tracing/filters: improve subsystem filter

Currently a subsystem filter should be applicable to all events
under the subsystem, and if it failed, all the event filters
will be cleared. Those behaviors make subsys filter much less
useful:

  # echo 'vec == 1' > irq/softirq_entry/filter
  # echo 'irq == 5' > irq/filter
  bash: echo: write error: Invalid argument
  # cat irq/softirq_entry/filter
  none

I'd expect it set the filter for irq_handler_entry/exit, and
not touch softirq_entry/exit.

The basic idea is, try to see if the filter can be applied
to which events, and then just apply to the those events:

  # echo 'vec == 1' > softirq_entry/filter
  # echo 'irq == 5' > filter
  # cat irq_handler_entry/filter
  irq == 5
  # cat softirq_entry/filter
  vec == 1

Changelog for v2:
- do some cleanups to address Frederic's comments.

Inspired-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A63D485.7030703@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 5c093ffc655..26d3673d514 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -101,6 +101,8 @@ void trace_current_buffer_discard_commit(struct ring_buffer_event *event);
 
 void tracing_record_cmdline(struct task_struct *tsk);
 
+struct event_filter;
+
 struct ftrace_event_call {
 	struct list_head	list;
 	char			*name;
@@ -116,7 +118,7 @@ struct ftrace_event_call {
 	int			(*define_fields)(void);
 	struct list_head	fields;
 	int			filter_active;
-	void			*filter;
+	struct event_filter	*filter;
 	void			*mod;
 
 #ifdef CONFIG_EVENT_PROFILE