linux-kernel - Re: [PATCH 1/3] mm/page_alloc: correct start page when guard page debug is enabled

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Date:   Thu, 10 Aug 2023 11:10:34 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Kemeng Shi <shikemeng@...weicloud.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        baolin.wang@...ux.alibaba.com, mgorman@...hsingularity.net,
        willy@...radead.org
Subject: Re: [PATCH 1/3] mm/page_alloc: correct start page when guard page
 debug is enabled

On 10.08.23 11:53, Kemeng Shi wrote:
> When guard page debug is enabled and set_page_guard returns success, we miss
> to forward page to point to start of next split range and we will do split
> unexpectedly in page range without target page. Move start page update
> before set_page_guard to fix this.
> 
> Signed-off-by: Kemeng Shi <shikemeng@...weicloud.com>
> ---
>   mm/page_alloc.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 96b7c1a7d1f2..fd93d1396ccd 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -6557,6 +6557,7 @@ static void break_down_buddy_pages(struct zone *zone, struct page *page,
>   			next_page = page;
>   			current_buddy = page + size;
>   		}
> +		page = next_page;
>   
>   		if (set_page_guard(zone, current_buddy, high, migratetype))
>   			continue;
> @@ -6564,7 +6565,6 @@ static void break_down_buddy_pages(struct zone *zone, struct page *page,
>   		if (current_buddy != target) {
>   			add_to_free_list(current_buddy, zone, high, migratetype);
>   			set_buddy_order(current_buddy, high);
> -			page = next_page;
>   		}
>   	}
>   }

Is this worth a Fixes: tag?

What is the user-visible result?

-- 
Cheers,

David / dhildenb