gfs2_rgrpd_get_first
if ((gfs2_rgrpd_get_first(sdp) == gfs2_rgrpd_get_next(rgd_end))
rgd = gfs2_rgrpd_get_first(sdp);
rgd = gfs2_rgrpd_get_first(sdp);
struct gfs2_rgrpd *gfs2_rgrpd_get_first(struct gfs2_sbd *sdp);
rgd_next = gfs2_rgrpd_get_first(sdp);