static void io_prep_async_link(struct io_kiocb *req)
{
	struct io_kiocb *cur;

	io_prep_async_work(req);
	if (req->flags & REQ_F_LINK_HEAD)
		list_for_each_entry(cur, &req->link_list, link_list)
			io_prep_async_work(cur);
}
static void io_prep_async_link(struct io_kiocb *req)
{
	struct io_kiocb *cur;

	io_prep_async_work(req);
	if (req->flags & REQ_F_LINK_HEAD)
		list_for_each_entry(cur, &req->link_list, link_list)
			io_prep_async_work(cur);
}