private void countFolderDiskSize(String folder, AtomicLong diskSize) {
    File file = FSFactoryProducer.getFSFactory().getFile(folder);
    File[] allFile = file.listFiles();
    if (allFile == null) {
      return;
    }
    for (File f : allFile) {
      if (f.isFile()) {
        diskSize.addAndGet(f.length());
      } else if (f.isDirectory()) {
        countFolderDiskSize(f.getAbsolutePath(), diskSize);
      }
    }
  }
@param folder the folder's path
@param diskSize the disk space occupied by this folder, unit is MB
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/DataRegion.java