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Date: Fri, 22 May 2009 14:40:34 +0530
From: Dhaval Giani <dhaval@linux.vnet.ibm.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>, Andrew Morton <akpm@linux-foundation.org>,
       Paul Menage <menage@google.com>, LKML <linux-kernel@vger.kernel.org>,
       Linux Containers <containers@lists.linux-foundation.org>,
       Balbir Singh <balbir@linux.vnet.ibm.com>,
       libcg-devel@lists.sourceforge.net
Subject: Re: [PATCH] cgroups: handle failure of cgroup_populate_dir() at
	mount/remount
Message-ID: <20090522091034.GC8696@linux.vnet.ibm.com>
Reply-To: Dhaval Giani <dhaval@linux.vnet.ibm.com>
References: <4A16153C.2080004@cn.fujitsu.com> <20090522172545.1e5e5f81.kamezawa.hiroyu@jp.fujitsu.com> <4A1663C2.4080401@cn.fujitsu.com> <20090522173421.ecacb40e.kamezawa.hiroyu@jp.fujitsu.com>
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On Fri, May 22, 2009 at 05:34:21PM +0900, KAMEZAWA Hiroyuki wrote:
> On Fri, 22 May 2009 16:35:14 +0800
> Li Zefan <lizf@cn.fujitsu.com> wrote:
> 
> > KAMEZAWA Hiroyuki wrote:
> > > On Fri, 22 May 2009 11:00:12 +0800
> > > Li Zefan <lizf@cn.fujitsu.com> wrote:
> > > 
> > >> Now we have 'stat' file in both memory and cpuacct subsystems. If we
> > >> mount these 2 subsystems with option 'noprefix', the creation of 'stat'
> > >> file for cpuacct will fail, but without any notificatin to the user.
> > >>
> > >> With this patch, we fail the mount/remount in this case.
> > >>
> > > 
> > > Hm, shouldn't we allow "noprefix" to be effective only agaisnt cpuset ?
> > > I think it's just for backward-compatibility of cpuset.
> > > (I don't like the option at all.)
> > > 
> > 
> > Yes, this mount option was introduced for cpuset. But it has been here for
> > a long time and people may use it when mounting other cgroup subsystems,
> > then is it OK to change to restrict its use within cpuset only?
> 
> Asking libcgroup people may be appropriate...added CC.

We just realized that we were not handling the noprefix usage in
libcgroup. From the pov of the library, the option should either not
exist for any subsystem or for all of them. Anything else would mean
having to add special cases.

thanks,
-- 
regards,
Dhaval