[PATCH 06/17] writeback: move task dirty fraction to balance_dirty_pages()

[Wu Fengguang]

This is simple code refactor preparing for a trace event that exposes
the fraction info. It may be merged with the next patch eventually.

CC: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
 mm/page-writeback.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

--- linux-next.orig/mm/page-writeback.c	2010-09-09 16:02:27.000000000 +0800
+++ linux-next/mm/page-writeback.c	2010-09-09 16:02:30.000000000 +0800
@@ -260,14 +260,12 @@ static inline void task_dirties_fraction
  * effectively curb the growth of dirty pages. Light dirtiers with high enough
  * dirty threshold may never get throttled.
  */
-static unsigned long task_dirty_limit(struct task_struct *tsk,
-				       unsigned long bdi_dirty)
+static unsigned long task_dirty_limit(unsigned long bdi_dirty,
+				      long numerator, long denominator)
 {
-	long numerator, denominator;
 	unsigned long dirty = bdi_dirty;
 	u64 inv = dirty / DIRTY_SOFT_THROTTLE_RATIO;
 
-	task_dirties_fraction(tsk, &numerator, &denominator);
 	inv *= numerator;
 	do_div(inv, denominator);
 
@@ -472,6 +470,7 @@ static void balance_dirty_pages(struct a
 	unsigned long bw;
 	bool dirty_exceeded = false;
 	struct backing_dev_info *bdi = mapping->backing_dev_info;
+	long numerator, denominator;
 
 	for (;;) {
 		/*
@@ -496,8 +495,10 @@ static void balance_dirty_pages(struct a
 				(background_thresh + dirty_thresh) / 2)
 			break;
 
+		task_dirties_fraction(current, &numerator, &denominator);
 		bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
-		bdi_thresh = task_dirty_limit(current, bdi_thresh);
+		bdi_thresh = task_dirty_limit(bdi_thresh,
+					      numerator, denominator);
 
 		/*
 		 * In order to avoid the stacked BDI deadlock we need


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