gfs2_jdesc_find
sdp->sd_jdesc = gfs2_jdesc_find(sdp, 0);
sdp->sd_jdesc = gfs2_jdesc_find(sdp, sdp->sd_lockstruct.ls_jid);
struct gfs2_jdesc *jd = gfs2_jdesc_find(sdp, x);
struct gfs2_jdesc *gfs2_jdesc_find(struct gfs2_sbd *sdp, unsigned int jid);