linux-kernel - Re: [RFC PATCH 0/6] Do not call ->writepage[s] from direct reclaim and use a

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Message-ID: <20100615163546.GA21250@infradead.org>
Date:	Tue, 15 Jun 2010 12:35:46 -0400
From:	Christoph Hellwig <hch@...radead.org>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Andrea Arcangeli <aarcange@...hat.com>,
	Christoph Hellwig <hch@...radead.org>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org, Dave Chinner <david@...morbit.com>,
	Chris Mason <chris.mason@...cle.com>,
	Nick Piggin <npiggin@...e.de>, Rik van Riel <riel@...hat.com>
Subject: Re: [RFC PATCH 0/6] Do not call ->writepage[s] from direct reclaim
 and use a_ops->writepages() where possible

On Tue, Jun 15, 2010 at 05:30:44PM +0100, Mel Gorman wrote:
> After grepping through fs/, it was only xfs and btrfs that I saw were
> specfically disabling writepage from reclaim context.

ext4 doesn't specificly disable writeback from reclaim context, but
in a rather convoluted way disabled basically all writeback through
->writepage.  The only thing allowed is overwrites of already allocated
blocks.

In addition to that reiserfs also frefuses to write back pages
from reclaim context if they require a transaction, which is the case
if the file was written to through mmap.
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