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

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Date: Thu, 9 May 2024 08:48:20 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Christian Brauner <brauner@...nel.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, 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".

             Linus