[PATCH] writeback: show writeback reason with __print_symbolic

[Wu Fengguang <fengguang.wu@intel.com>]

This makes the traces friendly to trace-cmd, at the cost of a bit code duplication.

CC: Curt Wohlgemuth <curtw@google.com>
CC: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
 include/trace/events/writeback.h |   17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

--- linux-next.orig/include/trace/events/writeback.h	2011-12-08 16:44:38.000000000 +0800
+++ linux-next/include/trace/events/writeback.h	2011-12-08 16:53:41.000000000 +0800
@@ -21,6 +21,18 @@
 		{I_REFERENCED,		"I_REFERENCED"}		\
 	)
 
+#define show_work_reason(reason)					\
+	__print_symbolic(reason,					\
+		{WB_REASON_BACKGROUND,		"background"},		\
+		{WB_REASON_TRY_TO_FREE_PAGES,	"try_to_free_pages"},	\
+		{WB_REASON_SYNC,		"sync"},		\
+		{WB_REASON_PERIODIC,		"periodic"},		\
+		{WB_REASON_LAPTOP_TIMER,	"laptop_timer"},	\
+		{WB_REASON_FREE_MORE_MEM,	"free_more_memory"},	\
+		{WB_REASON_FS_FREE_SPACE,	"fs_free_space"},	\
+		{WB_REASON_FORKER_THREAD,	"forker_thread"}	\
+	)
+
 struct wb_writeback_work;
 
 DECLARE_EVENT_CLASS(writeback_work_class,
@@ -55,7 +67,7 @@ DECLARE_EVENT_CLASS(writeback_work_class
 		  __entry->for_kupdate,
 		  __entry->range_cyclic,
 		  __entry->for_background,
-		  wb_reason_name[__entry->reason]
+		  show_work_reason(__entry->reason)
 	)
 );
 #define DEFINE_WRITEBACK_WORK_EVENT(name) \
@@ -184,7 +196,8 @@ TRACE_EVENT(writeback_queue_io,
 		__entry->older,	/* older_than_this in jiffies */
 		__entry->age,	/* older_than_this in relative milliseconds */
 		__entry->moved,
-		wb_reason_name[__entry->reason])
+		show_work_reason(__entry->reason)
+	)
 );
 
 TRACE_EVENT(global_dirty_state,