linux-kernel - Re: splice: move balance_dirty_pages_ratelimited() outside of splice actor

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Message-ID: <20070612173202.GO18832@kernel.dk>
Date:	Tue, 12 Jun 2007 19:32:02 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org
Subject: Re: splice: move balance_dirty_pages_ratelimited() outside of     splice actor

On Tue, Jun 12 2007, Andrew Morton wrote:
> On Tue, 12 Jun 2007 14:44:50 +0200 Jens Axboe <jens.axboe@...cle.com> wrote:
> 
> > splice
> 
> btw, I'm staring in profound mystification at this:
> 
> int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
> 			   struct pipe_buffer *buf)
> {
> 	struct page *page = buf->page;
> 
> 	if (page_count(page) == 1) {
> 		lock_page(page);
> 		return 0;
> 	}
> 
> 	return 1;
> }
> 
> 
> afacit that `if page_count(page)' test could be replaced by
> `if today_is_tuesday()'.  But then I don't have the foggiest idea
> what it's trying to do.
> 
> It would be nice to get some comments in and around here.
> 
> Also, I was trying to work out the role and responsibility of the ->pin
> callback, and gave up.
> 
> There isn't a lot of point in explaining this over email - one should be
> able to gain an understanding of these things by reading the code.  I think
> the best way of tackling this would be to comprehensively document
> pipe_buf_operations and pipe_inode_info, please...

OK so I wont explain it in detail here, I'll write up a good set of
comments tonight.

-- 
Jens Axboe

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