Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756735AbcLBGTX (ORCPT ); Fri, 2 Dec 2016 01:19:23 -0500 Received: from mx2.suse.de ([195.135.220.15]:53564 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755131AbcLBGTW (ORCPT ); Fri, 2 Dec 2016 01:19:22 -0500 Subject: Re: [PATCH 1/2] mm, page_alloc: Keep pcp count and list contents in sync if struct page is corrupted To: Hillf Danton , "'Mel Gorman'" , "'Andrew Morton'" References: <20161202002244.18453-1-mgorman@techsingularity.net> <20161202002244.18453-2-mgorman@techsingularity.net> <01d601d24c4e$dca6e190$95f4a4b0$@alibaba-inc.com> Cc: "'Christoph Lameter'" , "'Michal Hocko'" , "'Johannes Weiner'" , "'Jesper Dangaard Brouer'" , "'Linux-MM'" , "'Linux-Kernel'" From: Vlastimil Babka Message-ID: <55e1d640-72cf-d7b5-695b-87863ca7a843@suse.cz> Date: Fri, 2 Dec 2016 07:19:16 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.0 MIME-Version: 1.0 In-Reply-To: <01d601d24c4e$dca6e190$95f4a4b0$@alibaba-inc.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1860 Lines: 56 On 12/02/2016 04:47 AM, Hillf Danton wrote: > On Friday, December 02, 2016 8:23 AM Mel Gorman wrote: >> 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. 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+] Acked-by: Vlastimil Babka >> --- >> mm/page_alloc.c | 5 +++-- >> 1 file changed, 3 insertions(+), 2 deletions(-) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 6de9440e3ae2..777ed59570df 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 +2217,14 @@ 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)); >> } >> __mod_zone_page_state(zone, NR_FREE_PAGES, -(i << order)); > > Now i is a pure index, yes? No, even if a page fails the check_pcp_refill() check and is not "allocated", it is also no longer a free page, so it's correct to subtract it from NR_FREE_PAGES. >> spin_unlock(&zone->lock); >> - return i; >> + return alloced; >> } >> >> #ifdef CONFIG_NUMA >> -- >> 2.10.2 >