From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932333AbcEXJQq (ORCPT ); Tue, 24 May 2016 05:16:46 -0400 Received: from mail-am1on0125.outbound.protection.outlook.com ([157.56.112.125]:46021 "EHLO emea01-am1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754551AbcEXJQo (ORCPT ); Tue, 24 May 2016 05:16:44 -0400 Authentication-Results: kernel.org; dkim=none (message not signed) header.d=none;kernel.org; dmarc=none action=none header.from=virtuozzo.com; Date: Tue, 24 May 2016 11:43:19 +0300 From: Vladimir Davydov To: Michal Hocko CC: Andrew Morton , Johannes Weiner , , Subject: Re: [PATCH] mm: memcontrol: fix possible css ref leak on oom Message-ID: <20160524084319.GH7917@esperanza> References: <1464019330-7579-1-git-send-email-vdavydov@virtuozzo.com> <20160523174441.GA32715@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20160523174441.GA32715@dhcp22.suse.cz> X-Originating-IP: [195.214.232.10] X-ClientProxiedBy: AMSPR04CA0039.eurprd04.prod.outlook.com (10.242.87.157) To VI1PR08MB0591.eurprd08.prod.outlook.com (10.163.169.21) X-MS-Office365-Filtering-Correlation-Id: df0f9d82-050a-42ae-6f42-08d383af78f3 X-Microsoft-Exchange-Diagnostics: 1;VI1PR08MB0591;2:p2f/hqfwCfxzIdwN9JSKe2ybqgFGMZOzAFcpiXKNZRUBqWoLsTeJqSNSgV7asJEj84yVmaRxn4g1nfh3Y731BnZ3dZQsZINpMmuGyGxflgQ0qYf9vP5vzQbe9V4d+jwKVmokNueo15Cyl1hGQXbahcNeWW9UsSsth+r2lfRZXC5XAJA8rHAkZTN18HK8fUdl;3:Bi+zL2OkRVuoe5GjqsiJP8Q+pYvaEAgXinXssuxiqG28AqFzxcEFwrbniFm+mtwrVFX+xsE/GRWcc62E2m60NZJH/Z5yMSfc6TBAyYPihDO8Txyfqv6a/UCO7Th8uxSa;25:s2Tdg5aQaA2RS/j+GNhixiEspD55um0ikpojXqbwUY4offQikMlAjjFF0VgP1p31BEvVUCsyIFn36QwNbYHTV136SqDY9cuHTg4B9KHz4M4/5oWEfZVV2zY7dO2B53I7x7/eybb8ztz6FEYrd5XMvKuRoeNCi3xsxLEFgmmW2FlEQfp1U5/j+JQXfidjwb2rBvj+vMWyywal7Yj2xB+ma8u9f0JrrM//I80YF89Q1ZjnNqmR1+k4G6Xpj4rCD+fSKocAvdySiDlo64Vuh99pDuQUqvc1DUbHCLWtRQSHp9JQ+mDeX/OhRtSRIXlvmElnU4UfjcQ53vJebmUKAAlwC7JZoTwpRGJbqgYK7vwepdaUJnYXNbA+cx0+RvNlzy0jJWQ0P4MdoWJzRjogobW0NuuXeoZqenJq43fAdIl1O/s= X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:;SRVR:VI1PR08MB0591; X-Microsoft-Antispam-PRVS: X-Exchange-Antispam-Report-Test: UriScan:; X-Exchange-Antispam-Report-CFA-Test: BCL:0;PCL:0;RULEID:(6040130)(601004)(2401047)(8121501046)(5005006)(3002001)(10201501046)(6041072)(6043046);SRVR:VI1PR08MB0591;BCL:0;PCL:0;RULEID:;SRVR:VI1PR08MB0591; X-Microsoft-Exchange-Diagnostics: 1;VI1PR08MB0591;4:8renZcP1ELc2S0JPQ9cdPAQ6m13ZO2mDug8lMd3/QvkeJmheW8jpZ/RSo/vhprJgUhHVTRB/35qNzFjK6AQGDNvXITGq+dkbnWodOh9yiX8MKASaUwJhVnBHLY93uTBzN5b2BjvSVgyOZ5G6I1eZxhHVEIdi3FIxwUcrrZ247ogAg4pCqVW00RPGlJD4FMYCu2TzLPkpcOVogrlm3FJMI0N4F0P4/y2MKRGNZ/JVKVrp/91pJI5lMjud7OMUu6a50Phh8eP3OTKHqslz7HT6gyKRmCnNudxaIG0sNAv52qFP8eCW6i2XSGuZ/mtQsVops8I9tDJaDuvI/2BxYydMxzy/I31e521L4AsnuwxPFuSBCGgtzLWmlebYgnWxdzkpdqGFVcRmRi4u2I5+iVN/NffMQoV19/RJIEFMYhyAbJA= X-Forefront-PRVS: 09525C61DB X-Forefront-Antispam-Report: SFV:NSPM;SFS:(10019020)(4630300001)(6009001)(377424004)(24454002)(2906002)(110136002)(86362001)(4326007)(189998001)(80792005)(50466002)(8676002)(33656002)(586003)(3846002)(23726003)(33716001)(6116002)(46406003)(1076002)(97756001)(66066001)(50986999)(76176999)(54356999)(19580405001)(19580395003)(5008740100001)(81166006)(9686002)(77096005)(92566002)(2950100001)(47776003)(42186005)(5004730100002);DIR:OUT;SFP:1102;SCL:1;SRVR:VI1PR08MB0591;H:esperanza;FPR:;SPF:None;MLV:sfv;LANG:en; X-Microsoft-Exchange-Diagnostics: =?us-ascii?Q?1;VI1PR08MB0591;23:w5p0K/x78FEnAgo9udjoCM6ZHH/faFW41t0IJW6wG?