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Date:   Thu, 28 Mar 2019 11:38:15 +0100
From:   Christian Brauner <christian@brauner.io>
To:     Jonathan Kowalski <bl0pbl33p@gmail.com>
Cc:     Jann Horn <jannh@google.com>,
        Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
        Andy Lutomirski <luto@kernel.org>,
        David Howells <dhowells@redhat.com>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Linux API <linux-api@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Kees Cook <keescook@chromium.org>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Michael Kerrisk-manpages <mtk.manpages@gmail.com>,
        "Dmitry V. Levin" <ldv@altlinux.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Oleg Nesterov <oleg@redhat.com>,
        Nagarathnam Muthusamy <nagarathnam.muthusamy@oracle.com>,
        Aleksa Sarai <cyphar@cyphar.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Joel Fernandes <joel@joelfernandes.org>,
        Daniel Colascione <dancol@google.com>
Subject: Re: [PATCH 2/4] pid: add pidfd_open()
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> All that said, thanks for the work on this once again. My intention is
> just that we don't end up with an API that could have been done better
> and be cleaner to use for potential users in the coming years.

Thanks for your input on all of this. I still don't find multiplexers in
the style of seccomp()/fsconfig()/keyctl() to be a problem since they
deal with a specific task. They are very much different from ioctl()s in
that regard. But since Joel, you, and Daniel found the pidctl() approach
not very nice I dropped it. The interface needs to be satisfactory for
all of us especially since Android and other system managers will be the
main consumers.
So let's split this into pidfd_open(pid_t pid, unsigned int flags) which
allows to cleanly get pidfds independent procfs and do the translation
to procpidfds in an ioctl() as we've discussed in prior threads. This
should also accommodate comments and ideas from Andy and Jann.
I'm coding this up now.

Christian