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>

@@ -34,26 +34,24 @@
  * Return an empty bpobj, preferably the empty dummy one (dp_empty_bpobj).
  */
 uint64_t
 bpobj_alloc_empty(objset_t *os, int blocksize, dmu_tx_t *tx)
 {
-        zfeature_info_t *empty_bpobj_feat =
-            &spa_feature_table[SPA_FEATURE_EMPTY_BPOBJ];
         spa_t *spa = dmu_objset_spa(os);
         dsl_pool_t *dp = dmu_objset_pool(os);
 
-        if (spa_feature_is_enabled(spa, empty_bpobj_feat)) {
-                if (!spa_feature_is_active(spa, empty_bpobj_feat)) {
+        if (spa_feature_is_enabled(spa, SPA_FEATURE_EMPTY_BPOBJ)) {
+                if (!spa_feature_is_active(spa, SPA_FEATURE_EMPTY_BPOBJ)) {
                         ASSERT0(dp->dp_empty_bpobj);
                         dp->dp_empty_bpobj =
                             bpobj_alloc(os, SPA_MAXBLOCKSIZE, tx);
                         VERIFY(zap_add(os,
                             DMU_POOL_DIRECTORY_OBJECT,
                             DMU_POOL_EMPTY_BPOBJ, sizeof (uint64_t), 1,
                             &dp->dp_empty_bpobj, tx) == 0);
                 }
-                spa_feature_incr(spa, empty_bpobj_feat, tx);
+                spa_feature_incr(spa, SPA_FEATURE_EMPTY_BPOBJ, tx);
                 ASSERT(dp->dp_empty_bpobj != 0);
                 return (dp->dp_empty_bpobj);
         } else {
                 return (bpobj_alloc(os, blocksize, tx));
         }

@@ -60,16 +58,15 @@
 }
 
 void
 bpobj_decr_empty(objset_t *os, dmu_tx_t *tx)
 {
-        zfeature_info_t *empty_bpobj_feat =
-            &spa_feature_table[SPA_FEATURE_EMPTY_BPOBJ];
         dsl_pool_t *dp = dmu_objset_pool(os);
 
-        spa_feature_decr(dmu_objset_spa(os), empty_bpobj_feat, tx);
-        if (!spa_feature_is_active(dmu_objset_spa(os), empty_bpobj_feat)) {
+        spa_feature_decr(dmu_objset_spa(os), SPA_FEATURE_EMPTY_BPOBJ, tx);
+        if (!spa_feature_is_active(dmu_objset_spa(os),
+            SPA_FEATURE_EMPTY_BPOBJ)) {
                 VERIFY3U(0, ==, zap_remove(dp->dp_meta_objset,
                     DMU_POOL_DIRECTORY_OBJECT,
                     DMU_POOL_EMPTY_BPOBJ, tx));
                 VERIFY3U(0, ==, dmu_object_free(os, dp->dp_empty_bpobj, tx));
                 dp->dp_empty_bpobj = 0;

@@ -263,10 +260,11 @@
         err = dmu_object_info(bpo->bpo_os, bpo->bpo_phys->bpo_subobjs, &doi);
         if (err) {
                 mutex_exit(&bpo->bpo_lock);
                 return (err);
         }
+        ASSERT3U(doi.doi_type, ==, DMU_OT_BPOBJ_SUBOBJ);
         epb = doi.doi_data_block_size / sizeof (uint64_t);
 
         for (i = bpo->bpo_phys->bpo_num_subobjs - 1; i >= 0; i--) {
                 uint64_t *objarray;
                 uint64_t offset, blkoff;