btrfs: cleanup orphans while looking up default subvolume

Orphans in the fs tree are cleaned up via open_ctree and subvolume
orphans are cleaned via btrfs_lookup_dentry -- except when a default
subvolume is in use.  The name for the default subvolume uses a manual
lookup that doesn't trigger orphan cleanup and needs to trigger it
manually as well. This doesn't apply to the remount case since the
subvolumes are cleaned up by walking the root radix tree.
Signed-off-by: NJeff Mahoney <jeffm@suse.com>
Reviewed-by: NDavid Sterba <dsterba@suse.cz>
Signed-off-by: NChris Mason <clm@fb.com>

fs/btrfs/super.c

@@ -901,6 +901,15 @@ static struct dentry *get_default_root(struct super_block *sb,
 	if (IS_ERR(new_root))
 		return ERR_CAST(new_root);
 
+	if (!(sb->s_flags & MS_RDONLY)) {
+		int ret;
+		down_read(&fs_info->cleanup_work_sem);
+		ret = btrfs_orphan_cleanup(new_root);
+		up_read(&fs_info->cleanup_work_sem);
+		if (ret)
+			return ERR_PTR(ret);
+	}
+
 	dir_id = btrfs_root_dirid(&new_root->root_item);
 setup_root:
 	location.objectid = dir_id;