BLKSIZE
size = BLKSIZE(fs, ip, lbn) - bp->b_resid;
#define BLKMASK (BLKSIZE - 1)
char Buf[BLKSIZE];
skip = BLKSIZE;
read(fd, Buf, BLKSIZE);
skip += BLKSIZE;
if (skip < BLKSIZE * 25)
skip += BLKSIZE;