nodejs提示：cross-device link not permitted, rename错误的解决方法

form.parse(request, function(error, fields, files) {
 console.log(“parsing done”);
 fs.renameSync(files.upload.path, “/tmp/test.png”);
});

form.parse(request, function(error, fields, files) {
 console.log(“parsing done”);

 // fs.renameSync(files.upload.path, “/nodejs/case/two/img/test.png”);

 var readStream=fs.createReadStream(files.upload.path);
 var writeStream=fs.createWriteStream("./tmp/test.jpg");
 readStream.pipe(writeStream);
 readStream.on('end',function(){
  fs.unlinkSync(files.upload.path);
 });
});

util.pump(readStream,writeStream, function() {
 fs.unlinkSync('files.upload.path');
});

function upload(response,request){
 console.log(“upload called”);
 var form = new formidable.IncomingForm();
 form.uploadDir='tmp';

 console.log(“about to parse”);
 form.parse(request, function(error, fields, files) {
  console.log(“parsing done”);
  fs.renameSync(files.upload.path, “./tmp/test.jpg”);
  response.writeHead(200, {“Content-Type”: “text/html”});
  response.write(“received image:<br/>”);
  response.write(“<img src='/show' />”);
  response.end();
 });
}