message: fscache: no need to clone string
  This is only a tiny improvement that we don't have
  to clone string each time. It will cause memory footprint.
diff: @@ -394,11 +394,12 @@ impl FsCacheHandler {
  fn handle_open_request(&self, hdr: &FsCacheMsgHeader, msg: &FsCacheMsgOpen) {
  // Drop the 'erofs,' prefix if any
  - let domain_id = match msg.volume_key.clone().strip_prefix("erofs,") {
  - None => msg.volume_key.clone(),
  - Some(str) => str.to_string(),
  - };
  - let key = generate_blob_key(&domain_id, &msg.cookie_key);
  + let domain_id = msg
  + .volume_key
  + .strip_prefix("erofs,")
  + .unwrap_or(msg.volume_key.as_str());
  +
  + let key = generate_blob_key(domain_id, &msg.cookie_key);
  let msg = match self.get_config(&key) {
  None => {
  unsafe { libc::close(msg.fd as i32) };
  