writeback: remove writeback_inodes_wbc

This was just an odd wrapper around writeback_inodes_wb.  Removing this
also allows to get rid of the bdi member of struct writeback_control
which was rather out of place there.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index d63ef8f..f6756f6 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -27,8 +27,6 @@
  * in a manner such that unspecified fields are set to zero.
  */
 struct writeback_control {
-	struct backing_dev_info *bdi;	/* If !NULL, only write back this
-					   queue */
 	struct super_block *sb;		/* if !NULL, only write inodes from
 					   this super_block */
 	enum writeback_sync_modes sync_mode;
@@ -66,7 +64,8 @@
 void writeback_inodes_sb(struct super_block *);
 int writeback_inodes_sb_if_idle(struct super_block *);
 void sync_inodes_sb(struct super_block *);
-void writeback_inodes_wbc(struct writeback_control *wbc);
+void writeback_inodes_wb(struct bdi_writeback *wb,
+		struct writeback_control *wbc);
 long wb_do_writeback(struct bdi_writeback *wb, int force_wait);
 void wakeup_flusher_threads(long nr_pages);