diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index 962b0e05ce50..c7dfbec3e7d6 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -360,6 +360,7 @@ nullb_device_##NAME##_store(struct config_item *item, const char *page,	\
 	ret = nullb_device_##TYPE##_attr_store(&new_value, page, count);\
 	if (ret < 0)							\
 		return ret;						\
+	guard(mutex)(&lock);						\
 	if (apply_fn)							\
 		ret = apply_fn(dev, new_value);				\
 	else if (test_bit(NULLB_DEV_FL_CONFIGURED, &dev->flags)) 	\
@@ -430,25 +431,13 @@ static int nullb_update_nr_hw_queues(struct nullb_device *dev,
 static int nullb_apply_submit_queues(struct nullb_device *dev,
 				     unsigned int submit_queues)
 {
-	int ret;
-
-	mutex_lock(&lock);
-	ret = nullb_update_nr_hw_queues(dev, submit_queues, dev->poll_queues);
-	mutex_unlock(&lock);
-
-	return ret;
+	return nullb_update_nr_hw_queues(dev, submit_queues, dev->poll_queues);
 }
 
 static int nullb_apply_poll_queues(struct nullb_device *dev,
 				   unsigned int poll_queues)
 {
-	int ret;
-
-	mutex_lock(&lock);
-	ret = nullb_update_nr_hw_queues(dev, dev->submit_queues, poll_queues);
-	mutex_unlock(&lock);
-
-	return ret;
+	return nullb_update_nr_hw_queues(dev, dev->submit_queues, poll_queues);
 }
 
 NULLB_DEVICE_ATTR(size, ulong, NULL);