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=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT 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 010F1C43381 for ; Wed, 20 Mar 2019 09:06:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CBEAF2186A for ; Wed, 20 Mar 2019 09:06:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727203AbfCTJGa (ORCPT ); Wed, 20 Mar 2019 05:06:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40804 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726006AbfCTJGa (ORCPT ); Wed, 20 Mar 2019 05:06:30 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id AF3D830821FA; Wed, 20 Mar 2019 09:06:29 +0000 (UTC) Received: from localhost (ovpn-12-38.pek2.redhat.com [10.72.12.38]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 26FE02E02C; Wed, 20 Mar 2019 09:06:26 +0000 (UTC) Date: Wed, 20 Mar 2019 17:06:24 +0800 From: Baoquan He To: Michal Hocko Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, osalvador@suse.de, david@redhat.com, richard.weiyang@gmail.com, rppt@linux.ibm.com Subject: Re: [PATCH] mm, memory_hotplug: Fix the wrong usage of N_HIGH_MEMORY Message-ID: <20190320090624.GN18740@MiWiFi-R3L-srv> References: <20190320080732.14933-1-bhe@redhat.com> <20190320084600.GG30433@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190320084600.GG30433@dhcp22.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.47]); Wed, 20 Mar 2019 09:06:29 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/20/19 at 09:46am, Michal Hocko wrote: > On Wed 20-03-19 16:07:32, Baoquan He wrote: > > In function node_states_check_changes_online(), N_HIGH_MEMORY is used > > to substitute ZONE_HIGHMEM directly. This is not right. N_HIGH_MEMORY > > always has value '3' if CONFIG_HIGHMEM=y, while ZONE_HIGHMEM's value > > is not. It depends on whether CONFIG_ZONE_DMA/CONFIG_ZONE_DMA32 are > > enabled. Obviously it's not true for CONFIG_ZONE_DMA32 on 32bit system, > > and CONFIG_ZONE_DMA is also optional. > > > > Replace it with ZONE_HIGHMEM. > > N*MEMORY is confusing as hell but I am really curious whether we have > ZONE_DMA32 and ZONE_HIGMEM together? Not sure. AFAIK, on x86_32 it can't be. > > That being said N.*MEMORY is intended to check for nodes rather than > zones so the patch looks good to me but I think the above explanation is > misleading and will add even more mud to the picture when somebody tries > to understand what the heck is going on here. Yes, agree. I also thought this again after I sent out patch, feel log is not good. As you said, they are value of enum node_states and enum zone_type separately. How about this: ~~~ In function node_states_check_changes_online(), N_HIGH_MEMORY is used to substitute ZONE_HIGHMEM directly. This is not right. N_HIGH_MEMORY is to mark the memory state of node. Here zone index is checked, which should be compared with 'ZONE_HIGHMEM' accordingly. Replace it with ZONE_HIGHMEM. ~~~ > > > Fixes: 8efe33f40f3e ("mm/memory_hotplug.c: simplify node_states_check_changes_online") > > Signed-off-by: Baoquan He > > --- > > mm/memory_hotplug.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > > index 6b05576fb4ec..09911d34a3be 100644 > > --- a/mm/memory_hotplug.c > > +++ b/mm/memory_hotplug.c > > @@ -712,7 +712,7 @@ static void node_states_check_changes_online(unsigned long nr_pages, > > if (zone_idx(zone) <= ZONE_NORMAL && !node_state(nid, N_NORMAL_MEMORY)) > > arg->status_change_nid_normal = nid; > > #ifdef CONFIG_HIGHMEM > > - if (zone_idx(zone) <= N_HIGH_MEMORY && !node_state(nid, N_HIGH_MEMORY)) > > + if (zone_idx(zone) <= ZONE_HIGHMEM && !node_state(nid, N_HIGH_MEMORY)) > > arg->status_change_nid_high = nid; > > #endif > > } > > -- > > 2.17.2 > > -- > Michal Hocko > SUSE Labs