Re: [PATCH v2 0/5] pid: add pidfd_open()

[Andy Lutomirski]

> On Apr 1, 2019, at 9:36 AM, Linus Torvalds <torva...@linux-foundation.org> 
> wrote:
> 
>> On Mon, Apr 1, 2019 at 4:41 AM Aleksa Sarai <cyp...@cyphar.com> wrote:
>> 
>> Eric pitched a procfs2 which would *just* be the PIDs some time ago (in
>> an attempt to make it possible one day to mount /proc inside a container
>> without adding a bunch of masked paths), though it was just an idea and
>> I don't know if he ever had a patch for it.
> 
> I wonder if we really want a fill procfs2, or maybe we could just make
> the pidfd readable (yes, it's a directory file descriptor, but we
> could allow reading).


There were patches to make procfs mount options work sensibly, and I think they 
got merged. So we could probably avoid a whole procfs2 by instead having it be 
procfs plus a special (maybe purely internal) mount option to restrict it.