Adding upstream version 6.1.76.upstream/6.1.76

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

1 files changed, 2427 insertions, 0 deletions

diff --git a/fs/nilfs2/btree.c b/fs/nilfs2/btree.c
new file mode 100644
index 000000000..40ce92a33
--- /dev/null
+++ b/fs/nilfs2/btree.c
@@ -0,0 +1,2427 @@
+// 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_page->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 pagevec pvec;
+	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]);
+
+	pagevec_init(&pvec);
+
+	while (pagevec_lookup_tag(&pvec, btcache, &index,
+					PAGECACHE_TAG_DIRTY)) {
+		for (i = 0; i < pagevec_count(&pvec); i++) {
+			bh = head = page_buffers(pvec.pages[i]);
+			do {
+				if (buffer_dirty(bh))
+					nilfs_btree_add_dirty_buffer(btree,
+								     lists, bh);
+			} while ((bh = bh->b_this_page) != head);
+		}
+		pagevec_release(&pvec);
+		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;
+
+	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));
+}