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[195.135.220.15]) by mx.google.com with ESMTPS id m29si511702edb.245.2019.01.28.10.45.29 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 28 Jan 2019 10:45:29 -0800 (PST) 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 3FFE7B00C; Mon, 28 Jan 2019 18:45:29 +0000 (UTC) Date: Mon, 28 Jan 2019 19:45:28 +0100 From: Michal Hocko To: Andrew Morton Cc: Mikhail Zaslonko , Mikhail Gavrilov , Pavel Tatashin , schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, gerald.schaefer@de.ibm.com, linux-mm@kvack.org, LKML Subject: Re: [PATCH 0/2] mm, memory_hotplug: fix uninitialized pages fallouts. Message-ID: <20190128184528.GU18811@dhcp22.suse.cz> References: <20190128144506.15603-1-mhocko@kernel.org> <20190128095054.4103093dec81f1c904df7929@linux-foundation.org> <20190128184139.GR18811@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190128184139.GR18811@dhcp22.suse.cz> 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 Mon 28-01-19 19:41:39, Michal Hocko wrote: > On Mon 28-01-19 09:50:54, Andrew Morton wrote: > > On Mon, 28 Jan 2019 15:45:04 +0100 Michal Hocko wrote: > > > > > Mikhail has posted fixes for the two bugs quite some time ago [1]. I > > > have pushed back on those fixes because I believed that it is much > > > better to plug the problem at the initialization time rather than play > > > whack-a-mole all over the hotplug code and find all the places which > > > expect the full memory section to be initialized. We have ended up with > > > 2830bf6f05fb ("mm, memory_hotplug: initialize struct pages for the full > > > memory section") merged and cause a regression [2][3]. The reason is > > > that there might be memory layouts when two NUMA nodes share the same > > > memory section so the merged fix is simply incorrect. > > > > > > In order to plug this hole we really have to be zone range aware in > > > those handlers. I have split up the original patch into two. One is > > > unchanged (patch 2) and I took a different approach for `removable' > > > crash. It would be great if Mikhail could test it still works for his > > > memory layout. > > > > > > [1] http://lkml.kernel.org/r/20181105150401.97287-2-zaslonko@linux.ibm.com > > > [2] https://bugzilla.redhat.com/show_bug.cgi?id=1666948 > > > [3] http://lkml.kernel.org/r/20190125163938.GA20411@dhcp22.suse.cz > > > > Any thoughts on which kernel version(s) need these patches? > > My remark in 2830bf6f05fb still holds > : This has alwways been problem AFAIU. It just went unnoticed because we > : have zeroed memmaps during allocation before f7f99100d8d9 ("mm: stop > : zeroing memory during allocation in vmemmap") and so the above test > : would simply skip these ranges as belonging to zone 0 or provided a > : garbage. > : > : So I guess we do care for post f7f99100d8d9 kernels mostly and > : therefore Fixes: f7f99100d8d9 ("mm: stop zeroing memory during > : allocation in vmemmap") > > But, please let's wait for the patch 1 to be confirmed to fix the issue. Also the revert [1] should be applied first. I thought Linus would pick it up but he hasn't done so yet. [1] http://lkml.kernel.org/r/20190125181549.GE20411@dhcp22.suse.cz -- Michal Hocko SUSE Labs