void btrfs_add_dead_root(struct btrfs_root *root)
{
	struct btrfs_fs_info *fs_info = root->fs_info;

	spin_lock(&fs_info->trans_lock);
	if (list_empty(&root->root_list)) {
		btrfs_grab_root(root);
		list_add_tail(&root->root_list, &fs_info->dead_roots);
	}
	spin_unlock(&fs_info->trans_lock);
}
void btrfs_add_dead_root(struct btrfs_root *root)
{
	struct btrfs_fs_info *fs_info = root->fs_info;

	spin_lock(&fs_info->trans_lock);
	if (list_empty(&root->root_list)) {
		btrfs_grab_root(root);
		list_add_tail(&root->root_list, &fs_info->dead_roots);
	}
	spin_unlock(&fs_info->trans_lock);
}