invalidate_subdisks
invalidate_subdisks(&PLEX[plexno], sd_stale); /* make the subdisks invalid */
void invalidate_subdisks(struct plex *, enum sdstate);
invalidate_subdisks(plex, sd_down); /* and down all up subdisks */
invalidate_subdisks(plex, sd_crashed); /* and crash all up subdisks */