/* check whether the @pc is valid for moving account and call __mem_cgroup_move_account()  */
static int mem_cgroup_move_account(struct page_cgroup *pc, struct mem_cgroup *from, struct mem_cgroup *to)
/* check whether the @pc is valid for moving account and call __mem_cgroup_move_account()  */
static int mem_cgroup_move_account(struct page_cgroup *pc, struct mem_cgroup *from, struct mem_cgroup *to)
{
	int ret = -EINVAL;
	lock_page_cgroup(pc);
	if (PageCgroupUsed(pc) && pc->mem_cgroup == from) {
		__mem_cgroup_move_account(pc, from, to);
		ret = 0;
	}
	unlock_page_cgroup(pc);
	return ret;
}