lockmgr
lockmgr(nvp->v_vnlock, LK_EXCLUSIVE | LK_NOWITNESS, NULL);
lockmgr(&(pmp)->pm_fatlock, LK_EXCLUSIVE, NULL)
lockmgr(&(pmp)->pm_fatlock, LK_RELEASE, NULL)
void lockmgr(struct lock* lk, u_int flags, struct mtx* ilk);
lockmgr(vp->v_vnlock, LK_RELEASE, NULL);