i_rdev
ip->i_rdev = 0; /* Zero in core version of rdev */
ip->i_rdev = makedevice(ip->i_major, ip->i_minor);
vp->v_rdev = ip->i_rdev;
vap->va_rdev = ip->i_rdev;
ITOV(ip)->v_rdev = ip->i_rdev = d;
ip->i_rdev = 0;
vp->v_rdev = ip->i_rdev = dv;
dev_t d = ip->i_rdev;
ip->i_rdev = 0;
vap->va_rdev = ip->i_rdev;
dev_t i_rdev; /* INCORE rdev from */
dev_t i_rdev; /* INCORE rdev from i_oldrdev by ufs_iget */