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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Fri, 26 Jul 2019 14:26:45 -0700
Message-ID: <CAHk-=wibXtQ9pjB9ctpy5jWJK93DL19Lj09Et6cYEQE+h7tPpg@mail.gmail.com>
Subject: Re: [PATCH v1 1/2] pidfd: add P_PIDFD to waitid()
To:     Christian Brauner <christian@brauner.io>
Cc:     Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
        Oleg Nesterov <oleg@redhat.com>, Arnd Bergmann <arnd@arndb.de>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Kees Cook <keescook@chromium.org>,
        Joel Fernandes <joel@joelfernandes.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Tejun Heo <tj@kernel.org>, David Howells <dhowells@redhat.com>,
        Jann Horn <jannh@google.com>,
        Andrew Lutomirski <luto@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Aleksa Sarai <cyphar@cyphar.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Android Kernel Team <kernel-team@android.com>
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On Fri, Jul 26, 2019 at 2:41 AM Christian Brauner <christian@brauner.io> wrote:
>
> -       if (type < PIDTYPE_MAX)
> +       if (type < PIDTYPE_MAX && !pid)
>                 pid = find_get_pid(upid);

So now we have four cases in the switch statement, and two of them do
*not* want that "find_get_pid()" call.

Honestly, let's just move that whole thing into the switch statement
for the two cases that do want it. Particulartly since I think the
"upid == 0" case for P_PGID will prefer it that way anyway.

Let's not check 'type' in two different places in two completely
different ways.

Ok?

             Linus