On Wed, Oct 13, 2021 at 06:33:06PM +0200, David Hildenbrand wrote:

quoted

@@ -9317,6 +9319,7 @@ void __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
 	struct page *page;
 	struct zone *zone;
 	unsigned int order;
+	unsigned int migratetype;
 	unsigned long flags;
 
 	offline_mem_sections(pfn, end_pfn);

@@ -9346,7 +9349,8 @@ void __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
 		BUG_ON(page_count(page));
 		BUG_ON(!PageBuddy(page));
 		order = buddy_order(page);
-		del_page_from_free_list(page, zone, order);
+		migratetype = get_pfnblock_migratetype(page, pfn);

As the free pages are isolated, theoretically this should be
MIGRATE_ISOLATE.

Thanks for noticing that - I somehow missed the fact that pageblock migratetypes
change at runtime, so my patch is wrong. I'm going to have to rework my patch to
store the migratetype of free pages in the page itself.