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

[Linus Torvalds]

On Sun, Mar 31, 2019 at 2:10 PM Christian Brauner <christian@xxxxxxxxxx> wrote:
>
> I don't think that we want or can make them equivalent since that would
> mean we depend on procfs.

Sure we can.

If /proc is enabled, then you always do that dance YOU ALREADY WROTE
THE CODE FOR to do the stupid ioctl.

And if /procfs isn't enabled, then you don't do that.

Ta-daa. Done. No stupid ioctl, and now /proc and pidfd_open() return
the same damn thing.

And guess what? If /proc isn't enabled, then obviously pidfd_open()
gives you the /proc-less thing, but at least there is no crazy "two
different file descriptors for the same thing" situation, because then
the /proc one doesn't exist.

Notice? No incompatibility. No crazy stupid new "convert one to the
other", because "the other model" NEVER EXISTS. There is only one
pidfd - it might be proc-less if CONFIG_PROC isn't there, but let's
face it, nobody even cares, because nobody ever disabled /proc anyway.

And no need for some new "convert" interface (ioctl or other).

Problem solved.

                   Linus