diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index 35b390a785dd4f36d63898351b37958cf792c8a4..91c8412442d0583714ac4dec5283630571addd6a 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -323,11 +323,9 @@ CONFIGFS_ATTR(nullb_device_, NAME);
 static int nullb_apply_submit_queues(struct nullb_device *dev,
 				     unsigned int submit_queues)
 {
-	struct nullb *nullb = dev->nullb;
+	struct nullb *nullb;
 	struct blk_mq_tag_set *set;
-
-	if (!nullb)
-		return 0;
+	int ret = 0;
 
 	/*
 	 * Make sure that null_init_hctx() does not access nullb->queues[] past
@@ -335,9 +333,20 @@ static int nullb_apply_submit_queues(struct nullb_device *dev,
 	 */
 	if (submit_queues > nr_cpu_ids)
 		return -EINVAL;
+
+	mutex_lock(&lock);
+
+	nullb = dev->nullb;
+	if (!nullb)
+		goto out;
+
 	set = nullb->tag_set;
 	blk_mq_update_nr_hw_queues(set, submit_queues);
-	return set->nr_hw_queues == submit_queues ? 0 : -ENOMEM;
+	ret = set->nr_hw_queues == submit_queues ? 0 : -ENOMEM;
+
+out:
+	mutex_unlock(&lock);
+	return ret;
 }
 
 NULLB_DEVICE_ATTR(size, ulong, NULL);
@@ -378,27 +387,31 @@ static ssize_t nullb_device_power_store(struct config_item *item,
 	if (ret < 0)
 		return ret;
 
+	ret = count;
+	mutex_lock(&lock);
 	if (!dev->power && newp) {
 		if (test_and_set_bit(NULLB_DEV_FL_UP, &dev->flags))
-			return count;
+			goto out;
+
 		if (null_add_dev(dev)) {
 			clear_bit(NULLB_DEV_FL_UP, &dev->flags);
-			return -ENOMEM;
+			ret = -ENOMEM;
+			goto out;
 		}
 
 		set_bit(NULLB_DEV_FL_CONFIGURED, &dev->flags);
 		dev->power = newp;
 	} else if (dev->power && !newp) {
 		if (test_and_clear_bit(NULLB_DEV_FL_UP, &dev->flags)) {
-			mutex_lock(&lock);
 			dev->power = newp;
 			null_del_dev(dev->nullb);
-			mutex_unlock(&lock);
 		}
 		clear_bit(NULLB_DEV_FL_CONFIGURED, &dev->flags);
 	}
 
-	return count;
+out:
+	mutex_unlock(&lock);
+	return ret;
 }
 
 CONFIGFS_ATTR(nullb_device_, power);
@@ -1880,15 +1893,11 @@ static int null_add_dev(struct nullb_device *dev)
 	blk_queue_flag_set(QUEUE_FLAG_NONROT, nullb->q);
 	blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, nullb->q);
 
-	mutex_lock(&lock);
 	rv = ida_simple_get(&nullb_indexes, 0, 0, GFP_KERNEL);
-	if (rv < 0) {
-		mutex_unlock(&lock);
+	if (rv < 0)
 		goto out_cleanup_zone;
-	}
 	nullb->index = rv;
 	dev->index = rv;
-	mutex_unlock(&lock);
 
 	blk_queue_logical_block_size(nullb->q, dev->blocksize);
 	blk_queue_physical_block_size(nullb->q, dev->blocksize);
@@ -1901,9 +1910,7 @@ static int null_add_dev(struct nullb_device *dev)
 	if (rv)
 		goto out_ida_free;
 
-	mutex_lock(&lock);
 	list_add_tail(&nullb->list, &nullb_list);
-	mutex_unlock(&lock);
 
 	return 0;
 
@@ -1985,7 +1992,9 @@ static int __init null_init(void)
 			ret = -ENOMEM;
 			goto err_dev;
 		}
+		mutex_lock(&lock);
 		ret = null_add_dev(dev);
+		mutex_unlock(&lock);
 		if (ret) {
 			null_free_dev(dev);
 			goto err_dev;