Fix test failures

btr_page_reorganize_low(), btr_page_empty(): Create the page in the
flexible format if needed.

page_copy_rec_list_end_no_locks(): Adjust for dual-format tables.
FIXME: It may still be necessary to support conversion. Perhaps
the caller should invoke btr_page_reorganize_low() to do that.

mysql-test/main/disabled.def

@@ -22,4 +22,3 @@ innodb_bug12902967       : broken upstream
 file_contents            : MDEV-6526 these files are not installed anymore
 max_statement_time       : cannot possibly work, depends on timing
 connect-abstract         : waiting for libmariadb update
-function_defaults_innodb : MDEV-17520 work in progress (crashing test)

mysql-test/suite/innodb/disabled.def

@@ -11,4 +11,3 @@
 ##############################################################################
 
 create-index-debug : MDEV-13680 InnoDB may crash when btr_page_alloc() fails
-instant_alter_null : MDEV-17520 work in progress (crashing test)

mysql-test/suite/innodb/r/instant_alter_null.result

@@ -37,10 +37,10 @@ TABLE_ID	b	2	6	1027	4
 TABLE_ID	c	3	6	1027	4
 select * from t;
 id	a	b	c
-4	NULL	NULL	NULL
-3	NULL	NULL	3
-2	NULL	2	2
 1	1	1	1
+2	NULL	2	2
+3	NULL	NULL	3
+4	NULL	NULL	NULL
 check table t;
 Table	Op	Msg_type	Msg_text
 test.t	check	status	OK

storage/innobase/btr/btr0btr.cc

@@ -1606,7 +1606,9 @@ btr_page_reorganize_low(
 	/* Recreate the page: note that global data on page (possible
 	segment headers, next page-field, etc.) is preserved intact */
 
-	page_create(block, mtr, dict_table_is_comp(index->table), is_spatial);
+	page_create(block, mtr, index->table->not_redundant()
+		    && (!page_is_leaf(page) || !index->dual_format()),
+		    is_spatial);
 
 	/* Copy the records from the temporary space to the recreated page;
 	do not copy the lock bits yet */
@@ -1920,9 +1922,11 @@ btr_page_empty(
 		: 0;
 
 	if (page_zip) {
+		ut_ad(!index->table->dual_format());
 		page_create_zip(block, index, level, autoinc, mtr);
 	} else {
-		page_create(block, mtr, page_is_comp(block->frame),
+		page_create(block, mtr, index->table->not_redundant()
+			    && (level || !index->dual_format()),
 			    dict_index_is_spatial(index));
 		btr_page_set_level(page, NULL, level, mtr);
 		if (autoinc) {

storage/innobase/page/page0page.cc

@@ -556,9 +556,7 @@ page_copy_rec_list_end_no_locks(
 	dict_index_t*	index,		/*!< in: record descriptor */
 	mtr_t*		mtr)		/*!< in: mtr */
 {
-	page_t*		new_page	= buf_block_get_frame(new_block);
 	page_cur_t	cur1;
-	rec_t*		cur2;
 	mem_heap_t*	heap		= NULL;
 	ulint		offsets_[REC_OFFS_NORMAL_SIZE];
 	ulint*		offsets		= offsets_;
@@ -573,13 +571,17 @@ page_copy_rec_list_end_no_locks(
 
 	btr_assert_not_corrupted(new_block, index);
 	// FIXME: If needed, copy and convert to REC_FMT_LEAF_FLEXIBLE
-	ut_a(page_is_comp(new_page) == page_rec_is_comp(rec));
-	ut_a(mach_read_from_2(new_page + srv_page_size - 10) == (ulint)
-	     (page_is_comp(new_page) ? PAGE_NEW_INFIMUM : PAGE_OLD_INFIMUM));
+	ut_ad(page_is_comp(new_block->frame) == page_rec_is_comp(rec)
+	      || index->dual_format());
+	ut_ad(mach_read_from_2(new_block->frame + srv_page_size - 10) ==
+	      (page_is_comp(new_block->frame)
+	       ? PAGE_NEW_INFIMUM : PAGE_OLD_INFIMUM));
 	const rec_fmt_t format = page_is_leaf(block->frame)
-		? REC_FMT_LEAF : REC_FMT_NODE_PTR;
+		? (page_is_comp(block->frame)
+		   ? REC_FMT_LEAF : REC_FMT_LEAF_FLEXIBLE)
+		: REC_FMT_NODE_PTR;
 
-	cur2 = page_get_infimum_rec(buf_block_get_frame(new_block));
+	rec_t* cur2 = page_get_infimum_rec(new_block->frame);
 
 	/* Copy records from the original page to the new page */