ftrace: Use guard to lock ftrace_lock in cache_mod()

The ftrace_lock is held throughout cache_mod(), use guard to simplify the
error paths.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/20241028071308.088458856@goodmis.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Author: rostedt

kernel/trace/ftrace.c

@@ -4947,14 +4947,14 @@ static int cache_mod(struct trace_array *tr,
 {
 	struct ftrace_mod_load *ftrace_mod, *n;
 	struct list_head *head = enable ? &tr->mod_trace : &tr->mod_notrace;
-	int ret;
 
-	mutex_lock(&ftrace_lock);
+	guard(mutex)(&ftrace_lock);
 
 	/* We do not cache inverse filters */
 	if (func[0] == '!') {
+		int ret = -EINVAL;
+
 		func++;
-		ret = -EINVAL;
 
 		/* Look to remove this hash */
 		list_for_each_entry_safe(ftrace_mod, n, head, list) {
@@ -4970,20 +4970,15 @@ static int cache_mod(struct trace_array *tr,
 				continue;
 			}
 		}
-		goto out;
+		return ret;
 	}
 
-	ret = -EINVAL;
 	/* We only care about modules that have not been loaded yet */
 	if (module_exists(module))
-		goto out;
+		return -EINVAL;
 
 	/* Save this string off, and execute it when the module is loaded */
-	ret = ftrace_add_mod(tr, func, module, enable);
- out:
-	mutex_unlock(&ftrace_lock);
-
-	return ret;
+	return ftrace_add_mod(tr, func, module, enable);
 }
 
 static int