From: Wu Fengguang <fengguang.wu@intel.com>
Date: Mon, 8 Aug 2011 21:22:00 +0000 (-0600)
Subject: writeback: fix dirtied pages accounting on redirty
X-Git-Tag: v3.2.44~22
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=40e5c2b17933a25380494548391126affae73c58;p=pandora-kernel.git

writeback: fix dirtied pages accounting on redirty

commit 2f800fbd777b792de54187088df19a7df0251254 upstream.

De-account the accumulative dirty counters on page redirty.

Page redirties (very common in ext4) will introduce mismatch between
counters (a) and (b)

a) NR_DIRTIED, BDI_DIRTIED, tsk->nr_dirtied
b) NR_WRITTEN, BDI_WRITTEN

This will introduce systematic errors in balanced_rate and result in
dirty page position errors (ie. the dirty pages are no longer balanced
around the global/bdi setpoints).

Acked-by: Jan Kara <jack@suse.cz>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

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