From mboxrd@z Thu Jan  1 00:00:00 1970
From: Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PATCH 2/2] exec: move core_pattern pipe helper into the
	crashing namespace
Date: Mon, 20 Sep 2010 20:50:01 +0200
Message-ID: <20100920185001.GA955@redhat.com>
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Cc: Andi Kleen <andi@firstfloor.org>, linux-kernel@vger.kernel.org,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Andrew Morton <akpm@linux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
	Roland McGrath <roland@redhat.com>,
	Neil Horman <nhorman@tuxdriver.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	containers@lists.linux-foundation.org,
	Eugene Teo <eteo@redhat.com>, Tejun Heo <tj@kernel.org>,
	Serge Hallyn <serue@us.ibm.com>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	linux-fsdevel@vger.kernel.org
To: Will Drewry <wad@chromium.org>
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On 09/17, Will Drewry wrote:
>
> On Fri, Sep 17, 2010 at 8:29 PM, Oleg Nesterov <oleg@redhat.com> wrote:
> >
> > This looks overcomplicated to me, or I missed something.
> >
> > I do not understand why should we do this beforehand, and why we need
> > copy_namespaces_unattached().
> >
> > Can't you just pass current to umh_pipe_setup() (or another helper) as
> > the argument? Then this helper can copy ->fs and ->nsproxy itself.
>
> I wasn't sure if it was reasonable to pass the current task_struct
> over, but I certainly can.

Why not? current calls call_usermodehelper_exec(), it can't go away
until subprocess_info->init() returns, it sleeps on wait_for_completion().

> In practice, this seems to amount to just adding a refcount to all the
> namespaces and creating a new nsproxy which isn't really needed.  Most
> likely, doing what you've suggested above plus the copy_fs_struct and
> the swap out will do the trick.  I'll try it out and see.  That's make
> it much clearer I think.

Yes, just get_nsproxy() (like fork() does) should be fine in this case.

As for copying ->fs, I am not sure actually. core_pattern is global,
say it is "|/coredumper". If you change ->root, then exec can fail
because that binary is not visible to the coredumping process?

Probably we should move core_pattern into ->pid_ns, I dunno.

Oleg.