res := make(dataUsageHashMap, len(ch))
	for k := range ch {
		res[k] = struct{}{}
	}
	return res
}

// searchParent will search for the parent of h.
// This is an O(N*N) operation if there is no parent or it cannot be guessed.
func (d *dataUsageCache) searchParent(h dataUsageHash) *dataUsageHash {
	want := h.Key()
	if idx := strings.LastIndexByte(want, '/'); idx >= 0 {
		if v := d.find(want[:idx]); v != nil {

				for parent != hashPath(f.updateCache.Info.Name) {
					e := f.updateCache.find(parent.Key())
					if e == nil || e.Compacted {
						foundAny = true
						break
					}
					next := f.updateCache.searchParent(parent)
					if next == nil {
						foundAny = true
						break
					}
					parent = *next
				}
				if !foundAny {
					// Add non-compacted empty entry.