3 files changed, 24 insertions, 17 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 4fcca4f74940..0079bf59b583 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -200,7 +200,6 @@ static void bdi_queue_work_onstack(struct wb_writeback_args *args)
 /**
  * bdi_start_writeback - start writeback
  * @bdi: the backing device to write from
- * @sb: write inodes from this super_block
  * @nr_pages: the number of pages to write
  *
  * Description:
@@ -209,25 +208,34 @@ static void bdi_queue_work_onstack(struct wb_writeback_args *args)
  *   completion. Caller need not hold sb s_umount semaphore.
  *
  */
-void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
-                         long nr_pages)
+void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages)
 {
         struct wb_writeback_args args = {
-                .sb             = sb,
                 .sync_mode      = WB_SYNC_NONE,
                 .nr_pages       = 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);
+}
 
+/**
+ * bdi_start_background_writeback - start background writeback
+ * @bdi: the backing device to write from
+ *
+ * Description:
+ *   This does WB_SYNC_NONE background writeback. The IO is only
+ *   started when this function returns, we make no guarentees on
+ *   completion. Caller need not hold sb s_umount semaphore.
+ */
+void bdi_start_background_writeback(struct backing_dev_info *bdi)
+{
+        struct wb_writeback_args args = {
+                .sync_mode      = WB_SYNC_NONE,
+                .nr_pages       = LONG_MAX,
+                .for_background = 1,
+                .range_cyclic   = 1,
+        };
         bdi_alloc_queue_work(bdi, &args);
 }
 
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index aee5f6ce166e..9ae2889096b6 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -105,8 +105,8 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
 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, struct super_block *sb,
-                                long nr_pages);
+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_has_dirty_io(struct backing_dev_info *bdi);
 void bdi_arm_supers_timer(void);
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index bbd396ac9546..54f28bd493d3 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -597,7 +597,7 @@ static void balance_dirty_pages(struct address_space *mapping,
             (!laptop_mode && ((global_page_state(NR_FILE_DIRTY)
                                + global_page_state(NR_UNSTABLE_NFS))
                                           > background_thresh)))
-                bdi_start_writeback(bdi, NULL, 0);
+                bdi_start_background_writeback(bdi);
 }
 
 void set_page_dirty_balance(struct page *page, int page_mkwrite)
@@ -705,9 +705,8 @@ void laptop_mode_timer_fn(unsigned long data)
          * We want to write everything out, not just down to the dirty
          * threshold
          */
-
         if (bdi_has_dirty_io(&q->backing_dev_info))
-                bdi_start_writeback(&q->backing_dev_info, NULL, nr_pages);
+                bdi_start_writeback(&q->backing_dev_info, nr_pages);
 }
 
 /*