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

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

Signed-off-by: Cody 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Cody P Schafer 2013-07-03 15:01:32 -07:00 committed by Linus Torvalds
parent 8d7a8fa97a
commit 998d39cb23
1 changed files with 7 additions and 4 deletions
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11
mm/page_alloc.c
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@ -1182,10 +1182,12 @@ void drain_zone_pages(struct zone *zone, struct per_cpu_pages *pcp)
{
unsigned long flags;
int to_drain;
unsigned long batch;
local_irq_save(flags);
if (pcp->count >= pcp->batch)
to_drain = pcp->batch;
batch = ACCESS_ONCE(pcp->batch);
if (pcp->count >= batch)
to_drain = batch;
else
to_drain = pcp->count;
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]);
pcp->count++;
if (pcp->count >= pcp->high) {
free_pcppages_bulk(zone, pcp->batch, pcp);
pcp->count -= pcp->batch;
unsigned long batch = ACCESS_ONCE(pcp->batch);
free_pcppages_bulk(zone, batch, pcp);
pcp->count -= batch;
}
out: