[PATCH 1/2] mm, page_alloc: Keep pcp count and list contents in sync if struct page is corrupted

From: Mel Gorman
Date: Thu Dec 01 2016 - 19:22:55 EST


Vlastimil Babka pointed out that commit 479f854a207c ("mm, page_alloc:
defer debugging checks of pages allocated from the PCP") will allow the
per-cpu list counter to be out of sync with the per-cpu list contents
if a struct page is corrupted. This patch keeps the accounting in sync.

Fixes: 479f854a207c ("mm, page_alloc: defer debugging checks of pages allocated from the PCP")
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
cc: stable@xxxxxxxxxxxxxxx [4.7+]
---
mm/page_alloc.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6de9440e3ae2..777ed59570df 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2192,7 +2192,7 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order,
unsigned long count, struct list_head *list,
int migratetype, bool cold)
{
- int i;
+ int i, alloced = 0;

spin_lock(&zone->lock);
for (i = 0; i < count; ++i) {
@@ -2217,13 +2217,14 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order,
else
list_add_tail(&page->lru, list);
list = &page->lru;
+ alloced++;
if (is_migrate_cma(get_pcppage_migratetype(page)))
__mod_zone_page_state(zone, NR_FREE_CMA_PAGES,
-(1 << order));
}
__mod_zone_page_state(zone, NR_FREE_PAGES, -(i << order));
spin_unlock(&zone->lock);
- return i;
+ return alloced;
}

#ifdef CONFIG_NUMA
--
2.10.2