code: function ensure_root_directory(context, callback) {
    var superNode;
    var directoryNode;
    var directoryData;
  
    function ensure_super_node(error, existingNode) {
      if(!error && existingNode) {
        // Another instance has beat us and already created the super node.
        callback();
      } else if(error && !(error instanceof Errors.ENOENT)) {
        callback(error);
      } else {
        SuperNode.create({guid: context.guid}, function(error, result) {
          if(error) {
            callback(error);
            return;
          }
          superNode = result;
          context.putObject(superNode.id, superNode, write_directory_node);
        });
      }
    }
  
    function write_directory_node(error) {
      if(error) {
        callback(error);
      } else {
        Node.create({
          guid: context.guid,
          id: superNode.rnode,
          type: NODE_TYPE_DIRECTORY
        }, function(error, result) {
          if(error) {
            callback(error);
            return;
          }
          directoryNode = result;
          directoryNode.nlinks += 1;
          context.putObject(directoryNode.id, directoryNode, write_directory_data);
        });
      }
    }
  
    function write_directory_data(error) {
      if(error) {
        callback(error);
      } else {
        directoryData = {};
        context.putObject(directoryNode.data, directoryData, callback);
      }
    }
  
    context.getObject(SUPER_NODE_ID, ensure_super_node);
  }
docs: ensure_root_directory. Creates a root node if necessary.
  
  Note: this should only be invoked when formatting a new file system.
  Multiple invocations of this by separate instances will still result
  in only a single super node.