linux-kernel - Re: [PATCH v2 3/4]: sendfile: remove flags paramter of do_splice

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Message-ID: <AANLkTilGP6lF61zuG8L6u54g1R2YItrx6df3RWfxvCqf@mail.gmail.com>
Date:	Sun, 30 May 2010 11:25:19 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	rostedt@...dmis.org
Cc:	Miklos Szeredi <miklos@...redi.hu>, axboe@...nel.dk,
	Al Viro <viro@...iv.linux.org.uk>, mszeredi@...e.cz,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH v2 3/4]: sendfile: remove flags paramter of 
	do_splice_direct()

On Sun, May 30, 2010 at 8:39 AM, Steven Rostedt <rostedt@...dmis.org> wrote:
> Probably because I copied the code from something that used
> SPLICE_F_NONBLOCK ;-)
>

>From the relay API implementation?

> But userspace passes that flag too. Although, maybe I just don't
> understand the API fully.
>

this flag is a little confusing. It is much like:

flags = fcntl(pipe_fd, F_GETFL);
fcntl(pipe_fd, F_SETFL, flags | O_NONBLOCK);
splice(..pipe_fd..., 0); // without O_NONBLOCK
fcntl(pipe_fd, F_SETFL, falgs);

In fact, setting O_NONBLOCK is the only way of letting splice pipe
operations non-blockable currently. When splicing, splice doesn't
refer to the pipe file's f_flags. :(

-- 
Regards，
Changli Gao(xiaosuo@...il.com)
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