5056 ZFS deadlock on db_mtx and dn_holds
Reviewed by: Will Andrews <willa@spectralogic.com>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Approved by: Dan McDonald <danmcd@omniti.com>

*** 161,183 ****
  dsl_prop_get_ds(dsl_dataset_t *ds, const char *propname,
      int intsz, int numints, void *buf, char *setpoint)
  {
          zfs_prop_t prop = zfs_name_to_prop(propname);
          boolean_t inheritable;
-         boolean_t snapshot;
          uint64_t zapobj;
  
          ASSERT(dsl_pool_config_held(ds->ds_dir->dd_pool));
          inheritable = (prop == ZPROP_INVAL || zfs_prop_inheritable(prop));
-         snapshot = dsl_dataset_is_snapshot(ds);
          zapobj = dsl_dataset_phys(ds)->ds_props_obj;
  
          if (zapobj != 0) {
                  objset_t *mos = ds->ds_dir->dd_pool->dp_meta_objset;
                  int err;
  
!                 ASSERT(snapshot);
  
                  /* Check for a local value. */
                  err = zap_lookup(mos, zapobj, propname, intsz, numints, buf);
                  if (err != ENOENT) {
                          if (setpoint != NULL && err == 0)
--- 161,181 ----
  dsl_prop_get_ds(dsl_dataset_t *ds, const char *propname,
      int intsz, int numints, void *buf, char *setpoint)
  {
          zfs_prop_t prop = zfs_name_to_prop(propname);
          boolean_t inheritable;
          uint64_t zapobj;
  
          ASSERT(dsl_pool_config_held(ds->ds_dir->dd_pool));
          inheritable = (prop == ZPROP_INVAL || zfs_prop_inheritable(prop));
          zapobj = dsl_dataset_phys(ds)->ds_props_obj;
  
          if (zapobj != 0) {
                  objset_t *mos = ds->ds_dir->dd_pool->dp_meta_objset;
                  int err;
  
!                 ASSERT(ds->ds_is_snapshot);
  
                  /* Check for a local value. */
                  err = zap_lookup(mos, zapobj, propname, intsz, numints, buf);
                  if (err != ENOENT) {
                          if (setpoint != NULL && err == 0)
*** 213,223 ****
                          }
                  }
          }
  
          return (dsl_prop_get_dd(ds->ds_dir, propname,
!             intsz, numints, buf, setpoint, snapshot));
  }
  
  /*
   * Register interest in the named property.  We'll call the callback
   * once to notify it of the current property value, and again each time
--- 211,221 ----
                          }
                  }
          }
  
          return (dsl_prop_get_dd(ds->ds_dir, propname,
!             intsz, numints, buf, setpoint, ds->ds_is_snapshot));
  }
  
  /*
   * Register interest in the named property.  We'll call the callback
   * once to notify it of the current property value, and again each time
*** 543,553 ****
          int err;
          uint64_t version = spa_version(ds->ds_dir->dd_pool->dp_spa);
  
          isint = (dodefault(propname, 8, 1, &intval) == 0);
  
!         if (dsl_dataset_is_snapshot(ds)) {
                  ASSERT(version >= SPA_VERSION_SNAP_PROPS);
                  if (dsl_dataset_phys(ds)->ds_props_obj == 0) {
                          dmu_buf_will_dirty(ds->ds_dbuf, tx);
                          dsl_dataset_phys(ds)->ds_props_obj =
                              zap_create(mos,
--- 541,551 ----
          int err;
          uint64_t version = spa_version(ds->ds_dir->dd_pool->dp_spa);
  
          isint = (dodefault(propname, 8, 1, &intval) == 0);
  
!         if (ds->ds_is_snapshot) {
                  ASSERT(version >= SPA_VERSION_SNAP_PROPS);
                  if (dsl_dataset_phys(ds)->ds_props_obj == 0) {
                          dmu_buf_will_dirty(ds->ds_dbuf, tx);
                          dsl_dataset_phys(ds)->ds_props_obj =
                              zap_create(mos,
*** 640,650 ****
          strfree(recvdstr);
  
          if (isint) {
                  VERIFY0(dsl_prop_get_int_ds(ds, propname, &intval));
  
!                 if (dsl_dataset_is_snapshot(ds)) {
                          dsl_prop_cb_record_t *cbr;
                          /*
                           * It's a snapshot; nothing can inherit this
                           * property, so just look for callbacks on this
                           * ds here.
--- 638,648 ----
          strfree(recvdstr);
  
          if (isint) {
                  VERIFY0(dsl_prop_get_int_ds(ds, propname, &intval));
  
!                 if (ds->ds_is_snapshot) {
                          dsl_prop_cb_record_t *cbr;
                          /*
                           * It's a snapshot; nothing can inherit this
                           * property, so just look for callbacks on this
                           * ds here.
*** 758,768 ****
                                  return (E2BIG);
                          }
                  }
          }
  
!         if (dsl_dataset_is_snapshot(ds) && version < SPA_VERSION_SNAP_PROPS) {
                  dsl_dataset_rele(ds, FTAG);
                  return (SET_ERROR(ENOTSUP));
          }
          dsl_dataset_rele(ds, FTAG);
          return (0);
--- 756,766 ----
                                  return (E2BIG);
                          }
                  }
          }
  
!         if (ds->ds_is_snapshot && version < SPA_VERSION_SNAP_PROPS) {
                  dsl_dataset_rele(ds, FTAG);
                  return (SET_ERROR(ENOTSUP));
          }
          dsl_dataset_rele(ds, FTAG);
          return (0);
*** 981,991 ****
          int err = 0;
          char setpoint[MAXNAMELEN];
  
          VERIFY(nvlist_alloc(nvp, NV_UNIQUE_NAME, KM_SLEEP) == 0);
  
!         if (dsl_dataset_is_snapshot(ds))
                  flags |= DSL_PROP_GET_SNAPSHOT;
  
          ASSERT(dsl_pool_config_held(dp));
  
          if (dsl_dataset_phys(ds)->ds_props_obj != 0) {
--- 979,989 ----
          int err = 0;
          char setpoint[MAXNAMELEN];
  
          VERIFY(nvlist_alloc(nvp, NV_UNIQUE_NAME, KM_SLEEP) == 0);
  
!         if (ds->ds_is_snapshot)
                  flags |= DSL_PROP_GET_SNAPSHOT;
  
          ASSERT(dsl_pool_config_held(dp));
  
          if (dsl_dataset_phys(ds)->ds_props_obj != 0) {