dmu_buf_set_user_ie
winner = dmu_buf_set_user_ie(dbuf, &ds->ds_dbu);
winner = dmu_buf_set_user_ie(dbuf, &dd->dd_dbu);
winner = dmu_buf_set_user_ie(db, &handle->sa_dbu);
void *dmu_buf_set_user_ie(dmu_buf_t *db, dmu_buf_user_t *user);