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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Wed, 23 Aug 2017 18:49:38 -0700
Message-ID: <CA+55aFw737C9OVC2nQgGcazhi7Ca2K-frzgN2MiD=XqqFAp8YA@mail.gmail.com>
Subject: Re: [PATCH 0/1] devpts: use dynamic_dname() to generate proc name
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Stefan Lippers-Hollmann <s.l-h@gmx.de>,
        Christian Brauner <christian.brauner@canonical.com>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Thorsten Leemhuis <regressions@leemhuis.info>
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On Wed, Aug 23, 2017 at 6:32 PM, Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> It should all be _fairly_ straightforward, but it's definitely a
> rather bigger change than that "just fix the path" patch was.

Argh. And it's *not* fairly straightforward, because the
tty_operations "ioctl()" function pointer only gets 'struct tty *'.

So in the TIOCGPTPEER path, we don't actually have access to the file
pointer of the fd we're doing the ioctl on.

And that's where the 'struct path' to the 'ptmx' node is - which we
need to then look up the 'pts' directory.

How very annoying. I think that's why we did it all at ptmx_open()
time, because then we had all the information.

                Linus