Re: [RFC] fix devpts mount behavior

[Serge Hallyn <serge.hallyn-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>]

Quoting Linus Torvalds (torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org):
> On Mon, Jan 23, 2012 at 4:05 PM, Serge Hallyn
> <serge.hallyn-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org> wrote:
> >
> > I've been playing for the last week with ways to fix this, and in the
> > end I can see two ways.
> 
> How about a third way:
> 
>  - make "newinstance" mandatory (and "-o newinstance" is a no-op) and
> forget about the whole issue.
> 
>  - if you really want to remount the old global one, you have to use a
> bind mount of that original mount instead.
> 
> There may be some subtle reason why the above is totally broken and
> just fundamnetally wouldn't work, and breaks all existing setups, but
> maybe it's worth at least discussing as an option?
> 
> Or did I entirely misunderstand the problem?
> 
>                       Linus

I like it.

The only place that *might* be a problem is if initramsfs does a devpts
mount, and later init blindly mounts tmpfs on /dev and mounts a new
devpts.  But it seems unlikely there would be any open pty's so it
shouldn't really matter.

I could go ahead and test that, say, ubuntu and fedora systems boot fine
with this change.  But of course I can't be sure there is no userspace
out there that won't cope...

-serge