Hi,
On 09/07/2016 11:56 PM, Darrick J. Wong wrote:
On Wed, Sep 07, 2016 at 08:17:38PM +0800, Wang Xiaoguang wrote:
Below test script 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 <= $count; i++)); do
dst_offset=$((blocksize * i))
xfs_io -f -c "reflink testfile 0 $dst_offset $blocksize"\
testfile > /dev/null
done
sync
truncate --size 0 testfile
The last truncate operation will fail for ENOSPC reason, but indeed
it should not fail.
Could you make this into an xfstest so we can avoid future regressions, please?
OK.
Regards,
Xiaoguang Wang
--D
In btrfs_truncate(), we use a temporary block_rsv to do truncate
operation. With every btrfs_truncate_inode_items() call, we migrate space
to this block_rsv, but forget to cleanup previous reservation, which
will make this block_rsv's reserved bytes keep growing, and this reserved
space will only be released in the end of btrfs_truncate(), this metadata
leak will impact other's metadata reservation. In this case, it's
"btrfs_start_transaction(root, 2);" fails for enospc error, which make
this truncate operation fail.
Call btrfs_block_rsv_release() to fix this bug.
Signed-off-by: Wang Xiaoguang <wangxg.fnst@xxxxxxxxxxxxxx>
---
fs/btrfs/inode.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index e6811c4..40f0762 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -9206,6 +9206,7 @@ static int btrfs_truncate(struct inode *inode)
break;
}
+ btrfs_block_rsv_release(root, rsv, -1);
ret = btrfs_block_rsv_migrate(&root->fs_info->trans_block_rsv,
rsv, min_size, 0);
BUG_ON(ret); /* shouldn't happen */
--
2.9.0
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