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; in response to the delete notification, performing acts comprising: 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 to have the secondary data continue taking up the storage resources; and if the secondary data is not to continue taking up the storage resources, then freeing the storage resources.