code: func findDiskWWIDs(wwid string, io ioHandler, deviceUtil volumeutil.DeviceUtil) (string, string) {
  	// Example wwid format:
  	//   3600508b400105e210000900000490000
  	//   <VENDOR NAME> <IDENTIFIER NUMBER>
  	// Example of symlink under by-id:
  	//   /dev/by-id/scsi-3600508b400105e210000900000490000
  	//   /dev/by-id/scsi-<VENDOR NAME>_<IDENTIFIER NUMBER>
  	// The wwid could contain white space and it will be replaced
  	// underscore when wwid is exposed under /dev/by-id.
  
  	fcPath := "scsi-" + wwid
  	devID := byID
  	if dirs, err := io.ReadDir(devID); err == nil {
  		for _, f := range dirs {
  			name := f.Name()
  			if name == fcPath {
  				disk, err := io.EvalSymlinks(devID + name)
  				if err != nil {
  					klog.V(2).Infof("fc: failed to find a corresponding disk from symlink[%s], error %v", devID+name, err)
  					return "", ""
  				}
  				dm := deviceUtil.FindMultipathDeviceForDevice(disk)
  				klog.Infof("fc: find disk: %v, dm: %v", disk, dm)
  				return disk, dm
  			}
  		}
  	}
  	klog.V(2).Infof("fc: failed to find a disk [%s]", devID+fcPath)
  	return "", ""
  }
docs: // given a wwid, find the device and associated devicemapper parent