private Block allocateBlock(String src, INode[] inodes) throws IOException {

    Block b = null;

    do {

      b = new Block(FSNamesystem.randBlockId.nextLong(), 0, 

                    getGenerationStamp());

    } while (isValidBlock(b));

    b = dir.addBlock(src, inodes, b);

    NameNode.stateChangeLog.info("BLOCK* NameSystem.allocateBlock: "

                                 +src+ ". "+b);

    return b;

  }