code: private boolean delBlockFromDisk(File blockFile, File metaFile, Block b) {
      if (blockFile == null) {
        DataNode.LOG.warn("No file exists for block: " + b);
        return true;
      }
  
      if (!blockFile.delete()) {
        DataNode.LOG.warn("Not able to delete the block file: " + blockFile);
        return false;
      } else { // remove the meta file
        if (metaFile != null && !metaFile.delete()) {
          DataNode.LOG.warn(
              "Not able to delete the meta block file: " + metaFile);
          return false;
        }
      }
      return true;
    }
docs: Remove a block from disk
  @param blockFile block file
  @param metaFile block meta file
  @param b a block
  @return true if on-disk files are deleted; false otherwise