A non-overwrite storage system, such as a log-structured file system, that includes a non-volatile storage having multiple storage segments, a volatile storage having an unsafe free segments list (UFSL), and a controller for managing storage resources of the non-volatile storage. The controller can be configured to copy page data from used segment(s) of the non-volatile storage, write the copied page data to free segment(s) of the non-volatile storage, index the UFSL with indications of the used segment(s), and thereafter prevent reuse of the used segment(s) while the indications of the used segment(s) remain indexed in the UFSL. In some implementations, the non-overwrite storage system may be associated with flash storage system, and a flash controller can be configured perform a flush track cache operation to clear the indications of the used segment(s) from the UFSL, to enable reuse of segment(s) that were previously indexed to the UFSL.