Btrfs: add missing extents release on file extent cluster relocation error

If we error out when finding a page at relocate_file_extent_cluster(), we
need to release the outstanding extents counter on the relocation inode,
set by the previous call to btrfs_delalloc_reserve_metadata(), otherwise
the inode's block reserve size can never decrease to zero and metadata
space is leaked. Therefore add a call to btrfs_delalloc_release_extents()
in case we can't find the target page.

Fixes: 8b62f87b ("Btrfs: rework outstanding_extents")
CC: stable@vger.kernel.org # 4.19+
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/relocation.c

@@ -3277,6 +3277,8 @@ static int relocate_file_extent_cluster(struct inode *inode,
 			if (!page) {
 				btrfs_delalloc_release_metadata(BTRFS_I(inode),
 							PAGE_SIZE, true);
+				btrfs_delalloc_release_extents(BTRFS_I(inode),
+							PAGE_SIZE, true);
 				ret = -ENOMEM;
 				goto out;
 			}