From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759777Ab2IGDwv (ORCPT ); Thu, 6 Sep 2012 23:52:51 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:60507 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759443Ab2IGDwu (ORCPT ); Thu, 6 Sep 2012 23:52:50 -0400 X-SecurityPolicyCheck: OK by SHieldMailChecker v1.7.4 Message-ID: <50496F7E.4080309@jp.fujitsu.com> Date: Fri, 7 Sep 2012 12:52:30 +0900 From: Yasuaki Ishimatsu User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:15.0) Gecko/20120824 Thunderbird/15.0 MIME-Version: 1.0 To: Minchan Kim CC: Andrew Morton , , , Mel Gorman , Kamezawa Hiroyuki , Xishi Qiu , Wen Congyang Subject: Re: [PATCH v3 3/4] memory-hotplug: bug fix race between isolation and allocation References: <1346978372-17903-1-git-send-email-minchan@kernel.org> <1346978372-17903-4-git-send-email-minchan@kernel.org> In-Reply-To: <1346978372-17903-4-git-send-email-minchan@kernel.org> Content-Type: text/plain; charset="ISO-2022-JP" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2012/09/07 9:39, Minchan Kim wrote: > Like below, memory-hotplug makes race between page-isolation > and page-allocation so it can hit BUG_ON in __offline_isolated_pages. > > CPU A CPU B > > start_isolate_page_range > set_migratetype_isolate > spin_lock_irqsave(zone->lock) > > free_hot_cold_page(Page A) > /* without zone->lock */ > migratetype = get_pageblock_migratetype(Page A); > /* > * Page could be moved into MIGRATE_MOVABLE > * of per_cpu_pages > */ > list_add_tail(&page->lru, &pcp->lists[migratetype]); > > set_pageblock_isolate > move_freepages_block > drain_all_pages > > /* Page A could be in MIGRATE_MOVABLE of free_list. */ > > check_pages_isolated > __test_page_isolated_in_pageblock > /* > * We can't catch freed page which > * is free_list[MIGRATE_MOVABLE] > */ > if (PageBuddy(page A)) > pfn += 1 << page_order(page A); > > /* So, Page A could be allocated */ > > __offline_isolated_pages > /* > * BUG_ON hit or offline page > * which is used by someone > */ > BUG_ON(!PageBuddy(page A)); > > This patch checks page's migratetype in freelist in __test_page_isolated_in_pageblock. > So now __test_page_isolated_in_pageblock can check the page caused by above race and > can fail of memory offlining. > > * from v2 > * Add Acked-by of Kame > > Acked-by: KAMEZAWA Hiroyuki > Signed-off-by: Minchan Kim Reviewed-by: Yasuaki Ishimatsu Thanks, Yasuaki Ishimatsu > --- > mm/page_isolation.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/mm/page_isolation.c b/mm/page_isolation.c > index 87a7929..7ba7405 100644 > --- a/mm/page_isolation.c > +++ b/mm/page_isolation.c > @@ -193,8 +193,11 @@ __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn) > continue; > } > page = pfn_to_page(pfn); > - if (PageBuddy(page)) > + if (PageBuddy(page)) { > + if (get_freepage_migratetype(page) != MIGRATE_ISOLATE) > + break; > pfn += 1 << page_order(page); > + } > else if (page_count(page) == 0 && > get_freepage_migratetype(page) == MIGRATE_ISOLATE) > pfn += 1; >