Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760478AbcLBLaH (ORCPT ); Fri, 2 Dec 2016 06:30:07 -0500 Received: from outbound-smtp04.blacknight.com ([81.17.249.35]:48513 "EHLO outbound-smtp04.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750750AbcLBLaE (ORCPT ); Fri, 2 Dec 2016 06:30:04 -0500 From: Mel Gorman To: Andrew Morton Cc: Christoph Lameter , Michal Hocko , Vlastimil Babka , Johannes Weiner , Jesper Dangaard Brouer , Joonsoo Kim , Linux-MM , Linux-Kernel , Mel Gorman Subject: [PATCH 1/2] mm, page_alloc: Keep pcp count and list contents in sync if struct page is corrupted Date: Fri, 2 Dec 2016 11:29:50 +0000 Message-Id: <20161202112951.23346-2-mgorman@techsingularity.net> X-Mailer: git-send-email 2.10.2 In-Reply-To: <20161202112951.23346-1-mgorman@techsingularity.net> References: <20161202112951.23346-1-mgorman@techsingularity.net> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2230 Lines: 66 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)); >From a user perspective, it's 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") Signed-off-by: Mel Gorman cc: stable@vger.kernel.org [4.7+] --- mm/page_alloc.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 6de9440e3ae2..34ada718ef47 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 +2217,21 @@ 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)); } + + /* + * 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 -- 2.10.2