Adding upstream version 5.10.209.upstream/5.10.209

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

1 files changed, 1137 insertions, 0 deletions

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
new file mode 100644
index 000000000..cbea4f572
--- /dev/null
+++ b/fs/btrfs/file-item.c
@@ -0,0 +1,1137 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2007 Oracle.  All rights reserved.
+ */
+
+#include <linux/bio.h>
+#include <linux/slab.h>
+#include <linux/pagemap.h>
+#include <linux/highmem.h>
+#include <linux/sched/mm.h>
+#include <crypto/hash.h>
+#include "ctree.h"
+#include "disk-io.h"
+#include "transaction.h"
+#include "volumes.h"
+#include "print-tree.h"
+#include "compression.h"
+
+#define __MAX_CSUM_ITEMS(r, size) ((unsigned long)(((BTRFS_LEAF_DATA_SIZE(r) - \
+				   sizeof(struct btrfs_item) * 2) / \
+				  size) - 1))
+
+#define MAX_CSUM_ITEMS(r, size) (min_t(u32, __MAX_CSUM_ITEMS(r, size), \
+				       PAGE_SIZE))
+
+/**
+ * @inode - the inode we want to update the disk_i_size for
+ * @new_i_size - the i_size we want to set to, 0 if we use i_size
+ *
+ * With NO_HOLES set this simply sets the disk_is_size to whatever i_size_read()
+ * returns as it is perfectly fine with a file that has holes without hole file
+ * extent items.
+ *
+ * However without NO_HOLES we need to only return the area that is contiguous
+ * from the 0 offset of the file.  Otherwise we could end up adjust i_size up
+ * to an extent that has a gap in between.
+ *
+ * Finally new_i_size should only be set in the case of truncate where we're not
+ * ready to use i_size_read() as the limiter yet.
+ */
+void btrfs_inode_safe_disk_i_size_write(struct inode *inode, u64 new_i_size)
+{
+	struct btrfs_fs_info *fs_info = BTRFS_I(inode)->root->fs_info;
+	u64 start, end, i_size;
+	int ret;
+
+	i_size = new_i_size ?: i_size_read(inode);
+	if (btrfs_fs_incompat(fs_info, NO_HOLES)) {
+		BTRFS_I(inode)->disk_i_size = i_size;
+		return;
+	}
+
+	spin_lock(&BTRFS_I(inode)->lock);
+	ret = find_contiguous_extent_bit(&BTRFS_I(inode)->file_extent_tree, 0,
+					 &start, &end, EXTENT_DIRTY);
+	if (!ret && start == 0)
+		i_size = min(i_size, end + 1);
+	else
+		i_size = 0;
+	BTRFS_I(inode)->disk_i_size = i_size;
+	spin_unlock(&BTRFS_I(inode)->lock);
+}
+
+/**
+ * @inode - the inode we're modifying
+ * @start - the start file offset of the file extent we've inserted
+ * @len - the logical length of the file extent item
+ *
+ * Call when we are inserting a new file extent where there was none before.
+ * Does not need to call this in the case where we're replacing an existing file
+ * extent, however if not sure it's fine to call this multiple times.
+ *
+ * The start and len must match the file extent item, so thus must be sectorsize
+ * aligned.
+ */
+int btrfs_inode_set_file_extent_range(struct btrfs_inode *inode, u64 start,
+				      u64 len)
+{
+	if (len == 0)
+		return 0;
+
+	ASSERT(IS_ALIGNED(start + len, inode->root->fs_info->sectorsize));
+
+	if (btrfs_fs_incompat(inode->root->fs_info, NO_HOLES))
+		return 0;
+	return set_extent_bits(&inode->file_extent_tree, start, start + len - 1,
+			       EXTENT_DIRTY);
+}
+
+/**
+ * @inode - the inode we're modifying
+ * @start - the start file offset of the file extent we've inserted
+ * @len - the logical length of the file extent item
+ *
+ * Called when we drop a file extent, for example when we truncate.  Doesn't
+ * need to be called for cases where we're replacing a file extent, like when
+ * we've COWed a file extent.
+ *
+ * The start and len must match the file extent item, so thus must be sectorsize
+ * aligned.
