private Set<DistributedRegion> getRegions(final ClusterDistributionManager dm) {
      Set<DistributedRegion> regions;
      if (allRegions) {
        regions = getAllRegions(dm);
      } else {
        regions = Collections.singleton(getRegion(dm));
      }
      return regions;
    }
returns a set of all DistributedRegions for allRegions processing
geode-core/src/main/java/org/apache/geode/internal/cache/StateFlushOperation.java