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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no 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 3F393C4CECE for ; Mon, 14 Oct 2019 09:35:26 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id EAD8A20659 for ; Mon, 14 Oct 2019 09:35:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EAD8A20659 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 46sD1l56tFzDqhl for ; Mon, 14 Oct 2019 20:35:23 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=redhat.com (client-ip=209.132.183.28; helo=mx1.redhat.com; envelope-from=david@redhat.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=redhat.com Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 46sCyC0MFSzDqDB for ; Mon, 14 Oct 2019 20:32:19 +1100 (AEDT) Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 13146A3CD7D; Mon, 14 Oct 2019 09:32:17 +0000 (UTC) Received: from [10.36.116.28] (ovpn-116-28.ams2.redhat.com [10.36.116.28]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9106F600CD; Mon, 14 Oct 2019 09:32:14 +0000 (UTC) Subject: Re: [PATCH v6 04/10] mm/memory_hotplug: Don't access uninitialized memmaps in shrink_zone_span() To: linux-kernel@vger.kernel.org, Andrew Morton References: <20191006085646.5768-1-david@redhat.com> <20191006085646.5768-5-david@redhat.com> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <5a4573de-bd8a-6cd3-55d0-86d503a236fd@redhat.com> Date: Mon, 14 Oct 2019 11:32:13 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.0 MIME-Version: 1.0 In-Reply-To: <20191006085646.5768-5-david@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.68]); Mon, 14 Oct 2019 09:32:17 +0000 (UTC) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-s390@vger.kernel.org, Michal Hocko , linux-ia64@vger.kernel.org, Pavel Tatashin , linux-sh@vger.kernel.org, "Aneesh Kumar K . V" , x86@kernel.org, linux-mm@kvack.org, Dan Williams , linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, Oscar Salvador Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 06.10.19 10:56, David Hildenbrand wrote: > Let's limit shrinking to !ZONE_DEVICE so we can fix the current code. We > should never try to touch the memmap of offline sections where we could > have uninitialized memmaps and could trigger BUGs when calling > page_to_nid() on poisoned pages. > > There is no reliable way to distinguish an uninitialized memmap from an > initialized memmap that belongs to ZONE_DEVICE, as we don't have > anything like SECTION_IS_ONLINE we can use similar to > pfn_to_online_section() for !ZONE_DEVICE memory. E.g., > set_zone_contiguous() similarly relies on pfn_to_online_section() and > will therefore never set a ZONE_DEVICE zone consecutive. Stopping to > shrink the ZONE_DEVICE therefore results in no observable changes, > besides /proc/zoneinfo indicating different boundaries - something we > can totally live with. > > Before commit d0dc12e86b31 ("mm/memory_hotplug: optimize memory > hotplug"), the memmap was initialized with 0 and the node with the > right value. So the zone might be wrong but not garbage. After that > commit, both the zone and the node will be garbage when touching > uninitialized memmaps. > > Cc: Andrew Morton > Cc: Oscar Salvador > Cc: David Hildenbrand > Cc: Michal Hocko > Cc: Pavel Tatashin > Cc: Dan Williams > Fixes: d0dc12e86b31 ("mm/memory_hotplug: optimize memory hotplug") @Andrew, can you convert that to Fixes: f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to zones until online") # visible after d0dc12e86b319 and add Cc: stable@vger.kernel.org # v4.13+ -- Thanks, David / dhildenb