+ */
+int btrfs_inode_clear_file_extent_range(struct btrfs_inode *inode, u64 start,
+					u64 len)
+{
+	if (len == 0)
+		return 0;
+
+	ASSERT(IS_ALIGNED(start + len, inode->root->fs_info->sectorsize) ||
+	       len == (u64)-1);
+
+	if (btrfs_fs_incompat(inode->root->fs_info, NO_HOLES))
+		return 0;
+	return clear_extent_bit(&inode->file_extent_tree, start,
+				start + len - 1, EXTENT_DIRTY, 0, 0, NULL);
+}
+
+static inline u32 max_ordered_sum_bytes(struct btrfs_fs_info *fs_info,
+					u16 csum_size)
+{
+	u32 ncsums = (PAGE_SIZE - sizeof(struct btrfs_ordered_sum)) / csum_size;
+
+	return ncsums * fs_info->sectorsize;
+}
+
+int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
+			     struct btrfs_root *root,
+			     u64 objectid, u64 pos,
+			     u64 disk_offset, u64 disk_num_bytes,
+			     u64 num_bytes, u64 offset, u64 ram_bytes,
+			     u8 compression, u8 encryption, u16 other_encoding)
+{
+	int ret = 0;
+	struct btrfs_file_extent_item *item;
+	struct btrfs_key file_key;
+	struct btrfs_path *path;
+	struct extent_buffer *leaf;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+	file_key.objectid = objectid;
+	file_key.offset = pos;
+	file_key.type = BTRFS_EXTENT_DATA_KEY;
+
+	path->leave_spinning = 1;
+	ret = btrfs_insert_empty_item(trans, root, path, &file_key,
+				      sizeof(*item));
+	if (ret < 0)
+		goto out;
+	BUG_ON(ret); /* Can't happen */
+	leaf = path->nodes[0];
+	item = btrfs_item_ptr(leaf, path->slots[0],
+			      struct btrfs_file_extent_item);
+	btrfs_set_file_extent_disk_bytenr(leaf, item, disk_offset);
+	btrfs_set_file_extent_disk_num_bytes(leaf, item, disk_num_bytes);
+	btrfs_set_file_extent_offset(leaf, item, offset);
+	btrfs_set_file_extent_num_bytes(leaf, item, num_bytes);
+	btrfs_set_file_extent_ram_bytes(leaf, item, ram_bytes);
+	btrfs_set_file_extent_generation(leaf, item, trans->transid);
+	btrfs_set_file_extent_type(leaf, item, BTRFS_FILE_EXTENT_REG);
+	btrfs_set_file_extent_compression(leaf, item, compression);
+	btrfs_set_file_extent_encryption(leaf, item, encryption);
+	btrfs_set_file_extent_other_encoding(leaf, item, other_encoding);
+
+	btrfs_mark_buffer_dirty(leaf);
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+static struct btrfs_csum_item *
+btrfs_lookup_csum(struct btrfs_trans_handle *trans,
+		  struct btrfs_root *root,
+		  struct btrfs_path *path,
+		  u64 bytenr, int cow)
+{
+	struct btrfs_fs_info *fs_info = root->fs_info;
+	int ret;
+	struct btrfs_key file_key;
+	struct btrfs_key found_key;
+	struct btrfs_csum_item *item;
+	struct extent_buffer *leaf;
+	u64 csum_offset = 0;
+	u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
+	int csums_in_item;
+
+	file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
+	file_key.offset = bytenr;
+	file_key.type = BTRFS_EXTENT_CSUM_KEY;
+	ret = btrfs_search_slot(trans, root, &file_key, path, 0, cow);
+	if (ret < 0)
+		goto fail;
+	leaf = path->nodes[0];
+	if (ret > 0) {
+		ret = 1;
+		if (path->slots[0] == 0)
+			goto fail;
+		path->slots[0]--;
+		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+		if (found_key.type != BTRFS_EXTENT_CSUM_KEY)
+			goto fail;
+
+		csum_offset = (bytenr - found_key.offset) >>
+				fs_info->sb->s_blocksize_bits;
+		csums_in_item = btrfs_item_size_nr(leaf, path->slots[0]);
+		csums_in_item /= csum_size;
+
+		if (csum_offset == csums_in_item) {
+			ret = -EFBIG;
+			goto fail;
+		} else if (csum_offset > csums_in_item) {
+			goto fail;
+		}
+	}
+	item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
+	item = (struct btrfs_csum_item *)((unsigned char *)item +
+					  csum_offset * csum_size);
+	return item;
+fail:
+	if (ret > 0)
+		ret = -ENOENT;
+	return ERR_PTR(ret);
+}
+
+int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
+			     struct btrfs_root *root,
+			     struct btrfs_path *path, u64 objectid,
+			     u64 offset, int mod)
+{
+	int ret;
+	struct btrfs_key file_key;
+	int ins_len = mod < 0 ? -1 : 0;
+	int cow = mod != 0;
+
+	file_key.objectid = objectid;
+	file_key.offset = offset;
+	file_key.type = BTRFS_EXTENT_DATA_KEY;
+	ret = btrfs_search_slot(trans, root, &file_key, path, ins_len, cow);
+	return ret;
+}
+
+/**
+ * btrfs_lookup_bio_sums - Look up checksums for a bio.
+ * @inode: inode that the bio is for.
+ * @bio: bio to look up.
+ * @offset: Unless (u64)-1, look up checksums for this offset in the file.
+ *          If (u64)-1, use the page offsets from the bio instead.
+ * @dst: Buffer of size nblocks * btrfs_super_csum_size() used to return
+ *       checksum (nblocks = bio->bi_iter.bi_size / fs_info->sectorsize). If
+ *       NULL, the checksum buffer is allocated and returned in
+ *       btrfs_io_bio(bio)->csum instead.
+ *
+ * Return: BLK_STS_RESOURCE if allocating memory fails, BLK_STS_OK otherwise.
