BO_NOBUFS
odevvp->v_bufobj.bo_flag |= BO_NOBUFS;
odevvp->v_bufobj.bo_flag &= ~BO_NOBUFS;
pmp->pm_odevvp->v_bufobj.bo_flag &= ~BO_NOBUFS;
KASSERT((bo->bo_flag & BO_NOBUFS) == 0,
odevvp->v_bufobj.bo_flag &= ~BO_NOBUFS;
ump->um_odevvp->v_bufobj.bo_flag &= ~BO_NOBUFS;
odevvp->v_bufobj.bo_flag |= BO_NOBUFS;