protected ISchemaPage replacePageInCache(ISchemaPage page, SchemaPageContext cxt) {
    // no need to lock since the root of B+Tree is locked
    cxt.markDirty(page, true);
    pagePool.put(page);
    return page;
  }
Any page returned will be pinned/referred by the cxt. *
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/schemaregion/mtree/impl/pbtree/schemafile/pagemgr/PageManager.java