+ */
+blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
+				   u64 offset, u8 *dst)
+{
+	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
+	struct bio_vec bvec;
+	struct bvec_iter iter;
+	struct btrfs_csum_item *item = NULL;
+	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
+	struct btrfs_path *path;
+	const bool page_offsets = (offset == (u64)-1);
+	u8 *csum;
+	u64 item_start_offset = 0;
+	u64 item_last_offset = 0;
+	u64 disk_bytenr;
+	u64 page_bytes_left;
+	u32 diff;
+	int nblocks;
+	int count = 0;
+	u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return BLK_STS_RESOURCE;
+
+	nblocks = bio->bi_iter.bi_size >> inode->i_sb->s_blocksize_bits;
+	if (!dst) {
+		struct btrfs_io_bio *btrfs_bio = btrfs_io_bio(bio);
+
+		if (nblocks * csum_size > BTRFS_BIO_INLINE_CSUM_SIZE) {
+			btrfs_bio->csum = kmalloc_array(nblocks, csum_size,
+							GFP_NOFS);
+			if (!btrfs_bio->csum) {
+				btrfs_free_path(path);
+				return BLK_STS_RESOURCE;
+			}
+		} else {
+			btrfs_bio->csum = btrfs_bio->csum_inline;
+		}
+		csum = btrfs_bio->csum;
+	} else {
+		csum = dst;
+	}
+
+	if (bio->bi_iter.bi_size > PAGE_SIZE * 8)
+		path->reada = READA_FORWARD;
+
+	/*
+	 * the free space stuff is only read when it hasn't been
+	 * updated in the current transaction.  So, we can safely
+	 * read from the commit root and sidestep a nasty deadlock
+	 * between reading the free space cache and updating the csum tree.
+	 */
+	if (btrfs_is_free_space_inode(BTRFS_I(inode))) {
+		path->search_commit_root = 1;
+		path->skip_locking = 1;
+	}
+
+	disk_bytenr = (u64)bio->bi_iter.bi_sector << 9;
+
+	bio_for_each_segment(bvec, bio, iter) {
+		page_bytes_left = bvec.bv_len;
+		if (count)
+			goto next;
+
+		if (page_offsets)
+			offset = page_offset(bvec.bv_page) + bvec.bv_offset;
+		count = btrfs_find_ordered_sum(BTRFS_I(inode), offset,
+					       disk_bytenr, csum, nblocks);
+		if (count)
+			goto found;
+
+		if (!item || disk_bytenr < item_start_offset ||
+		    disk_bytenr >= item_last_offset) {
+			struct btrfs_key found_key;
+			u32 item_size;
+
+			if (item)
+				btrfs_release_path(path);
+			item = btrfs_lookup_csum(NULL, fs_info->csum_root,
+						 path, disk_bytenr, 0);
+			if (IS_ERR(item)) {
+				count = 1;
+				memset(csum, 0, csum_size);
+				if (BTRFS_I(inode)->root->root_key.objectid ==
+				    BTRFS_DATA_RELOC_TREE_OBJECTID) {
+					set_extent_bits(io_tree, offset,
+						offset + fs_info->sectorsize - 1,
+						EXTENT_NODATASUM);
+				} else {
+					btrfs_info_rl(fs_info,
+						   "no csum found for inode %llu start %llu",
+					       btrfs_ino(BTRFS_I(inode)), offset);
+				}
+				item = NULL;
+				btrfs_release_path(path);
+				goto found;
+			}
+			btrfs_item_key_to_cpu(path->nodes[0], &found_key,
+					      path->slots[0]);
+
+			item_start_offset = found_key.offset;
+			item_size = btrfs_item_size_nr(path->nodes[0],
+						       path->slots[0]);
+			item_last_offset = item_start_offset +
+				(item_size / csum_size) *
+				fs_info->sectorsize;
+			item = btrfs_item_ptr(path->nodes[0], path->slots[0],
+					      struct btrfs_csum_item);
+		}
+		/*
+		 * this byte range must be able to fit inside
+		 * a single leaf so it will also fit inside a u32
+		 */
+		diff = disk_bytenr - item_start_offset;
+		diff = diff / fs_info->sectorsize;
+		diff = diff * csum_size;
+		count = min_t(int, nblocks, (item_last_offset - disk_bytenr) >>
+					    inode->i_sb->s_blocksize_bits);
+		read_extent_buffer(path->nodes[0], csum,
+				   ((unsigned long)item) + diff,
+				   csum_size * count);
+found:
+		csum += count * csum_size;
+		nblocks -= count;
+next:
+		while (count > 0) {
+			count--;
+			disk_bytenr += fs_info->sectorsize;
+			offset += fs_info->sectorsize;
+			page_bytes_left -= fs_info->sectorsize;
+			if (!page_bytes_left)
+				break; /* move to next bio */
+		}
+	}
+
+	WARN_ON_ONCE(count);
+	btrfs_free_path(path);
+	return BLK_STS_OK;
+}
+
+int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
+			     struct list_head *list, int search_commit)
+{
+	struct btrfs_fs_info *fs_info = root->fs_info;
+	struct btrfs_key key;
+	struct btrfs_path *path;
+	struct extent_buffer *leaf;
+	struct btrfs_ordered_sum *sums;
+	struct btrfs_csum_item *item;
+	LIST_HEAD(tmplist);
+	unsigned long offset;
+	int ret;
+	size_t size;
+	u64 csum_end;
+	u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
+
+	ASSERT(IS_ALIGNED(start, fs_info->sectorsize) &&
+	       IS_ALIGNED(end + 1, fs_info->sectorsize));
