Revert "dmu_objset_userquota_get_ids uses dn_bonus unsafely"

This reverts commit 5f8e1e8.  It
was determined that this patch introduced the quota regression
described in #3789.

Signed-off-by: Tim Chase <[email protected]>
Signed-off-by: Ned Bass <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Issue #3443
Issue #3789

module/zfs/dmu_objset.c

@@ -1342,7 +1342,6 @@ dmu_objset_userquota_get_ids(dnode_t *dn, boolean_t before, dmu_tx_t *tx)
 	int flags = dn->dn_id_flags;
 	int error;
 	boolean_t have_spill = B_FALSE;
-	boolean_t have_bonus = B_FALSE;
 
 	if (!dmu_objset_userused_enabled(dn->dn_objset))
 		return;
@@ -1354,21 +1353,8 @@ dmu_objset_userquota_get_ids(dnode_t *dn, boolean_t before, dmu_tx_t *tx)
 	if (before && dn->dn_bonuslen != 0)
 		data = DN_BONUS(dn->dn_phys);
 	else if (!before && dn->dn_bonuslen != 0) {
-		db = dn->dn_bonus;
-		if (db != NULL) {
-			if (!RW_WRITE_HELD(&dn->dn_struct_rwlock)) {
-				have_bonus = dbuf_try_add_ref((dmu_buf_t *)db,
-				    dn->dn_objset, dn->dn_object,
-				    DMU_BONUS_BLKID, FTAG);
-
-				/*
-				 * The hold will fail if the buffer is
-				 * being evicted due to unlink, in which
-				 * case nothing needs to be done.
-				 */
-				if (!have_bonus)
-					return;
-			}
+		if (dn->dn_bonus) {
+			db = dn->dn_bonus;
 			mutex_enter(&db->db_mtx);
 			data = dmu_objset_userquota_find_data(db, tx);
 		} else {
@@ -1443,7 +1429,7 @@ dmu_objset_userquota_get_ids(dnode_t *dn, boolean_t before, dmu_tx_t *tx)
 		dn->dn_id_flags |= DN_ID_CHKED_BONUS;
 	}
 	mutex_exit(&dn->dn_mtx);
-	if (have_spill || have_bonus)
+	if (have_spill)
 		dmu_buf_rele((dmu_buf_t *)db, FTAG);
 }