= =?us-ascii?Q?+39Czpo6kpJoG2WJECMmzYHC58KqMY0PPLW1XbzaJt3s2eFZiz4aeAtMy6ew?= =?us-ascii?Q?r0G4IAv0tbS0oFkmX4uZiGg25chn8J1uxkgMHqzqfwxRmt2JGCqc3+Ynzl+g?= =?us-ascii?Q?e+Tn8/Ml2GHz6VHQf1hLO6zjC+4gAlSU0f/miuvsWQgwKO/eKFN2jwi7jfos?= =?us-ascii?Q?euZbiQ6hdLDN7OD7gP+mRBFdFC4+drKw2N2ZolmlXAE61mD9NY298cc1x+fU?= =?us-ascii?Q?ofw5pRWEKXpr9D/qXAkWXLllzKZbBB23wBD5RrH4pbc/qOl5msgJM8HJ/PUQ?= =?us-ascii?Q?mYAC44Uaed2YISZFRTQmwW7MUNn12VKglKKOYJw2bA+UNdTFlah6Y7upKFyM?= =?us-ascii?Q?IZWPE7aA5ueZyCAfPrIwEjNfPC6TuFCvLdXm9Ug8XlBOAjmAv6tv/Xn0pcq5?= =?us-ascii?Q?ucr5FIdfas2jZ05ND8WC4HxarT6vF6202MWhLw8ybUjheTCcW1siayJkvTFs?= =?us-ascii?Q?mFouIIkf74DkI2swzCsptPInddHj306hhw/AI0m/MOlF82Tzzo7n3lgIEjrn?= =?us-ascii?Q?f7HGvmH+ydyX6zRNUeMK6Za7F41/jGeJdZ/jpWZpti2Q1q6hHdyvT9J8UDVL?= =?us-ascii?Q?AbkNhw0gtl4nXTE1KgCTd9AVofePreOmaGP3kDQRosz2kPEvw+NcXoyDf73K?= =?us-ascii?Q?Acz4ex00CwKPnm88x3V0BxadCOVLcwPwRJn9pq2R26EgpiFArETNEFUSyvob?= =?us-ascii?Q?I95YaaQHWEMzsig0mQai60mpETI5Ugz3LxuKIcSSOnwAadizZBF3MtJGW7gt?= =?us-ascii?Q?xmPeDQatjW5nrkQmFYEJrt/4S1lQLD8cxy9JSBr0ySAAPHT7WMbw25c48jPz?= =?us-ascii?Q?lwuTHWqhZ+Ds0a1wGAwx0TH7rc5a7z0WbMQJ71GM5lr6RZ1/PIaPyf+q7NtN?= =?us-ascii?Q?vpgkBt3LQX6UND26asC0nBl2e6GgCXfKZT9VEO/nA=3D=3D?= X-Microsoft-Exchange-Diagnostics: 1;VI1PR08MB0591;5:hMOArftyL4UTgHO1p2N/Ttk1+XWGYJNqXQgahlQq3AwNHv2GwuDAcM8nv5yg/2aRBOYJwaFH1r4OAfJCpcQ8ufLwB+tKc7c6l5cClOvTUX5ZIiygDWaxBJvAFpOoM/Vhviz8nyxpGgcdZe1Lu0E8AA==;24:3dCduI7Gf4bbeXxrswVQn8+YE/zvZ2n3VxoNMlSK86lTNjzeBRhc5EGhI7Wo0CJSK2EBxzZpVoEOG0kcgzy/KHdYIfnsDj4j137PoCy6Bu8=;7:xuJv9pC32+hQSwcPq278Vf6bb87ULeonlkORws/I0PlBkQACQp2bcxBxTsWXYnRfjAbmcGaq8wyUl/ti73aDHhOZNrcv3xI0ic809impzKuqoR6bcjh3+WJGAHhboDNKSVjTbgGyOcbczKMiacP+FW/s2Gtvqg3Wfj0Yasaj/IFyd774rNN703Xp4xeRAQeS;20:lDgjl33NN5BdimWl+A7tS75MUzmcO0ekoH3AFRdWrbnGf7JcqAt4vuV2g3hcyt5QBaR1oyE33lWJuvJWhVJovUd2fc2XD9Dv6s1whTMGro02itMFW1HnSFiWOPN5+vnshTtgAgaxtdCvUVAtpLJ/PKFhuUGKxmmRa4egonNghIw= SpamDiagnosticOutput: 1:23 SpamDiagnosticMetadata: NSPM X-OriginatorOrg: virtuozzo.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 24 May 2016 08:43:25.5481 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR08MB0591 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 23, 2016 at 07:44:43PM +0200, Michal Hocko wrote: > On Mon 23-05-16 19:02:10, Vladimir Davydov wrote: > > mem_cgroup_oom may be invoked multiple times while a process is handling > > a page fault, in which case current->memcg_in_oom will be overwritten > > leaking the previously taken css reference. > > Have you seen this happening? I was under impression that the page fault > paths that have oom enabled will not retry allocations. filemap_fault will, for readahead. This is rather unlikely, just like the whole oom scenario, so I haven't faced this leak in production yet, although it's pretty easy to reproduce using a contrived test. However, even if this leak happened on my host, I would probably not notice, because currently we have no clear means of catching css leaks. I'm thinking about adding a file to debugfs containing brief information about all memory cgroups, including dead ones, so that we could at least see how many dead memory cgroups are dangling out there. > > > Signed-off-by: Vladimir Davydov > > That being said I do not have anything against the patch. It is a good > safety net I am just not sure this might happen right now and so the > patch is not stable candidate. > > After clarification > Acked-by: Michal Hocko Thanks.