btrfs: Fix quota reservation leak on preallocated files

Commit c6887cd11149 ("Btrfs: don't do nocow check unless we have to")
changed the behavior of __btrfs_buffered_write() so that it first tries
to get a data space reservation, and then skips the relatively expensive
nocow check if the reservation succeeded.

If we have quotas enabled, the data space reservation also includes a
quota reservation.  But in the rewrite case, the space has already been
accounted for in qgroups.  So btrfs_check_data_free_space() increases
the quota reservation, but it never gets decreased when the data
actually gets written and overwrites the pre-existing data.  So we're
left with both the qgroup and qgroup reservation accounting for the same
space.

This commit adds the missing btrfs_qgroup_free_data() call in the case
of BTRFS_ORDERED_PREALLOC extents.

Fixes: c6887cd11149 ("Btrfs: don't do nocow check unless we have to")
Signed-off-by: Justin Maggard <jmaggard@netgear.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 993061f83067..e1a7f3cb5be9 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3005,6 +3005,8 @@ static int btrfs_finish_ordered_io(struct btrfs_ordered_extent *ordered_extent)
                 compress_type = ordered_extent->compress_type;
         if (test_bit(BTRFS_ORDERED_PREALLOC, &ordered_extent->flags)) {
                 BUG_ON(compress_type);
+                btrfs_qgroup_free_data(inode, NULL, ordered_extent->file_offset,
+                                       ordered_extent->len);
                 ret = btrfs_mark_extent_written(trans, BTRFS_I(inode),
                                                 ordered_extent->file_offset,
                                                 ordered_extent->file_offset +