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Date:   Fri, 7 Jul 2023 19:21:43 +0200
From:   Christian Brauner <brauner@kernel.org>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Ahelenia =?utf-8?Q?Ziemia=C5=84ska?= 
        <nabijaczleweli@nabijaczleweli.xyz>, Jens Axboe <axboe@kernel.dk>,
        David Howells <dhowells@redhat.com>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: Pending splice(file -> FIFO) excludes all other FIFO operations
 forever (was: ... always blocks read(FIFO), regardless of O_NONBLOCK on read
 side?)
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On Thu, Jul 06, 2023 at 02:56:45PM -0700, Linus Torvalds wrote:
> On Mon, 26 Jun 2023 at 09:14, Ahelenia Ziemiańska
> <nabijaczleweli@nabijaczleweli.xyz> wrote:
> >
> > And even if that was a working work-around, the fundamental problem of
> > ./spl>fifo excluding all other access to fifo is quite unfortunate too.
> 
> So I already sent an earlier broken version of this patch to Ahelenia
> and Christian, but here's an actually slightly tested version with the
> obvious bugs fixed.
> 
> The keyword here being "obvious". It's probably broken in many
> non-obvious ways, but I'm sending it out in case anybody wants to play
> around with it.
> 
> It boots for me. It even changes behavior of programs that splice()
> and used to keep the pipe lock over the IO and no longer do.
> 
> But it might do unspeakable things to your pets, so caveat emptor. It
> "feels" right to me. But it's a rather quick hack, and really needs
> more eyes and more thought. I mention O_NDELAY in the (preliminary)
> commit message, but there are probably other issues that need thinking
> about.

Forgot to say, fwiw, I've been running this through the LTP splice,
pipe, and ipc tests without issues. A hanging reader can be signaled
away cleanly with this.