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	if (search_commit) {
+		path->skip_locking = 1;
+		path->reada = READA_FORWARD;
+		path->search_commit_root = 1;
+	}
+
+	key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
+	key.offset = start;
+	key.type = BTRFS_EXTENT_CSUM_KEY;
+
+	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+	if (ret < 0)
+		goto fail;
+	if (ret > 0 && path->slots[0] > 0) {
+		leaf = path->nodes[0];
+		btrfs_item_key_to_cpu(leaf, &key, path->slots[0] - 1);
+		if (key.objectid == BTRFS_EXTENT_CSUM_OBJECTID &&
+		    key.type == BTRFS_EXTENT_CSUM_KEY) {
+			offset = (start - key.offset) >>
+				 fs_info->sb->s_blocksize_bits;
+			if (offset * csum_size <
+			    btrfs_item_size_nr(leaf, path->slots[0] - 1))
+				path->slots[0]--;
+		}
+	}
+
+	while (start <= end) {
+		leaf = path->nodes[0];
+		if (path->slots[0] >= btrfs_header_nritems(leaf)) {
+			ret = btrfs_next_leaf(root, path);
+			if (ret < 0)
+				goto fail;
+			if (ret > 0)
+				break;
+			leaf = path->nodes[0];
+		}
+
+		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+		if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
+		    key.type != BTRFS_EXTENT_CSUM_KEY ||
+		    key.offset > end)
+			break;
+
+		if (key.offset > start)
+			start = key.offset;
+
+		size = btrfs_item_size_nr(leaf, path->slots[0]);
+		csum_end = key.offset + (size / csum_size) * fs_info->sectorsize;
+		if (csum_end <= start) {
+			path->slots[0]++;
+			continue;
+		}
+
+		csum_end = min(csum_end, end + 1);
+		item = btrfs_item_ptr(path->nodes[0], path->slots[0],
+				      struct btrfs_csum_item);
+		while (start < csum_end) {
+			size = min_t(size_t, csum_end - start,
+				     max_ordered_sum_bytes(fs_info, csum_size));
+			sums = kzalloc(btrfs_ordered_sum_size(fs_info, size),
+				       GFP_NOFS);
+			if (!sums) {
+				ret = -ENOMEM;
+				goto fail;
+			}
+
+			sums->bytenr = start;
+			sums->len = (int)size;
+
+			offset = (start - key.offset) >>
+				fs_info->sb->s_blocksize_bits;
+			offset *= csum_size;
+			size >>= fs_info->sb->s_blocksize_bits;
+
+			read_extent_buffer(path->nodes[0],
+					   sums->sums,
+					   ((unsigned long)item) + offset,
+					   csum_size * size);
+
+			start += fs_info->sectorsize * size;
+			list_add_tail(&sums->list, &tmplist);
+		}
+		path->slots[0]++;
+	}
+	ret = 0;
+fail:
+	while (ret < 0 && !list_empty(&tmplist)) {
+		sums = list_entry(tmplist.next, struct btrfs_ordered_sum, list);
+		list_del(&sums->list);
+		kfree(sums);
+	}
+	list_splice_tail(&tmplist, list);
+
+	btrfs_free_path(path);
+	return ret;
+}
+
+/*
+ * btrfs_csum_one_bio - Calculates checksums of the data contained inside a bio
+ * @inode:	 Owner of the data inside the bio
+ * @bio:	 Contains the data to be checksummed
+ * @file_start:  offset in file this bio begins to describe
+ * @contig:	 Boolean. If true/1 means all bio vecs in this bio are
+ *		 contiguous and they begin at @file_start in the file. False/0
+ *		 means this bio can contains potentially discontigous bio vecs
+ *		 so the logical offset of each should be calculated separately.
+ */
+blk_status_t btrfs_csum_one_bio(struct btrfs_inode *inode, struct bio *bio,
+		       u64 file_start, int contig)
+{
+	struct btrfs_fs_info *fs_info = inode->root->fs_info;
+	SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
+	struct btrfs_ordered_sum *sums;
+	struct btrfs_ordered_extent *ordered = NULL;
+	char *data;
+	struct bvec_iter iter;
+	struct bio_vec bvec;
+	int index;
+	int nr_sectors;
+	unsigned long total_bytes = 0;
+	unsigned long this_sum_bytes = 0;
+	int i;
+	u64 offset;
+	unsigned nofs_flag;
+	const u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
+
+	nofs_flag = memalloc_nofs_save();
+	sums = kvzalloc(btrfs_ordered_sum_size(fs_info, bio->bi_iter.bi_size),
+		       GFP_KERNEL);
+	memalloc_nofs_restore(nofs_flag);
+
+	if (!sums)
+		return BLK_STS_RESOURCE;
+
+	sums->len = bio->bi_iter.bi_size;
+	INIT_LIST_HEAD(&sums->list);
+
+	if (contig)
+		offset = file_start;
+	else
+		offset = 0; /* shut up gcc */
+
+	sums->bytenr = (u64)bio->bi_iter.bi_sector << 9;
+	index = 0;
+
+	shash->tfm = fs_info->csum_shash;
+
+	bio_for_each_segment(bvec, bio, iter) {
+		if (!contig)
+			offset = page_offset(bvec.bv_page) + bvec.bv_offset;
+
+		if (!ordered) {
+			ordered = btrfs_lookup_ordered_extent(inode, offset);
+			/*
+			 * The bio range is not covered by any ordered extent,
+			 * must be a code logic error.
