1. A computer-implemented method, comprising: receiving a storage stack delete notification at a storage stack filter, the delete notification indicating deletion of primary data in a primary storage region; identifying secondary data that is taking up storage resources managed by the storage stack filter, the secondary data being associated with the primary storage region, and the storage resources being resources other than the primary storage region; determining whether it is useful to have the secondary data continue taking up the storage resources; and if having the secondary data continue taking up the storage resources is not useful, then freeing the storage resources.