public void loadFromFileToBuffer(ByteBuffer dst, int pageIndex) throws IOException {
    dst.clear();
    if (!readChannel.isOpen()) {
      readChannel = FileChannel.open(pmtFile.toPath(), StandardOpenOption.READ);
    }
    readChannel.read(dst, getPageAddress(pageIndex));
  }
Load bytes from log, deserialize and flush directly into channel, return current length
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/schemaregion/mtree/impl/pbtree/schemafile/pagemgr/PageIOChannel.java