List<ServerName> getTopBlockLocations(RegionInfo region) {
    List<String> topHosts = getBlockDistribution(region).getTopHosts();
    return mapHostNameToServerName(topHosts);
  }
Refresh all the region locations.
@return true if user created regions got refreshed.
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/RegionHDFSBlockLocationFinder.java