block: nbd: convert to blkdev_reread_part()

Reviewed-by: NChristoph Hellwig <hch@lst.de>
Tested-by: NJarod Wilson <jarod@redhat.com>
Acked-by: NJarod Wilson <jarod@redhat.com>
Signed-off-by: NMing Lei <ming.lei@canonical.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

drivers/block/nbd.c

@@ -711,7 +711,7 @@ static int __nbd_ioctl(struct block_device *bdev, struct nbd_device *nbd,
 		bdev->bd_inode->i_size = 0;
 		set_capacity(nbd->disk, 0);
 		if (max_part > 0)
-			ioctl_by_bdev(bdev, BLKRRPART, 0);
+			blkdev_reread_part(bdev);
 		if (nbd->disconnect) /* user requested, ignore socket errors */
 			return 0;
 		return nbd->harderror;