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

[Al Viro]

On Mon, Apr 11, 2016 at 07:10:47PM -0500, Eric W. Biederman wrote:
> Actually for me this is about keeping the semantics simpler, and coming
> up with a higher performance implementation.
> 
> A dentry that does an automount is already well defined.
> 
> Making the rule that accessing /dev/ptmx causes an automount of
> /dev/pts/ptmx on top of the device node at /dev/ptmx is really simple,
> with no special games.  It also makes it more obvious to userspace what
> is going on.  AKA allows userspace to know which superblock does an open
> ptmx master tty belongs to (and it happens in a backwards and forwards
> compatible way).

_What_ dentry?  Which filesystem would that be done to?  Whatever we have
on /dev?  Or we suddenly get the fucking dentry operations change when
dentry is attached to magical cdev inode?