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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Tue, 7 May 2024 12:07:10 -0700
Message-ID: <CAHk-=whFyOn4vp7+++MTOd1Y3wgVFxRoVdSuPmN1_b6q_Jjkxg@mail.gmail.com>
Subject: Re: [Linaro-mm-sig] Re: [PATCH] epoll: try to be a _bit_ better about
 file lifetimes
To: Daniel Vetter <daniel@ffwll.ch>
Cc: Simon Ser <contact@emersion.fr>, Pekka Paalanen <pekka.paalanen@collabora.com>, 
	=?UTF-8?Q?Christian_K=C3=B6nig?= <ckoenig.leichtzumerken@gmail.com>, 
	Christian Brauner <brauner@kernel.org>, Al Viro <viro@zeniv.linux.org.uk>, keescook@chromium.org, 
	axboe@kernel.dk, christian.koenig@amd.com, dri-devel@lists.freedesktop.org, 
	io-uring@vger.kernel.org, jack@suse.cz, laura@labbott.name, 
	linaro-mm-sig@lists.linaro.org, linux-fsdevel@vger.kernel.org, 
	linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, 
	minhquangbui99@gmail.com, sumit.semwal@linaro.org, 
	syzbot+045b454ab35fd82a35fb@syzkaller.appspotmail.com, 
	syzkaller-bugs@googlegroups.com
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On Tue, 7 May 2024 at 11:04, Daniel Vetter <daniel@ffwll.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