typedef struct BlockDev BlockDev;
typedef struct BlockRun BlockRun;

struct BlockDev
{
	int rfd;
	int wfd;

	/* sector size */
	vlong sectsize;

	/* starting sector */
	vlong start;

	/* number of sectors */
	vlong nsect;
};

struct BlockRun
{
	u64int off;
	
};

long	blockread(int fd, void *buf, long blocksize, long nblocks, vlong offset);
long	blockwrite(int fd, void *buf, long blocksize, long nblocks, vlong offset);
int	blocksync(int fd);