[RFC][PATCH 11/16] writeback: move last_active to bdi

[Artem Bityutskiy <dedekind1@gmail.com>]

From: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

bdi threads use local variable 'last_active' which stores last
jiffies when the bdi thread did some useful work. Move this
local variable to 'struct bdi_writeback'. This is just a
preparation for the further patches which will make the
forker thread decide when bdi threads should be killed.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
---
 fs/fs-writeback.c           |    6 +++---
 include/linux/backing-dev.h |   13 +++++++------
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index f045450..8469b93 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -800,7 +800,6 @@ int bdi_writeback_thread(void *data)
 {
 	struct bdi_writeback *wb = data;
 	struct backing_dev_info *bdi = wb->bdi;
-	unsigned long last_active = jiffies;
 	unsigned long wait_jiffies = -1UL;
 	long pages_written;
 
@@ -813,6 +812,7 @@ int bdi_writeback_thread(void *data)
 
 	current->flags |= PF_FLUSHER | PF_SWAPWRITE;
 	set_freezable();
+	wb->last_active = jiffies;
 
 	/*
 	 * Our parent may run at a different priority, just set us to normal
@@ -834,7 +834,7 @@ int bdi_writeback_thread(void *data)
 		trace_writeback_pages_written(pages_written);
 
 		if (pages_written)
-			last_active = jiffies;
+			wb->last_active = jiffies;
 		else if (wait_jiffies != -1UL) {
 			unsigned long max_idle;
 
@@ -844,7 +844,7 @@ int bdi_writeback_thread(void *data)
 			 * recreated automatically.
 			 */
 			max_idle = max(5UL * 60 * HZ, wait_jiffies);
-			if (time_after(jiffies, max_idle + last_active))
+			if (time_after(jiffies, max_idle + wb->last_active))
 				break;
 		}
 
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 95ecb2b..71b6223 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -45,15 +45,16 @@ enum bdi_stat_item {
 #define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
 
 struct bdi_writeback {
-	struct backing_dev_info *bdi;		/* our parent bdi */
+	struct backing_dev_info *bdi;	/* our parent bdi */
 	unsigned int nr;
 
-	unsigned long last_old_flush;		/* last old data flush */
+	unsigned long last_old_flush;	/* last old data flush */
+	unsigned long last_active;	/* last time bdi thread was active */
 
-	struct task_struct	*task;		/* writeback thread */
-	struct list_head	b_dirty;	/* dirty inodes */
-	struct list_head	b_io;		/* parked for writeback */
-	struct list_head	b_more_io;	/* parked for more writeback */
+	struct task_struct *task;	/* writeback thread */
+	struct list_head b_dirty;	/* dirty inodes */
+	struct list_head b_io;		/* parked for writeback */
+	struct list_head b_more_io;	/* parked for more writeback */
 };
 
 struct backing_dev_info {
-- 
1.7.1.1