netdev - Re: Bug in short splice to socket?

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Message-ID: <CAHk-=wjvgL5nyZmpYRWBfab4NKvfQ7NjUvUhE3a3wYTyTEHdfQ@mail.gmail.com>
Date: Fri, 2 Jun 2023 07:28:05 -0400
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: David Howells <dhowells@...hat.com>
Cc: Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Paolo Abeni <pabeni@...hat.com>, Willem de Bruijn <willemdebruijn.kernel@...il.com>, 
	David Ahern <dsahern@...nel.org>, Matthew Wilcox <willy@...radead.org>, Jens Axboe <axboe@...nel.dk>, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
	Chuck Lever <chuck.lever@...cle.com>, Boris Pismenny <borisp@...dia.com>, 
	John Fastabend <john.fastabend@...il.com>, Christoph Hellwig <hch@...radead.org>
Subject: Re: Bug in short splice to socket?

On Fri, Jun 2, 2023 at 4:23 AM David Howells <dhowells@...hat.com> wrote:
>
> +/*
> + * Pass a zero-length record to the splice-write actor with SPLICE_F_MORE
> + * turned off to allow the network to see MSG_MORE deasserted.
> + */
> +static ssize_t splice_from_pipe_zero(struct pipe_inode_info *pipe,

David, STOP.

Stop doing these crazy hacks to generic splice code. None of this makes sense.

Those zero-sized splices have never worked, don't try to make them work.

The splice() system call has always had that

        if (!len)
                return 0;

since being introduced. We're not adding any crazy stuff now.

Do what I already suggested: making SPLICE_F_MORE reflect reality.

Or don't do anything at all. Because this kind of hacky garbage is not
even amusing.

               Linus