linux-kernel - Re: [PATCH] autofs: fix the wrong usage of the deprecated task_pgrp

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Date:	Mon, 19 Jan 2009 22:31:46 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	Ian Kent <raven@...maw.net>,
	Andrew Morton <akpm@...ux-foundation.org>, hpa@...or.com,
	Pavel Emelyanov <xemul@...nvz.org>,
	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] autofs: fix the wrong usage of the deprecated
	task_pgrp_nr()

On 01/19, Serge E. Hallyn wrote:
>
> Quoting Oleg Nesterov (oleg@...hat.com):
> > 
> > This is the next patch. This one does
> > 
> > 	--- CUR/fs/autofs/inode.c~1_AUTOFS	2009-01-12 23:07:46.000000000 +0100
> > 	+++ CUR/fs/autofs/inode.c	2009-01-18 06:18:49.000000000 +0100
> > 	@@ -78,7 +78,7 @@ static int parse_options(char *options, 
> > 	 
> > 		*uid = current_uid();
> > 		*gid = current_gid();
> > 	-	*pgrp = task_pgrp_nr(current);
> > 	+	*pgrp = task_pgrp_vnr(current);
> 
> Ok, that was the one I had looked at earlier (though now I can't find
> it).  But that just seems wrong to me.  We should certainly not be
> caching a pid_vnr in the kernel.  That is imo incomparably worse than
> storing a pid_nr.

We do not cache it. We use this pgrp as an argument for find_pid()
right after return from parse_options(). And find_pid() uses
current->nsproxy->pid_ns. That is why this is bugfix.

> Can we just jump straight to caching the struct pid?

Of course it is ugly to store pid_t and then call find_pid(),
I don't understand why the code was written this way. But I
am not going to cleanup this code ;)

(note also that the 2nd patch I sent for autofs4 does not use
 pid_t at all).

> > passing pid_t's in from userspace uses current namespace, with
> > or without the patch.
>
> Which makes sense on the one hand, but OTOH could be confusing
> if as I requested we print out init_pid_ns values.  (sigh)

But it is not possible to pass the global pid_t from within
the subnamespace via "pgrp=" option, automount (or whatever)
just can't know it when it runs in the subnamespace.

> Yes... would it be overkill to just print both?

perharps, I don't know...

But this is imho a bit off-topic, we can change the debugging
output later any way we like.

Oleg.

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