) {
+			nilfs_err(sb,
+				  "couldn't proceed with recovery because of unsupported optional features (%llx)",
+				  (unsigned long long)features);
+			err = -EROFS;
+			goto failed_unload;
+		}
+		if (really_read_only) {
+			nilfs_err(sb,
+				  "write access unavailable, cannot proceed");
+			err = -EROFS;
+			goto failed_unload;
+		}
+		sb->s_flags &= ~SB_RDONLY;
+	} else if (nilfs_test_opt(nilfs, NORECOVERY)) {
+		nilfs_err(sb,
+			  "recovery cancelled because norecovery option was specified for a read/write mount");
+		err = -EINVAL;
+		goto failed_unload;
+	}
+
+	err = nilfs_salvage_orphan_logs(nilfs, sb, &ri);
+	if (err)
+		goto failed_unload;
+
+	down_write(&nilfs->ns_sem);
+	nilfs->ns_mount_state |= NILFS_VALID_FS; /* set "clean" flag */
+	err = nilfs_cleanup_super(sb);
+	up_write(&nilfs->ns_sem);
+
+	if (err) {
+		nilfs_err(sb,
+			  "error %d updating super block. recovery unfinished.",
+			  err);
+		goto failed_unload;
+	}
+	nilfs_info(sb, "recovery complete");
+
+ skip_recovery:
+	nilfs_clear_recovery_info(&ri);
+	sb->s_flags = s_flags;
+	return 0;
+
+ scan_error:
+	nilfs_err(sb, "error %d while searching super root", err);
+	goto failed;
+
+ failed_unload:
+	nilfs_sysfs_delete_device_group(nilfs);
+
+ sysfs_error:
+	iput(nilfs->ns_cpfile);
+	iput(nilfs->ns_sufile);
+	iput(nilfs->ns_dat);
+
+ failed:
+	nilfs_clear_recovery_info(&ri);
+	sb->s_flags = s_flags;
+	return err;
+}
+
+static unsigned long long nilfs_max_size(unsigned int blkbits)
+{
+	unsigned int max_bits;
+	unsigned long long res = MAX_LFS_FILESIZE; /* page cache limit */
+
+	max_bits = blkbits + NILFS_BMAP_KEY_BIT; /* bmap size limit */
+	if (max_bits < 64)
+		res = min_t(unsigned long long, res, (1ULL << max_bits) - 1);
+	return res;
+}
+
+/**
+ * nilfs_nrsvsegs - calculate the number of reserved segments
+ * @nilfs: nilfs object
+ * @nsegs: total number of segments
+ */
+unsigned long nilfs_nrsvsegs(struct the_nilfs *nilfs, unsigned long nsegs)
+{
+	return max_t(unsigned long, NILFS_MIN_NRSVSEGS,
+		     DIV_ROUND_UP(nsegs * nilfs->ns_r_segments_percentage,
+				  100));
+}
+
+/**
+ * nilfs_max_segment_count - calculate the maximum number of segments
+ * @nilfs: nilfs object
+ */
+static u64 nilfs_max_segment_count(struct the_nilfs *nilfs)
+{
+	u64 max_count = U64_MAX;
+
+	do_div(max_count, nilfs->ns_blocks_per_segment);
+	return min_t(u64, max_count, ULONG_MAX);
+}
+
+void nilfs_set_nsegments(struct the_nilfs *nilfs, unsigned long nsegs)
+{
+	nilfs->ns_nsegments = nsegs;
+	nilfs->ns_nrsvsegs = nilfs_nrsvsegs(nilfs, nsegs);
+}
+
+static int nilfs_store_disk_layout(struct the_nilfs *nilfs,
+				   struct nilfs_super_block *sbp)
+{
+	u64 nsegments, nblocks;
+
+	if (le32_to_cpu(sbp->s_rev_level) < NILFS_MIN_SUPP_REV) {
+		nilfs_err(nilfs->ns_sb,
+			  "unsupported revision (superblock rev.=%d.%d, current rev.=%d.%d). Please check the version of mkfs.nilfs(2).",
+			  le32_to_cpu(sbp->s_rev_level),
+			  le16_to_cpu(sbp->s_minor_rev_level),
+			  NILFS_CURRENT_REV, NILFS_MINOR_REV);
+		return -EINVAL;
+	}
+	nilfs->ns_sbsize = le16_to_cpu(sbp->s_bytes);
+	if (nilfs->ns_sbsize > BLOCK_SIZE)
+		return -EINVAL;
+
+	nilfs->ns_inode_size = le16_to_cpu(sbp->s_inode_size);
