if mbc := bal.mountsByClass[class]; mbc == nil {
bal.classes = append(bal.classes, class)
bal.mountsByClass[class] = map[*KeepMount]bool{mnt: true}
if mbc := bal.mountsByClass[class]; mbc == nil {
bal.classes = append(bal.classes, class)
bal.mountsByClass[class] = map[*KeepMount]bool{mnt: true}