linux-kernel - Re: [PATCH v2 09/11] fuse: file: limit splice

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Message-ID: <CAJfpeguE6E=s_t8WFVrJcXUar9ifr5+rhsmoJZYW5xWrTzRbMw@mail.gmail.com>
Date: Wed, 10 Jan 2024 16:47:23 +0100
From: Miklos Szeredi <miklos@...redi.hu>
To: Ahelenia Ziemiańska <nabijaczleweli@...ijaczleweli.xyz>
Cc: Jens Axboe <axboe@...nel.dk>, Christian Brauner <brauner@...nel.org>, 
	Alexander Viro <viro@...iv.linux.org.uk>, linux-fsdevel@...r.kernel.org, 
	Vivek Goyal <vgoyal@...hat.com>, Stefan Hajnoczi <stefanha@...hat.com>, linux-kernel@...r.kernel.org, 
	virtualization@...ts.linux.dev
Subject: Re: [PATCH v2 09/11] fuse: file: limit splice_read to virtiofs

On Wed, 10 Jan 2024 at 16:19, Ahelenia Ziemiańska
<nabijaczleweli@...ijaczleweli.xyz> wrote:

> > We need to find an alternative to refusing splice, since this is not
> > going to fly, IMO.
> The alternative is to not hold the lock. See the references in the
> cover letter for why this wasn't done. IMO a potential slight perf
> hit flies more than a total exclusion on the pipe.

IDGI.  This will make splice(2) return EINVAL for unprivileged fuse
files, right?

That would be a regression, not a perf hit, if the application is not
falling back to plain read; a reasonable scenario, considering splice
from files (including fuse) has worked on linux for a *long* time.

Thanks,
Mikos