Commit 83b9355b authored Jun 03, 2016 by Vlastimil Babka Committed by Linus Torvalds Jun 03, 2016

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: 479f854a ("mm, page_alloc: defer debugging checks of pages allocated from the PCP")
Link: http://lkml.kernel.org/r/20160530090154.GM2527@techsingularity.net


Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reported-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 879be4f3

mm/page_alloc.c

+5 −4

Original line number	Diff line number	Diff line
		@@ -2615,11 +2615,12 @@ struct page buffered_rmqueue(struct zone preferred_zone,
		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--;

		} while (check_new_pcp(page));
		} else {
		/*
		* We most definitely don't want callers attempting to

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