From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 30D22C433FE for ; Mon, 7 Dec 2020 13:42:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E52CE233EA for ; Mon, 7 Dec 2020 13:42:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726061AbgLGNmw (ORCPT ); Mon, 7 Dec 2020 08:42:52 -0500 Received: from mx2.suse.de ([195.135.220.15]:41974 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725800AbgLGNmw (ORCPT ); Mon, 7 Dec 2020 08:42:52 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id ACE32AD18; Mon, 7 Dec 2020 13:42:10 +0000 (UTC) Date: Mon, 7 Dec 2020 14:42:08 +0100 From: Oscar Salvador To: Muchun Song Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vlastimil Babka Subject: Re: [PATCH v2] mm/page_isolation: do not isolate the max order page Message-ID: <20201207134208.GB12191@linux> References: <20201203162237.21885-1-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201203162237.21885-1-songmuchun@bytedance.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 04, 2020 at 12:22:37AM +0800, Muchun Song wrote: > The max order page has no buddy page and never merge to other order. > So isolating and then freeing it is pointless. And if order == MAX_ORDER > - 1, then the buddy can actually be a !pfn_valid() in some corner case? > pfn_valid_within(buddy_pfn) that follows would only catch it on archs > with holes in zone. Then is_migrate_isolate_page(buddy) might access an > invalid buddy. So this is also a bug fix. > > Fixes: 3c605096d315 ("mm/page_alloc: restrict max order of merging on isolated pageblock") > Signed-off-by: Muchun Song > Acked-by: Vlastimil Babka Reviewed-by: Oscar Salvador > --- > Changes in v2: > - Add Fixes tag in the commit log. > > mm/page_isolation.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/page_isolation.c b/mm/page_isolation.c > index a254e1f370a3..bddf788f45bf 100644 > --- a/mm/page_isolation.c > +++ b/mm/page_isolation.c > @@ -88,7 +88,7 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype) > */ > if (PageBuddy(page)) { > order = buddy_order(page); > - if (order >= pageblock_order) { > + if (order >= pageblock_order && order < MAX_ORDER - 1) { > pfn = page_to_pfn(page); > buddy_pfn = __find_buddy_pfn(pfn, order); > buddy = page + (buddy_pfn - pfn); > -- > 2.11.0 > > -- Oscar Salvador SUSE L3