linux-kernel - Re: [PATCH 08/16] mm/page_alloc: add missing is_migrate_isolate() check in set_page

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Date:   Fri, 9 Sep 2022 13:31:01 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Miaohe Lin <linmiaohe@...wei.com>, akpm@...ux-foundation.org
Cc:     osalvador@...e.de, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/16] mm/page_alloc: add missing is_migrate_isolate()
 check in set_page_guard()

On 09.09.22 11:24, Miaohe Lin wrote:
> In MIGRATE_ISOLATE case, zone freepage state shouldn't be modified as
> caller will take care of it. Add missing is_migrate_isolate() here to
> avoid possible unbalanced freepage state.
> 
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> ---
>   mm/page_alloc.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index a35ef385d906..94baf33da865 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -873,7 +873,8 @@ static inline bool set_page_guard(struct zone *zone, struct page *page,
>   	INIT_LIST_HEAD(&page->buddy_list);
>   	set_page_private(page, order);
>   	/* Guard pages are not available for any usage */
> -	__mod_zone_freepage_state(zone, -(1 << order), migratetype);
> +	if (!is_migrate_isolate(migratetype))
> +		__mod_zone_freepage_state(zone, -(1 << order), migratetype);
>   
>   	return true;
>   }

Do we have a fixes: tag for this one?

Can it even happen that the pageblock is isolated when we end up in this 
function? IIUC, we'd have an allocation in an isolated pageblock, which 
would be wrong already?

-- 
Thanks,

David / dhildenb