pr_debug("major=%u, first minor=%u, minors=%u, name=%s",bdev->bd_disk->major,bdev->bd_disk->first_minor,bdev->bd_disk->minors,bdev->bd_disk->disk_name);
pos,nr_pages,iter->type,iter->iov_offset,iter->count,iter->iov->iov_base,iter->iov->iov_len,iter->nr_segs);// pos - in file