code: public void rollbackJournal(NamespaceInfo nsInfo) throws IOException {
      Preconditions.checkState(nsInfo.getLayoutVersion() != 0,
          "can't rollback with uninitialized layout version : %s",
          nsInfo.toColonSeparatedString());
      LOG.info("Rolling back journal " + this.getJournalId()
          + " with namespace info: (" + nsInfo.toColonSeparatedString() + ")");
      journalStorage.rollback(nsInfo);
  
      refreshCachedData();
    }
docs: Rollback the local journal storage with the given namespace.