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[209.132.183.28]) by mx.google.com with ESMTPS id r17si2411903qte.289.2019.04.11.04.18.11 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 11 Apr 2019 04:18:11 -0700 (PDT) Received-SPF: pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9C65137E7B; Thu, 11 Apr 2019 11:18:10 +0000 (UTC) Received: from [10.36.118.43] (unknown [10.36.118.43]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9DE4E60BF7; Thu, 11 Apr 2019 11:18:08 +0000 (UTC) Subject: Re: [PATCH] mm/memory_hotplug: Drop memory device reference after find_memory_block() To: Michal Hocko Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Oscar Salvador , Pavel Tatashin , Wei Yang , Qian Cai , Arun KS , Mathieu Malaterre References: <20190410101455.17338-1-david@redhat.com> <20190411084141.GQ10383@dhcp22.suse.cz> <0bbe632f-cb85-4a98-0c79-ded11cf39081@redhat.com> <20190411105617.GS10383@dhcp22.suse.cz> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190411105617.GS10383@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Thu, 11 Apr 2019 11:18:10 +0000 (UTC) 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 11.04.19 12:56, Michal Hocko wrote: > On Thu 11-04-19 11:11:05, David Hildenbrand wrote: >> On 11.04.19 10:41, Michal Hocko wrote: >>> On Wed 10-04-19 12:14:55, David Hildenbrand wrote: >>>> While current node handling is probably terribly broken for memory block >>>> devices that span several nodes (only possible when added during boot, >>>> and something like that should be blocked completely), properly put the >>>> device reference we obtained via find_memory_block() to get the nid. >>> >>> The changelog could see some improvements I believe. (Half) stating >>> broken status of multinode memblock is not really useful without a wider >>> context so I would simply remove it. More to the point, it would be much >>> better to actually describe the actual problem and the user visible >>> effect. >>> >>> " >>> d0dc12e86b31 ("mm/memory_hotplug: optimize memory hotplug") has started >>> using find_memory_block to get a nodeid for the beginnig of the onlined >>> pfn range. The commit has missed that the memblock contains a reference >>> counted object and a missing put_device will leak the kobject behind >>> which ADD THE USER VISIBLE EFFECT HERE. >>> " >> >> I don't think mentioning the commit a second time is really needed. >> >> " >> Right now we are using find_memory_block() to get the node id for the >> pfn range to online. We are missing to drop a reference to the memory >> block device. While the device still gets unregistered via >> device_unregister(), resulting in no user visible problem, the device is >> never released via device_release(), resulting in a memory leak. Fix >> that by properly using a put_device(). >> " > > OK, sounds good to me. I was not sure about all the sysfs machinery > and the kobj dependencies but if there are no sysfs files leaking and > crashing upon a later access then a leak of a small amount of memory > that is not user controlable then this is not super urgent. > > Thanks! I think it can be triggered by onlining/offlining memory in a loop. But as you said, only leaks of small amount of memory. Thanks! -- Thanks, David / dhildenb