@Override
  public void flushPageToChannel(FileChannel channel) throws IOException {
    this.pageBuffer.clear();
    channel.write(pageBuffer, SchemaFile.getPageAddress(pageIndex));
    dirtyFlag = false;
  }
compatible constructor with no existing ref or lock
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/schemaregion/mtree/impl/pbtree/schemafile/SchemaPage.java