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btrfs: fix disk_i_size update bug when fallocate() fails

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When doing truncate operation, btrfs_setsize() will first call
truncate_setsize() to set new inode->i_size, but if later
btrfs_truncate() fails, btrfs_setsize() will call
"i_size_write(inode, BTRFS_I(inode)->disk_i_size)" to reset the
inmemory inode size, now bug occurs. It's because for truncate
case btrfs_ordered_update_i_size() directly uses inode->i_size
to update BTRFS_I(inode)->disk_i_size, indeed we should use the
"offset" argument to update disk_i_size. Here is the call graph:
==>btrfs_truncate()
====>btrfs_truncate_inode_items()
======>btrfs_ordered_update_i_size(inode, last_size, NULL);
Here btrfs_ordered_update_i_size()'s offset argument is last_size.

And below test case can reveal this bug:

dd if=/dev/zero of=fs.img bs=$((1024*1024)) count=100
dev=$(losetup --show -f fs.img)
mkdir -p /mnt/mntpoint
mkfs.btrfs  -f $dev
mount $dev /mnt/mntpoint
cd /mnt/mntpoint

echo "workdir is: /mnt/mntpoint"
blocksize=$((128 * 1024))
dd if=/dev/zero of=testfile bs=$blocksize count=1
sync
count=$((17*1024*1024*1024/blocksize))
echo "file size is:" $((count*blocksize))
for ((i = 1; i <= $count; i++)); do
	i=$((i + 1))
	dst_offset=$((blocksize * i))
	xfs_io -f -c "reflink testfile 0 $dst_offset $blocksize"\
		testfile > /dev/null
done
sync

truncate --size 0 testfile
ls -l testfile
du -sh testfile
exit

In this case, truncate operation will fail for enospc reason and
"du -sh testfile" returns value greater than 0, but testfile's
size is 0, we need to reflect correct inode->i_size.

Signed-off-by: Wang Xiaoguang <wangxg.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
This commit is contained in:
Wang Xiaoguang 2016-06-22 09:57:01 +08:00 committed by Chris Mason
parent 415b35a55b
commit c0d2f6104e
1 changed files with 2 additions and 1 deletions
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3
fs/btrfs/ordered-data.c
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@ -968,6 +968,7 @@ int btrfs_ordered_update_i_size(struct inode *inode, u64 offset,
struct rb_node *prev = NULL;
struct btrfs_ordered_extent *test;
int ret = 1;
u64 orig_offset = offset;
spin_lock_irq(&tree->lock);
if (ordered) {
@ -983,7 +984,7 @@ int btrfs_ordered_update_i_size(struct inode *inode, u64 offset,
/* truncate file */
if (disk_i_size > i_size) {
BTRFS_I(inode)->disk_i_size = i_size;
BTRFS_I(inode)->disk_i_size = orig_offset;
ret = 0;
goto out;
}