irqbypass: Use guard(mutex) in lieu of manual lock+unlock

Use guard(mutex) to clean up irqbypass's error handling.

Reviewed-by: Kevin Tian <[e-mail]>
Acked-by: Michael S. Tsirkin <[e-mail]>
Reviewed-by: Alex Williamson <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Sean Christopherson <[e-mail]>

virt/lib/irqbypass.c

···
 	if (WARN_ON_ONCE(producer->eventfd))
 		return -EINVAL;
 
-	mutex_lock(&lock);
+	guard(mutex)(&lock);
 
 	list_for_each_entry(tmp, &producers, node) {
-		if (tmp->eventfd == eventfd) {
-			ret = -EBUSY;
-			goto out_err;
-		}
+		if (tmp->eventfd == eventfd)
+			return -EBUSY;
 	}
 
 	list_for_each_entry(consumer, &consumers, node) {
 		if (consumer->eventfd == eventfd) {
 			ret = __connect(producer, consumer);
 			if (ret)
-				goto out_err;
+				return ret;
 			break;
 		}
 	}
 
 	producer->eventfd = eventfd;
 	list_add(&producer->node, &producers);
-
-	mutex_unlock(&lock);
-
 	return 0;
-out_err:
-	mutex_unlock(&lock);
-	return ret;
 }
 EXPORT_SYMBOL_GPL(irq_bypass_register_producer);
 
···
 	if (!producer->eventfd)
 		return;
 
-	mutex_lock(&lock);
+	guard(mutex)(&lock);
 
 	if (producer->consumer)
 		__disconnect(producer, producer->consumer);
 
 	producer->eventfd = NULL;
 	list_del(&producer->node);
-	mutex_unlock(&lock);
 }
 EXPORT_SYMBOL_GPL(irq_bypass_unregister_producer);
 
···
 	if (!consumer->add_producer || !consumer->del_producer)
 		return -EINVAL;
 
-	mutex_lock(&lock);
+	guard(mutex)(&lock);
 
 	list_for_each_entry(tmp, &consumers, node) {
-		if (tmp->eventfd == eventfd) {
-			ret = -EBUSY;
-			goto out_err;
-		}
+		if (tmp->eventfd == eventfd)
+			return -EBUSY;
 	}
 
 	list_for_each_entry(producer, &producers, node) {
 		if (producer->eventfd == eventfd) {
 			ret = __connect(producer, consumer);
 			if (ret)
-				goto out_err;
+				return ret;
 			break;
 		}
 	}
 
 	consumer->eventfd = eventfd;
 	list_add(&consumer->node, &consumers);
-
-	mutex_unlock(&lock);
-
 	return 0;
-out_err:
-	mutex_unlock(&lock);
-	return ret;
 }
 EXPORT_SYMBOL_GPL(irq_bypass_register_consumer);
 
···
 	if (!consumer->eventfd)
 		return;
 
-	mutex_lock(&lock);
+	guard(mutex)(&lock);
 
 	if (consumer->producer)
 		__disconnect(consumer->producer, consumer);
 
 	consumer->eventfd = NULL;
 	list_del(&consumer->node);
-	mutex_unlock(&lock);
 }
 EXPORT_SYMBOL_GPL(irq_bypass_unregister_consumer);