When rolling back the initial instant ADD COLUMN, restore the root page to non-instant format

storage/innobase/include/page0page.ic

@@ -1138,6 +1138,7 @@ page_set_instant(page_t* page, unsigned n, mtr_t* mtr)
 	ut_ad(n > 0);
 	ut_ad(n < 1U << 10);
 	uint16_t i = page_header_get_field(page, PAGE_INSTANT);
+	ut_ad(i <= PAGE_NO_DIRECTION);
 	i |= n << 6;
 	mlog_write_ulint(PAGE_HEADER + PAGE_INSTANT + page, i,
 			 MLOG_2BYTES, mtr);

storage/innobase/row/row0uins.cc

@@ -78,6 +78,7 @@ row_undo_ins_remove_clust_rec(
 
 	mtr.start();
 	if (index->table->is_temporary()) {
+		ut_ad(node->rec_type == TRX_UNDO_INSERT_REC);
 		mtr.set_log_mode(MTR_LOG_NO_REDO);
 	} else {
 		mtr.set_named_space(index->space);
@@ -122,9 +123,9 @@ row_undo_ins_remove_clust_rec(
 
 	switch (node->table->id) {
 	case DICT_INDEXES_ID:
-
 		ut_ad(!online);
 		ut_ad(node->trx->dict_operation_lock_mode == RW_X_LATCH);
+		ut_ad(node->rec_type == TRX_UNDO_INSERT_REC);
 
 		dict_drop_index_tree(
 			btr_pcur_get_rec(&node->pcur), &(node->pcur), &mtr);
@@ -145,6 +146,7 @@ row_undo_ins_remove_clust_rec(
 		been rolled back. */
 		ut_ad(!online);
 		ut_ad(node->trx->dict_operation_lock_mode == RW_X_LATCH);
+		ut_ad(node->rec_type == TRX_UNDO_INSERT_REC);
 		const rec_t* rec = btr_pcur_get_rec(&node->pcur);
 		if (rec_get_n_fields_old(rec)
 		    != DICT_NUM_FIELDS__SYS_COLUMNS) {
@@ -254,6 +256,27 @@ row_undo_ins_remove_clust_rec(
 
 func_exit:
 	btr_pcur_commit_specify_mtr(&node->pcur, &mtr);
+	if (err == DB_SUCCESS && node->rec_type == TRX_UNDO_INSERT_DEFAULT) {
+		/* When rolling back the very first instant ADD COLUMN
+		operation, reset the root page to the basic state. */
+		ut_ad(!index->table->is_temporary());
+		mtr.start();
+		if (page_t* root = btr_root_get(index, &mtr)) {
+			byte* page_type = root + FIL_PAGE_TYPE;
+			ut_ad(mach_read_from_2(page_type)
+			      == FIL_PAGE_TYPE_INSTANT
+			      || mach_read_from_2(page_type)
+			      == FIL_PAGE_INDEX);
+			mtr.set_named_space(index->space);
+			mlog_write_ulint(page_type, FIL_PAGE_INDEX,
+					 MLOG_2BYTES, &mtr);
+			byte* instant = PAGE_INSTANT + PAGE_HEADER + root;
+			mlog_write_ulint(instant,
+					 page_ptr_get_direction(instant + 1),
+					 MLOG_2BYTES, &mtr);
+		}
+		mtr.commit();
+	}
 
 	return(err);
 }
@@ -567,6 +590,11 @@ row_undo_ins(
 
 	node->index = dict_table_get_first_index(node->table);
 	ut_ad(dict_index_is_clust(node->index));
+
+	switch (node->rec_type) {
+	default:
+		ut_ad(!"wrong undo record type");
+	case TRX_UNDO_INSERT_REC:
 		/* Skip the clustered index (the first index) */
 		node->index = dict_table_get_next_index(node->index);
 
@@ -574,11 +602,16 @@ row_undo_ins(
 
 		err = row_undo_ins_remove_sec_rec(node, thr);
 
-	if (err == DB_SUCCESS) {
+		if (err != DB_SUCCESS) {
+			break;
+		}
 
+		/* fall through */
+	case TRX_UNDO_INSERT_DEFAULT:
 		log_free_check();
 
 		if (node->table->id == DICT_INDEXES_ID) {
+			ut_ad(node->rec_type == TRX_UNDO_INSERT_REC);
 
 			if (!dict_locked) {
 				mutex_enter(&dict_sys->mutex);