tracing: Create class struct for events

This patch creates a ftrace_event_class struct that event structs point to.
This class struct will be made to hold information to modify the
events. Currently the class struct only holds the events system name.

This patch slightly increases the size, but this change lays the ground work
of other changes to make the footprint of tracepoints smaller.

With 82 standard tracepoints, and 618 system call tracepoints
(two tracepoints per syscall: enter and exit):

   text	   data	    bss	    dec	    hex	filename
4913961	1088356	 861512	6863829	 68bbd5	vmlinux.orig
4914025	1088868	 861512	6864405	 68be15	vmlinux.class

This patch also cleans up some stale comments in ftrace.h.

v2: Fixed missing semi-colon in macro.

Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace_events.c

@@ -176,10 +176,10 @@ static int __ftrace_set_clr_event(const char *match, const char *sub,
 
 		if (match &&
 		    strcmp(match, call->name) != 0 &&
-		    strcmp(match, call->system) != 0)
+		    strcmp(match, call->class->system) != 0)
 			continue;
 
-		if (sub && strcmp(sub, call->system) != 0)
+		if (sub && strcmp(sub, call->class->system) != 0)
 			continue;
 
 		if (event && strcmp(event, call->name) != 0)
@@ -355,8 +355,8 @@ static int t_show(struct seq_file *m, void *v)
 {
 	struct ftrace_event_call *call = v;
 
-	if (strcmp(call->system, TRACE_SYSTEM) != 0)
-		seq_printf(m, "%s:", call->system);
+	if (strcmp(call->class->system, TRACE_SYSTEM) != 0)
+		seq_printf(m, "%s:", call->class->system);
 	seq_printf(m, "%s\n", call->name);
 
 	return 0;
@@ -453,7 +453,7 @@ system_enable_read(struct file *filp, char __user *ubuf, size_t cnt,
 		if (!call->name || !call->regfunc)
 			continue;
 
-		if (system && strcmp(call->system, system) != 0)
+		if (system && strcmp(call->class->system, system) != 0)
 			continue;
 
 		/*
@@ -925,8 +925,8 @@ event_create_dir(struct ftrace_event_call *call, struct dentry *d_events,
 	 * If the trace point header did not define TRACE_SYSTEM
 	 * then the system would be called "TRACE_SYSTEM".
 	 */
-	if (strcmp(call->system, TRACE_SYSTEM) != 0)
-		d_events = event_subsystem_dir(call->system, d_events);
+	if (strcmp(call->class->system, TRACE_SYSTEM) != 0)
+		d_events = event_subsystem_dir(call->class->system, d_events);
 
 	call->dir = debugfs_create_dir(call->name, d_events);
 	if (!call->dir) {
@@ -1041,7 +1041,7 @@ static void __trace_remove_event_call(struct ftrace_event_call *call)
 	list_del(&call->list);
 	trace_destroy_fields(call);
 	destroy_preds(call);
-	remove_subsystem_dir(call->system);
+	remove_subsystem_dir(call->class->system);
 }
 
 /* Remove an event_call */
@@ -1399,8 +1399,8 @@ static __init void event_trace_self_tests(void)
  * syscalls as we test.
  */
 #ifndef CONFIG_EVENT_TRACE_TEST_SYSCALLS
-		if (call->system &&
-		    strcmp(call->system, "syscalls") == 0)
+		if (call->class->system &&
+		    strcmp(call->class->system, "syscalls") == 0)
 			continue;
 #endif