code: func (ed *emptyDir) setupTmpfs(dir string) error {
  	if ed.mounter == nil {
  		return fmt.Errorf("memory storage requested, but mounter is nil")
  	}
  	if err := ed.setupDir(dir); err != nil {
  		return err
  	}
  	// Make SetUp idempotent.
  	medium, isMnt, err := ed.mountDetector.GetMountMedium(dir)
  	if err != nil {
  		return err
  	}
  	// If the directory is a mountpoint with medium memory, there is no
  	// work to do since we are already in the desired state.
  	if isMnt && medium == v1.StorageMediumMemory {
  		return nil
  	}
  
  	klog.V(3).Infof("pod %v: mounting tmpfs for volume %v", ed.pod.UID, ed.volName)
  	return ed.mounter.Mount("tmpfs", dir, "tmpfs", nil /* options */)
  }
docs: // setupTmpfs creates a tmpfs mount at the specified directory.