linux-ext4 - Re: bio splits unnecessarily due to BH

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Message-ID: <20130319193132.GE5222@quack.suse.cz>
Date:	Tue, 19 Mar 2013 20:31:32 +0100
From:	Jan Kara <jack@...e.cz>
To:	Kazuya Mio <k-mio@...jp.nec.com>
Cc:	Jan Kara <jack@...e.cz>, akpm@...ux-foundation.org,
	adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org
Subject: Re: bio splits unnecessarily due to BH_Boundary in ext3 direct I/O

On Tue 19-03-13 17:36:17, Kazuya Mio wrote:
> 2013/03/07 19:48, Jan Kara wrote:
> >Then we properly mark bio should be submitted only if we are mapping last
> >part of the mapped extent from the filesystem. Can you give this change a
> >try (full patch with changelog attached)?
> 
> Sorry for the late response.
> After applying your patch, the problem I reported was fixed.
> 
> One matter for concern is that submit_bio() is called twice per one buffer_head.
> Because submit_page_section() calls dio_bio_submit() before adding
> the old page (sdio->cur_page) and the current page to struct dio_submit.
> Does it work as required?
  I'm not sure I understand. Looking into dio_send_cur_page() it seems may
prematurely submit the bio if sdio->boundary is set - in that case we
should probably first try to add the page to the bio and submit the bio
only after that. Is that what you mean?

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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