xen: balloon: Use static attribute groups for sysfs entries

Instead of manual calls of device_create_file(), device_remove_file()
and sysfs_create_group(), assign static attribute groups to the device
to register.  This simplifies the code and avoids possible races.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

drivers/xen/xen-balloon.c

@@ -193,13 +193,18 @@ static DEVICE_ATTR(target, S_IRUGO | S_IWUSR,
 		   show_target, store_target);
 
 
-static struct device_attribute *balloon_attrs[] = {
-	&dev_attr_target_kb,
-	&dev_attr_target,
-	&dev_attr_schedule_delay.attr,
-	&dev_attr_max_schedule_delay.attr,
-	&dev_attr_retry_count.attr,
-	&dev_attr_max_retry_count.attr
+static struct attribute *balloon_attrs[] = {
+	&dev_attr_target_kb.attr,
+	&dev_attr_target.attr,
+	&dev_attr_schedule_delay.attr.attr,
+	&dev_attr_max_schedule_delay.attr.attr,
+	&dev_attr_retry_count.attr.attr,
+	&dev_attr_max_retry_count.attr.attr,
+	NULL
+};
+
+static const struct attribute_group balloon_group = {
+	.attrs = balloon_attrs
 };
 
 static struct attribute *balloon_info_attrs[] = {
@@ -214,46 +219,36 @@ static const struct attribute_group balloon_info_group = {
 	.attrs = balloon_info_attrs
 };
 
+static const struct attribute_group *balloon_groups[] = {
+	&balloon_group,
+	&balloon_info_group,
+	NULL
+};
+
 static struct bus_type balloon_subsys = {
 	.name = BALLOON_CLASS_NAME,
 	.dev_name = BALLOON_CLASS_NAME,
 };
 
 static int register_balloon(struct device *dev)
 {
-	int i, error;
+	int error;
 
 	error = subsys_system_register(&balloon_subsys, NULL);
 	if (error)
 		return error;
 
 	dev->id = 0;
 	dev->bus = &balloon_subsys;
+	dev->groups = balloon_groups;
 
 	error = device_register(dev);
 	if (error) {
 		bus_unregister(&balloon_subsys);
 		return error;
 	}
 
-	for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) {
-		error = device_create_file(dev, balloon_attrs[i]);
-		if (error)
-			goto fail;
-	}
-
-	error = sysfs_create_group(&dev->kobj, &balloon_info_group);
-	if (error)
-		goto fail;
-
 	return 0;
-
- fail:
-	while (--i >= 0)
-		device_remove_file(dev, balloon_attrs[i]);
-	device_unregister(dev);
-	bus_unregister(&balloon_subsys);
-	return error;
 }
 
 MODULE_LICENSE("GPL");