+			 */
+			if (unlikely(!ordered)) {
+				WARN(1, KERN_WARNING
+			"no ordered extent for root %llu ino %llu offset %llu\n",
+				     inode->root->root_key.objectid,
+				     btrfs_ino(inode), offset);
+				kvfree(sums);
+				return BLK_STS_IOERR;
+			}
+		}
+
+		nr_sectors = BTRFS_BYTES_TO_BLKS(fs_info,
+						 bvec.bv_len + fs_info->sectorsize
+						 - 1);
+
+		for (i = 0; i < nr_sectors; i++) {
+			if (offset >= ordered->file_offset + ordered->num_bytes ||
+			    offset < ordered->file_offset) {
+				unsigned long bytes_left;
+
+				sums->len = this_sum_bytes;
+				this_sum_bytes = 0;
+				btrfs_add_ordered_sum(ordered, sums);
+				btrfs_put_ordered_extent(ordered);
+
+				bytes_left = bio->bi_iter.bi_size - total_bytes;
+
+				nofs_flag = memalloc_nofs_save();
+				sums = kvzalloc(btrfs_ordered_sum_size(fs_info,
+						      bytes_left), GFP_KERNEL);
+				memalloc_nofs_restore(nofs_flag);
+				if (!sums)
+					return BLK_STS_RESOURCE;
+
+				sums->len = bytes_left;
+				ordered = btrfs_lookup_ordered_extent(inode,
+								offset);
+				ASSERT(ordered); /* Logic error */
+				sums->bytenr = ((u64)bio->bi_iter.bi_sector << 9)
+					+ total_bytes;
+				index = 0;
+			}
+
+			data = kmap_atomic(bvec.bv_page);
+			crypto_shash_digest(shash, data + bvec.bv_offset
+					    + (i * fs_info->sectorsize),
+					    fs_info->sectorsize,
+					    sums->sums + index);
+			kunmap_atomic(data);
+			index += csum_size;
+			offset += fs_info->sectorsize;
+			this_sum_bytes += fs_info->sectorsize;
+			total_bytes += fs_info->sectorsize;
+		}
+
+	}
+	this_sum_bytes = 0;
+	btrfs_add_ordered_sum(ordered, sums);
+	btrfs_put_ordered_extent(ordered);
+	return 0;
+}
+
+/*
+ * helper function for csum removal, this expects the
+ * key to describe the csum pointed to by the path, and it expects
+ * the csum to overlap the range [bytenr, len]
+ *
+ * The csum should not be entirely contained in the range and the
+ * range should not be entirely contained in the csum.
+ *
+ * This calls btrfs_truncate_item with the correct args based on the
+ * overlap, and fixes up the key as required.
+ */
+static noinline void truncate_one_csum(struct btrfs_fs_info *fs_info,
+				       struct btrfs_path *path,
+				       struct btrfs_key *key,
+				       u64 bytenr, u64 len)
+{
+	struct extent_buffer *leaf;
+	u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
+	u64 csum_end;
+	u64 end_byte = bytenr + len;
+	u32 blocksize_bits = fs_info->sb->s_blocksize_bits;
+
+	leaf = path->nodes[0];
+	csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
+	csum_end <<= fs_info->sb->s_blocksize_bits;
+	csum_end += key->offset;
+
+	if (key->offset < bytenr && csum_end <= end_byte) {
+		/*
+		 *         [ bytenr - len ]
+		 *         [   ]
+		 *   [csum     ]
+		 *   A simple truncate off the end of the item
+		 */
+		u32 new_size = (bytenr - key->offset) >> blocksize_bits;
+		new_size *= csum_size;
+		btrfs_truncate_item(path, new_size, 1);
+	} else if (key->offset >= bytenr && csum_end > end_byte &&
+		   end_byte > key->offset) {
+		/*
+		 *         [ bytenr - len ]
+		 *                 [ ]
+		 *                 [csum     ]
+		 * we need to truncate from the beginning of the csum
+		 */
+		u32 new_size = (csum_end - end_byte) >> blocksize_bits;
+		new_size *= csum_size;
+
+		btrfs_truncate_item(path, new_size, 0);
+
+		key->offset = end_byte;
+		btrfs_set_item_key_safe(fs_info, path, key);
+	} else {
+		BUG();
+	}
+}
+
+/*
+ * deletes the csum items from the csum tree for a given
+ * range of bytes.
