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: Cody P Schafer <[email protected]>
Cc: Gilad Ben-Yossef <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Pekka Enberg <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index eaaef2a..97b8f86 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1182,10 +1182,12 @@
{
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 @@
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:
