--- x/block/bdev.c
+++ y/block/bdev.c
@@ -1137,12 +1137,12 @@ void bdev_release(struct file *bdev_file
 	 * from userland - e.g. eject(1).
 	 */
 	disk_flush_events(disk, DISK_EVENT_MEDIA_CHANGE);
+	mutex_unlock(&disk->open_mutex);
 
 	if (bdev_is_partition(bdev))
 		blkdev_put_part(bdev);
 	else
 		blkdev_put_whole(bdev);
-	mutex_unlock(&disk->open_mutex);
 
 	module_put(disk->fops->owner);
 put_no_open:
--- l/drivers/block/nbd.c
+++ y/drivers/block/nbd.c
@@ -1700,21 +1700,23 @@ static int nbd_open(struct gendisk *disk
 
 	config = nbd_get_config_unlocked(nbd);
 	if (!config) {
+		mutex_unlock(&nbd_index_mutex);
 		mutex_lock(&nbd->config_lock);
 		if (refcount_inc_not_zero(&nbd->config_refs)) {
 			mutex_unlock(&nbd->config_lock);
-			goto out;
+			return 0;
 		}
 		ret = nbd_alloc_and_init_config(nbd);
 		if (ret) {
 			mutex_unlock(&nbd->config_lock);
-			goto out;
+			return ret;
 		}
 
 		refcount_inc(&nbd->refs);
 		mutex_unlock(&nbd->config_lock);
 		if (max_part)
 			set_bit(GD_NEED_PART_SCAN, &disk->state);
+		return 0;
 	} else if (nbd_disconnected(config)) {
 		if (max_part)
 			set_bit(GD_NEED_PART_SCAN, &disk->state);