writeback: send work item to queue_io, move_expired_inodes

Instead of sending ->older_than_this to queue_io() and
move_expired_inodes(), send the entire wb_writeback_work
structure.  There are other fields of a work item that are
useful in these routines and in tracepoints.

Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Curt Wohlgemuth <curtw@google.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index 0ce9f06..1261db3 100644
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -157,9 +157,9 @@
 
 TRACE_EVENT(writeback_queue_io,
 	TP_PROTO(struct bdi_writeback *wb,
-		 unsigned long *older_than_this,
+		 struct wb_writeback_work *work,
 		 int moved),
-	TP_ARGS(wb, older_than_this, moved),
+	TP_ARGS(wb, work, moved),
 	TP_STRUCT__entry(
 		__array(char,		name, 32)
 		__field(unsigned long,	older)
@@ -167,6 +167,7 @@
 		__field(int,		moved)
 	),
 	TP_fast_assign(
+		unsigned long *older_than_this = work->older_than_this;
 		strncpy(__entry->name, dev_name(wb->bdi->dev), 32);
 		__entry->older	= older_than_this ?  *older_than_this : 0;
 		__entry->age	= older_than_this ?