Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751530AbcLEDkO (ORCPT ); Sun, 4 Dec 2016 22:40:14 -0500 Received: from out0-129.mail.aliyun.com ([140.205.0.129]:36522 "EHLO out0-129.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751120AbcLEDkN (ORCPT ); Sun, 4 Dec 2016 22:40:13 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R981e4;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e02c03299;MF=hillf.zj@alibaba-inc.com;NM=1;PH=DS;RN=10;SR=0;TI=SMTPD_---.7Fv0UQ5_1480909171; Reply-To: "Hillf Danton" From: "Hillf Danton" To: "'Mel Gorman'" , "'Andrew Morton'" Cc: "'Christoph Lameter'" , "'Michal Hocko'" , "'Vlastimil Babka'" , "'Johannes Weiner'" , "'Jesper Dangaard Brouer'" , "'Joonsoo Kim'" , "'Linux-MM'" , "'Linux-Kernel'" References: <20161202112951.23346-1-mgorman@techsingularity.net> <20161202112951.23346-2-mgorman@techsingularity.net> In-Reply-To: <20161202112951.23346-2-mgorman@techsingularity.net> Subject: Re: [PATCH 1/2] mm, page_alloc: Keep pcp count and list contents in sync if struct page is corrupted Date: Mon, 05 Dec 2016 11:39:31 +0800 Message-ID: <026001d24ea9$30a895c0$91f9c140$@alibaba-inc.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 14.0 Thread-Index: AQJFIZaWoWTrixt3JqFe6RfoNqYDlQJxTNj7n/+DQOA= Content-Language: zh-cn Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2464 Lines: 69 On Friday, December 02, 2016 7:30 PM 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. > > 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+] > --- Acked-by: Hillf Danton > 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