From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759600Ab2IGDrm (ORCPT ); Thu, 6 Sep 2012 23:47:42 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:42543 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752564Ab2IGDrl (ORCPT ); Thu, 6 Sep 2012 23:47:41 -0400 X-SecurityPolicyCheck: OK by SHieldMailChecker v1.7.4 Message-ID: <50496E44.9070007@jp.fujitsu.com> Date: Fri, 7 Sep 2012 12:47:16 +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> <5048697F.5060200@jp.fujitsu.com> <20120906233745.GE16231@bbox> In-Reply-To: <20120906233745.GE16231@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, 2012/09/07 8:37, Minchan Kim wrote: > Hello Yasuaki, > > On Thu, Sep 06, 2012 at 06:14:39PM +0900, Yasuaki Ishimatsu wrote: >> 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 > > It seems you are misunderstanding my point. > Before my patch, Yes. It could be allocated by someone but > after my patch, it couldn't be allocated and inconsistency between > pageblock's migratetype and page's migratetype is detected so that > memory offline would be just failed simply. Thank you for your explanation. My concern disappeared. Thanks, Yasuaki Ishimatsu > >> 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 > From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx179.postini.com [74.125.245.179]) by kanga.kvack.org (Postfix) with SMTP id 21E606B005A for ; Thu, 6 Sep 2012 23:47:41 -0400 (EDT) Received: from m2.gw.fujitsu.co.jp (unknown [10.0.50.72]) by fgwmail5.fujitsu.co.jp (Postfix) with ESMTP id 64E3F3EE0BC for ; Fri, 7 Sep 2012 12:47:39 +0900 (JST) Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 4FBBD45DD74 for ; Fri, 7 Sep 2012 12:47:39 +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 262FC45DE4E for ; Fri, 7 Sep 2012 12:47:39 +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 186091DB8040 for ; Fri, 7 Sep 2012 12:47:39 +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 CB9C31DB803A for ; Fri, 7 Sep 2012 12:47:38 +0900 (JST) Message-ID: <50496E44.9070007@jp.fujitsu.com> Date: Fri, 7 Sep 2012 12:47:16 +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> <5048697F.5060200@jp.fujitsu.com> <20120906233745.GE16231@bbox> In-Reply-To: <20120906233745.GE16231@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, 2012/09/07 8:37, Minchan Kim wrote: > Hello Yasuaki, > > On Thu, Sep 06, 2012 at 06:14:39PM +0900, Yasuaki Ishimatsu wrote: >> 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 > > It seems you are misunderstanding my point. > Before my patch, Yes. It could be allocated by someone but > after my patch, it couldn't be allocated and inconsistency between > pageblock's migratetype and page's migratetype is detected so that > memory offline would be just failed simply. Thank you for your explanation. My concern disappeared. Thanks, Yasuaki Ishimatsu > >> 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 > -- 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