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

*** 239,254 ****
          return (B_TRUE);
  }
  
  /* ARGSUSED */
  static void
! dsl_dataset_evict(dmu_buf_t *db, void *dsv)
  {
-         dsl_dataset_t *ds = dsv;
  
          ASSERT(ds->ds_owner == NULL);
  
          unique_remove(ds->ds_fsid_guid);
  
          if (ds->ds_objset != NULL)
                  dmu_objset_evict(ds->ds_objset);
  
--- 239,255 ----
          return (B_TRUE);
  }
  
  /* ARGSUSED */
  static void
! dsl_dataset_evict_impl(dsl_dataset_t *ds, boolean_t evict_deadlist)
  {
  
          ASSERT(ds->ds_owner == NULL);
  
+         ds->ds_dbuf = NULL;
+ 
          unique_remove(ds->ds_fsid_guid);
  
          if (ds->ds_objset != NULL)
                  dmu_objset_evict(ds->ds_objset);
  
*** 256,266 ****
                  dsl_dataset_rele(ds->ds_prev, ds);
                  ds->ds_prev = NULL;
          }
  
          bplist_destroy(&ds->ds_pending_deadlist);
!         if (ds->ds_phys->ds_deadlist_obj != 0)
                  dsl_deadlist_close(&ds->ds_deadlist);
          if (ds->ds_dir)
                  dsl_dir_rele(ds->ds_dir, ds);
  
          ASSERT(!list_link_active(&ds->ds_synced_link));
--- 257,267 ----
                  dsl_dataset_rele(ds->ds_prev, ds);
                  ds->ds_prev = NULL;
          }
  
          bplist_destroy(&ds->ds_pending_deadlist);
!         if (evict_deadlist)
                  dsl_deadlist_close(&ds->ds_deadlist);
          if (ds->ds_dir)
                  dsl_dir_rele(ds->ds_dir, ds);
  
          ASSERT(!list_link_active(&ds->ds_synced_link));
*** 270,279 ****
--- 271,287 ----
          refcount_destroy(&ds->ds_longholds);
  
          kmem_free(ds, sizeof (dsl_dataset_t));
  }
  
+ /* ARGSUSED */
+ static void
+ dsl_dataset_evict(dmu_buf_user_t *dbu)
+ {
+         dsl_dataset_evict_impl((dsl_dataset_t *)dbu, B_TRUE);
+ }
+ 
  int
  dsl_dataset_get_snapname(dsl_dataset_t *ds)
  {
          dsl_dataset_phys_t *headphys;
          int err;
*** 357,374 ****
          /* Make sure dsobj has the correct object type. */
          dmu_object_info_from_db(dbuf, &doi);
          if (doi.doi_type != DMU_OT_DSL_DATASET)
                  return (SET_ERROR(EINVAL));
  
!         ds = dmu_buf_get_user(dbuf);
          if (ds == NULL) {
                  dsl_dataset_t *winner = NULL;
  
                  ds = kmem_zalloc(sizeof (dsl_dataset_t), KM_SLEEP);
                  ds->ds_dbuf = dbuf;
                  ds->ds_object = dsobj;
-                 ds->ds_phys = dbuf->db_data;
  
                  mutex_init(&ds->ds_lock, NULL, MUTEX_DEFAULT, NULL);
                  mutex_init(&ds->ds_opening_lock, NULL, MUTEX_DEFAULT, NULL);
                  mutex_init(&ds->ds_sendstream_lock, NULL, MUTEX_DEFAULT, NULL);
                  refcount_create(&ds->ds_longholds);
--- 365,381 ----
          /* Make sure dsobj has the correct object type. */
          dmu_object_info_from_db(dbuf, &doi);
          if (doi.doi_type != DMU_OT_DSL_DATASET)
                  return (SET_ERROR(EINVAL));
  
!         ds = (dsl_dataset_t *)dmu_buf_get_user(dbuf);
          if (ds == NULL) {
                  dsl_dataset_t *winner = NULL;
  
                  ds = kmem_zalloc(sizeof (dsl_dataset_t), KM_SLEEP);
                  ds->ds_dbuf = dbuf;
                  ds->ds_object = dsobj;
  
                  mutex_init(&ds->ds_lock, NULL, MUTEX_DEFAULT, NULL);
                  mutex_init(&ds->ds_opening_lock, NULL, MUTEX_DEFAULT, NULL);
                  mutex_init(&ds->ds_sendstream_lock, NULL, MUTEX_DEFAULT, NULL);
                  refcount_create(&ds->ds_longholds);
*** 424,435 ****
                          }
                  } else {
                          ds->ds_reserved = ds->ds_quota = 0;
                  }
  
!                 if (err != 0 || (winner = dmu_buf_set_user_ie(dbuf, ds,
!                     &ds->ds_phys, dsl_dataset_evict)) != NULL) {
                          bplist_destroy(&ds->ds_pending_deadlist);
                          dsl_deadlist_close(&ds->ds_deadlist);
                          if (ds->ds_prev)
                                  dsl_dataset_rele(ds->ds_prev, ds);
                          dsl_dir_rele(ds->ds_dir, ds);
--- 431,446 ----
                          }
                  } else {
                          ds->ds_reserved = ds->ds_quota = 0;
                  }
  
!                 dmu_buf_init_user(&ds->db_evict, dsl_dataset_evict);
!                 if (err == 0)
!                         winner = (dsl_dataset_t *)
!                             dmu_buf_set_user_ie(dbuf, &ds->db_evict);
! 
!                 if (err || winner) {
                          bplist_destroy(&ds->ds_pending_deadlist);
                          dsl_deadlist_close(&ds->ds_deadlist);
                          if (ds->ds_prev)
                                  dsl_dataset_rele(ds->ds_prev, ds);
                          dsl_dir_rele(ds->ds_dir, ds);
*** 630,640 ****
          mutex_exit(&ds->ds_lock);
          dsl_dataset_long_rele(ds, tag);
          if (ds->ds_dbuf != NULL)
                  dsl_dataset_rele(ds, tag);
          else
!                 dsl_dataset_evict(NULL, ds);
  }
  
  boolean_t
  dsl_dataset_tryown(dsl_dataset_t *ds, void *tag)
  {
--- 641,651 ----
          mutex_exit(&ds->ds_lock);
          dsl_dataset_long_rele(ds, tag);
          if (ds->ds_dbuf != NULL)
                  dsl_dataset_rele(ds, tag);
          else
!                 dsl_dataset_evict_impl(ds, B_FALSE);
  }
  
  boolean_t
  dsl_dataset_tryown(dsl_dataset_t *ds, void *tag)
  {