extern metaslab_t *metaslab_init(metaslab_group_t *mg, space_map_obj_t *smo,
uint64_t start, uint64_t size, uint64_t txg);
extern void metaslab_fini(metaslab_t *msp);
extern metaslab_t *metaslab_init(metaslab_group_t *mg, space_map_obj_t *smo,
uint64_t start, uint64_t size, uint64_t txg);
extern void metaslab_fini(metaslab_t *msp);