firewire: core: use guard macro to maintain the list of cdev clients

The core function maintains userspace clients by the list in fw_device
object associated to the operated character device. The concurrent
access to the list is protected by mutex in the object.

This commit uses guard macro to maintain the mutex.

Link: https://lore.kernel.org/r/20240805085408.251763-4-o-takashi@sakamocchi.jpSigned-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>

drivers/firewire/core-cdev.c

@@ -375,10 +375,10 @@ static void for_each_client(struct fw_device *device,
 {
 	struct client *c;
 
-	mutex_lock(&device->client_list_mutex);
+	guard(mutex)(&device->client_list_mutex);
+
 	list_for_each_entry(c, &device->client_list, link)
 		callback(c);
-	mutex_unlock(&device->client_list_mutex);
 }
 
 static int schedule_reallocations(int id, void *p, void *data)
@@ -470,7 +470,7 @@ static int ioctl_get_info(struct client *client, union ioctl_arg *arg)
 	if (ret != 0)
 		return -EFAULT;
 
-	mutex_lock(&client->device->client_list_mutex);
+	guard(mutex)(&client->device->client_list_mutex);
 
 	client->bus_reset_closure = a->bus_reset_closure;
 	if (a->bus_reset != 0) {
@@ -481,8 +481,6 @@ static int ioctl_get_info(struct client *client, union ioctl_arg *arg)
 	if (ret == 0 && list_empty(&client->link))
 		list_add_tail(&client->link, &client->device->client_list);
 
-	mutex_unlock(&client->device->client_list_mutex);
-
 	return ret ? -EFAULT : 0;
 }
 
@@ -1884,9 +1882,8 @@ static int fw_device_op_release(struct inode *inode, struct file *file)
 	list_del(&client->phy_receiver_link);
 	spin_unlock_irq(&client->device->card->lock);
 
-	mutex_lock(&client->device->client_list_mutex);
-	list_del(&client->link);
-	mutex_unlock(&client->device->client_list_mutex);
+	scoped_guard(mutex, &client->device->client_list_mutex)
+		list_del(&client->link);
 
 	if (client->iso_context)
 		fw_iso_context_destroy(client->iso_context);