Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup

[Al Viro]

On Mon, Apr 11, 2016 at 08:23:00PM -0500, Eric W. Biederman wrote:

> Perhaps I am reading the code wrong but as I read it that information is
> simply not available in get_super.

Correct.  For a very good reason - the same superblock can bloody well end up
in many places; having it tied to _the_ mountpoint is just plain wrong.

You know how it would look done right?
	a) mount --after support
	b) devpts containing both /ptmx and /pts/1,...
	c) mount --type devpts --after none /dev

That's it.  And this would be way, way more useful that overlay-style unions;
it would *NOT* recurse into subdirectories.  Just a search list done right...

Not an option, unfortunately, since it obviously breaks userland setups -
even if we go ahead and implement that kind of non-recursive unions.  But
if we had a chance to design it from scratch, that would've been an interesting
option.