feature_get_refcount_from_disk
VERIFY0(feature_get_refcount_from_disk(spa, feature, &refcount));
VERIFY0(feature_get_refcount_from_disk(spa, feature, &refcount));
if (feature_get_refcount_from_disk(spa, &feature,
error = feature_get_refcount_from_disk(spa,
extern int feature_get_refcount_from_disk(spa_t *spa, zfeature_info_t *feature,