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[195.135.220.15]) by mx.google.com with ESMTPS id m8si928348ejk.24.2019.03.20.12.53.23 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 20 Mar 2019 12:53:23 -0700 (PDT) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org 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 2C219AEF5; Wed, 20 Mar 2019 19:53:23 +0000 (UTC) Date: Wed, 20 Mar 2019 20:53:21 +0100 From: Michal Hocko To: Andrew Morton Cc: Baoquan He , linux-kernel@vger.kernel.org, osalvador@suse.de, david@redhat.com, richard.weiyang@gmail.com, rppt@linux.ibm.com, linux-mm@kvack.org Subject: Re: [PATCH] mm, memory_hotplug: Fix the wrong usage of N_HIGH_MEMORY Message-ID: <20190320195321.GE8696@dhcp22.suse.cz> References: <20190320080732.14933-1-bhe@redhat.com> <20190320121209.5cd30d7b15f299df7d97d51e@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190320121209.5cd30d7b15f299df7d97d51e@linux-foundation.org> 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 20-03-19 12:12:09, Andrew Morton wrote: > On Wed, 20 Mar 2019 16:07:32 +0800 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. > > > > Fixes: 8efe33f40f3e ("mm/memory_hotplug.c: simplify node_states_check_changes_online") > > What are the runtime effects of this change? There shouldn't be none. The code is just messy. The newer changelog should make it more clear I believe. > > --- 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 > > } > -- Michal Hocko SUSE Labs