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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 B6AEFC4320D for ; Wed, 25 Sep 2019 06:53:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8D3CE217F4 for ; Wed, 25 Sep 2019 06:53:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1569394421; bh=3I9N81YtR67BwSWbd01l59e9PfoymVO7oHoRVWCccdg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=QvZkY4fHHWhtOsgntouK+zjC1fdbhan1YQIXhqjv+dMaRY1hreqShS2bE0os0uO6p 5SN6US93EeqwYcTn6aeSXeMzlVCxNxa93VML6RNQQLvT/Qirta+HI+577+RmZ5GsIp lFQ+MOipR6dj6V5/7GflQd9bAcboWEYkVxoCA4+g= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2442387AbfIYGxk (ORCPT ); Wed, 25 Sep 2019 02:53:40 -0400 Received: from mx2.suse.de ([195.135.220.15]:46232 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2436671AbfIYGxk (ORCPT ); Wed, 25 Sep 2019 02:53:40 -0400 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) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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