tracing/filters: use ring_buffer_discard_commit for discarded events

The ring_buffer_discard_commit makes better usage of the ring_buffer
when an event has been discarded. It tries to remove it completely if
possible.

This patch converts the trace event filtering to use
ring_buffer_discard_commit instead of the ring_buffer_event_discard.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/trace.c

@@ -884,13 +884,18 @@ trace_current_buffer_lock_reserve(unsigned char type, unsigned long len,
 void trace_current_buffer_unlock_commit(struct ring_buffer_event *event,
 					unsigned long flags, int pc)
 {
-	return __trace_buffer_unlock_commit(&global_trace, event, flags, pc, 1);
+	__trace_buffer_unlock_commit(&global_trace, event, flags, pc, 1);
 }
 
 void trace_nowake_buffer_unlock_commit(struct ring_buffer_event *event,
 					unsigned long flags, int pc)
 {
-	return __trace_buffer_unlock_commit(&global_trace, event, flags, pc, 0);
+	__trace_buffer_unlock_commit(&global_trace, event, flags, pc, 0);
+}
+
+void trace_current_buffer_discard_commit(struct ring_buffer_event *event)
+{
+	ring_buffer_discard_commit(global_trace.buffer, event);
 }
 
 void

kernel/trace/trace.h

@@ -497,6 +497,7 @@ void trace_current_buffer_unlock_commit(struct ring_buffer_event *event,
 					unsigned long flags, int pc);
 void trace_nowake_buffer_unlock_commit(struct ring_buffer_event *event,
 					unsigned long flags, int pc);
+void trace_current_buffer_discard_commit(struct ring_buffer_event *event);
 
 struct trace_entry *tracing_get_trace_entry(struct trace_array *tr,
 						struct trace_array_cpu *data);

kernel/trace/trace_events_stage_3.h

@@ -223,9 +223,9 @@ static void ftrace_raw_event_##call(proto)				\
 	assign;								\
 									\
 	if (call->preds && !filter_match_preds(call, entry))		\
-		ring_buffer_event_discard(event);			\
-									\
-	trace_nowake_buffer_unlock_commit(event, irq_flags, pc);	\
+		trace_current_buffer_discard_commit(event);		\
+	else								\
+		trace_nowake_buffer_unlock_commit(event, irq_flags, pc); \
 									\
 }									\
 									\