Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 4.8 59/85] mm, page_alloc: keep pcp count and list contents in sync if struct page is corrupted | Date | Wed, 4 Jan 2017 21:47:44 +0100 |
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4.8-stable review patch. If anyone has any objections, please let me know.
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From: Mel Gorman <mgorman@techsingularity.net>
commit a6de734bc002fe2027ccc074fbbd87d72957b7a4 upstream.
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.
The consequence is an infinite loop if the per-cpu lists get fully drained by free_pcppages_bulk because all the lists are empty but the count is positive. The infinite loop occurs here
do { batch_free++; if (++migratetype == MIGRATE_PCPTYPES) migratetype = 0; list = &pcp->lists[migratetype]; } while (list_empty(list));
What the user sees is a bad page warning followed by a soft lockup with interrupts disabled in free_pcppages_bulk().
This patch keeps the accounting in sync.
Fixes: 479f854a207c ("mm, page_alloc: defer debugging checks of pages allocated from the PCP") Link: http://lkml.kernel.org/r/20161202112951.23346-2-mgorman@techsingularity.net Signed-off-by: Mel Gorman <mgorman@suse.de> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Christoph Lameter <cl@linux.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Jesper Dangaard Brouer <brouer@redhat.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- mm/page_alloc.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)
--- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2173,7 +2173,7 @@ static int rmqueue_bulk(struct zone *zon 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) { @@ -2198,13 +2198,21 @@ static int rmqueue_bulk(struct zone *zon 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)); } + + /* + * i pages were removed from the buddy list even if some leak due + * to check_pcp_refill failing so adjust NR_FREE_PAGES based + * on i. Do not confuse with 'alloced' which is the number of + * pages added to the pcp list. + */ __mod_zone_page_state(zone, NR_FREE_PAGES, -(i << order)); spin_unlock(&zone->lock); - return i; + return alloced; } #ifdef CONFIG_NUMA
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