DRBD_MAJOR
unregister_blkdev(DRBD_MAJOR, "drbd");
disk->major = DRBD_MAJOR;
err = register_blkdev(DRBD_MAJOR, "drbd");
DRBD_MAJOR);
pr_info("registered as block device major %d\n", DRBD_MAJOR);
MODULE_ALIAS_BLOCKDEV_MAJOR(DRBD_MAJOR);