code: public static void checkVersionUpgradable(int oldVersion) 
                                       throws IOException {
      if (oldVersion > LAST_UPGRADABLE_LAYOUT_VERSION) {
        String msg = "*********** Upgrade is not supported from this older" +
                     " version of storage to the current version." + 
                     " Please upgrade to " + LAST_UPGRADABLE_HADOOP_VERSION +
                     " or a later version and then upgrade to current" +
                     " version. Old layout version is " + 
                     (oldVersion == 0 ? "'too old'" : (""+oldVersion)) +
                     " and latest layout version this software version can" +
                     " upgrade from is " + LAST_UPGRADABLE_LAYOUT_VERSION +
                     ". ************";
        LOG.error(msg);
        throw new IOException(msg); 
      }
      
    }
docs: Checks if the upgrade from the given old version is supported. If
  no upgrade is supported, it throws IncorrectVersionException.
  
  @param oldVersion