3752 want more verifiable dbuf user eviction
Submitted by:   Justin Gibbs <justing@spectralogic.com>
Submitted by:   Will Andrews <willa@spectralogic.com>

*** 41,56 ****
  
  static uint64_t dsl_dir_space_towrite(dsl_dir_t *dd);
  
  /* ARGSUSED */
  static void
! dsl_dir_evict(dmu_buf_t *db, void *arg)
  {
!         dsl_dir_t *dd = arg;
          dsl_pool_t *dp = dd->dd_pool;
          int t;
  
          for (t = 0; t < TXG_SIZE; t++) {
                  ASSERT(!txg_list_member(&dp->dp_dirty_dirs, dd, t));
                  ASSERT(dd->dd_tempreserved[t] == 0);
                  ASSERT(dd->dd_space_towrite[t] == 0);
          }
--- 41,58 ----
  
  static uint64_t dsl_dir_space_towrite(dsl_dir_t *dd);
  
  /* ARGSUSED */
  static void
! dsl_dir_evict(dmu_buf_user_t *dbu)
  {
!         dsl_dir_t *dd = (dsl_dir_t *)dbu;
          dsl_pool_t *dp = dd->dd_pool;
          int t;
  
+         dd->dd_dbuf = NULL;
+ 
          for (t = 0; t < TXG_SIZE; t++) {
                  ASSERT(!txg_list_member(&dp->dp_dirty_dirs, dd, t));
                  ASSERT(dd->dd_tempreserved[t] == 0);
                  ASSERT(dd->dd_space_towrite[t] == 0);
          }
*** 80,90 ****
          ASSERT(dsl_pool_config_held(dp));
  
          err = dmu_bonus_hold(dp->dp_meta_objset, ddobj, tag, &dbuf);
          if (err != 0)
                  return (err);
!         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);
--- 82,92 ----
          ASSERT(dsl_pool_config_held(dp));
  
          err = dmu_bonus_hold(dp->dp_meta_objset, ddobj, tag, &dbuf);
          if (err != 0)
                  return (err);
!         dd = (dsl_dir_t *)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);
*** 96,106 ****
  
                  dd = kmem_zalloc(sizeof (dsl_dir_t), KM_SLEEP);
                  dd->dd_object = ddobj;
                  dd->dd_dbuf = dbuf;
                  dd->dd_pool = dp;
-                 dd->dd_phys = dbuf->db_data;
                  mutex_init(&dd->dd_lock, NULL, MUTEX_DEFAULT, NULL);
  
                  list_create(&dd->dd_prop_cbs, sizeof (dsl_prop_cb_record_t),
                      offsetof(dsl_prop_cb_record_t, cbr_node));
  
--- 98,107 ----
*** 149,160 ****
                          dd->dd_origin_txg =
                              origin_phys->ds_creation_txg;
                          dmu_buf_rele(origin_bonus, FTAG);
                  }
  
!                 winner = dmu_buf_set_user_ie(dbuf, dd, &dd->dd_phys,
!                     dsl_dir_evict);
                  if (winner) {
                          if (dd->dd_parent)
                                  dsl_dir_rele(dd->dd_parent, dd);
                          mutex_destroy(&dd->dd_lock);
                          kmem_free(dd, sizeof (dsl_dir_t));
--- 150,161 ----
                          dd->dd_origin_txg =
                              origin_phys->ds_creation_txg;
                          dmu_buf_rele(origin_bonus, FTAG);
                  }
  
!                 dmu_buf_init_user(&dd->db_evict, dsl_dir_evict);
!                 winner = (dsl_dir_t *)dmu_buf_set_user_ie(dbuf, &dd->db_evict);
                  if (winner) {
                          if (dd->dd_parent)
                                  dsl_dir_rele(dd->dd_parent, dd);
                          mutex_destroy(&dd->dd_lock);
                          kmem_free(dd, sizeof (dsl_dir_t));