code: func (p *glusterBlockProvisioner) sortTargetPortal(vol *iscsiSpec) error {
  	if len(vol.Portals) == 0 {
  		return fmt.Errorf("portal is empty")
  	}
  
  	if len(vol.Portals) == 1 && vol.Portals[0] != "" {
  		vol.TargetPortal = vol.Portals[0]
  		vol.Portals = nil
  	} else {
  		portals := vol.Portals
  		vol.Portals = nil
  		for _, v := range portals {
  			if v != "" && vol.TargetPortal == "" {
  				vol.TargetPortal = v
  				continue
  			} else {
  				vol.Portals = append(vol.Portals, v)
  			}
  		}
  	}
  	return nil
  }
docs: //sortTargetPortal extract TP