From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753419Ab3LQNMp (ORCPT ); Tue, 17 Dec 2013 08:12:45 -0500 Received: from cantor2.suse.de ([195.135.220.15]:55204 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752135Ab3LQNMn (ORCPT ); Tue, 17 Dec 2013 08:12:43 -0500 Date: Tue, 17 Dec 2013 14:12:41 +0100 From: Michal Hocko To: Tejun Heo Cc: Li Zefan , Hugh Dickins , Johannes Weiner , Andrew Morton , KAMEZAWA Hiroyuki , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: 3.13-rc breaks MEMCG_SWAP Message-ID: <20131217131241.GE28991@dhcp22.suse.cz> References: <52AEC989.4080509@huawei.com> <20131216095345.GB23582@dhcp22.suse.cz> <20131216104042.GC23582@dhcp22.suse.cz> <20131216163530.GH32509@htj.dyndns.org> <20131216171937.GG26797@dhcp22.suse.cz> <20131216172143.GJ32509@htj.dyndns.org> <52AFC163.5010507@huawei.com> <20131217122926.GC29989@htj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20131217122926.GC29989@htj.dyndns.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 17-12-13 07:29:26, Tejun Heo wrote: > Hello, Li. > > On Tue, Dec 17, 2013 at 11:13:39AM +0800, Li Zefan wrote: > > diff --git a/kernel/cgroup.c b/kernel/cgroup.c > > index c36d906..769b5bb 100644 > > --- a/kernel/cgroup.c > > +++ b/kernel/cgroup.c > > @@ -868,6 +868,15 @@ static void cgroup_diput(struct dentry *dentry, struct inode *inode) > > struct cgroup *cgrp = dentry->d_fsdata; > > > > BUG_ON(!(cgroup_is_dead(cgrp))); > > + > > + /* > > + * We should remove the cgroup object from idr before its > > + * grace period starts, so we won't be looking up a cgroup > > + * while the cgroup is being freed. > > + */ > > Let's remove this comment and instead comment that this is to be made > per-css. I mixed up the lifetime rules of the cgroup and css and > thought css_from_id() should fail once css is confirmed to be offline, > so the above comment. It looks like we'll eventually have to move > cgrp->id to css->id (just simple per-ss idr) as the two objects' > lifetime rules will be completely separate. Other than that, looks > good to me. Yeah, please remove it. It made me think that idr_remove cannot be pulled to later and that's why I ruled out css based solution from the beginning. -- Michal Hocko SUSE Labs