linux-kernel - Re: regression in page writeback

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Message-ID: <20090928130804.GA25880@infradead.org>
Date:	Mon, 28 Sep 2009 09:08:04 -0400
From:	Christoph Hellwig <hch@...radead.org>
To:	Wu Fengguang <fengguang.wu@...el.com>
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 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
write-around recently?) but not those brave filesystems only
implementing the multi-page writeout from writepages as designed.

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