btrfs: qgroup: Fix the wrong target io_tree when freeing reserved data space
authorQu Wenruo <>
Mon, 16 Sep 2019 12:02:38 +0000 (20:02 +0800)
committerDavid Sterba <>
Fri, 27 Sep 2019 13:24:28 +0000 (15:24 +0200)
Under the following 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;

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;

In the above case, btrfs_delalloc_reserve_space() will call
btrfs_qgroup_reserve_data() and mark the io_tree range with

In the error handling path, we have the following call stack:
|- 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 the wrong target io_tree.

Reported-by: Josef Bacik <>
Fixes: bc42bda22345 ("btrfs: qgroup: Fix qgroup reserved space underflow by only freeing reserved ranges")
CC: # 4.14+
Reviewed-by: Nikolay Borisov <>
Signed-off-by: Qu Wenruo <>
Signed-off-by: David Sterba <>

index 52701c1be1096b92e63788b3fc8910da59048594..4ab85555a947f68d2a130fd2f8d46301d7c33ebe 100644 (file)
@@ -3486,7 +3486,7 @@ 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)