Re: [PATCH] mm/page_alloc: Clarify some migratetype fallback code

[Brendan Jackman]

On Tue, 18 Feb 2025 at 21:38, Johannes Weiner <hannes@xxxxxxxxxxx> wrote:
>
> @@ -1930,7 +1929,7 @@ steal_suitable_fallback(struct zone *zone, struct page *page,
/*
 * This can happen due to races and we want to prevent broken
 * highatomic accounting.
 */
>         if (is_migrate_highatomic(block_type))
> -               goto single_page;
> +               return NULL;

Side question: when does this happen? Might have a spooky gap in my
understanding here as I thought the only reason the pageblock typed
was changed without the zone lock held was during memory hotplug.