+	if (nilfs->ns_inode_size > nilfs->ns_blocksize) {
+		nilfs_err(nilfs->ns_sb, "too large inode size: %d bytes",
+			  nilfs->ns_inode_size);
+		return -EINVAL;
+	} else if (nilfs->ns_inode_size < NILFS_MIN_INODE_SIZE) {
+		nilfs_err(nilfs->ns_sb, "too small inode size: %d bytes",
+			  nilfs->ns_inode_size);
+		return -EINVAL;
+	}
+
+	nilfs->ns_first_ino = le32_to_cpu(sbp->s_first_ino);
+
+	nilfs->ns_blocks_per_segment = le32_to_cpu(sbp->s_blocks_per_segment);
+	if (nilfs->ns_blocks_per_segment < NILFS_SEG_MIN_BLOCKS) {
+		nilfs_err(nilfs->ns_sb, "too short segment: %lu blocks",
+			  nilfs->ns_blocks_per_segment);
+		return -EINVAL;
+	}
+
+	nilfs->ns_first_data_block = le64_to_cpu(sbp->s_first_data_block);
+	nilfs->ns_r_segments_percentage =
+		le32_to_cpu(sbp->s_r_segments_percentage);
+	if (nilfs->ns_r_segments_percentage < 1 ||
+	    nilfs->ns_r_segments_percentage > 99) {
+		nilfs_err(nilfs->ns_sb,
+			  "invalid reserved segments percentage: %lu",
+			  nilfs->ns_r_segments_percentage);
+		return -EINVAL;
+	}
+
+	nsegments = le64_to_cpu(sbp->s_nsegments);
+	if (nsegments > nilfs_max_segment_count(nilfs)) {
+		nilfs_err(nilfs->ns_sb,
+			  "segment count %llu exceeds upper limit (%llu segments)",
+			  (unsigned long long)nsegments,
+			  (unsigned long long)nilfs_max_segment_count(nilfs));
+		return -EINVAL;
+	}
+
+	nblocks = sb_bdev_nr_blocks(nilfs->ns_sb);
+	if (nblocks) {
+		u64 min_block_count = nsegments * nilfs->ns_blocks_per_segment;
+		/*
+		 * To avoid failing to mount early device images without a
+		 * second superblock, exclude that block count from the
+		 * "min_block_count" calculation.
+		 */
+
+		if (nblocks < min_block_count) {
+			nilfs_err(nilfs->ns_sb,
+				  "total number of segment blocks %llu exceeds device size (%llu blocks)",
+				  (unsigned long long)min_block_count,
+				  (unsigned long long)nblocks);
+			return -EINVAL;
+		}
+	}
+
+	nilfs_set_nsegments(nilfs, nsegments);
+	nilfs->ns_crc_seed = le32_to_cpu(sbp->s_crc_seed);
+	return 0;
+}
+
+static int nilfs_valid_sb(struct nilfs_super_block *sbp)
+{
+	static unsigned char sum[4];
+	const int sumoff = offsetof(struct nilfs_super_block, s_sum);
+	size_t bytes;
+	u32 crc;
+
+	if (!sbp || le16_to_cpu(sbp->s_magic) != NILFS_SUPER_MAGIC)
+		return 0;
+	bytes = le16_to_cpu(sbp->s_bytes);
+	if (bytes < sumoff + 4 || bytes > BLOCK_SIZE)
+		return 0;
+	crc = crc32_le(le32_to_cpu(sbp->s_crc_seed), (unsigned char *)sbp,
+		       sumoff);
+	crc = crc32_le(crc, sum, 4);
+	crc = crc32_le(crc, (unsigned char *)sbp + sumoff + 4,
+		       bytes - sumoff - 4);
+	return crc == le32_to_cpu(sbp->s_sum);
+}
+
+/**
+ * nilfs_sb2_bad_offset - check the location of the second superblock
+ * @sbp: superblock raw data buffer
+ * @offset: byte offset of second superblock calculated from device size
+ *
+ * nilfs_sb2_bad_offset() checks if the position on the second
+ * superblock is valid or not based on the filesystem parameters
+ * stored in @sbp.  If @offset points to a location within the segment
+ * area, or if the parameters themselves are not normal, it is
+ * determined to be invalid.
+ *
+ * Return Value: true if invalid, false if valid.
