extent_alloc_with_descr
error = extent_alloc_with_descr(sgmap->aps_ex, sgvalen, alignment,
error = extent_alloc_with_descr(as->as_dvamap, len,
error = extent_alloc_with_descr(dom->sd_iovamap, len + PAGE_SIZE,
err = extent_alloc_with_descr(sc->sc_dvmamap, sgsize, align, 0,