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

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Date: Wed, 8 May 2024 10:05:40 +0200
From: Christian Brauner <brauner@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Daniel Vetter <daniel@...ll.ch>, Simon Ser <contact@...rsion.fr>, 
	Pekka Paalanen <pekka.paalanen@...labora.com>, 
	Christian König <ckoenig.leichtzumerken@...il.com>, 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, May 07, 2024 at 12:07:10PM -0700, Linus Torvalds wrote:
> 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

+1
See
https://github.com/systemd/systemd/blob/a4f0e0da3573a10bc5404142be8799418760b1d1/src/basic/fd-util.c#L517
that's another heavy user of this kind of functionality.