+ */
+static bool nilfs_sb2_bad_offset(struct nilfs_super_block *sbp, u64 offset)
+{
+	unsigned int shift_bits = le32_to_cpu(sbp->s_log_block_size);
+	u32 blocks_per_segment = le32_to_cpu(sbp->s_blocks_per_segment);
+	u64 nsegments = le64_to_cpu(sbp->s_nsegments);
+	u64 index;
+
+	if (blocks_per_segment < NILFS_SEG_MIN_BLOCKS ||
+	    shift_bits > ilog2(NILFS_MAX_BLOCK_SIZE) - BLOCK_SIZE_BITS)
+		return true;
+
+	index = offset >> (shift_bits + BLOCK_SIZE_BITS);
+	do_div(index, blocks_per_segment);
+	return index < nsegments;
+}
+
+static void nilfs_release_super_block(struct the_nilfs *nilfs)
+{
+	int i;
+
+	for (i = 0; i < 2; i++) {
+		if (nilfs->ns_sbp[i]) {
+			brelse(nilfs->ns_sbh[i]);
+			nilfs->ns_sbh[i] = NULL;
+			nilfs->ns_sbp[i] = NULL;
+		}
+	}
+}
+
+void nilfs_fall_back_super_block(struct the_nilfs *nilfs)
+{
+	brelse(nilfs->ns_sbh[0]);
+	nilfs->ns_sbh[0] = nilfs->ns_sbh[1];
+	nilfs->ns_sbp[0] = nilfs->ns_sbp[1];
+	nilfs->ns_sbh[1] = NULL;
+	nilfs->ns_sbp[1] = NULL;
+}
+
+void nilfs_swap_super_block(struct the_nilfs *nilfs)
+{
+	struct buffer_head *tsbh = nilfs->ns_sbh[0];
+	struct nilfs_super_block *tsbp = nilfs->ns_sbp[0];
+
+	nilfs->ns_sbh[0] = nilfs->ns_sbh[1];
+	nilfs->ns_sbp[0] = nilfs->ns_sbp[1];
+	nilfs->ns_sbh[1] = tsbh;
+	nilfs->ns_sbp[1] = tsbp;
+}
+
+static int nilfs_load_super_block(struct the_nilfs *nilfs,
+				  struct super_block *sb, int blocksize,
+				  struct nilfs_super_block **sbpp)
+{
+	struct nilfs_super_block **sbp = nilfs->ns_sbp;
+	struct buffer_head **sbh = nilfs->ns_sbh;
+	u64 sb2off, devsize = bdev_nr_bytes(nilfs->ns_bdev);
+	int valid[2], swp = 0;
+
+	if (devsize < NILFS_SEG_MIN_BLOCKS * NILFS_MIN_BLOCK_SIZE + 4096) {
+		nilfs_err(sb, "device size too small");
+		return -EINVAL;
+	}
+	sb2off = NILFS_SB2_OFFSET_BYTES(devsize);
+
+	sbp[0] = nilfs_read_super_block(sb, NILFS_SB_OFFSET_BYTES, blocksize,
+					&sbh[0]);
+	sbp[1] = nilfs_read_super_block(sb, sb2off, blocksize, &sbh[1]);
+
+	if (!sbp[0]) {
+		if (!sbp[1]) {
+			nilfs_err(sb, "unable to read superblock");
+			return -EIO;
+		}
+		nilfs_warn(sb,
+			   "unable to read primary superblock (blocksize = %d)",
+			   blocksize);
+	} else if (!sbp[1]) {
+		nilfs_warn(sb,
+			   "unable to read secondary superblock (blocksize = %d)",
+			   blocksize);
+	}
+
+	/*
+	 * Compare two super blocks and set 1 in swp if the secondary
+	 * super block is valid and newer.  Otherwise, set 0 in swp.
+	 */
+	valid[0] = nilfs_valid_sb(sbp[0]);
+	valid[1] = nilfs_valid_sb(sbp[1]);
+	swp = valid[1] && (!valid[0] ||
+			   le64_to_cpu(sbp[1]->s_last_cno) >
+			   le64_to_cpu(sbp[0]->s_last_cno));
+
+	if (valid[swp] && nilfs_sb2_bad_offset(sbp[swp], sb2off)) {
+		brelse(sbh[1]);
+		sbh[1] = NULL;
+		sbp[1] = NULL;
+		valid[1] = 0;
+		swp = 0;
+	}
+	if (!valid[swp]) {
+		nilfs_release_super_block(nilfs);
+		nilfs_err(sb, "couldn't find nilfs on the device");
+		return -EINVAL;
+	}
+
+	if (!valid[!swp])
+		nilfs_warn(sb,
+			   "broken superblock, retrying with spare superblock (blocksize = %d)",
+			   blocksize);
+	if (swp)
+		nilfs_swap_super_block(nilfs);
+
+	nilfs->ns_sbwcount = 0;
+	nilfs->ns_sbwtime = le64_to_cpu(sbp[0]->s_wtime);
+	nilfs->ns_prot_seq = le64_to_cpu(sbp[valid[1] & !swp]->s_last_seq);
+	*sbpp = sbp[0];
+	return 0;
+}
+
+/**
+ * init_nilfs - initialize a NILFS instance.
+ * @nilfs: the_nilfs structure
+ * @sb: super block
+ * @data: mount options
+ *
+ * init_nilfs() performs common initialization per block device (e.g.
+ * reading the super block, getting disk layout information, initializing
+ * shared fields in the_nilfs).
+ *
+ * Return Value: On success, 0 is returned. On error, a negative error
+ * code is returned.
