From: Vlastimil Babka <vbabka@xxxxxxx>
Subject: mm, page_alloc: prevent infinite loop in buffered_rmqueue()
In DEBUG_VM kernel, we can hit infinite loop for order == 0 in
buffered_rmqueue() when check_new_pcp() returns 1, because the bad page is
never removed from the pcp list. Fix this by removing the page before
retrying. Also we don't need to check if page is non-NULL, because we
simply grab it from the list which was just tested for being non-empty.
Fixes: 479f854a207c ("mm, page_alloc: defer debugging checks of pages allocated from the PCP")
Link: http://lkml.kernel.org/r/20160530090154.GM2527@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Reported-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff -puN mm/page_alloc.c~mm-page_alloc-prevent-infinite-loop-in-buffered_rmqueue mm/page_alloc.c
--- a/mm/page_alloc.c~mm-page_alloc-prevent-infinite-loop-in-buffered_rmqueue
+++ a/mm/page_alloc.c
@@ -2615,11 +2615,12 @@ struct page *buffered_rmqueue(struct zon
page = list_last_entry(list, struct page, lru);
else
page = list_first_entry(list, struct page, lru);
- } while (page && check_new_pcp(page));
- __dec_zone_state(zone, NR_ALLOC_BATCH);
- list_del(&page->lru);
- pcp->count--;
+ __dec_zone_state(zone, NR_ALLOC_BATCH);
+ list_del(&page->lru);
+ pcp->count--;
+
+ } while (check_new_pcp(page));
} else {
/*
* We most definitely don't want callers attempting to
_
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