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[195.135.220.15]) by mx.google.com with ESMTPS id p14si448901edx.81.2019.03.13.01.01.06 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 13 Mar 2019 01:01:06 -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 EE063AE84; Wed, 13 Mar 2019 08:01:05 +0000 (UTC) Date: Wed, 13 Mar 2019 09:01:05 +0100 From: Michal Hocko To: Oscar Salvador Cc: Qian Cai , akpm@linux-foundation.org, vbabka@suse.cz, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/hotplug: fix offline undo_isolate_page_range() Message-ID: <20190313080105.GG5721@dhcp22.suse.cz> References: <20190313014216.36782-1-cai@lca.pw> <20190313075212.wc3pbwixx3ppwxua@d104.suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190313075212.wc3pbwixx3ppwxua@d104.suse.de> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000295, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed 13-03-19 08:52:16, Oscar Salvador wrote: > On Tue, Mar 12, 2019 at 09:42:16PM -0400, Qian Cai wrote: > > + > > + /* > > + * Onlining will reset pagetype flags and makes migrate type > > + * MOVABLE, so just need to decrease the number of isolated > > + * pageblocks zone counter here. > > + */ > > + for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) { > > + int i; > > + > > + for (i = 0; i < pageblock_nr_pages; i++) > > + if (pfn_valid_within(pfn + i)) { > > + zone->nr_isolate_pageblock--; > > + break; > > + } > > + } > > + > > I do not really like this. > > I first thought about saving the value before entering start_isolate_page_range, > but that could race with alloc_contig_range for instance. Yup. We need to take the zone lock. > So, why not make start_isolate_page_range to return the actual number of isolated > pageblocks? That makes more sense indeed. -- Michal Hocko SUSE Labs