Re: [PATCH 2/4] fs: allow dev accesses in userns in controlled situations

[Serge Hallyn <serge.hallyn-GeWIH/nMZzLQT0dZR+AlfA@public.gmane.org>]

Quoting Janne Karhunen (janne.karhunen-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org):
> On Tue, Mar 19, 2013 at 5:37 PM, Serge Hallyn <serge.hallyn-GeWIH/nMZzLQT0dZR+AlfA@public.gmane.org> wrote:
> 
> >> > Well the devcg was meant to be a temporary stopgap solution until we
> >> > have device namespaces, and this seems to entrench them further, but
> >> > it does make sense.
> >>
> >> Just out of interest, what would such device namespace actually
> >> do other than switch the device access on/off according to callers
> >> namespace?
> >
> > It could also support mapping of <type>:maj:min inside namespace to
> > a different device on host.  In most cases we probably don't actually
> > want that, but it's an interesting enough thing to be worth thinking
> > through.
> 
> It sounds to me that what you really want to do is likely use case and
> device specific. Hence the idea about namespace specific ioctl device
> action(s) might not be so bad. It would certainly be less intrusive than
> tampering with device registrations or rerouting nod file_operations for
> instance.
> 
> Classic on/off toggle case is easy though, but are there enough
> reasons for merging such 'noop' namespace?

Eric's point is precisely that we may be able to work aruond it
sufficiently that we don't need to.  Noone has proposed a specific
design let alone code, so it's premature to talk about merging
anything :)