[PATCH 04/47] writeback: consolidate variable names in balance_dirty_pages()

[Wu Fengguang]

Lots of lengthy tests.. Let's compact the names

	nr_dirty = NR_FILE_DIRTY + NR_WRITEBACK + NR_UNSTABLE_NFS

balance_dirty_pages() only cares about the above dirty sum except
in one place -- on starting background writeback.

Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
 mm/page-writeback.c |   30 ++++++++++++++----------------
 1 file changed, 14 insertions(+), 16 deletions(-)

--- linux-next.orig/mm/page-writeback.c	2010-12-08 22:44:22.000000000 +0800
+++ linux-next/mm/page-writeback.c	2010-12-08 22:44:22.000000000 +0800
@@ -497,8 +497,9 @@ unsigned long bdi_dirty_limit(struct bac
 static void balance_dirty_pages(struct address_space *mapping,
 				unsigned long pages_dirtied)
 {
-	long nr_reclaimable, bdi_nr_reclaimable;
-	long nr_writeback, bdi_nr_writeback;
+	long nr_reclaimable;
+	long nr_dirty;
+	long bdi_dirty;  /* = file_dirty + writeback + unstable_nfs */
 	unsigned long background_thresh;
 	unsigned long dirty_thresh;
 	unsigned long bdi_thresh;
@@ -516,7 +517,7 @@ static void balance_dirty_pages(struct a
 		 */
 		nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
 					global_page_state(NR_UNSTABLE_NFS);
-		nr_writeback = global_page_state(NR_WRITEBACK);
+		nr_dirty = nr_reclaimable + global_page_state(NR_WRITEBACK);
 
 		global_dirty_limits(&background_thresh, &dirty_thresh);
 
@@ -525,12 +526,10 @@ static void balance_dirty_pages(struct a
 		 * catch-up. This avoids (excessively) small writeouts
 		 * when the bdi limits are ramping up.
 		 */
-		if (nr_reclaimable + nr_writeback <=
-				(background_thresh + dirty_thresh) / 2)
+		if (nr_dirty <= (background_thresh + dirty_thresh) / 2)
 			break;
 
-		bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh,
-					     nr_reclaimable + nr_writeback);
+		bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh, nr_dirty);
 		bdi_thresh = task_dirty_limit(current, bdi_thresh);
 
 		/*
@@ -544,21 +543,21 @@ static void balance_dirty_pages(struct a
 		 * deltas.
 		 */
 		if (bdi_thresh < 2*bdi_stat_error(bdi)) {
-			bdi_nr_reclaimable = bdi_stat_sum(bdi, BDI_RECLAIMABLE);
-			bdi_nr_writeback = bdi_stat_sum(bdi, BDI_WRITEBACK);
+			bdi_dirty = bdi_stat_sum(bdi, BDI_RECLAIMABLE) +
+				    bdi_stat_sum(bdi, BDI_WRITEBACK);
 		} else {
-			bdi_nr_reclaimable = bdi_stat(bdi, BDI_RECLAIMABLE);
-			bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK);
+			bdi_dirty = bdi_stat(bdi, BDI_RECLAIMABLE) +
+				    bdi_stat(bdi, BDI_WRITEBACK);
 		}
 
-		if (bdi_nr_reclaimable + bdi_nr_writeback >= bdi_thresh) {
+		if (bdi_dirty >= bdi_thresh) {
 			pause = HZ/10;
 			goto pause;
 		}
 
 		bw = 100 << 20; /* use static 100MB/s for the moment */
 
-		bw = bw * (bdi_thresh - (bdi_nr_reclaimable + bdi_nr_writeback));
+		bw = bw * (bdi_thresh - bdi_dirty);
 		bw = bw / (bdi_thresh / TASK_SOFT_DIRTY_LIMIT + 1);
 
 		pause = HZ * (pages_dirtied << PAGE_CACHE_SHIFT) / (bw + 1);
@@ -574,9 +573,8 @@ pause:
 		 * bdi or process from holding back light ones; The latter is
 		 * the last resort safeguard.
 		 */
-		dirty_exceeded =
-			(bdi_nr_reclaimable + bdi_nr_writeback > bdi_thresh)
-			|| (nr_reclaimable + nr_writeback > dirty_thresh);
+		dirty_exceeded = (bdi_dirty > bdi_thresh) ||
+				  (nr_dirty > dirty_thresh);
 
 		if (!dirty_exceeded)
 			break;


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