From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx168.postini.com [74.125.245.168]) by kanga.kvack.org (Postfix) with SMTP id 8B4CF6B005A for ; Thu, 6 Sep 2012 03:18:16 -0400 (EDT) Received: from m2.gw.fujitsu.co.jp (unknown [10.0.50.72]) by fgwmail5.fujitsu.co.jp (Postfix) with ESMTP id BCCA13EE0BD for ; Thu, 6 Sep 2012 16:18:14 +0900 (JST) Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id A1DD945DE50 for ; Thu, 6 Sep 2012 16:18:14 +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 88B6345DE4D for ; Thu, 6 Sep 2012 16:18:14 +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 72E3CE08003 for ; Thu, 6 Sep 2012 16:18:14 +0900 (JST) Received: from g01jpexchyt08.g01.fujitsu.local (g01jpexchyt08.g01.fujitsu.local [10.128.194.47]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 202511DB803C for ; Thu, 6 Sep 2012 16:18:14 +0900 (JST) Message-ID: <50484E22.5010304@jp.fujitsu.com> Date: Thu, 6 Sep 2012 16:17:54 +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> In-Reply-To: <1346908619-16056-4-git-send-email-minchan@kernel.org> Content-Type: text/plain; charset="ISO-2022-JP" 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 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. 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