prog_pread
ret = prog_pread(fd, buf, SCANSIZE, 0);
ret = prog_pread(fd, buf, SCANSIZE, 0);
ret = prog_pread(fd, buf, SCANSIZE, 0);
ssize_t ret = prog_pread(fd, vdev_phys, sizeof(*vdev_phys),
ret = prog_pread(fd, &u, sizeof(u), sblock_try[i]);