+ */
+int init_nilfs(struct the_nilfs *nilfs, struct super_block *sb, char *data)
+{
+	struct nilfs_super_block *sbp;
+	int blocksize;
+	int err;
+
+	down_write(&nilfs->ns_sem);
+
+	blocksize = sb_min_blocksize(sb, NILFS_MIN_BLOCK_SIZE);
+	if (!blocksize) {
+		nilfs_err(sb, "unable to set blocksize");
+		err = -EINVAL;
+		goto out;
+	}
+	err = nilfs_load_super_block(nilfs, sb, blocksize, &sbp);
+	if (err)
+		goto out;
+
+	err = nilfs_store_magic_and_option(sb, sbp, data);
+	if (err)
+		goto failed_sbh;
+
+	err = nilfs_check_feature_compatibility(sb, sbp);
+	if (err)
+		goto failed_sbh;
+
+	err = nilfs_get_blocksize(sb, sbp, &blocksize);
+	if (err)
+		goto failed_sbh;
+
+	if (blocksize < NILFS_MIN_BLOCK_SIZE) {
+		nilfs_err(sb,
+			  "couldn't mount because of unsupported filesystem blocksize %d",
+			  blocksize);
+		err = -EINVAL;
+		goto failed_sbh;
+	}
+	if (sb->s_blocksize != blocksize) {
+		int hw_blocksize = bdev_logical_block_size(sb->s_bdev);
+
+		if (blocksize < hw_blocksize) {
+			nilfs_err(sb,
+				  "blocksize %d too small for device (sector-size = %d)",
+				  blocksize, hw_blocksize);
+			err = -EINVAL;
+			goto failed_sbh;
+		}
+		nilfs_release_super_block(nilfs);
+		if (!sb_set_blocksize(sb, blocksize)) {
+			nilfs_err(sb, "bad blocksize %d", blocksize);
+			err = -EINVAL;
+			goto out;
+		}
+
+		err = nilfs_load_super_block(nilfs, sb, blocksize, &sbp);
+		if (err)
+			goto out;
+			/*
+			 * Not to failed_sbh; sbh is released automatically
+			 * when reloading fails.
+			 */
+	}
+	nilfs->ns_blocksize_bits = sb->s_blocksize_bits;
+	nilfs->ns_blocksize = blocksize;
+
+	get_random_bytes(&nilfs->ns_next_generation,
+			 sizeof(nilfs->ns_next_generation));
+
+	err = nilfs_store_disk_layout(nilfs, sbp);
+	if (err)
+		goto failed_sbh;
+
+	sb->s_maxbytes = nilfs_max_size(sb->s_blocksize_bits);
+
+	nilfs->ns_mount_state = le16_to_cpu(sbp->s_state);
+
+	err = nilfs_store_log_cursor(nilfs, sbp);
+	if (err)
+		goto failed_sbh;
+
+	set_nilfs_init(nilfs);
+	err = 0;
+ out:
+	up_write(&nilfs->ns_sem);
+	return err;
+
+ failed_sbh:
+	nilfs_release_super_block(nilfs);
+	goto out;
+}
+
+int nilfs_discard_segments(struct the_nilfs *nilfs, __u64 *segnump,
+			    size_t nsegs)
+{
+	sector_t seg_start, seg_end;
+	sector_t start = 0, nblocks = 0;
+	unsigned int sects_per_block;
+	__u64 *sn;
+	int ret = 0;
+
+	sects_per_block = (1 << nilfs->ns_blocksize_bits) /
+		bdev_logical_block_size(nilfs->ns_bdev);
+	for (sn = segnump; sn < segnump + nsegs; sn++) {
+		nilfs_get_segment_range(nilfs, *sn, &seg_start, &seg_end);
+
+		if (!nblocks) {
+			start = seg_start;
+			nblocks = seg_end - seg_start + 1;
+		} else if (start + nblocks == seg_start) {
+			nblocks += seg_end - seg_start + 1;
+		} else {
+			ret = blkdev_issue_discard(nilfs->ns_bdev,
+						   start * sects_per_block,
+						   nblocks * sects_per_block,
+						   GFP_NOFS);
+			if (ret < 0)
+				return ret;
+			nblocks = 0;
+		}
+	}
+	if (nblocks)
+		ret = blkdev_issue_discard(nilfs->ns_bdev,
+					   start * sects_per_block,
+					   nblocks * sects_per_block,
+					   GFP_NOFS);
+	return ret;
+}
+
+int nilfs_count_free_blocks(struct the_nilfs *nilfs, sector_t *nblocks)
+{
+	unsigned long ncleansegs;
+
+	ncleansegs = nilfs_sufile_get_ncleansegs(nilfs->ns_sufile);
+	*nblocks = (sector_t)ncleansegs * nilfs->ns_blocks_per_segment;
+	return 0;
+}
+
+int nilfs_near_disk_full(struct the_nilfs *nilfs)
+{
+	unsigned long ncleansegs, nincsegs;
+
+	ncleansegs = nilfs_sufile_get_ncleansegs(nilfs->ns_sufile);
+	nincsegs = atomic_read(&nilfs->ns_ndirtyblks) /
+		nilfs->ns_blocks_per_segment + 1;
+
+	return ncleansegs <= nilfs->ns_nrsvsegs + nincsegs;
+}
+
+struct nilfs_root *nilfs_lookup_root(struct the_nilfs *nilfs, __u64 cno)
+{
+	struct rb_node *n;
