tracing: filter fix for TRACE_EVENT_FORMAT events

Impact: fix crash (hang) when using TRACE_EVENT_FORMAT filter files

filters are only hooked up to the tracepoint events defined using
TRACE_EVENT but not the tracers that use TRACE_EVENT_FORMAT, such
as ftrace.

Do not display the filter files at all for TRACE_EVENT_FORMAT events
for the time being.

Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: =?ISO-8859-1?Q?Fr=E9d=E9ric?= Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1237878882.8339.61.camel@charm-linux>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/trace_events.c

@@ -680,7 +680,6 @@ static struct dentry *
 event_subsystem_dir(const char *name, struct dentry *d_events)
 {
 	struct event_subsystem *system;
-	struct dentry *entry;
 
 	/* First see if we did not already create this dir */
 	list_for_each_entry(system, &event_subsystems, list) {
@@ -709,12 +708,6 @@ event_subsystem_dir(const char *name, struct dentry *d_events)
 
 	system->preds = NULL;
 
-	entry = debugfs_create_file("filter", 0644, system->entry, system,
-				    &ftrace_subsystem_filter_fops);
-	if (!entry)
-		pr_warning("Could not create debugfs "
-			   "'%s/filter' entry\n", name);
-
 	return system->entry;
 }
 
@@ -770,14 +763,13 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events)
 				   " events/%s\n", call->name);
 			return ret;
 		}
+		entry = debugfs_create_file("filter", 0644, call->dir, call,
+					    &ftrace_event_filter_fops);
+		if (!entry)
+			pr_warning("Could not create debugfs "
+				   "'%s/filter' entry\n", call->name);
 	}
 
-	entry = debugfs_create_file("filter", 0644, call->dir, call,
-				    &ftrace_event_filter_fops);
-	if (!entry)
-		pr_warning("Could not create debugfs "
-			   "'%s/filter' entry\n", call->name);
-
 	/* A trace may not want to export its format */
 	if (!call->show_format)
 		return 0;