- struct block_dev* bdev = (struct block_dev*)dev->underlay;
- size_t bsize = bdev->blk_size, rd_block = offset / bsize + bdev->start_lba,
+ struct block_dev* bdev = block_dev(dev);
+ size_t bsize = bdev->blk_size,
+ rd_block = offset / bsize + bdev->start_lba,