commit 2f800fbd777b792de54187088df19a7df0251254
author Wu Fengguang <fengguang.wu@intel.com> Mon Aug 08 15:22:00 2011 -0600
committer Wu Fengguang <fengguang.wu@intel.com> Sun Dec 18 14:20:23 2011 +0800
tree 2dc813b41da42d647468dafcf49a0b9e673df8b5
parent d3bc1fef9389e409a772ea174a5e41a6f93d9b7b

writeback: fix dirtied pages accounting on redirty

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>