writeback: merge bdi_writeback_task and bdi_start_fn

Move all code for the writeback thread into fs/fs-writeback.c instead of
splitting it over two functions in two files.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

fs/fs-writeback.c

@@ -775,12 +775,36 @@ long wb_do_writeback(struct bdi_writeback *wb, int force_wait)
  * Handle writeback of dirty data for the device backed by this bdi. Also
  * wakes up periodically and does kupdated style flushing.
  */
-int bdi_writeback_task(struct bdi_writeback *wb)
+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;
 
+	/*
+	 * Add us to the active bdi_list
+	 */
+	spin_lock_bh(&bdi_lock);
+	list_add_rcu(&bdi->bdi_list, &bdi_list);
+	spin_unlock_bh(&bdi_lock);
+
+	current->flags |= PF_FLUSHER | PF_SWAPWRITE;
+	set_freezable();
+
+	/*
+	 * Our parent may run at a different priority, just set us to normal
+	 */
+	set_user_nice(current, 0);
+
+	/*
+	 * Clear pending bit and wakeup anybody waiting to tear us down
+	 */
+	clear_bit(BDI_pending, &bdi->state);
+	smp_mb__after_clear_bit();
+	wake_up_bit(&bdi->state, BDI_pending);
+
 	while (!kthread_should_stop()) {
 		pages_written = wb_do_writeback(wb, 0);
 
@@ -813,9 +837,18 @@ int bdi_writeback_task(struct bdi_writeback *wb)
 		try_to_freeze();
 	}
 
+	wb->task = NULL;
+
+	/*
+	 * Flush any work that raced with us exiting. No new work
+	 * will be added, since this bdi isn't discoverable anymore.
+	 */
+	if (!list_empty(&bdi->work_list))
+		wb_do_writeback(wb, 1);
 	return 0;
 }
 
+
 /*
  * Start writeback of `nr_pages' pages.  If `nr_pages' is zero, write back
  * the whole world.

include/linux/backing-dev.h

@@ -102,7 +102,7 @@ void bdi_unregister(struct backing_dev_info *bdi);
 int bdi_setup_and_register(struct backing_dev_info *, char *, unsigned int);
 void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages);
 void bdi_start_background_writeback(struct backing_dev_info *bdi);
-int bdi_writeback_task(struct bdi_writeback *wb);
+int bdi_writeback_thread(void *data);
 int bdi_has_dirty_io(struct backing_dev_info *bdi);
 void bdi_arm_supers_timer(void);
 

mm/backing-dev.c

@@ -260,48 +260,6 @@ static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
 	INIT_LIST_HEAD(&wb->b_more_io);
 }
 
-static int bdi_start_fn(void *ptr)
-{
-	struct bdi_writeback *wb = ptr;
-	struct backing_dev_info *bdi = wb->bdi;
-	int ret;
-
-	/*
-	 * Add us to the active bdi_list
-	 */
-	spin_lock_bh(&bdi_lock);
-	list_add_rcu(&bdi->bdi_list, &bdi_list);
-	spin_unlock_bh(&bdi_lock);
-
-	current->flags |= PF_FLUSHER | PF_SWAPWRITE;
-	set_freezable();
-
-	/*
-	 * Our parent may run at a different priority, just set us to normal
-	 */
-	set_user_nice(current, 0);
-
-	/*
-	 * Clear pending bit and wakeup anybody waiting to tear us down
-	 */
-	clear_bit(BDI_pending, &bdi->state);
-	smp_mb__after_clear_bit();
-	wake_up_bit(&bdi->state, BDI_pending);
-
-	ret = bdi_writeback_task(wb);
-
-	wb->task = NULL;
-
-	/*
-	 * Flush any work that raced with us exiting. No new work
-	 * will be added, since this bdi isn't discoverable anymore.
-	 */
-	if (!list_empty(&bdi->work_list))
-		wb_do_writeback(wb, 1);
-
-	return ret;
-}
-
 int bdi_has_dirty_io(struct backing_dev_info *bdi)
 {
 	return wb_has_dirty_io(&bdi->wb);
@@ -425,7 +383,7 @@ static int bdi_forker_task(void *ptr)
 		spin_unlock_bh(&bdi_lock);
 
 		wb = &bdi->wb;
-		wb->task = kthread_run(bdi_start_fn, wb, "flush-%s",
+		wb->task = kthread_run(bdi_writeback_thread, wb, "flush-%s",
 					dev_name(bdi->dev));
 		/*
 		 * If task creation fails, then readd the bdi to