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=-8.5 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, 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 6CE0CC432C1 for ; Wed, 25 Sep 2019 06:53:41 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 384D7217F4 for ; Wed, 25 Sep 2019 06:53:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 384D7217F4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id DB63F6B027D; Wed, 25 Sep 2019 02:53:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D8AE86B027E; Wed, 25 Sep 2019 02:53:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CA0AA6B027F; Wed, 25 Sep 2019 02:53:40 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0120.hostedemail.com [216.40.44.120]) by kanga.kvack.org (Postfix) with ESMTP id A98E26B027D for ; Wed, 25 Sep 2019 02:53:40 -0400 (EDT) Received: from smtpin30.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id 509BA82437CF for ; Wed, 25 Sep 2019 06:53:40 +0000 (UTC) X-FDA: 75972527400.30.blood35_3d187e107ad27 X-HE-Tag: blood35_3d187e107ad27 X-Filterd-Recvd-Size: 4555 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf22.hostedemail.com (Postfix) with ESMTP for ; Wed, 25 Sep 2019 06:53:39 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 0B72DB044; Wed, 25 Sep 2019 06:53:38 +0000 (UTC) Date: Wed, 25 Sep 2019 08:53:37 +0200 From: Michal Hocko To: Anshuman Khandual Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Oscar Salvador , David Hildenbrand , Pavel Tatashin , Dan Williams Subject: Re: [PATCH V2] mm/hotplug: Reorder memblock_[free|remove]() calls in try_remove_memory() Message-ID: <20190925065337.GG23050@dhcp22.suse.cz> References: <1569380273-7708-1-git-send-email-anshuman.khandual@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1569380273-7708-1-git-send-email-anshuman.khandual@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Wed 25-09-19 08:27:53, Anshuman Khandual wrote: > Currently during memory hot add procedure, memory gets into memblock before > calling arch_add_memory() which creates it's linear mapping. > > add_memory_resource() { > .................. > memblock_add_node() > .................. > arch_add_memory() > .................. > } > > But during memory hot remove procedure, removal from memblock happens first > before it's linear mapping gets teared down with arch_remove_memory() which > is not consistent. Resource removal should happen in reverse order as they > were added. However this does not pose any problem for now, unless there is > an assumption regarding linear mapping. One example was a subtle failure on > arm64 platform [1]. Though this has now found a different solution. > > try_remove_memory() { > .................. > memblock_free() > memblock_remove() > .................. > arch_remove_memory() > .................. > } > > This changes the sequence of resource removal including memblock and linear > mapping tear down during memory hot remove which will now be the reverse > order in which they were added during memory hot add. The changed removal > order looks like the following. > > try_remove_memory() { > .................. > arch_remove_memory() > .................. > memblock_free() > memblock_remove() > .................. > } > > [1] https://patchwork.kernel.org/patch/11127623/ > > Cc: Andrew Morton > Cc: Oscar Salvador > Cc: Michal Hocko > Cc: David Hildenbrand > Cc: Pavel Tatashin > Cc: Dan Williams > Signed-off-by: Anshuman Khandual Acked-by: Michal Hocko > --- > Changes in V2: > > - Changed the commit message as per Michal and David > > Changed in V1: https://patchwork.kernel.org/patch/11146361/ > > Original patch https://lkml.org/lkml/2019/9/3/327 > > Memory hot remove now works on arm64 without this because a recent commit > 60bb462fc7ad ("drivers/base/node.c: simplify unregister_memory_block_under_nodes()"). > > David mentioned that re-ordering should still make sense for consistency > purpose (removing stuff in the reverse order they were added). This patch > is now detached from arm64 hot-remove series. > > https://lkml.org/lkml/2019/9/3/326 > > mm/memory_hotplug.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 49f7bf91c25a..4f7d426a84d0 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1763,13 +1763,13 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size) > > /* remove memmap entry */ > firmware_map_remove(start, start + size, "System RAM"); > - memblock_free(start, size); > - memblock_remove(start, size); > > /* remove memory block devices before removing memory */ > remove_memory_block_devices(start, size); > > arch_remove_memory(nid, start, size, NULL); > + memblock_free(start, size); > + memblock_remove(start, size); > __release_memory_resource(start, size); > > try_offline_node(nid); > -- > 2.20.1 -- Michal Hocko SUSE Labs