+	struct nilfs_root *root;
+
+	spin_lock(&nilfs->ns_cptree_lock);
+	n = nilfs->ns_cptree.rb_node;
+	while (n) {
+		root = rb_entry(n, struct nilfs_root, rb_node);
+
+		if (cno < root->cno) {
+			n = n->rb_left;
+		} else if (cno > root->cno) {
+			n = n->rb_right;
+		} else {
+			refcount_inc(&root->count);
+			spin_unlock(&nilfs->ns_cptree_lock);
+			return root;
+		}
+	}
+	spin_unlock(&nilfs->ns_cptree_lock);
+
+	return NULL;
+}
+
+struct nilfs_root *
+nilfs_find_or_create_root(struct the_nilfs *nilfs, __u64 cno)
+{
+	struct rb_node **p, *parent;
+	struct nilfs_root *root, *new;
+	int err;
+
+	root = nilfs_lookup_root(nilfs, cno);
+	if (root)
+		return root;
+
+	new = kzalloc(sizeof(*root), GFP_KERNEL);
+	if (!new)
+		return NULL;
+
+	spin_lock(&nilfs->ns_cptree_lock);
+
+	p = &nilfs->ns_cptree.rb_node;
+	parent = NULL;
+
+	while (*p) {
+		parent = *p;
+		root = rb_entry(parent, struct nilfs_root, rb_node);
+
+		if (cno < root->cno) {
+			p = &(*p)->rb_left;
+		} else if (cno > root->cno) {
+			p = &(*p)->rb_right;
+		} else {
+			refcount_inc(&root->count);
+			spin_unlock(&nilfs->ns_cptree_lock);
+			kfree(new);
+			return root;
+		}
+	}
+
+	new->cno = cno;
+	new->ifile = NULL;
+	new->nilfs = nilfs;
+	refcount_set(&new->count, 1);
+	atomic64_set(&new->inodes_count, 0);
+	atomic64_set(&new->blocks_count, 0);
+
+	rb_link_node(&new->rb_node, parent, p);
+	rb_insert_color(&new->rb_node, &nilfs->ns_cptree);
+
+	spin_unlock(&nilfs->ns_cptree_lock);
+
+	err = nilfs_sysfs_create_snapshot_group(new);
+	if (err) {
+		kfree(new);
+		new = NULL;
+	}
+
+	return new;
+}
+
+void nilfs_put_root(struct nilfs_root *root)
+{
+	struct the_nilfs *nilfs = root->nilfs;
+
+	if (refcount_dec_and_lock(&root->count, &nilfs->ns_cptree_lock)) {
+		rb_erase(&root->rb_node, &nilfs->ns_cptree);
+		spin_unlock(&nilfs->ns_cptree_lock);
+
+		nilfs_sysfs_delete_snapshot_group(root);
+		iput(root->ifile);
+
+		kfree(root);
+	}
+}
diff --git a/fs/nilfs2/the_nilfs.h b/fs/nilfs2/the_nilfs.h
new file mode 100644
index 0000000000..cd4ae1b8ae
--- /dev/null
+++ b/fs/nilfs2/the_nilfs.h
@@ -0,0 +1,386 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * the_nilfs shared structure.
+ *
+ * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
+ *
+ * Written by Ryusuke Konishi.
+ *
+ */
+
+#ifndef _THE_NILFS_H
+#define _THE_NILFS_H
+
+#include <linux/types.h>
+#include <linux/buffer_head.h>
+#include <linux/rbtree.h>
+#include <linux/fs.h>
+#include <linux/blkdev.h>
+#include <linux/backing-dev.h>
+#include <linux/slab.h>
+#include <linux/refcount.h>
+
+struct nilfs_sc_info;
+struct nilfs_sysfs_dev_subgroups;
+
+/* the_nilfs struct */
+enum {
+	THE_NILFS_INIT = 0,     /* Information from super_block is set */
+	THE_NILFS_DISCONTINUED,	/* 'next' pointer chain has broken */
+	THE_NILFS_GC_RUNNING,	/* gc process is running */
+	THE_NILFS_SB_DIRTY,	/* super block is dirty */
+	THE_NILFS_PURGING,	/* disposing dirty files for cleanup */
+};
+
+/**
+ * struct the_nilfs - struct to supervise multiple nilfs mount points
+ * @ns_flags: flags
+ * @ns_flushed_device: flag indicating if all volatile data was flushed
+ * @ns_sb: back pointer to super block instance
+ * @ns_bdev: block device
+ * @ns_sem: semaphore for shared states
+ * @ns_snapshot_mount_mutex: mutex to protect snapshot mounts
+ * @ns_sbh: buffer heads of on-disk super blocks
+ * @ns_sbp: pointers to super block data
+ * @ns_sbwtime: previous write time of super block
+ * @ns_sbwcount: write count of super block
+ * @ns_sbsize: size of valid data in super block
+ * @ns_mount_state: file system state
+ * @ns_sb_update_freq: interval of periodical update of superblocks (in seconds)
+ * @ns_seg_seq: segment sequence counter
+ * @ns_segnum: index number of the latest full segment.
