From: Sargun Dhillon <sargun@sargun.me>
To: Christian Brauner <christian.brauner@ubuntu.com>
Cc: "Arnd Bergmann" <arnd@arndb.de>,
"Oleg Nesterov" <oleg@redhat.com>,
"Florian Weimer" <fweimer@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Linux Containers" <containers@lists.linux-foundation.org>,
"Linux API" <linux-api@vger.kernel.org>,
"Linux FS-devel Mailing List" <linux-fsdevel@vger.kernel.org>,
"Tycho Andersen" <tycho@tycho.ws>, "Jann Horn" <jannh@google.com>,
"Aleksa Sarai" <cyphar@cyphar.com>,
"Andy Lutomirski" <luto@amacapital.net>,
"Al Viro" <viro@zeniv.linux.org.uk>,
"Gian-Carlo Pascutto" <gpascutto@mozilla.com>,
"Emilio Cobos Álvarez" <ealvarez@mozilla.com>,
"Jed Davis" <jld@mozilla.com>
Subject: Re: [PATCH v4 2/5] pid: Add PIDFD_IOCTL_GETFD to fetch file descriptors from processes
Date: Thu, 19 Dec 2019 08:15:29 -0800 [thread overview]
Message-ID: <CAMp4zn_z-CCQYMpT=GjZeGVLobjHBCSbmfha1rtWdmptOQ8JtA@mail.gmail.com> (raw)
In-Reply-To: <20191219103525.yqb5f4pbd2dvztkb@wittgenstein>
On Thu, Dec 19, 2019 at 2:35 AM Christian Brauner
<christian.brauner@ubuntu.com> wrote:
> I guess this is the remaining question we should settle, i.e. what do we
> prefer.
> I still think that adding a new syscall for this seems a bit rich. On
> the other hand it seems that a lot more people agree that using a
> dedicated syscall instead of an ioctl is the correct way; especially
> when it touches core kernel functionality. I mean that was one of the
> takeaways from the pidfd API ioctl-vs-syscall discussion.
>
> A syscall is nicer especially for core-kernel code like this.
> So I guess the only way to find out is to try the syscall approach and
> either get yelled and switch to an ioctl() or have it accepted.
>
> What does everyone else think? Arnd, still in favor of a syscall I take
> it. Oleg, you had suggested a syscall too, right? Florian, any
> thoughts/worries on/about this from the glibc side?
>
> Christian
My feelings towards this are that syscalls might pose a problem if we
ever want to extend this API. Of course we can have a reserved
"flags" field, and populate it later, but what if we turn out to need
a proper struct? I already know we're going to want to add one
around cgroup metadata (net_cls), and likely we'll want to add
a "steal" flag as well. As Arnd mentioned earlier, this is trivial to
fix in a traditional ioctl environment, as ioctls are "cheap". How
do we feel about potentially adding a pidfd_getfd2? Or are we
confident that reserved flags will save us?
next prev parent reply other threads:[~2019-12-19 16:16 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-18 23:55 [PATCH v4 2/5] pid: Add PIDFD_IOCTL_GETFD to fetch file descriptors from processes Sargun Dhillon
2019-12-19 8:03 ` Arnd Bergmann
2019-12-19 10:35 ` Christian Brauner
2019-12-19 11:31 ` Arnd Bergmann
2019-12-19 16:15 ` Sargun Dhillon [this message]
2019-12-20 4:35 ` Aleksa Sarai
2019-12-21 13:53 ` Arnd Bergmann
2019-12-19 10:23 ` Christian Brauner
2019-12-20 1:43 ` Andy Lutomirski
2019-12-20 5:21 ` Sargun Dhillon
2019-12-20 9:20 ` Christian Brauner
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAMp4zn_z-CCQYMpT=GjZeGVLobjHBCSbmfha1rtWdmptOQ8JtA@mail.gmail.com' \
--to=sargun@sargun.me \
--cc=arnd@arndb.de \
--cc=christian.brauner@ubuntu.com \
--cc=containers@lists.linux-foundation.org \
--cc=cyphar@cyphar.com \
--cc=ealvarez@mozilla.com \
--cc=fweimer@redhat.com \
--cc=gpascutto@mozilla.com \
--cc=jannh@google.com \
--cc=jld@mozilla.com \
--cc=linux-api@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@amacapital.net \
--cc=oleg@redhat.com \
--cc=tycho@tycho.ws \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).