static int slab_memory_callback(struct notifier_block *self,
				unsigned long action, void *arg)
{
	int ret = 0;

	switch (action) {
	case MEM_GOING_ONLINE:
		ret = slab_mem_going_online_callback(arg);
		break;
	case MEM_GOING_OFFLINE:
		ret = slab_mem_going_offline_callback(arg);
		break;
	case MEM_OFFLINE:
	case MEM_CANCEL_ONLINE:
		slab_mem_offline_callback(arg);
		break;
	case MEM_ONLINE:
	case MEM_CANCEL_OFFLINE:
		break;
	}
	if (ret)
		ret = notifier_from_errno(ret);
	else
		ret = NOTIFY_OK;
	return ret;
}