[Devel] Re: [PATCH 2/13] Small preparations for namespaces

[Serge E. Hallyn]

Quoting Pavel Emelianov (xemul at openvz.org):
> Serge E. Hallyn wrote:
> > Quoting Pavel Emelianov (xemul at openvz.org):
> >> This includes #ifdefs in get/put_pid_ns and rewriting
> >> the child_reaper() function to the more logical view.
> >>
> >> This doesn't fit logically into any other patch so
> >> I decided to make it separate.
> >>
> >> Signed-off-by: Pavel Emelianov <xemul at openvz.org>
> >>
> >> ---
> >>
> >> diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
> >> index 169c6c2..7af7191 100644
> >> --- a/include/linux/pid_namespace.h
> >> +++ b/include/linux/pid_namespace.h
> >> @@ -26,7 +26,9 @@ extern struct pid_namespace init_pid_ns;
> >>
> >>  static inline void get_pid_ns(struct pid_namespace *ns)
> >>  {
> >> +#ifdef CONFIG_PID_NS
> >>  	kref_get(&ns->kref);
> >> +#endif
> >>  }
> >>
> >>  extern struct pid_namespace *copy_pid_ns(int flags, struct pid_namespace *ns);
> >> @@ -34,12 +36,15 @@ extern void free_pid_ns(struct kref *kre
> >>
> >>  static inline void put_pid_ns(struct pid_namespace *ns)
> >>  {
> >> +#ifdef CONFIG_PID_NS
> >>  	kref_put(&ns->kref, free_pid_ns);
> >> +#endif
> >>  }
> >>
> >>  static inline struct task_struct *child_reaper(struct task_struct *tsk)
> >>  {
> >> -	return init_pid_ns.child_reaper;
> >> +	BUG_ON(tsk != current);
> >> +	return tsk->nsproxy->pid_ns->child_reaper;
> >>  }
> >>
> >>  #endif /* _LINUX_PID_NS_H */
> > 
> > This can't be bisect-safe, right?  You can't just use
> > tsk->nsproxy->pid_ns, as you've pointed out yourself.
> 
> I can :) See - I have a proving BUG_ON() here.

I didn't know BUG_ON()'s actually warded off bugs  :)

You've tested this with the infamous NFS testcase?

I don't see *why* it would work for you, but if you claim it does, I
guess you'd know better than I  :)

-serge