Date: Mon, 19 Jan 2009 08:08:01 +0100
From: Oleg Nesterov <oleg@redhat.com>
To: Ian Kent <raven@themaw.net>
Cc: Andrew Morton <akpm@linux-foundation.org>, hpa@zytor.com,
       Pavel Emelyanov <xemul@openvz.org>,
       Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>,
       linux-kernel@vger.kernel.org, "SergeE.Hallyn" <serue@us.ibm.com>
Subject: Re: [PATCH] autofs: fix the wrong usage of the deprecated
	task_pgrp_nr()
Message-ID: <20090119070801.GA21686@redhat.com>
References: <20090118073441.GA699@redhat.com> <1232331602.3136.19.camel@zeus.themaw.net>
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On 01/19, Ian Kent wrote:
>
> On Sun, 2009-01-18 at 08:34 +0100, Oleg Nesterov wrote:
> > parse_options(&pgid) sets pgid = task_pgrp_nr() which uses the global
> > namespace. This is wrong, we use this pgid to find "struct pid" in the
> > current's namespace. Change parse_options() to use task_pgrp_vnr().
> >
> > Also do s/task_pgrp_nr/task_pgrp_vnr/ in the debugging printks.
> > checkpatch.pl complains about "line over 80 characters", but it should
> > blame the cuurent code, not the patch.
>
> This changelog entry doesn't really have anything that I can use to work
> out if this change might introduce regressions.
>
> It would be helpful to me if you could include:
> 1) A brief statement about what your trying to achieve and why.

First of all, I think this patch fixes a bug.

What we are doing in autofs_fill_super()->parse_options() path
is find_get_pid(task_pgrp_vnr(current)), this is wrong.

task_pgrp_vnr() reporst the pid_t in the global namespace, but
find_get_pid() searches "struct pid" in the current namespace.
We can get the wrong pid. I tried to document this in changelog.

Another reason is that task_pgrp_nr() is deprecated. We are wasting
2 words in signal_struct without good reason. Please look at

	http://marc.info/?l=linux-kernel&m=123228947019281

> 2) The reason why task_pgrp_nr() has changed to task_pgrp_vnr() since
> you made the change (that is someone working on pid namespaces) to
> task_pgrp_nr().

see above.

> 3) Why you believe this change won't introduce a regression.

Ah, sorry. I forgot to mention this patch is only compile tested
(like the next one, but at least it has the note in changelog).

But again, I think this is bugfix.

Oleg.

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