图片上传定义了$upload->subType，但是仍然没有产生目录

import('ORG.Net.UploadFile');
$upload = new UploadFile();
$upload->maxSize = 3292200;
$upload->allowExts = explode(',', 'jpg,gif,png,jpeg');
$upload->savePath = './uploads/';
$upload->thumb = true;
$upload->imageClassPath = 'ORG.Util.Image';
$upload->thumbPrefix = 's,m,b'; //生产1张缩略图
$upload->thumbMaxWidth = '68,350,800';
$upload->thumbMaxHeight = '68,350,800';
$upload->saveRule = 'uniqid';
$upload->thumbRemoveOrigin = true;
$upload->subType = 'date';
$upload->dateFormat = 'Y/m/d/';

if (!$upload->upload()) {
$this->error($upload->getErrorMsg());
} else {
return $upload->getUploadFileInfo();
}