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[195.135.220.15]) by mx.google.com with ESMTPS id w21si22920106eda.367.2019.08.01.00.40.09 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 01 Aug 2019 00:40:09 -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 55B34B11C; Thu, 1 Aug 2019 07:40:09 +0000 (UTC) Date: Thu, 1 Aug 2019 09:39:57 +0200 From: Michal Hocko To: David Hildenbrand Cc: Rashmica Gupta , Oscar Salvador , Andrew Morton , Dan Williams , pasha.tatashin@soleen.com, Jonathan.Cameron@huawei.com, anshuman.khandual@arm.com, Vlastimil Babka , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 0/5] Allocate memmap from hotadded memory Message-ID: <20190801073957.GH11627@dhcp22.suse.cz> References: <9143f64391d11aa0f1988e78be9de7ff56e4b30b.camel@gmail.com> <20190702074806.GA26836@linux> <20190731120859.GJ9330@dhcp22.suse.cz> <4ddee0dd719abd50350f997b8089fa26f6004c0c.camel@gmail.com> <20190801071709.GE11627@dhcp22.suse.cz> <9bcbd574-7e23-5cfe-f633-646a085f935a@redhat.com> <20190801072430.GF11627@dhcp22.suse.cz> <5e6137c9-5269-5756-beaa-d116652be8b9@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5e6137c9-5269-5756-beaa-d116652be8b9@redhat.com> 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 Thu 01-08-19 09:31:09, David Hildenbrand wrote: > On 01.08.19 09:26, David Hildenbrand wrote: [...] > > I am not sure about the implications of having > > pfn_valid()/pfn_present()/pfn_online() return true but accessing it > > results in crashes. (suspend, kdump, whatever other technology touches > > online memory) > > (oneidea: we could of course go ahead and mark the pages PG_offline > before unmapping the pfn range to work around these issues) PG_reserved and an elevated reference count should be enough to drive any pfn walker out. Pfn walkers shouldn't touch any page unless they know and recognize their type. -- Michal Hocko SUSE Labs