int mem_online_node(int nid)
{
	pg_data_t	*pgdat;
	int	ret;

	lock_memory_hotplug();
	pgdat = hotadd_new_pgdat(nid, 0);
	if (!pgdat) {
		ret = -ENOMEM;
		goto out;
	}
	node_set_online(nid);
	ret = register_one_node(nid);
	BUG_ON(ret);

out:
	unlock_memory_hotplug();
	return ret;
}

Unknown