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Subject[patch v2] vmscan: protect zone rotation stats by lru lock
Date
The zone's rotation statistics must not be accessed without the
corresponding LRU lock held. Fix an unprotected write in
shrink_active_list().

Acked-by: Rik van Riel <riel@redhat.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Johannes Weiner <hannes@saeurebad.de>
---
mm/vmscan.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
Applies to your tree, Linus, and should probably go into .28.

--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1243,32 +1243,32 @@ static void shrink_active_list(unsigned
/* page_referenced clears PageReferenced */
if (page_mapping_inuse(page) &&
page_referenced(page, 0, sc->mem_cgroup))
pgmoved++;

list_add(&page->lru, &l_inactive);
}

+ spin_lock_irq(&zone->lru_lock);
/*
* Count referenced pages from currently used mappings as
* rotated, even though they are moved to the inactive list.
* This helps balance scan pressure between file and anonymous
* pages in get_scan_ratio.
*/
zone->recent_rotated[!!file] += pgmoved;

/*
* Move the pages to the [file or anon] inactive list.
*/
pagevec_init(&pvec, 1);

pgmoved = 0;
lru = LRU_BASE + file * LRU_FILE;
- spin_lock_irq(&zone->lru_lock);
while (!list_empty(&l_inactive)) {
page = lru_to_page(&l_inactive);
prefetchw_prev_lru_page(page, &l_inactive, flags);
VM_BUG_ON(PageLRU(page));
SetPageLRU(page);
VM_BUG_ON(!PageActive(page));
ClearPageActive(page);


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