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Commit 998d39cb authored by Cody P Schafer's avatar Cody P Schafer Committed by Linus Torvalds
Browse files

mm/page_alloc: protect pcp->batch accesses with ACCESS_ONCE 



pcp->batch could change at any point, avoid relying on it being a stable
value.

Signed-off-by: default avatarCody P Schafer <cody@linux.vnet.ibm.com>
Cc: Gilad Ben-Yossef <gilad@benyossef.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 8d7a8fa9

mm/page_alloc.c

+7 −4
Original line number Original line Diff line number Diff line
@@ -1182,10 +1182,12 @@ void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp) 
{

{

	unsigned long flags;

	unsigned long flags;

	int to_drain;

	int to_drain;

	unsigned long batch;





	local_irq_save(flags);

	local_irq_save(flags);

	if (pcp->count >= pcp->batch)

	batch = ACCESS_ONCE(pcp->batch);

		to_drain = pcp->batch;

	if (pcp->count >= batch)

		to_drain = batch;

	else

	else

		to_drain = pcp->count;

		to_drain = pcp->count;

	if (to_drain > 0) {

	if (to_drain > 0) {
@@ -1353,8 +1355,9 @@ void free_hot_cold_page(struct page *page, int cold) 
		list_add(&page->lru, &pcp->lists[migratetype]);

		list_add(&page->lru, &pcp->lists[migratetype]);

	pcp->count++;

	pcp->count++;

	if (pcp->count >= pcp->high) {

	if (pcp->count >= pcp->high) {

		free_pcppages_bulk(zone, pcp->batch, pcp);

		unsigned long batch = ACCESS_ONCE(pcp->batch);

		pcp->count -= pcp->batch;

		free_pcppages_bulk(zone, batch, pcp);

		pcp->count -= batch;

	}

	}





out:

out: