Re: [PATCH 2/6] user namespaces: move user_ns from nsproxy into user struct

[ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org (Eric W. Biederman)]

"Serge E. Hallyn" <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org> writes:

>>From ec5f54faf5afd16cb6cef40ebaaf3da25989d185 Mon Sep 17 00:00:00 2001
> From: Serge Hallyn <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
> Date: Thu, 24 Jul 2008 17:52:41 -0500
> Subject: [PATCH 2/6] user namespaces: move user_ns from nsproxy into user struct
>
> When we get the sysfs support needed to support fair user scheduling
> along with user namespaces, then we will need to be able to get the
> user namespace from the user struct.
>
> So we need the user_ns to be a part of struct user.  Once we can
> access it from tsk->user, we no longer have a use for
> tsk->nsproxy->user_ns.

Is this true?  Even in the general case of supporting setuid and setgid
and everything else that potentially is in the user namespace?

I certainly support the cleanups you have made for the reasons you describe.
I think however that there is there are no technical reasons not to have
 nsproxy->user_ns after the changes have been made.  I also agree that
there are no technical reasons for keeping nsproxy->user_ns at the moment.

> When a user_namespace is created, the user which created it is
> marked as its 'creator'.  The user_namespace pins the creator.
> Each userid in a user_ns pins the user_ns.  This keeps refcounting
> nice and simple.

Eric