linux-kernel - Re: [PATCH] autofs4: turn ->oz

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Date:	Fri, 23 Jan 2009 18:13:08 +0900
From:	Ian Kent <raven@...maw.net>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, hpa@...or.com,
	Cedric Le Goater <clg@...ibm.com>,
	Dave Hansen <haveblue@...ibm.com>,
	Eric Biederman <ebiederm@...ssion.com>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Serge Hallyn <serue@...ibm.com>,
	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] autofs4: turn ->oz_pgrp into "struct pid *"

On Fri, 2009-01-23 at 09:06 +0100, Oleg Nesterov wrote:
> On 01/23, Ian Kent wrote:
> >
> > On Sun, 2009-01-18 at 08:34 +0100, Oleg Nesterov wrote:
> > >
> > > I guess autofs4_show_options()->pid_vnr() is not exactly right, but hopefully
> > > not worse than the current code.
> >
> > But shouldn't pid_vnr(sbi->oz_pgrp) report the pid as seen in the
> > namespace of the calling process? In which case the only problem would
> > be listing the mount table from a subordinate namespace that cannot see
> > the process which did the mount, assuming fs namespace is not linked in
> > some strict way to pid namespace, this could give an odd result. What
> > might happen in this case Oleg?
> 
> Yes, nothing bad can happen. pid_vnr() just returns 0 if the calling
> process can't see the namespace.
> 
> But I was worried about the case when, say, we are looking at
> /subnamespace_root_mount/proc/mounts.
> 
> In that case pid_vnr() will report the pid_t in the global namespace,
> this differs from the case when this file is read by its own namespace
> as /proc/mounts.
> 
> I do not know whether this is right or not, though.

Right, but mostly a source of confusion than anything else as things
will still function OK. Not sure how to deal with that!

Ian


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