From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753486AbaDCTnp (ORCPT ); Thu, 3 Apr 2014 15:43:45 -0400 Received: from mail-qc0-f180.google.com ([209.85.216.180]:63692 "EHLO mail-qc0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753334AbaDCTnn (ORCPT ); Thu, 3 Apr 2014 15:43:43 -0400 Date: Thu, 3 Apr 2014 15:43:35 -0400 From: Tejun Heo To: Linus Torvalds Cc: "Eric W. Biederman" , David Miller , Linux Kernel Mailing List , Li Zefan , Linux Containers , cgroups@vger.kernel.org Subject: Re: [GIT PULL] cgroup changes for v3.15-rc1 Message-ID: <20140403194335.GC2472@mtj.dyndns.org> References: <20140403164911.GE24119@htj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Hello, On Thu, Apr 03, 2014 at 12:01:23PM -0700, Linus Torvalds wrote: > [ Extending the participants list a bit ] > > On Thu, Apr 3, 2014 at 11:34 AM, Tejun Heo wrote: > > On the road so sending from phone. Iirc the param is necessary to > > distinguishe when a new sb is created so that it can be put properly later. > > I think cgroup is leaking super ref now and li was planning to send a fix > > once things are merged. > > So as far as I can tell, cgroup is fine, because the superblock itself > is properly refcounted by the mounting code. It's the magic hidden Ah, I remembered the other way around. We could leak cgroup_root reference, not the other way around. cgroup_mount() can be called multiple times for the same sb and we inc cgroup_root's ref each time but cgroup_kill_sb() only happens when the sb is released, so if we do the following, # mkdir cpuset cpuset1 # mount -t cgroup -o cpuset cgroup cpuset # mount -t cgroup -o cpuset cgroup cpuset1 # umount cpuset # umount cpuset1 The cgroup_root should be destroyed but it isn't, I think. We'd need to bump cgroup_root's refcnt only when a new sb is created. It's kinda ugly. Hmmm... As for using specific type for ns tag, yeah, that'd be better regardless of this. The opaqueness is a bit extreme now. Thanks. -- tejun