Btrfs: fix memory patcher through fs_info->qgroup_ulist

Commit 5b7c665e introduced fs_info->qgroup_ulist, that is allocated during
btrfs_read_qgroup_config and meant to be used later by the qgroup accounting
code. However, it is always freed before btrfs_read_qgroup_config returns,
becuase the commit mentioned above adds a check for (ret), where a check
for (ret < 0) would have been the right choice. This commit fixes the check.

Cc: Wang Shilong <wangsl-fnst@cn.fujitsu.com>
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

fs/btrfs/qgroup.c

@@ -430,7 +430,7 @@ int btrfs_read_qgroup_config(struct btrfs_fs_info *fs_info)
 	}
 	btrfs_free_path(path);
 
-	if (ret)
+	if (ret < 0)
 		ulist_free(fs_info->qgroup_ulist);
 
 	return ret < 0 ? ret : 0;