4171 clean up spa_feature_*() interfaces
4172 implement extensible_dataset feature for use by other zpool features
Reviewed by: Max Grossman <max.grossman@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>

@@ -472,22 +472,20 @@
 void
 space_map_truncate(space_map_t *sm, dmu_tx_t *tx)
 {
         objset_t *os = sm->sm_os;
         spa_t *spa = dmu_objset_spa(os);
-        zfeature_info_t *space_map_histogram =
-            &spa_feature_table[SPA_FEATURE_SPACEMAP_HISTOGRAM];
         dmu_object_info_t doi;
         int bonuslen;
 
         ASSERT(dsl_pool_sync_context(dmu_objset_pool(os)));
         ASSERT(dmu_tx_is_syncing(tx));
 
         VERIFY0(dmu_free_range(os, space_map_object(sm), 0, -1ULL, tx));
         dmu_object_info_from_db(sm->sm_dbuf, &doi);
 
-        if (spa_feature_is_enabled(spa, space_map_histogram)) {
+        if (spa_feature_is_enabled(spa, SPA_FEATURE_SPACEMAP_HISTOGRAM)) {
                 bonuslen = sizeof (space_map_phys_t);
                 ASSERT3U(bonuslen, <=, dmu_bonus_max());
         } else {
                 bonuslen = SPACE_MAP_SIZE_V0;
         }

@@ -523,17 +521,15 @@
 
 uint64_t
 space_map_alloc(objset_t *os, dmu_tx_t *tx)
 {
         spa_t *spa = dmu_objset_spa(os);
-        zfeature_info_t *space_map_histogram =
-            &spa_feature_table[SPA_FEATURE_SPACEMAP_HISTOGRAM];
         uint64_t object;
         int bonuslen;
 
-        if (spa_feature_is_enabled(spa, space_map_histogram)) {
-                spa_feature_incr(spa, space_map_histogram, tx);
+        if (spa_feature_is_enabled(spa, SPA_FEATURE_SPACEMAP_HISTOGRAM)) {
+                spa_feature_incr(spa, SPA_FEATURE_SPACEMAP_HISTOGRAM, tx);
                 bonuslen = sizeof (space_map_phys_t);
                 ASSERT3U(bonuslen, <=, dmu_bonus_max());
         } else {
                 bonuslen = SPACE_MAP_SIZE_V0;
         }

@@ -547,24 +543,24 @@
 
 void
 space_map_free(space_map_t *sm, dmu_tx_t *tx)
 {
         spa_t *spa;
-        zfeature_info_t *space_map_histogram =
-            &spa_feature_table[SPA_FEATURE_SPACEMAP_HISTOGRAM];
 
         if (sm == NULL)
                 return;
 
         spa = dmu_objset_spa(sm->sm_os);
-        if (spa_feature_is_enabled(spa, space_map_histogram)) {
+        if (spa_feature_is_enabled(spa, SPA_FEATURE_SPACEMAP_HISTOGRAM)) {
                 dmu_object_info_t doi;
 
                 dmu_object_info_from_db(sm->sm_dbuf, &doi);
                 if (doi.doi_bonus_size != SPACE_MAP_SIZE_V0) {
-                        VERIFY(spa_feature_is_active(spa, space_map_histogram));
-                        spa_feature_decr(spa, space_map_histogram, tx);
+                        VERIFY(spa_feature_is_active(spa,
+                            SPA_FEATURE_SPACEMAP_HISTOGRAM));
+                        spa_feature_decr(spa,
+                            SPA_FEATURE_SPACEMAP_HISTOGRAM, tx);
                 }
         }
 
         VERIFY3U(dmu_object_free(sm->sm_os, space_map_object(sm), tx), ==, 0);
         sm->sm_object = 0;