if !ok {
		return update, errFileNotFound
	}
	existing.update(update)
	b.caches[update.id] = existing
	b.updated = true
	return existing, nil
}

// cloneCaches will return a clone of all current caches.
func (b *bucketMetacache) cloneCaches() (map[string]metacache, map[string][]string) {
	b.mu.RLock()
	defer b.mu.RUnlock()
	dst := make(map[string]metacache, len(b.caches))
	for k, v := range b.caches {