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_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 9BE93C43381 for ; Wed, 20 Mar 2019 08:46:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 60AFE21841 for ; Wed, 20 Mar 2019 08:46:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553071565; bh=btRyjQpK7yxpBhZugLt+6V0RHkBriw83jEf8jL4OmUg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=Fvx4p0gzRlfW07yUR6dyK8xOoT/KuAwcoxY7bCPlaZyEz4DOhkjjyOmb8VKnN7seA XTothRh3iQEYRKEhBCkFHC10O6C2w29KY0EisvnYRQXLZJH0gIkE4tYBF3heKx8Y+y UgjBNmJl6X6DTEXR4vsnWlALk4UIIo5ip0steFac= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726891AbfCTIqD (ORCPT ); Wed, 20 Mar 2019 04:46:03 -0400 Received: from mx2.suse.de ([195.135.220.15]:56874 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726417AbfCTIqC (ORCPT ); Wed, 20 Mar 2019 04:46:02 -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 5A0E0ADE1; Wed, 20 Mar 2019 08:46:01 +0000 (UTC) Date: Wed, 20 Mar 2019 09:46:00 +0100 From: Michal Hocko To: Baoquan He 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: <20190320084600.GG30433@dhcp22.suse.cz> References: <20190320080732.14933-1-bhe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190320080732.14933-1-bhe@redhat.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 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? 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. > 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