--- x/block/ioctl.c
+++ y/block/ioctl.c
@@ -367,12 +367,10 @@ static int blkdev_flushbuf(struct block_
 	if (!capable(CAP_SYS_ADMIN))
 		return -EACCES;
 
-	mutex_lock(&bdev->bd_holder_lock);
 	if (bdev->bd_holder_ops && bdev->bd_holder_ops->sync)
 		bdev->bd_holder_ops->sync(bdev);
 	else
 		sync_blockdev(bdev);
-	mutex_unlock(&bdev->bd_holder_lock);
 
 	invalidate_bdev(bdev);
 	return 0;