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>

*** 30,39 ****
--- 30,40 ----
  #include <sys/dsl_dataset.h>
  #include <sys/dsl_dir.h>
  #include <sys/dsl_prop.h>
  #include <sys/dsl_synctask.h>
  #include <sys/dsl_deleg.h>
+ #include <sys/dmu_impl.h>
  #include <sys/spa.h>
  #include <sys/metaslab.h>
  #include <sys/zap.h>
  #include <sys/zio.h>
  #include <sys/arc.h>
*** 86,96 ****
          dd = dmu_buf_get_user(dbuf);
  #ifdef ZFS_DEBUG
          {
                  dmu_object_info_t doi;
                  dmu_object_info_from_db(dbuf, &doi);
!                 ASSERT3U(doi.doi_type, ==, DMU_OT_DSL_DIR);
                  ASSERT3U(doi.doi_bonus_size, >=, sizeof (dsl_dir_phys_t));
          }
  #endif
          if (dd == NULL) {
                  dsl_dir_t *winner;
--- 87,97 ----
          dd = dmu_buf_get_user(dbuf);
  #ifdef ZFS_DEBUG
          {
                  dmu_object_info_t doi;
                  dmu_object_info_from_db(dbuf, &doi);
!                 ASSERT3U(doi.doi_bonus_type, ==, DMU_OT_DSL_DIR);
                  ASSERT3U(doi.doi_bonus_size, >=, sizeof (dsl_dir_phys_t));
          }
  #endif
          if (dd == NULL) {
                  dsl_dir_t *winner;
*** 1349,1354 ****
--- 1350,1362 ----
  
          gethrestime(&t);
          mutex_enter(&dd->dd_lock);
          dd->dd_snap_cmtime = t;
          mutex_exit(&dd->dd_lock);
+ }
+ 
+ void
+ dsl_dir_zapify(dsl_dir_t *dd, dmu_tx_t *tx)
+ {
+         objset_t *mos = dd->dd_pool->dp_meta_objset;
+         dmu_object_zapify(mos, dd->dd_object, DMU_OT_DSL_DIR, tx);
  }