IMPLIES
#define IFF(a, b) (IMPLIES(a, b) && IMPLIES(b, a))
KASSERT(IMPLIES(cnp->cn_namelen == 1, cnp->cn_nameptr[0] != '.'));
KASSERT(IMPLIES(cnp->cn_namelen == 2, !(cnp->cn_nameptr[0] == '.' &&
KASSERT(IMPLIES(ip->ch_type == CHT_DIR && chvc->pvno == chvc->vno,
KASSERT(IMPLIES(tvp != NULL, VOP_ISLOCKED(tvp) == LK_EXCLUSIVE));