+ * @ns_nextnum: index number of the full segment index to be used next
+ * @ns_pseg_offset: offset of next partial segment in the current full segment
+ * @ns_cno: next checkpoint number
+ * @ns_ctime: write time of the last segment
+ * @ns_nongc_ctime: write time of the last segment not for cleaner operation
+ * @ns_ndirtyblks: Number of dirty data blocks
+ * @ns_last_segment_lock: lock protecting fields for the latest segment
+ * @ns_last_pseg: start block number of the latest segment
+ * @ns_last_seq: sequence value of the latest segment
+ * @ns_last_cno: checkpoint number of the latest segment
+ * @ns_prot_seq: least sequence number of segments which must not be reclaimed
+ * @ns_prev_seq: base sequence number used to decide if advance log cursor
+ * @ns_writer: log writer
+ * @ns_segctor_sem: semaphore protecting log write
+ * @ns_dat: DAT file inode
+ * @ns_cpfile: checkpoint file inode
+ * @ns_sufile: segusage file inode
+ * @ns_cptree: rb-tree of all mounted checkpoints (nilfs_root)
+ * @ns_cptree_lock: lock protecting @ns_cptree
+ * @ns_dirty_files: list of dirty files
+ * @ns_inode_lock: lock protecting @ns_dirty_files
+ * @ns_gc_inodes: dummy inodes to keep live blocks
+ * @ns_next_generation: next generation number for inodes
+ * @ns_next_gen_lock: lock protecting @ns_next_generation
+ * @ns_mount_opt: mount options
+ * @ns_resuid: uid for reserved blocks
+ * @ns_resgid: gid for reserved blocks
+ * @ns_interval: checkpoint creation interval
+ * @ns_watermark: watermark for the number of dirty buffers
+ * @ns_blocksize_bits: bit length of block size
+ * @ns_blocksize: block size
+ * @ns_nsegments: number of segments in filesystem
+ * @ns_blocks_per_segment: number of blocks per segment
+ * @ns_r_segments_percentage: reserved segments percentage
+ * @ns_nrsvsegs: number of reserved segments
+ * @ns_first_data_block: block number of first data block
+ * @ns_inode_size: size of on-disk inode
+ * @ns_first_ino: first not-special inode number
+ * @ns_crc_seed: seed value of CRC32 calculation
+ * @ns_dev_kobj: /sys/fs/<nilfs>/<device>
+ * @ns_dev_kobj_unregister: completion state
+ * @ns_dev_subgroups: <device> subgroups pointer
+ */
+struct the_nilfs {
+	unsigned long		ns_flags;
+	int			ns_flushed_device;
+
+	struct super_block     *ns_sb;
+	struct block_device    *ns_bdev;
+	struct rw_semaphore	ns_sem;
+	struct mutex		ns_snapshot_mount_mutex;
+
+	/*
+	 * used for
+	 * - loading the latest checkpoint exclusively.
+	 * - allocating a new full segment.
+	 */
+	struct buffer_head     *ns_sbh[2];
+	struct nilfs_super_block *ns_sbp[2];
+	time64_t		ns_sbwtime;
+	unsigned int		ns_sbwcount;
+	unsigned int		ns_sbsize;
+	unsigned int		ns_mount_state;
+	unsigned int		ns_sb_update_freq;
+
+	/*
+	 * The following fields are updated by a writable FS-instance.
+	 * These fields are protected by ns_segctor_sem outside load_nilfs().
+	 */
+	u64			ns_seg_seq;
+	__u64			ns_segnum;
+	__u64			ns_nextnum;
+	unsigned long		ns_pseg_offset;
+	__u64			ns_cno;
+	time64_t		ns_ctime;
+	time64_t		ns_nongc_ctime;
+	atomic_t		ns_ndirtyblks;
+
+	/*
+	 * The following fields hold information on the latest partial segment
+	 * written to disk with a super root.  These fields are protected by
+	 * ns_last_segment_lock.
+	 */
+	spinlock_t		ns_last_segment_lock;
+	sector_t		ns_last_pseg;
+	u64			ns_last_seq;
+	__u64			ns_last_cno;
+	u64			ns_prot_seq;
+	u64			ns_prev_seq;
+
+	struct nilfs_sc_info   *ns_writer;
+	struct rw_semaphore	ns_segctor_sem;
+
+	/*
+	 * Following fields are lock free except for the period before
+	 * the_nilfs is initialized.
