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=-8.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 1834CC4361A for ; Thu, 3 Dec 2020 16:28:11 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6E493221ED for ; Thu, 3 Dec 2020 16:28:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6E493221ED Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E15566B0073; Thu, 3 Dec 2020 11:28:09 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id DA16A6B0074; Thu, 3 Dec 2020 11:28:09 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C8F626B0075; Thu, 3 Dec 2020 11:28:09 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0160.hostedemail.com [216.40.44.160]) by kanga.kvack.org (Postfix) with ESMTP id B04886B0073 for ; Thu, 3 Dec 2020 11:28:09 -0500 (EST) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 7C4681F06 for ; Thu, 3 Dec 2020 16:28:09 +0000 (UTC) X-FDA: 77552503098.08.feet33_0807d6c273bd Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin08.hostedemail.com (Postfix) with ESMTP id 574491819E772 for ; Thu, 3 Dec 2020 16:28:09 +0000 (UTC) X-HE-Tag: feet33_0807d6c273bd X-Filterd-Recvd-Size: 3068 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by imf12.hostedemail.com (Postfix) with ESMTP for ; Thu, 3 Dec 2020 16:28:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1607012888; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=jRVA3W7T/pVqUV/EjG25mXlusVZvncykEwttIb9bhjQ=; b=FlIpSzuaZV5anw6adsZDwdXaBZIMeBXUpBfCNpara+nzSsOkSjFGsuP7Y2PM0nGQNXRU5w BczK+Hh69et7mspeRpXRWECG/kfWerwOVl6Pn/EjbRA5nV/Sa/mOIbN8T3YCmlv1oovXB3 Ghg7xoudnw1W0KPD9WfS0cX1QSE8bjk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-19-W2WSu9giO4W3Z0shG1n8lQ-1; Thu, 03 Dec 2020 11:28:04 -0500 X-MC-Unique: W2WSu9giO4W3Z0shG1n8lQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9A04F100671C; Thu, 3 Dec 2020 16:28:02 +0000 (UTC) Received: from [10.36.113.250] (ovpn-113-250.ams2.redhat.com [10.36.113.250]) by smtp.corp.redhat.com (Postfix) with ESMTP id 97CF110013C0; Thu, 3 Dec 2020 16:28:01 +0000 (UTC) Subject: Re: [PATCH v2] mm/page_isolation: do not isolate the max order page To: Muchun Song , akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vlastimil Babka References: <20201203162237.21885-1-songmuchun@bytedance.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <46fcf0c1-7c38-723b-8905-953d72f1d6bc@redhat.com> Date: Thu, 3 Dec 2020 17:28:00 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <20201203162237.21885-1-songmuchun@bytedance.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 03.12.20 17:22, 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") As just replied to v1, I don't think this is required and the patch description can be simplified - e.g., stating that we have/had not such users. -- Thanks, David / dhildenb