linux-kernel - Re: regression in page writeback

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Date:	Tue, 29 Sep 2009 10:32:27 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Dave Chinner <david@...morbit.com>,
	Chris Mason <chris.mason@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"Li, Shaohua" <shaohua.li@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"richard@....demon.co.uk" <richard@....demon.co.uk>,
	"jens.axboe@...cle.com" <jens.axboe@...cle.com>
Subject: Re: regression in page writeback

On Mon, Sep 28, 2009 at 09:08:04PM +0800, Christoph Hellwig wrote:
> On Mon, Sep 28, 2009 at 03:15:07PM +0800, Wu Fengguang wrote:
> > +		if (!PageActive(page))
> > +			SetPageReclaim(page);
> > +		err = mapping->a_ops->writepage(page, wbc);
> > +		if (err < 0)
> > +			handle_write_error(mapping, page, res);
> > +		if (err == AOP_WRITEPAGE_ACTIVATE) {
> > +			ClearPageReclaim(page);
> > +			res = PAGE_ACTIVATE;
> > +			break;
> > +		}
> 
> This should help a bit for XFS as it historically does multi-page
> writeouts from ->writepages (and apprently btrfs that added some

->writepage ?

> write-around recently?) but not those brave filesystems only
> implementing the multi-page writeout from writepages as designed.

Thanks.  Just tried write_cache_pages(), looks simple. Need to further
convert all aops->writepages to support lumpy pageout :)

> But really, the best would be to leave the writeout to the flusher
> threads and just reclaim the clean pages from the VM.

Yup, that's much larger behavior change, and could be pursued as a
long term goal.

Thanks,
Fengguang
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