From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756874Ab2IFJPJ (ORCPT ); Thu, 6 Sep 2012 05:15:09 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:46661 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753314Ab2IFJPI (ORCPT ); Thu, 6 Sep 2012 05:15:08 -0400 X-SecurityPolicyCheck: OK by SHieldMailChecker v1.7.4 Message-ID: <5048697F.5060200@jp.fujitsu.com> Date: Thu, 6 Sep 2012 18:14:39 +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 v2 3/3] memory-hotplug: bug fix race between isolation and allocation References: <1346908619-16056-1-git-send-email-minchan@kernel.org> <1346908619-16056-4-git-send-email-minchan@kernel.org> <50484E22.5010304@jp.fujitsu.com> <20120906073020.GB16231@bbox> In-Reply-To: <20120906073020.GB16231@bbox> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Minchan, 2012/09/06 16:30, Minchan Kim wrote: > Hello Yasuaki, > > On Thu, Sep 06, 2012 at 04:17:54PM +0900, Yasuaki Ishimatsu wrote: >> Hi Minchan, >> >> 2012/09/06 14:16, 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. >>> >>> Signed-off-by: Minchan Kim >>> --- >>> 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) >> >> When do the if statement, the page may be used by someone. > > I can't understand your point. > We already hold zone->lock so that allocator and this function should be atomic > when the page is in free_list. > If I miss something, could you elaborate it more? According to your description, the page might be allocated by someone at this point. So some value might be set the page->index by the intended purpose. Thus page->index has the potential to become MIGRATE_ISOLATE value. Thanks, Yasuaki Ishimatsu > >> In this case, page->index may have some number. If the number is same as >> MIGRATE_ISOLATE, the code goes worng. >> >> Thanks, >> Yasuaki Ishimatsu >> >>> pfn += 1; >>> >> >> >> -- >> To unsubscribe, send a message with 'unsubscribe linux-mm' in >> the body to majordomo@kvack.org. For more info on Linux MM, >> see: http://www.linux-mm.org/ . >> Don't email: email@kvack.org > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx162.postini.com [74.125.245.162]) by kanga.kvack.org (Postfix) with SMTP id 81FF26B005A for ; Thu, 6 Sep 2012 05:15:08 -0400 (EDT) Received: from m2.gw.fujitsu.co.jp (unknown [10.0.50.72]) by fgwmail6.fujitsu.co.jp (Postfix) with ESMTP id 696CC3EE0B6 for ; Thu, 6 Sep 2012 18:15:06 +0900 (JST) Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 4C75A45DE4E for ; Thu, 6 Sep 2012 18:15:06 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (s2.gw.fujitsu.co.jp [10.0.50.92]) by m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 2660345DD74 for ; Thu, 6 Sep 2012 18:15:06 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 106371DB802C for ; Thu, 6 Sep 2012 18:15:06 +0900 (JST) Received: from g01jpexchkw06.g01.fujitsu.local (g01jpexchkw06.g01.fujitsu.local [10.0.194.45]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id C2EC81DB803E for ; Thu, 6 Sep 2012 18:15:05 +0900 (JST) Message-ID: <5048697F.5060200@jp.fujitsu.com> Date: Thu, 6 Sep 2012 18:14:39 +0900 From: Yasuaki Ishimatsu MIME-Version: 1.0 Subject: Re: [PATCH v2 3/3] memory-hotplug: bug fix race between isolation and allocation References: <1346908619-16056-1-git-send-email-minchan@kernel.org> <1346908619-16056-4-git-send-email-minchan@kernel.org> <50484E22.5010304@jp.fujitsu.com> <20120906073020.GB16231@bbox> In-Reply-To: <20120906073020.GB16231@bbox> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Mel Gorman , Kamezawa Hiroyuki , Xishi Qiu , Wen Congyang Hi, Minchan, 2012/09/06 16:30, Minchan Kim wrote: > Hello Yasuaki, > > On Thu, Sep 06, 2012 at 04:17:54PM +0900, Yasuaki Ishimatsu wrote: >> Hi Minchan, >> >> 2012/09/06 14:16, 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. >>> >>> Signed-off-by: Minchan Kim >>> --- >>> 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) >> >> When do the if statement, the page may be used by someone. > > I can't understand your point. > We already hold zone->lock so that allocator and this function should be atomic > when the page is in free_list. > If I miss something, could you elaborate it more? According to your description, the page might be allocated by someone at this point. So some value might be set the page->index by the intended purpose. Thus page->index has the potential to become MIGRATE_ISOLATE value. Thanks, Yasuaki Ishimatsu > >> In this case, page->index may have some number. If the number is same as >> MIGRATE_ISOLATE, the code goes worng. >> >> Thanks, >> Yasuaki Ishimatsu >> >>> pfn += 1; >>> >> >> >> -- >> To unsubscribe, send a message with 'unsubscribe linux-mm' in >> the body to majordomo@kvack.org. For more info on Linux MM, >> see: http://www.linux-mm.org/ . >> Don't email: email@kvack.org > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org