private void postRollBackMergeRegions(final MasterProcedureEnv env) throws IOException {
    final MasterCoprocessorHost cpHost = env.getMasterCoprocessorHost();
    if (cpHost != null) {
      cpHost.postRollBackMergeRegionsAction(regionsToMerge, getUser());
    }
  }
Action after rollback a merge table regions action.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/assignment/MergeTableRegionsProcedure.java