resource := pathJoin(volume, path)

	n.lockMapMutex.Lock()
	nsLk, found := n.lockMap[resource]
	if !found {
		nsLk = &nsLock{
			LRWMutex: lsync.NewLRWMutex(),
		}
		// Add a count to indicate that a parallel unlock doesn't clear this entry.
	}
	nsLk.ref++
	n.lockMap[resource] = nsLk
	n.lockMapMutex.Unlock()

	// Locking here will block (until timeout).