btrfs: Add trace for btrfs_workqueue alloc/destroy

Since most of the btrfs_workqueue is printed as pointer address,
for easier analysis, add trace for btrfs_workqueue alloc/destroy.
So it is possible to determine the workqueue that a given work belongs
to(by comparing the wq pointer address with alloc trace event).

Signed-off-by: Qu Wenruo <quenruo@cn.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

include/trace/events/btrfs.h

@@ -22,6 +22,7 @@ struct btrfs_free_cluster;
 struct map_lookup;
 struct extent_buffer;
 struct btrfs_work;
+struct __btrfs_workqueue;
 
 #define show_ref_type(type)						\
 	__print_symbolic(type,						\
@@ -1063,6 +1064,60 @@ DEFINE_EVENT(btrfs__work, btrfs_ordered_sched,
 	TP_ARGS(work)
 );
 
+DECLARE_EVENT_CLASS(btrfs__workqueue,
+
+	TP_PROTO(struct __btrfs_workqueue *wq, const char *name, int high),
+
+	TP_ARGS(wq, name, high),
+
+	TP_STRUCT__entry(
+		__field(	void *,	wq			)
+		__string(	name,	name			)
+		__field(	int ,	high			)
+	),
+
+	TP_fast_assign(
+		__entry->wq		= wq;
+		__assign_str(name, name);
+		__entry->high		= high;
+	),
+
+	TP_printk("name=%s%s, wq=%p", __get_str(name),
+		  __print_flags(__entry->high, "",
+				{(WQ_HIGHPRI),	"-high"}),
+		  __entry->wq)
+);
+
+DEFINE_EVENT(btrfs__workqueue, btrfs_workqueue_alloc,
+
+	TP_PROTO(struct __btrfs_workqueue *wq, const char *name, int high),
+
+	TP_ARGS(wq, name, high)
+);
+
+DECLARE_EVENT_CLASS(btrfs__workqueue_done,
+
+	TP_PROTO(struct __btrfs_workqueue *wq),
+
+	TP_ARGS(wq),
+
+	TP_STRUCT__entry(
+		__field(	void *,	wq			)
+	),
+
+	TP_fast_assign(
+		__entry->wq		= wq;
+	),
+
+	TP_printk("wq=%p", __entry->wq)
+);
+
+DEFINE_EVENT(btrfs__workqueue_done, btrfs_workqueue_destroy,
+
+	TP_PROTO(struct __btrfs_workqueue *wq),
+
+	TP_ARGS(wq)
+);
 
 #endif /* _TRACE_BTRFS_H */