bd_prepare_to_claim
int err = bd_prepare_to_claim(bdev, truncate_bdev_range, NULL);
EXPORT_SYMBOL_GPL(bd_prepare_to_claim); /* only for the loop driver */
ret = bd_prepare_to_claim(bdev, holder, hops);
ret = bd_prepare_to_claim(disk->part0, disk_scan_partitions,
error = bd_prepare_to_claim(bdev, loop_configure, NULL);
err = bd_prepare_to_claim(bdev, loop_set_block_size, NULL);
int bd_prepare_to_claim(struct block_device *bdev, void *holder,