xfs_rmap_hook_add
int xfs_rmap_hook_add(struct xfs_group *xg, struct xfs_rmap_hook *hook);
error = xfs_rmap_hook_add(pag_group(sc->sa.pag), &rr->rhook);
error = xfs_rmap_hook_add(rtg_group(sc->sr.rtg), &rr->rhook);