+	 */
+	struct inode	       *ns_dat;
+	struct inode	       *ns_cpfile;
+	struct inode	       *ns_sufile;
+
+	/* Checkpoint tree */
+	struct rb_root		ns_cptree;
+	spinlock_t		ns_cptree_lock;
+
+	/* Dirty inode list */
+	struct list_head	ns_dirty_files;
+	spinlock_t		ns_inode_lock;
+
+	/* GC inode list */
+	struct list_head	ns_gc_inodes;
+
+	/* Inode allocator */
+	u32			ns_next_generation;
+	spinlock_t		ns_next_gen_lock;
+
+	/* Mount options */
+	unsigned long		ns_mount_opt;
+
+	uid_t			ns_resuid;
+	gid_t			ns_resgid;
+	unsigned long		ns_interval;
+	unsigned long		ns_watermark;
+
+	/* Disk layout information (static) */
+	unsigned int		ns_blocksize_bits;
+	unsigned int		ns_blocksize;
+	unsigned long		ns_nsegments;
+	unsigned long		ns_blocks_per_segment;
+	unsigned long		ns_r_segments_percentage;
+	unsigned long		ns_nrsvsegs;
+	unsigned long		ns_first_data_block;
+	int			ns_inode_size;
+	int			ns_first_ino;
+	u32			ns_crc_seed;
+
+	/* /sys/fs/<nilfs>/<device> */
+	struct kobject ns_dev_kobj;
+	struct completion ns_dev_kobj_unregister;
+	struct nilfs_sysfs_dev_subgroups *ns_dev_subgroups;
+};
+
+#define THE_NILFS_FNS(bit, name)					\
+static inline void set_nilfs_##name(struct the_nilfs *nilfs)		\
+{									\
+	set_bit(THE_NILFS_##bit, &(nilfs)->ns_flags);			\
+}									\
+static inline void clear_nilfs_##name(struct the_nilfs *nilfs)		\
+{									\
+	clear_bit(THE_NILFS_##bit, &(nilfs)->ns_flags);			\
+}									\
+static inline int nilfs_##name(struct the_nilfs *nilfs)			\
+{									\
+	return test_bit(THE_NILFS_##bit, &(nilfs)->ns_flags);		\
+}
+
+THE_NILFS_FNS(INIT, init)
+THE_NILFS_FNS(DISCONTINUED, discontinued)
+THE_NILFS_FNS(GC_RUNNING, gc_running)
+THE_NILFS_FNS(SB_DIRTY, sb_dirty)
+THE_NILFS_FNS(PURGING, purging)
+
+/*
+ * Mount option operations
+ */
+#define nilfs_clear_opt(nilfs, opt)  \
+	((nilfs)->ns_mount_opt &= ~NILFS_MOUNT_##opt)
+#define nilfs_set_opt(nilfs, opt)  \
+	((nilfs)->ns_mount_opt |= NILFS_MOUNT_##opt)
+#define nilfs_test_opt(nilfs, opt) ((nilfs)->ns_mount_opt & NILFS_MOUNT_##opt)
+#define nilfs_write_opt(nilfs, mask, opt)				\
+	((nilfs)->ns_mount_opt =					\
+		(((nilfs)->ns_mount_opt & ~NILFS_MOUNT_##mask) |	\
+		 NILFS_MOUNT_##opt))					\
+
+/**
+ * struct nilfs_root - nilfs root object
+ * @cno: checkpoint number
+ * @rb_node: red-black tree node
+ * @count: refcount of this structure
+ * @nilfs: nilfs object
+ * @ifile: inode file
+ * @inodes_count: number of inodes
+ * @blocks_count: number of blocks
+ * @snapshot_kobj: /sys/fs/<nilfs>/<device>/mounted_snapshots/<snapshot>
+ * @snapshot_kobj_unregister: completion state for kernel object
+ */
+struct nilfs_root {
+	__u64 cno;
+	struct rb_node rb_node;
+
+	refcount_t count;
+	struct the_nilfs *nilfs;
+	struct inode *ifile;
+
+	atomic64_t inodes_count;
+	atomic64_t blocks_count;
+
+	/* /sys/fs/<nilfs>/<device>/mounted_snapshots/<snapshot> */
+	struct kobject snapshot_kobj;
+	struct completion snapshot_kobj_unregister;
+};
+
+/* Special checkpoint number */
+#define NILFS_CPTREE_CURRENT_CNO	0
+
+/* Minimum interval of periodical update of superblocks (in seconds) */
+#define NILFS_SB_FREQ		10
+
+static inline int nilfs_sb_need_update(struct the_nilfs *nilfs)
+{
+	u64 t = ktime_get_real_seconds();
+
+	return t < nilfs->ns_sbwtime ||
+		t > nilfs->ns_sbwtime + nilfs->ns_sb_update_freq;
+}
+
+static inline int nilfs_sb_will_flip(struct the_nilfs *nilfs)
