Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756322AbdLVRlb (ORCPT ); Fri, 22 Dec 2017 12:41:31 -0500 Received: from fldsmtpe03.verizon.com ([140.108.26.142]:60221 "EHLO fldsmtpe03.verizon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753456AbdLVRlZ (ORCPT ); Fri, 22 Dec 2017 12:41:25 -0500 From: alexander.levin@verizon.com X-Host: surveyor.tdc.vzwcorp.com To: Michal Hocko CC: Greg Kroah-Hartman , "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" , Shakeel Butt , Paolo Bonzini Subject: Re: [PATCH 4.14 108/159] kvm, mm: account kvm related kmem slabs to kmemcg Thread-Topic: [PATCH 4.14 108/159] kvm, mm: account kvm related kmem slabs to kmemcg Thread-Index: AQHTe0vqtN8QY8G/8k28OSJBX8O1Rw== Date: Fri, 22 Dec 2017 17:40:10 +0000 Message-ID: <20171222174002.6qiqllf3bhmjangn@sasha-lappy> References: <20171222084623.668990192@linuxfoundation.org> <20171222084629.570989756@linuxfoundation.org> <20171222093407.GN4831@dhcp22.suse.cz> <20171222124122.GA30743@kroah.com> <20171222130607.GQ4831@dhcp22.suse.cz> In-Reply-To: <20171222130607.GQ4831@dhcp22.suse.cz> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: user-agent: NeoMutt/20170113 (1.7.2) x-ms-exchange-messagesentrepresentingtype: 1 x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.144.60.250] Content-Type: text/plain; charset="us-ascii" Content-ID: MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id vBMHfXXS003924 Content-Length: 2603 Lines: 58 On Fri, Dec 22, 2017 at 02:06:07PM +0100, Michal Hocko wrote: >On Fri 22-12-17 13:41:22, Greg KH wrote: >> On Fri, Dec 22, 2017 at 10:34:07AM +0100, Michal Hocko wrote: >> > On Fri 22-12-17 09:46:33, Greg KH wrote: >> > > 4.14-stable review patch. If anyone has any objections, please let me know. >> > > >> > > ------------------ >> > > >> > > From: Shakeel Butt >> > > >> > > >> > > [ Upstream commit 46bea48ac241fe0b413805952dda74dd0c09ba8b ] >> > > >> > > The kvm slabs can consume a significant amount of system memory >> > > and indeed in our production environment we have observed that >> > > a lot of machines are spending significant amount of memory that >> > > can not be left as system memory overhead. Also the allocations >> > > from these slabs can be triggered directly by user space applications >> > > which has access to kvm and thus a buggy application can leak >> > > such memory. So, these caches should be accounted to kmemcg. >> > > >> > > Signed-off-by: Shakeel Butt >> > > Signed-off-by: Paolo Bonzini >> > > Signed-off-by: Sasha Levin >> > > Signed-off-by: Greg Kroah-Hartman >> > >> > The patch is not marked for stable, neither it fixes an existing bug. >> > It is a nice to have thing for sure but I am wondering how this got >> > through stable-filter. >> >> Sasha picked it out, and it seemed like a sane thing to backport. If >> you think it's not worthy, I'll gladly drop it, but it seemed like such >> a simple bugfix to include. > >It is not that I would have some specific concerns about this particular >patch. It is more of a worry about the overal process. I thought that >_any_ patch backported to the stable tree would require a specific bug >to be fixed or in exceptional cases a performance issue. I have >experienced this pushback myself when trying to push "no real bug report >but better to have this plugged" patches. > >So something has apparently changed in the process, I just haven't >noticed it. I am worried this might lead to more regression in future. >Not that my worry counts all that much as I am not a stable kernel user >though. So this is just my 2c worth of worry. The way I see it is that stable commits are supposed to fix a bug that a user can hit/exploit, it doesn't have to have an actual user complaining about it. For this particular commit, the way I read it is that a user can avoid his kmemcg limits (maybe maliciously), which would qualify as an actual bug we want to get fixed. -- Thanks, Sasha