code: private <T extends INode> T addNode(String src, T child,
          long childDiskspace, boolean inheritPermission)
    throws QuotaExceededException {
      byte[][] components = INode.getPathComponents(src);
      byte[] path = components[components.length - 1];
      child.setLocalName(path);
      cacheName(child);
      INode[] inodes = new INode[components.length];
      writeLock();
      try {
        rootDir.getExistingPathINodes(components, inodes);
        return addChild(inodes, inodes.length-1, child, childDiskspace,
                        inheritPermission);
      } finally {
        writeUnlock();
      }
    }
docs: Add a node child to the namespace. The full path name of the node is src.
  childDiskspace should be -1, if unknown.
  QuotaExceededException is thrown if it violates quota limit