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

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Date: Fri, 10 May 2024 08:33:54 +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 Thu, May 09, 2024 at 08:48:20AM -0700, Linus Torvalds wrote:
> On Thu, 9 May 2024 at 04:39, Christian Brauner <brauner@...nel.org> wrote:
> >
> > Not worth it without someone explaining in detail why imho. First pass
> > should be to try and replace kcmp() in scenarios where it's obviously
> > not needed or overkill.
> 
> Ack.
> 
> > I've added a CLASS(fd_raw) in a preliminary patch since we'll need that
> > anyway which means that your comparison patch becomes even simpler imho.
> > I've also added a selftest patch:
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git/log/?h=vfs.misc
> 
> LGTM.
> 
> Maybe worth adding an explicit test for "open same file, but two
> separate opens, F_DUPFD_QUERY returns 0? Just to clarify the "it's not
> testing the file on the filesystem for equality, but the file pointer
> itself".

Yep, good point. Added now.