+ */
+int btrfs_del_csums(struct btrfs_trans_handle *trans,
+		    struct btrfs_root *root, u64 bytenr, u64 len)
+{
+	struct btrfs_fs_info *fs_info = trans->fs_info;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	u64 end_byte = bytenr + len;
+	u64 csum_end;
+	struct extent_buffer *leaf;
+	int ret = 0;
+	u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
+	int blocksize_bits = fs_info->sb->s_blocksize_bits;
+
+	ASSERT(root == fs_info->csum_root ||
+	       root->root_key.objectid == BTRFS_TREE_LOG_OBJECTID);
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	while (1) {
+		key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
+		key.offset = end_byte - 1;
+		key.type = BTRFS_EXTENT_CSUM_KEY;
+
+		path->leave_spinning = 1;
+		ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
+		if (ret > 0) {
+			ret = 0;
+			if (path->slots[0] == 0)
+				break;
+			path->slots[0]--;
+		} else if (ret < 0) {
+			break;
+		}
+
+		leaf = path->nodes[0];
+		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+
+		if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
+		    key.type != BTRFS_EXTENT_CSUM_KEY) {
+			break;
+		}
+
+		if (key.offset >= end_byte)
+			break;
+
+		csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
+		csum_end <<= blocksize_bits;
+		csum_end += key.offset;
+
+		/* this csum ends before we start, we're done */
+		if (csum_end <= bytenr)
+			break;
+
+		/* delete the entire item, it is inside our range */
+		if (key.offset >= bytenr && csum_end <= end_byte) {
+			int del_nr = 1;
+
+			/*
+			 * Check how many csum items preceding this one in this
+			 * leaf correspond to our range and then delete them all
+			 * at once.
+			 */
+			if (key.offset > bytenr && path->slots[0] > 0) {
+				int slot = path->slots[0] - 1;
+
+				while (slot >= 0) {
+					struct btrfs_key pk;
+
+					btrfs_item_key_to_cpu(leaf, &pk, slot);
+					if (pk.offset < bytenr ||
+					    pk.type != BTRFS_EXTENT_CSUM_KEY ||
+					    pk.objectid !=
+					    BTRFS_EXTENT_CSUM_OBJECTID)
+						break;
+					path->slots[0] = slot;
+					del_nr++;
+					key.offset = pk.offset;
+					slot--;
+				}
+			}
+			ret = btrfs_del_items(trans, root, path,
+					      path->slots[0], del_nr);
+			if (ret)
+				break;
+			if (key.offset == bytenr)
+				break;
+		} else if (key.offset < bytenr && csum_end > end_byte) {
+			unsigned long offset;
+			unsigned long shift_len;
+			unsigned long item_offset;
+			/*
+			 *        [ bytenr - len ]
+			 *     [csum                ]
+			 *
+			 * Our bytes are in the middle of the csum,
+			 * we need to split this item and insert a new one.
+			 *
+			 * But we can't drop the path because the
+			 * csum could change, get removed, extended etc.
+			 *
+			 * The trick here is the max size of a csum item leaves
+			 * enough room in the tree block for a single
+			 * item header.  So, we split the item in place,
+			 * adding a new header pointing to the existing
+			 * bytes.  Then we loop around again and we have
+			 * a nicely formed csum item that we can neatly
+			 * truncate.
+			 */
+			offset = (bytenr - key.offset) >> blocksize_bits;
+			offset *= csum_size;
+
+			shift_len = (len >> blocksize_bits) * csum_size;
+
+			item_offset = btrfs_item_ptr_offset(leaf,
+							    path->slots[0]);
+
+			memzero_extent_buffer(leaf, item_offset + offset,
+					     shift_len);
+			key.offset = bytenr;
+
+			/*
+			 * btrfs_split_item returns -EAGAIN when the
+			 * item changed size or key
+			 */
+			ret = btrfs_split_item(trans, root, path, &key, offset);
+			if (ret && ret != -EAGAIN) {
+				btrfs_abort_transaction(trans, ret);
+				break;
+			}
+			ret = 0;
+
+			key.offset = end_byte - 1;
+		} else {
+			truncate_one_csum(fs_info, path, &key, bytenr, len);
+			if (key.offset < bytenr)
+				break;
+		}
+		btrfs_release_path(path);
+	}
+	btrfs_free_path(path);
+	return ret;
+}
+
+int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
+			   struct btrfs_root *root,
+			   struct btrfs_ordered_sum *sums)
+{
+	struct btrfs_fs_info *fs_info = root->fs_info;
+	struct btrfs_key file_key;
+	struct btrfs_key found_key;
+	struct btrfs_path *path;
+	struct btrfs_csum_item *item;
+	struct btrfs_csum_item *item_end;
