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Date: Fri, 12 Feb 2010 11:39:55 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Jan Kara <jack@suse.cz>
Cc: LKML <linux-kernel@vger.kernel.org>, npiggin@suse.de,
       fengguang.wu@intel.com
Subject: Re: [PATCH 2/3] mm: Implement writeback livelock avoidance using
 page tagging
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On Fri, 12 Feb 2010 00:06:23 +0100
Jan Kara <jack@suse.cz> wrote:

> The idea is simple: Tag all pages that should be written back
> with a special tag (TOWRITE) in the radix tree. This can be done
> rather quickly and thus livelocks should not happen in practice.
> Then we start doing the hard work of locking pages and sending
> them to disk only for those pages that have TOWRITE tag set.

Adding a second pass across all the pages sounds expensive?