ftrace: Have unregister_ftrace_function_probe_func() return a value

Currently unregister_ftrace_function_probe_func() is a void function. It
does not give any feedback if an error occurred or no item was found to
remove and nothing was done.

Change it to return status and success if it removed something. Also update
the callers to return that feedback to the user.
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/ftrace.c

@@ -4102,7 +4102,7 @@ register_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
 	return count;
 }
 
-void
+int
 unregister_ftrace_function_probe_func(char *glob, struct ftrace_probe_ops *ops)
 {
 	struct ftrace_ops_hash old_hash_ops;
@@ -4131,7 +4131,7 @@ unregister_ftrace_function_probe_func(char *glob, struct ftrace_probe_ops *ops)
 
 		/* we do not support '!' for function probes */
 		if (WARN_ON(not))
-			return;
+			return -EINVAL;
 	}
 
 	mutex_lock(&trace_probe_ops.func_hash->regex_lock);
@@ -4140,9 +4140,9 @@ unregister_ftrace_function_probe_func(char *glob, struct ftrace_probe_ops *ops)
 	/* Probes only have filters */
 	old_hash_ops.notrace_hash = NULL;
 
+	ret = -ENOMEM;
 	hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, *orig_hash);
 	if (!hash)
-		/* Hmm, should report this somehow */
 		goto out_unlock;
 
 	INIT_LIST_HEAD(&free_list);
@@ -4173,6 +4173,13 @@ unregister_ftrace_function_probe_func(char *glob, struct ftrace_probe_ops *ops)
 			list_add(&entry->free_list, &free_list);
 		}
 	}
+
+	/* Nothing found? */
+	if (list_empty(&free_list)) {
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
 	mutex_lock(&ftrace_lock);
 	disabled = __disable_ftrace_function_probe();
 	/*
@@ -4198,6 +4205,7 @@ unregister_ftrace_function_probe_func(char *glob, struct ftrace_probe_ops *ops)
  out_unlock:
 	mutex_unlock(&trace_probe_ops.func_hash->regex_lock);
 	free_ftrace_hash(hash);
+	return ret;
 }
 
 static LIST_HEAD(ftrace_commands);

kernel/trace/trace.c

@@ -6829,10 +6829,8 @@ ftrace_trace_snapshot_callback(struct ftrace_hash *hash,
 
 	ops = param ? &snapshot_count_probe_ops :  &snapshot_probe_ops;
 
-	if (glob[0] == '!') {
-		unregister_ftrace_function_probe_func(glob+1, ops);
-		return 0;
-	}
+	if (glob[0] == '!')
+		return unregister_ftrace_function_probe_func(glob+1, ops);
 
 	if (!param)
 		goto out_reg;

kernel/trace/trace.h

@@ -963,7 +963,7 @@ void free_ftrace_func_mapper(struct ftrace_func_mapper *mapper,
 extern int
 register_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
 			      void *data);
-extern void
+extern int
 unregister_ftrace_function_probe_func(char *glob, struct ftrace_probe_ops *ops);
 
 int register_ftrace_command(struct ftrace_func_command *cmd);

kernel/trace/trace_events.c

@@ -2652,8 +2652,7 @@ event_enable_func(struct ftrace_hash *hash,
 		ops = param ? &event_disable_count_probe_ops : &event_disable_probe_ops;
 
 	if (glob[0] == '!') {
-		unregister_ftrace_function_probe_func(glob+1, ops);
-		ret = 0;
+		ret = unregister_ftrace_function_probe_func(glob+1, ops);
 		goto out;
 	}
 

kernel/trace/trace_functions.c

@@ -586,10 +586,8 @@ ftrace_trace_probe_callback(struct ftrace_probe_ops *ops,
 	if (!enable)
 		return -EINVAL;
 
-	if (glob[0] == '!') {
-		unregister_ftrace_function_probe_func(glob+1, ops);
-		return 0;
-	}
+	if (glob[0] == '!')
+		return unregister_ftrace_function_probe_func(glob+1, ops);
 
 	if (!param)
 		goto out_reg;