Re: [PATCH 09/17] file: Implement fnext_task

From: Christian Brauner <christian.brauner@ubuntu.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	"<linux-fsdevel@vger.kernel.org>" <linux-fsdevel@vger.kernel.org>,
	criu@openvz.org, bpf <bpf@vger.kernel.org>,
	"Alexander Viro" <viro@zeniv.linux.org.uk>,
	"Oleg Nesterov" <oleg@redhat.com>,
	"Cyrill Gorcunov" <gorcunov@gmail.com>,
	"Jann Horn" <jann@thejh.net>, "Kees Cook" <keescook@chromium.org>,
	"Daniel P. Berrangé" <berrange@redhat.com>,
	"Jeff Layton" <jlayton@redhat.com>,
	"Miklos Szeredi" <miklos@szeredi.hu>,
	"Matthew Wilcox" <willy@debian.org>,
	"J. Bruce Fields" <bfields@fieldses.org>,
	"Matthew Wilcox" <matthew@wil.cx>,
	"Trond Myklebust" <trond.myklebust@fys.uio.no>,
	"Chris Wright" <chrisw@redhat.com>,
	"Alexei Starovoitov" <ast@kernel.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"Martin KaFai Lau" <kafai@fb.com>,
	"Song Liu" <songliubraving@fb.com>, "Yonghong Song" <yhs@fb.com>,
	"Andrii Nakryiko" <andriin@fb.com>,
	"John Fastabend" <john.fastabend@gmail.com>,
	"KP Singh" <kpsingh@chromium.org>
Subject: Re: [PATCH 09/17] file: Implement fnext_task
Date: Tue, 18 Aug 2020 13:05:56 +0200	[thread overview]
Message-ID: <20200818110556.q5i5quflrcljv4wa@wittgenstein> (raw)
In-Reply-To: <CAHk-=wjk_CnGHt4LBi2WsOeYOxE5j79R8xHzZytCy8t-_9orQw@mail.gmail.com>

On Mon, Aug 17, 2020 at 06:17:35PM -0700, Linus Torvalds wrote:
> On Mon, Aug 17, 2020 at 6:06 PM Eric W. Biederman <ebiederm@xmission.com> wrote:
> >
> > I struggle with the fcheck name as I have not seen or at least not
> > registed on the the user that just checks to see if the result is NULL.
> > So the name fcheck never made a bit of sense to me.
> 
> Yeah, that name is not great. I just don't want to make things even worse.
> 
> > I will see if I can come up with some good descriptive comments around
> > these functions.  Along with describing what these things are doing I am
> > thinking maybe I should put "_rcu" in their names and have a debug check
> > that verifies "_rcu" is held.
> 
> Yeah, something along the lines of "rcu_lookup_fd_task(tsk,fd)" would
> be a *lot* more descriptive than fcheck_task().
> 
> And I think "fnext_task()" could be "rcu_lookup_next_fd_task(tsk,fd)".
> 
> Yes, those are much longer names, but it's not like you end up typing
> them all that often, and I think being descriptive would be worth it.
> 
> And "fcheck()" and "fcheck_files()" would be good to rename too along
> the same lines.
> 
> Something like "rcu_lookup_fd()" and "rcu_lookup_fd_files()" respectively?
> 
> I'm obviously trying to go for a "rcu_lookup_fd*()" kind of pattern,
> and I'm not married to _that_ particular pattern but I think it would
> be better than what we have now.

In fs/inode.c and a few other places we have the *_rcu suffix pattern
already so maybe:

fcheck() -> fd_file_rcu() or lookup_fd_rcu()
fcheck_files() -> fd_files_rcu() or lookup_fd_files_rcu()
fnext_task() -> fd_file_from_task_rcu() or lookup_next_fd_from_task_rcu()

rather than as prefix or sm.

Christian