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>

*** 472,493 ****
  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)) {
                  bonuslen = sizeof (space_map_phys_t);
                  ASSERT3U(bonuslen, <=, dmu_bonus_max());
          } else {
                  bonuslen = SPACE_MAP_SIZE_V0;
          }
--- 472,491 ----
  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);
          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, SPA_FEATURE_SPACEMAP_HISTOGRAM)) {
                  bonuslen = sizeof (space_map_phys_t);
                  ASSERT3U(bonuslen, <=, dmu_bonus_max());
          } else {
                  bonuslen = SPACE_MAP_SIZE_V0;
          }
*** 523,539 ****
  
  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);
                  bonuslen = sizeof (space_map_phys_t);
                  ASSERT3U(bonuslen, <=, dmu_bonus_max());
          } else {
                  bonuslen = SPACE_MAP_SIZE_V0;
          }
--- 521,535 ----
  
  uint64_t
  space_map_alloc(objset_t *os, dmu_tx_t *tx)
  {
          spa_t *spa = dmu_objset_spa(os);
          uint64_t object;
          int bonuslen;
  
!         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;
          }
*** 547,570 ****
  
  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)) {
                  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);
                  }
          }
  
          VERIFY3U(dmu_object_free(sm->sm_os, space_map_object(sm), tx), ==, 0);
          sm->sm_object = 0;
--- 543,566 ----
  
  void
  space_map_free(space_map_t *sm, dmu_tx_t *tx)
  {
          spa_t *spa;
  
          if (sm == NULL)
                  return;
  
          spa = dmu_objset_spa(sm->sm_os);
!         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,
!                             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;