A list of data structures (e.g., inodes) can be accessed, and the data structures in the list can be examined. If a data structure is examined, a counter value associated with the data structure is changed to a generation number that is associated with the examination. Subsequently, the counter values can be used to identify unreferenced data structures. More specifically, the counter value for an unreferenced data structure will be different from the generation number for the most recently performed examination.