4101 metaslab_debug should allow for fine-grained control
4102 space_maps should store more information about themselves
4103 space map object blocksize should be increased
4104 ::spa_space no longer works
4105 removing a mirrored log device results in a leaked object
4106 asynchronously load metaslab
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Sebastien Roy <seb@delphix.com>

*** 359,398 ****
          VERIFY3U(0, ==, feature_do_action(spa->spa_meta_objset,
              spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj,
              spa->spa_feat_desc_obj, feature, FEATURE_ACTION_ENABLE, tx));
  }
  
- /*
-  * If the specified feature has not yet been enabled, this function returns
-  * ENOTSUP; otherwise, this function increments the feature's refcount (or
-  * returns EOVERFLOW if the refcount cannot be incremented). This function must
-  * be called from syncing context.
-  */
  void
  spa_feature_incr(spa_t *spa, zfeature_info_t *feature, dmu_tx_t *tx)
  {
          ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES);
          VERIFY3U(0, ==, feature_do_action(spa->spa_meta_objset,
              spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj,
              spa->spa_feat_desc_obj, feature, FEATURE_ACTION_INCR, tx));
  }
  
- /*
-  * If the specified feature has not yet been enabled, this function returns
-  * ENOTSUP; otherwise, this function decrements the feature's refcount (or
-  * returns EOVERFLOW if the refcount is already 0). This function must
-  * be called from syncing context.
-  */
  void
  spa_feature_decr(spa_t *spa, zfeature_info_t *feature, dmu_tx_t *tx)
  {
          ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES);
          VERIFY3U(0, ==, feature_do_action(spa->spa_meta_objset,
              spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj,
              spa->spa_feat_desc_obj, feature, FEATURE_ACTION_DECR, tx));
  }
  
  boolean_t
  spa_feature_is_enabled(spa_t *spa, zfeature_info_t *feature)
  {
          int err;
          uint64_t refcount;
--- 359,408 ----
          VERIFY3U(0, ==, feature_do_action(spa->spa_meta_objset,
              spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj,
              spa->spa_feat_desc_obj, feature, FEATURE_ACTION_ENABLE, tx));
  }
  
  void
  spa_feature_incr(spa_t *spa, zfeature_info_t *feature, dmu_tx_t *tx)
  {
+         ASSERT(dmu_tx_is_syncing(tx));
          ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES);
          VERIFY3U(0, ==, feature_do_action(spa->spa_meta_objset,
              spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj,
              spa->spa_feat_desc_obj, feature, FEATURE_ACTION_INCR, tx));
  }
  
  void
  spa_feature_decr(spa_t *spa, zfeature_info_t *feature, dmu_tx_t *tx)
  {
+         ASSERT(dmu_tx_is_syncing(tx));
          ASSERT3U(spa_version(spa), >=, SPA_VERSION_FEATURES);
          VERIFY3U(0, ==, feature_do_action(spa->spa_meta_objset,
              spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj,
              spa->spa_feat_desc_obj, feature, FEATURE_ACTION_DECR, tx));
  }
  
+ /*
+  * This interface is for debugging only. Normal consumers should use
+  * spa_feature_is_enabled/spa_feature_is_active.
+  */
+ int
+ spa_feature_get_refcount(spa_t *spa, zfeature_info_t *feature)
+ {
+         int err;
+         uint64_t refcount;
+ 
+         if (spa_version(spa) < SPA_VERSION_FEATURES)
+                 return (B_FALSE);
+ 
+         err = feature_get_refcount(spa->spa_meta_objset,
+             spa->spa_feat_for_read_obj, spa->spa_feat_for_write_obj,
+             feature, &refcount);
+         ASSERT(err == 0 || err == ENOTSUP);
+         return (err == 0 ? refcount : 0);
+ }
+ 
  boolean_t
  spa_feature_is_enabled(spa_t *spa, zfeature_info_t *feature)
  {
          int err;
          uint64_t refcount;