+{
+	int flip_bits = nilfs->ns_sbwcount & 0x0FL;
+
+	return (flip_bits != 0x08 && flip_bits != 0x0F);
+}
+
+void nilfs_set_last_segment(struct the_nilfs *, sector_t, u64, __u64);
+struct the_nilfs *alloc_nilfs(struct super_block *sb);
+void destroy_nilfs(struct the_nilfs *nilfs);
+int init_nilfs(struct the_nilfs *nilfs, struct super_block *sb, char *data);
+int load_nilfs(struct the_nilfs *nilfs, struct super_block *sb);
+unsigned long nilfs_nrsvsegs(struct the_nilfs *nilfs, unsigned long nsegs);
+void nilfs_set_nsegments(struct the_nilfs *nilfs, unsigned long nsegs);
+int nilfs_discard_segments(struct the_nilfs *, __u64 *, size_t);
+int nilfs_count_free_blocks(struct the_nilfs *, sector_t *);
+struct nilfs_root *nilfs_lookup_root(struct the_nilfs *nilfs, __u64 cno);
+struct nilfs_root *nilfs_find_or_create_root(struct the_nilfs *nilfs,
+					     __u64 cno);
+void nilfs_put_root(struct nilfs_root *root);
+int nilfs_near_disk_full(struct the_nilfs *);
+void nilfs_fall_back_super_block(struct the_nilfs *);
+void nilfs_swap_super_block(struct the_nilfs *);
+
+
+static inline void nilfs_get_root(struct nilfs_root *root)
+{
+	refcount_inc(&root->count);
+}
+
+static inline int nilfs_valid_fs(struct the_nilfs *nilfs)
+{
+	unsigned int valid_fs;
+
+	down_read(&nilfs->ns_sem);
+	valid_fs = (nilfs->ns_mount_state & NILFS_VALID_FS);
+	up_read(&nilfs->ns_sem);
+	return valid_fs;
+}
+
+static inline void
+nilfs_get_segment_range(struct the_nilfs *nilfs, __u64 segnum,
+			sector_t *seg_start, sector_t *seg_end)
+{
+	*seg_start = (sector_t)nilfs->ns_blocks_per_segment * segnum;
+	*seg_end = *seg_start + nilfs->ns_blocks_per_segment - 1;
+	if (segnum == 0)
+		*seg_start = nilfs->ns_first_data_block;
+}
+
+static inline sector_t
+nilfs_get_segment_start_blocknr(struct the_nilfs *nilfs, __u64 segnum)
+{
+	return (segnum == 0) ? nilfs->ns_first_data_block :
+		(sector_t)nilfs->ns_blocks_per_segment * segnum;
+}
+
+static inline __u64
+nilfs_get_segnum_of_block(struct the_nilfs *nilfs, sector_t blocknr)
+{
+	sector_t segnum = blocknr;
+
+	sector_div(segnum, nilfs->ns_blocks_per_segment);
+	return segnum;
+}
+
+static inline void
+nilfs_terminate_segment(struct the_nilfs *nilfs, sector_t seg_start,
+			sector_t seg_end)
+{
+	/* terminate the current full segment (used in case of I/O-error) */
+	nilfs->ns_pseg_offset = seg_end - seg_start + 1;
+}
+
+static inline void nilfs_shift_to_next_segment(struct the_nilfs *nilfs)
+{
+	/* move forward with a full segment */
+	nilfs->ns_segnum = nilfs->ns_nextnum;
+	nilfs->ns_pseg_offset = 0;
+	nilfs->ns_seg_seq++;
+}
+
+static inline __u64 nilfs_last_cno(struct the_nilfs *nilfs)
+{
+	__u64 cno;
+
+	spin_lock(&nilfs->ns_last_segment_lock);
+	cno = nilfs->ns_last_cno;
+	spin_unlock(&nilfs->ns_last_segment_lock);
+	return cno;
+}
+
+static inline int nilfs_segment_is_active(struct the_nilfs *nilfs, __u64 n)
+{
+	return n == nilfs->ns_segnum || n == nilfs->ns_nextnum;
+}
+
+static inline int nilfs_flush_device(struct the_nilfs *nilfs)
+{
+	int err;
+
+	if (!nilfs_test_opt(nilfs, BARRIER) || nilfs->ns_flushed_device)
+		return 0;
+
+	nilfs->ns_flushed_device = 1;
+	/*
+	 * the store to ns_flushed_device must not be reordered after
+	 * blkdev_issue_flush().
+	 */
+	smp_wmb();
+
+	err = blkdev_issue_flush(nilfs->ns_bdev);
+	if (err != -EIO)
+		err = 0;
+	return err;
+}
+
+#endif /* _THE_NILFS_H */