Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752181AbcCAQ4o (ORCPT ); Tue, 1 Mar 2016 11:56:44 -0500 Received: from mx2.parallels.com ([199.115.105.18]:57257 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751652AbcCAQ4m (ORCPT ); Tue, 1 Mar 2016 11:56:42 -0500 Date: Tue, 1 Mar 2016 19:56:30 +0300 From: Vladimir Davydov To: Tejun Heo CC: Andrew Morton , Johannes Weiner , Michal Hocko , , , Subject: Re: [PATCH 2/2] cgroup: reset css on destruction Message-ID: <20160301165630.GB2426@esperanza> References: <69629961aefc48c021b895bb0c8297b56c11a577.1456830735.git.vdavydov@virtuozzo.com> <92b11b89791412df49e73597b87912e8f143a3f7.1456830735.git.vdavydov@virtuozzo.com> <20160301163018.GE3965@htj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20160301163018.GE3965@htj.duckdns.org> X-ClientProxiedBy: US-EXCH2.sw.swsoft.com (10.255.249.46) To US-EXCH2.sw.swsoft.com (10.255.249.46) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1585 Lines: 43 On Tue, Mar 01, 2016 at 11:30:18AM -0500, Tejun Heo wrote: > On Tue, Mar 01, 2016 at 02:13:13PM +0300, Vladimir Davydov wrote: > > @@ -5138,6 +5138,8 @@ static void kill_css(struct cgroup_subsys_state *css) > > * See seq_css() for details. > > */ > > css_clear_dir(css, NULL); > > + if (css->ss->css_reset) > > + css->ss->css_reset(css); > > I think the better spot for this is in offline_css() right before > ->css_offline() is called. Okay, here it goes. --- From: Vladimir Davydov Subject: [PATCH] cgroup: reset css on destruction An associated css can be around for quite a while after a cgroup directory has been removed. In general, it makes sense to reset it to defaults so as not to worry about any remnants. For instance, memory cgroup needs to reset memory.low, otherwise pages charged to a dead cgroup might never get reclaimed. There's ->css_reset callback, which would fit perfectly for the purpose. Currently, it's only called when a subsystem is disabled in the unified hierarchy and there are other subsystems dependant on it. Let's call it on css destruction as well. Suggested-by: Johannes Weiner Signed-off-by: Vladimir Davydov diff --git a/kernel/cgroup.c b/kernel/cgroup.c index cc40463e7b69..bb1900b70b01 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -4876,6 +4876,9 @@ static void offline_css(struct cgroup_subsys_state *css) if (!(css->flags & CSS_ONLINE)) return; + if (ss->css_reset) + ss->css_reset(css); + if (ss->css_offline) ss->css_offline(css);