From 705ce84bcd8cc9809697107dfd187ff0b595eecd Mon Sep 17 00:00:00 2001
From: Wu Fengguang <fengguang.wu@intel.com>
Date: Wed, 23 Sep 2009 20:33:40 +0800
Subject: [PATCH] --- yaml --- r: 166333 b: refs/heads/master c:
 d3ddec7635b6fb37cb49e3553bdeea59642be653 h: refs/heads/master i:   166331:
 8714d00122e8228f7f448bfbc22f8f87116a4e34 v: v3

---
 [refs]                    |  2 +-
 trunk/fs/fs-writeback.c   | 28 +++++++++++++++++-----------
 trunk/mm/page-writeback.c |  6 +++---
 3 files changed, 21 insertions(+), 15 deletions(-)

diff --git a/[refs] b/[refs]
index 7f0eba7da226..042a2724a465 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 3a2e9a5a2afc1a2d2c548b8987f133235cebe933
+refs/heads/master: d3ddec7635b6fb37cb49e3553bdeea59642be653
diff --git a/trunk/fs/fs-writeback.c b/trunk/fs/fs-writeback.c
index c59d6737036c..476be9b10881 100644
--- a/trunk/fs/fs-writeback.c
+++ b/trunk/fs/fs-writeback.c
@@ -41,8 +41,9 @@ struct wb_writeback_args {
 	long nr_pages;
 	struct super_block *sb;
 	enum writeback_sync_modes sync_mode;
-	int for_kupdate;
-	int range_cyclic;
+	int for_kupdate:1;
+	int range_cyclic:1;
+	int for_background:1;
 };
 
 /*
@@ -257,6 +258,15 @@ void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages)
 		.range_cyclic	= 1,
 	};
 
+	/*
+	 * We treat @nr_pages=0 as the special case to do background writeback,
+	 * ie. to sync pages until the background dirty threshold is reached.
+	 */
+	if (!nr_pages) {
+		args.nr_pages = LONG_MAX;
+		args.for_background = 1;
+	}
+
 	bdi_alloc_queue_work(bdi, &args);
 }
 
@@ -720,20 +730,16 @@ static long wb_writeback(struct bdi_writeback *wb,
 
 	for (;;) {
 		/*
-		 * Don't flush anything for non-integrity writeback where
-		 * no nr_pages was given
+		 * Stop writeback when nr_pages has been consumed
 		 */
-		if (!args->for_kupdate && args->nr_pages <= 0 &&
-		     args->sync_mode == WB_SYNC_NONE)
+		if (args->nr_pages <= 0)
 			break;
 
 		/*
-		 * If no specific pages were given and this is just a
-		 * periodic background writeout and we are below the
-		 * background dirty threshold, don't do anything
+		 * For background writeout, stop when we are below the
+		 * background dirty threshold
 		 */
-		if (args->for_kupdate && args->nr_pages <= 0 &&
-		    !over_bground_thresh())
+		if (args->for_background && !over_bground_thresh())
 			break;
 
 		wbc.more_io = 0;
diff --git a/trunk/mm/page-writeback.c b/trunk/mm/page-writeback.c
index cbd4cba468bd..3c78fc316202 100644
--- a/trunk/mm/page-writeback.c
+++ b/trunk/mm/page-writeback.c
@@ -593,10 +593,10 @@ static void balance_dirty_pages(struct address_space *mapping,
 	 * background_thresh, to keep the amount of dirty memory low.
 	 */
 	if ((laptop_mode && pages_written) ||
-	    (!laptop_mode && ((nr_writeback = global_page_state(NR_FILE_DIRTY)
-					  + global_page_state(NR_UNSTABLE_NFS))
+	    (!laptop_mode && ((global_page_state(NR_FILE_DIRTY)
+			       + global_page_state(NR_UNSTABLE_NFS))
 					  > background_thresh)))
-		bdi_start_writeback(bdi, nr_writeback);
+		bdi_start_writeback(bdi, 0);
 }
 
 void set_page_dirty_balance(struct page *page, int page_mkwrite)