code: private boolean checkBlockSize(Block block, INodeFile inode) {
      if (block.getNumBytes() < 0) {
        return false;
      }
      BlockInfo[] blocks = inode.getBlocks();
      if (blocks.length == 0) {
        return false;
      }
      return block.getNumBytes() <= inode.getPreferredBlockSize();
    }
docs: Return true if the block size number is valid