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

[Linus Torvalds]

On Sun, Mar 31, 2019 at 1:38 PM Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
>
> openat(fd to pidfdâs proc directory, âstatusâ, ...);
>
> And we want a non-utterly-crappy way to do this.  The ioctl is certainly ugly, but it *works*.

It's beyond clunky. It's a disgrace.

If people really want equivalency between open("/proc/%d") and some
new pidfd_open(), then just *make* the two equivalent.

No effing crappy ioctl idiocy to create one from the other. Just make
the damn things be the exact same thing (and then if we extend clone()
to return one, make that return the same exact thing too).

Btw, we have several clone bits left:

 - if we don't have CLONE_PARENT set, the low 8 bits are still available

 - ignoring that, wehave bit #12 free: It used to be CLONE_IDLETASK
long long ago, but it was always kernel-only so it's never been
exposed as a user space bit.

                  Linus