linux-kernel - Re: [PATCH 1/9] mm/compaction: use correct list in move_freelist

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Message-Id: <20230805101109.740fdc21418d0753c4658df1@linux-foundation.org>
Date:   Sat, 5 Aug 2023 10:11:09 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Kemeng Shi <shikemeng@...weicloud.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        baolin.wang@...ux.alibaba.com, mgorman@...hsingularity.net,
        david@...hat.com
Subject: Re: [PATCH 1/9] mm/compaction: use correct list in
 move_freelist_{head}/{tail}

On Sat,  5 Aug 2023 19:07:03 +0800 Kemeng Shi <shikemeng@...weicloud.com> wrote:

> The freepage is chained with buddy_list in freelist head. Use buddy_list
> instead of lru to correct the list operation.
> 
> ...
>
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1395,8 +1395,8 @@ move_freelist_head(struct list_head *freelist, struct page *freepage)
>  {
>  	LIST_HEAD(sublist);
>  
> -	if (!list_is_last(freelist, &freepage->lru)) {
> -		list_cut_before(&sublist, freelist, &freepage->lru);
> +	if (!list_is_last(freelist, &freepage->buddy_list)) {
> +		list_cut_before(&sublist, freelist, &freepage->buddy_list);
>  		list_splice_tail(&sublist, freelist);
>  	}
>  }
> @@ -1412,8 +1412,8 @@ move_freelist_tail(struct list_head *freelist, struct page *freepage)
>  {
>  	LIST_HEAD(sublist);
>  
> -	if (!list_is_first(freelist, &freepage->lru)) {
> -		list_cut_position(&sublist, freelist, &freepage->lru);
> +	if (!list_is_first(freelist, &freepage->buddy_list)) {
> +		list_cut_position(&sublist, freelist, &freepage->buddy_list);
>  		list_splice_tail(&sublist, freelist);
>  	}
>  }

This looks like a significant error.  Can we speculate about the
possible runtime effects?