memcg: don't uncharge in mem_cgroup_move_account()

 * @pc:	page_cgroup of the page.

 * @from: mem_cgroup which the page is moved from.

 * @to:	mem_cgroup which the page is moved to. @from != @to.

 * @uncharge: whether we should call uncharge and css_put against @from.

 *

 * The caller must confirm following.

 * - page is not on LRU (isolate_page() is useful.)

 * - compound_lock is held when nr_pages > 1

 *

 * This function doesn't do "charge" nor css_get to new cgroup. It should be

 * done by a caller(__mem_cgroup_try_charge would be useful). If @uncharge is

 * true, this function does "uncharge" from old cgroup, but it doesn't if

 * @uncharge is false, so a caller should do "uncharge".

 * This function doesn't do "charge" to new cgroup and doesn't do "uncharge"

 * from old cgroup.

 */

static int mem_cgroup_move_account(struct page *page,

				   unsigned int nr_pages,

				   struct page_cgroup *pc,

				   struct mem_cgroup *from,

				   struct mem_cgroup *to,

				   bool uncharge)

				   struct mem_cgroup *to)

{

	unsigned long flags;

	int ret;

		preempt_enable();

	}

	mem_cgroup_charge_statistics(from, anon, -nr_pages);

	if (uncharge)

		/* This is not "cancel", but cancel_charge does all we need. */

		__mem_cgroup_cancel_charge(from, nr_pages);

	/* caller should have done css_get */

	pc->mem_cgroup = to;

		flags = compound_lock_irqsave(page);

	ret = mem_cgroup_move_account(page, nr_pages,

				pc, child, parent, false);

				pc, child, parent);

	if (!ret)

		__mem_cgroup_cancel_local_charge(child, nr_pages);

			if (!isolate_lru_page(page)) {

				pc = lookup_page_cgroup(page);

				if (!mem_cgroup_move_account(page, HPAGE_PMD_NR,

							     pc, mc.from, mc.to,

							     false)) {

							pc, mc.from, mc.to)) {

					mc.precharge -= HPAGE_PMD_NR;

					mc.moved_charge += HPAGE_PMD_NR;

				}

				goto put;

			pc = lookup_page_cgroup(page);

			if (!mem_cgroup_move_account(page, 1, pc,

						     mc.from, mc.to, false)) {

						     mc.from, mc.to)) {

				mc.precharge--;

				/* we uncharge from mc.from later. */

				mc.moved_charge++;