+	struct extent_buffer *leaf = NULL;
+	u64 next_offset;
+	u64 total_bytes = 0;
+	u64 csum_offset;
+	u64 bytenr;
+	u32 nritems;
+	u32 ins_size;
+	int index = 0;
+	int found_next;
+	int ret;
+	u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+again:
+	next_offset = (u64)-1;
+	found_next = 0;
+	bytenr = sums->bytenr + total_bytes;
+	file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
+	file_key.offset = bytenr;
+	file_key.type = BTRFS_EXTENT_CSUM_KEY;
+
+	item = btrfs_lookup_csum(trans, root, path, bytenr, 1);
+	if (!IS_ERR(item)) {
+		ret = 0;
+		leaf = path->nodes[0];
+		item_end = btrfs_item_ptr(leaf, path->slots[0],
+					  struct btrfs_csum_item);
+		item_end = (struct btrfs_csum_item *)((char *)item_end +
+			   btrfs_item_size_nr(leaf, path->slots[0]));
+		goto found;
+	}
+	ret = PTR_ERR(item);
+	if (ret != -EFBIG && ret != -ENOENT)
+		goto out;
+
+	if (ret == -EFBIG) {
+		u32 item_size;
+		/* we found one, but it isn't big enough yet */
+		leaf = path->nodes[0];
+		item_size = btrfs_item_size_nr(leaf, path->slots[0]);
+		if ((item_size / csum_size) >=
+		    MAX_CSUM_ITEMS(fs_info, csum_size)) {
+			/* already at max size, make a new one */
+			goto insert;
+		}
+	} else {
+		int slot = path->slots[0] + 1;
+		/* we didn't find a csum item, insert one */
+		nritems = btrfs_header_nritems(path->nodes[0]);
+		if (!nritems || (path->slots[0] >= nritems - 1)) {
+			ret = btrfs_next_leaf(root, path);
+			if (ret < 0) {
+				goto out;
+			} else if (ret > 0) {
+				found_next = 1;
+				goto insert;
+			}
+			slot = path->slots[0];
+		}
+		btrfs_item_key_to_cpu(path->nodes[0], &found_key, slot);
+		if (found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
+		    found_key.type != BTRFS_EXTENT_CSUM_KEY) {
+			found_next = 1;
+			goto insert;
+		}
+		next_offset = found_key.offset;
+		found_next = 1;
+		goto insert;
+	}
+
+	/*
+	 * At this point, we know the tree has a checksum item that ends at an
+	 * offset matching the start of the checksum range we want to insert.
+	 * We try to extend that item as much as possible and then add as many
+	 * checksums to it as they fit.
+	 *
+	 * First check if the leaf has enough free space for at least one
+	 * checksum. If it has go directly to the item extension code, otherwise
+	 * release the path and do a search for insertion before the extension.
+	 */
+	if (btrfs_leaf_free_space(leaf) >= csum_size) {
+		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+		csum_offset = (bytenr - found_key.offset) >>
+			fs_info->sb->s_blocksize_bits;
+		goto extend_csum;
+	}
+
+	btrfs_release_path(path);
+	ret = btrfs_search_slot(trans, root, &file_key, path,
+				csum_size, 1);
+	if (ret < 0)
+		goto out;
+
+	if (ret > 0) {
+		if (path->slots[0] == 0)
+			goto insert;
+		path->slots[0]--;
+	}
+
+	leaf = path->nodes[0];
+	btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+	csum_offset = (bytenr - found_key.offset) >>
+			fs_info->sb->s_blocksize_bits;
+
+	if (found_key.type != BTRFS_EXTENT_CSUM_KEY ||
+	    found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
+	    csum_offset >= MAX_CSUM_ITEMS(fs_info, csum_size)) {
+		goto insert;
+	}
+
+extend_csum:
+	if (csum_offset == btrfs_item_size_nr(leaf, path->slots[0]) /
+	    csum_size) {
+		int extend_nr;
+		u64 tmp;
+		u32 diff;
+
+		tmp = sums->len - total_bytes;
+		tmp >>= fs_info->sb->s_blocksize_bits;
+		WARN_ON(tmp < 1);
+
+		extend_nr = max_t(int, 1, (int)tmp);
+		diff = (csum_offset + extend_nr) * csum_size;
+		diff = min(diff,
+			   MAX_CSUM_ITEMS(fs_info, csum_size) * csum_size);
+
+		diff = diff - btrfs_item_size_nr(leaf, path->slots[0]);
+		diff = min_t(u32, btrfs_leaf_free_space(leaf), diff);
+		diff /= csum_size;
+		diff *= csum_size;
+
+		btrfs_extend_item(path, diff);
+		ret = 0;
+		goto csum;
+	}
+
+insert:
+	btrfs_release_path(path);
+	csum_offset = 0;
+	if (found_next) {
+		u64 tmp;
+
+		tmp = sums->len - total_bytes;
+		tmp >>= fs_info->sb->s_blocksize_bits;
+		tmp = min(tmp, (next_offset - file_key.offset) >>
+					 fs_info->sb->s_blocksize_bits);
+
+		tmp = max_t(u64, 1, tmp);
+		tmp = min_t(u64, tmp, MAX_CSUM_ITEMS(fs_info, csum_size));
+		ins_size = csum_size * tmp;
+	} else {
+		ins_size = csum_size;
+	}
+	path->leave_spinning = 1;
