[BUG]
Under the follow case with qgroup enabled, if some error happened after
we have reserved delalloc space, then in error handling path, we could
cause qgroup data space leakage:
>From btrfs_truncate_block() in inode.c:
ret = btrfs_delalloc_reserve_space(inode, &data_reserved,
block_start, blocksize);
if (ret)
goto out;
again:
page = find_or_create_page(mapping, index, mask);
if (!page) {
btrfs_delalloc_release_space(inode, data_reserved,
block_start, blocksize, true);
btrfs_delalloc_release_extents(BTRFS_I(inode), blocksize, true);
ret = -ENOMEM;
goto out;
}
[CAUSE]
In above case, btrfs_delalloc_reserve_space() will call
btrfs_qgroup_reserve_data() and mark the io_tree range with
EXTENT_QGROUP_RESERVED flag.
In the error handling path, we have the following call stack:
btrfs_delalloc_release_space()
|- btrfs_free_reserved_data_space()
|- btrsf_qgroup_free_data()
|- __btrfs_qgroup_release_data(reserved=@reserved, free=1)
|- qgroup_free_reserved_data(reserved=@reserved)
|- clear_record_extent_bits();
|- freed += changeset.bytes_changed;
However due to a completion bug, qgroup_free_reserved_data() will clear
EXTENT_QGROUP_RESERVED flag in BTRFS_I(inode)->io_failure_tree, other
than the correct BTRFS_I(inode)->io_tree.
Since io_failure_tree is never marked with that flag,
btrfs_qgroup_free_data() will not free any data reserved space at all,
causing a leakage.
This type of error handling can only be triggered by errors outside of
qgroup code. So EDQUOT error from qgroup can't trigger it.
[FIX]
Fix the wrong target io_tree.
Reported-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Fixes: bc42bda22345 ("btrfs: qgroup: Fix qgroup reserved space underflow by only freeing reserved ranges")
Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
---
Changelog:
v2:
- Commit message polishment
Use proper call chain to describe the error, as it's pretty deep.
And rephrase how to trigger the bug.
---
fs/btrfs/qgroup.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
index 2891b57b9e1e..64bdc3e3652d 100644
--- a/fs/btrfs/qgroup.c
+++ b/fs/btrfs/qgroup.c
@@ -3492,7 +3492,7 @@ static int qgroup_free_reserved_data(struct inode *inode,
* EXTENT_QGROUP_RESERVED, we won't double free.
* So not need to rush.
*/
- ret = clear_record_extent_bits(&BTRFS_I(inode)->io_failure_tree,
+ ret = clear_record_extent_bits(&BTRFS_I(inode)->io_tree,
free_start, free_start + free_len - 1,
EXTENT_QGROUP_RESERVED, &changeset);
if (ret < 0)
--
2.23.0
