linux-kernel - Re: [Linaro-mm-sig] Re: [PATCH] epoll: try to be a _bit

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Date: Tue, 7 May 2024 12:07:10 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Daniel Vetter <daniel@...ll.ch>
Cc: Simon Ser <contact@...rsion.fr>, Pekka Paalanen <pekka.paalanen@...labora.com>, 
	Christian König <ckoenig.leichtzumerken@...il.com>, 
	Christian Brauner <brauner@...nel.org>, Al Viro <viro@...iv.linux.org.uk>, keescook@...omium.org, 
	axboe@...nel.dk, christian.koenig@....com, dri-devel@...ts.freedesktop.org, 
	io-uring@...r.kernel.org, jack@...e.cz, laura@...bott.name, 
	linaro-mm-sig@...ts.linaro.org, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org, 
	minhquangbui99@...il.com, sumit.semwal@...aro.org, 
	syzbot+045b454ab35fd82a35fb@...kaller.appspotmail.com, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [Linaro-mm-sig] Re: [PATCH] epoll: try to be a _bit_ better about
 file lifetimes

On Tue, 7 May 2024 at 11:04, Daniel Vetter <daniel@...ll.ch> wrote:
>
> On Tue, May 07, 2024 at 09:46:31AM -0700, Linus Torvalds wrote:
>
> > I'd be perfectly ok with adding a generic "FISAME" VFS level ioctl
> > too, if this is possibly a more common thing. and not just DRM wants
> > it.
> >
> > Would something like that work for you?
>
> Yes.
>
> Adding Simon and Pekka as two of the usual suspects for this kind of
> stuff. Also example code (the int return value is just so that callers know
> when kcmp isn't available, they all only care about equality):
>
> https://gitlab.freedesktop.org/mesa/mesa/-/blob/main/src/util/os_file.c#L239

That example thing shows that we shouldn't make it a FISAME ioctl - we
should make it a fcntl() instead, and it would just be a companion to
F_DUPFD.

Doesn't that strike everybody as a *much* cleaner interface? I think
F_ISDUP would work very naturally indeed with F_DUPFD.

Yes? No?

                       Linus