How to properly mark the file as not in sync using Cloud Files API?

I have implemented CF_CALLBACK_TYPE_FETCH_PLACEHOLDERS callback and CF_CALLBACK_TYPE_FETCH_DATA callback using Cloud Files Windows API and it is working well. Files sync from server to client properly.

Now at some point a file on a client becomes obsolete, because it is modified on the server. How do I properly mark it as not in sync on the client?

• Should I directly call the CfSetInSyncState() function? What is the
  role of StorageProviderSyncRootInfo.InSyncPolicy in this
  process?

• Do I dehydrate the placeholder manually on the client using
  CfUpdatePlaceholder()?