btrfs: fix root leak if its reloc root is unexpected in merge_reloc_roots()

[ Upstream commit ce6050bafb ]

If we have an unexpected reloc_root for our root, we jump to the out label
but never drop the reference we obtained for root, resulting in a leak.
Add a missing btrfs_put_root() call.

Fixes: 24213fa46c ("btrfs: do proper error handling in merge_reloc_roots")
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

fs/btrfs/relocation.c

@@ -1991,6 +1991,7 @@ again:
 				 * corruption, e.g. bad reloc tree key offset.
 				 */
 				ret = -EINVAL;
+				btrfs_put_root(root);
 				goto out;
 			}
 			ret = merge_reloc_root(rc, root);