btrfs: free qgroup rsv on io failure

If we do a write whose bio suffers an error, we will never reclaim the
qgroup reserved space for it. We allocate the space in the write_iter
codepath, then release the reservation as we allocate the ordered
extent, but we only create a delayed ref if the ordered extent finishes.
If it has an error, we simply leak the rsv. This is apparent in running
any error injecting (dmerror) fstests like btrfs/146 or btrfs/160. Such
tests fail due to dmesg on umount complaining about the leaked qgroup
data space.

When we clean up other aspects of space on failed ordered_extents, also
free the qgroup rsv.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
CC: stable@vger.kernel.org # 5.10+
Signed-off-by: Boris Burkov <boris@bur.io>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -3358,6 +3358,13 @@ int btrfs_finish_one_ordered(struct btrfs_ordered_extent *ordered_extent)
 			btrfs_free_reserved_extent(fs_info,
 					ordered_extent->disk_bytenr,
 					ordered_extent->disk_num_bytes, 1);
+			/*
+			 * Actually free the qgroup rsv which was released when
+			 * the ordered extent was created.
+			 */
+			btrfs_qgroup_free_refroot(fs_info, inode->root->root_key.objectid,
+						  ordered_extent->qgroup_rsv,
+						  BTRFS_QGROUP_RSV_DATA);
 		}
 	}