tracing: Switch trace_events_filter.c code over to use guard()

There are a couple functions in trace_events_filter.c that have "goto out"
or equivalent on error in order to release locks that were taken. This can
be error prone or just simply make the code more complex.

Switch every location that ends with unlocking a mutex on error over to
using the guard(mutex)() infrastructure to let the compiler worry about
releasing locks. This makes the code easier to read and understand.

Cc: Masami Hiramatsu <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: https://lore.kernel.org/[email protected]
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: rostedt

kernel/trace/trace_events_filter.c

@@ -2405,13 +2405,11 @@ int apply_subsystem_event_filter(struct trace_subsystem_dir *dir,
 	struct event_filter *filter = NULL;
 	int err = 0;
 
-	mutex_lock(&event_mutex);
+	guard(mutex)(&event_mutex);
 
 	/* Make sure the system still has events */
-	if (!dir->nr_events) {
-		err = -ENODEV;
-		goto out_unlock;
-	}
+	if (!dir->nr_events)
+		return -ENODEV;
 
 	if (!strcmp(strstrip(filter_string), "0")) {
 		filter_free_subsystem_preds(dir, tr);
@@ -2422,7 +2420,7 @@ int apply_subsystem_event_filter(struct trace_subsystem_dir *dir,
 		tracepoint_synchronize_unregister();
 		filter_free_subsystem_filters(dir, tr);
 		__free_filter(filter);
-		goto out_unlock;
+		return 0;
 	}
 
 	err = create_system_filter(dir, filter_string, &filter);
@@ -2434,8 +2432,6 @@ int apply_subsystem_event_filter(struct trace_subsystem_dir *dir,
 		__free_filter(system->filter);
 		system->filter = filter;
 	}
-out_unlock:
-	mutex_unlock(&event_mutex);
 
 	return err;
 }
@@ -2612,17 +2608,15 @@ int ftrace_profile_set_filter(struct perf_event *event, int event_id,
 	struct event_filter *filter = NULL;
 	struct trace_event_call *call;
 
-	mutex_lock(&event_mutex);
+	guard(mutex)(&event_mutex);
 
 	call = event->tp_event;
 
-	err = -EINVAL;
 	if (!call)
-		goto out_unlock;
+		return -EINVAL;
 
-	err = -EEXIST;
 	if (event->filter)
-		goto out_unlock;
+		return -EEXIST;
 
 	err = create_filter(NULL, call, filter_str, false, &filter);
 	if (err)
@@ -2637,9 +2631,6 @@ int ftrace_profile_set_filter(struct perf_event *event, int event_id,
 	if (err || ftrace_event_is_function(call))
 		__free_filter(filter);
 
-out_unlock:
-	mutex_unlock(&event_mutex);
-
 	return err;
 }