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 4F91DC4361A for ; Thu, 3 Dec 2020 16:29:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B1221207B0 for ; Thu, 3 Dec 2020 16:29:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727209AbgLCQ3c (ORCPT ); Thu, 3 Dec 2020 11:29:32 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:46845 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726032AbgLCQ3c (ORCPT ); Thu, 3 Dec 2020 11:29:32 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1607012886; 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=i29keSEe6ZZaoIBAdLM0CSsI8M2RaxTi60xgT7tJJ2Usy0THGX5CDTdpV8I0lfSP6s1Oui WWW1NmoLFjU2VL/KsHQLSc4fr1qU2J0SuUkFt+/sJF/u4kwQbSN94akcX2JhYs+4VIUOGZ oqm13Zlbs0ALVoDEl93HbScQIH8yPBo= 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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