DR_GATHER
reqp->dr_flags &= ~(DR_SCATTER | DR_GATHER);
reqp->dr_flags |= DR_SCATTER | DR_GATHER;
if (!(reqp->dr_flags & (DR_SCATTER | DR_GATHER))) {
if (reqp->dr_flags & DR_GATHER) {
reqp->dr_flags |= DR_SCATTER | DR_GATHER;