+	ret = btrfs_insert_empty_item(trans, root, path, &file_key,
+				      ins_size);
+	path->leave_spinning = 0;
+	if (ret < 0)
+		goto out;
+	if (WARN_ON(ret != 0))
+		goto out;
+	leaf = path->nodes[0];
+csum:
+	item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
+	item_end = (struct btrfs_csum_item *)((unsigned char *)item +
+				      btrfs_item_size_nr(leaf, path->slots[0]));
+	item = (struct btrfs_csum_item *)((unsigned char *)item +
+					  csum_offset * csum_size);
+found:
+	ins_size = (u32)(sums->len - total_bytes) >>
+		   fs_info->sb->s_blocksize_bits;
+	ins_size *= csum_size;
+	ins_size = min_t(u32, (unsigned long)item_end - (unsigned long)item,
+			      ins_size);
+	write_extent_buffer(leaf, sums->sums + index, (unsigned long)item,
+			    ins_size);
+
+	index += ins_size;
+	ins_size /= csum_size;
+	total_bytes += ins_size * fs_info->sectorsize;
+
+	btrfs_mark_buffer_dirty(path->nodes[0]);
+	if (total_bytes < sums->len) {
+		btrfs_release_path(path);
+		cond_resched();
+		goto again;
+	}
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+void btrfs_extent_item_to_extent_map(struct btrfs_inode *inode,
+				     const struct btrfs_path *path,
+				     struct btrfs_file_extent_item *fi,
+				     const bool new_inline,
+				     struct extent_map *em)
+{
+	struct btrfs_fs_info *fs_info = inode->root->fs_info;
+	struct btrfs_root *root = inode->root;
+	struct extent_buffer *leaf = path->nodes[0];
+	const int slot = path->slots[0];
+	struct btrfs_key key;
+	u64 extent_start, extent_end;
+	u64 bytenr;
+	u8 type = btrfs_file_extent_type(leaf, fi);
+	int compress_type = btrfs_file_extent_compression(leaf, fi);
+
+	btrfs_item_key_to_cpu(leaf, &key, slot);
+	extent_start = key.offset;
+	extent_end = btrfs_file_extent_end(path);
+	em->ram_bytes = btrfs_file_extent_ram_bytes(leaf, fi);
+	if (type == BTRFS_FILE_EXTENT_REG ||
+	    type == BTRFS_FILE_EXTENT_PREALLOC) {
+		em->start = extent_start;
+		em->len = extent_end - extent_start;
+		em->orig_start = extent_start -
+			btrfs_file_extent_offset(leaf, fi);
+		em->orig_block_len = btrfs_file_extent_disk_num_bytes(leaf, fi);
+		bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
+		if (bytenr == 0) {
+			em->block_start = EXTENT_MAP_HOLE;
+			return;
+		}
+		if (compress_type != BTRFS_COMPRESS_NONE) {
+			set_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
+			em->compress_type = compress_type;
+			em->block_start = bytenr;
+			em->block_len = em->orig_block_len;
+		} else {
+			bytenr += btrfs_file_extent_offset(leaf, fi);
+			em->block_start = bytenr;
+			em->block_len = em->len;
+			if (type == BTRFS_FILE_EXTENT_PREALLOC)
+				set_bit(EXTENT_FLAG_PREALLOC, &em->flags);
+		}
+	} else if (type == BTRFS_FILE_EXTENT_INLINE) {
+		em->block_start = EXTENT_MAP_INLINE;
+		em->start = extent_start;
+		em->len = extent_end - extent_start;
+		/*
+		 * Initialize orig_start and block_len with the same values
+		 * as in inode.c:btrfs_get_extent().
+		 */
+		em->orig_start = EXTENT_MAP_HOLE;
+		em->block_len = (u64)-1;
+		if (!new_inline && compress_type != BTRFS_COMPRESS_NONE) {
+			set_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
+			em->compress_type = compress_type;
+		}
+	} else {
+		btrfs_err(fs_info,
+			  "unknown file extent item type %d, inode %llu, offset %llu, "
+			  "root %llu", type, btrfs_ino(inode), extent_start,
+			  root->root_key.objectid);
+	}
+}
+
+/*
+ * Returns the end offset (non inclusive) of the file extent item the given path
+ * points to. If it points to an inline extent, the returned offset is rounded
+ * up to the sector size.
+ */
+u64 btrfs_file_extent_end(const struct btrfs_path *path)
+{
+	const struct extent_buffer *leaf = path->nodes[0];
+	const int slot = path->slots[0];
+	struct btrfs_file_extent_item *fi;
+	struct btrfs_key key;
+	u64 end;
+
+	btrfs_item_key_to_cpu(leaf, &key, slot);
+	ASSERT(key.type == BTRFS_EXTENT_DATA_KEY);
+	fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
+
+	if (btrfs_file_extent_type(leaf, fi) == BTRFS_FILE_EXTENT_INLINE) {
+		end = btrfs_file_extent_ram_bytes(leaf, fi);
+		end = ALIGN(key.offset + end, leaf->fs_info->sectorsize);
+	} else {
+		end = key.offset + btrfs_file_extent_num_bytes(leaf, fi);
+	}
+
+	return end;
+}