[Devel] Re: [PATCH 0/13] Pid namespaces (OpenVZ view)

[Serge E. Hallyn]

Quoting Eric W. Biederman (ebiederm at xmission.com):
> "Serge E. Hallyn" <serue at us.ibm.com> writes:
> 
> >> 3. Cleaner logic for namespace migration: with this approach
> >>    one need to save the virtual pid and let global one change;
> >>    with Suka's logic this is not clear how to migrate the level
> >>    2 namespace (concerning init to be level 0).
> >
> > This is a very good point.
> >
> > How *would* we migrate the pids at the second level?
> 
> As long as you don't try and restore pids into the initial pid namespace
> it isn't a problem.  You just record the pid hierarchy and the pid
> for a task in that hierarchy.  There really is nothing special going on
> that should make migration hard.
> 
> Or did I miss something?

Hmm, no, i guess you are right.  I was thinking that getting the pid for
a process woudl be done purely from userspace, but I guess along with a
kernel helper to *set* pids, we could also have a kernel helper to get
all pids for all pid namespaces "above" that of the process doing the
checkpoint.

Makes sense.

thanks,
-serge