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

[Linus Torvalds]

On Mon, Apr 1, 2019 at 4:41 AM Aleksa Sarai <cyphar@xxxxxxxxxx> 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).

What are the *actual* use cases for opening /proc files through it? If
it's really just for a small subset that android wants to do this
(getting basic process state like "running" etc), rather than anything
else, then we could skip the whole /proc linking entirely and go the
other way instead (ie open_pidfd() would get that limited IO model,
and we could make the /proc directory node get the same limited IO
model).

                  Linus