linux-kernel - Re: [PATCH 2/5] mm/huge_memory.c: use page->deferred

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Date:   Wed, 28 Apr 2021 08:37:26 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Miaohe Lin <linmiaohe@...wei.com>, akpm@...ux-foundation.org
Cc:     ziy@...dia.com, william.kucharski@...cle.com, willy@...radead.org,
        yang.shi@...ux.alibaba.com, aneesh.kumar@...ux.ibm.com,
        rcampbell@...dia.com, songliubraving@...com,
        kirill.shutemov@...ux.intel.com, riel@...riel.com,
        hannes@...xchg.org, minchan@...nel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 2/5] mm/huge_memory.c: use page->deferred_list


On 4/27/21 7:02 PM, Miaohe Lin wrote:
> Now that we can represent the location of ->deferred_list instead of
> ->mapping + ->index, make use of it to improve readability.

Could you please explain how page->deferred_list and page->mapping
are interchangeable here ?

> 
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> ---
>  mm/huge_memory.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 63ed6b25deaa..76ca1eb2a223 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2868,7 +2868,7 @@ static unsigned long deferred_split_scan(struct shrinker *shrink,
>  	spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
>  	/* Take pin on all head pages to avoid freeing them under us */
>  	list_for_each_safe(pos, next, &ds_queue->split_queue) {
> -		page = list_entry((void *)pos, struct page, mapping);
> +		page = list_entry((void *)pos, struct page, deferred_list);
>  		page = compound_head(page);
>  		if (get_page_unless_zero(page)) {
>  			list_move(page_deferred_list(page), &list);
> @@ -2883,7 +2883,7 @@ static unsigned long deferred_split_scan(struct shrinker *shrink,
>  	spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
>  
>  	list_for_each_safe(pos, next, &list) {
> -		page = list_entry((void *)pos, struct page, mapping);
> +		page = list_entry((void *)pos, struct page, deferred_list);
>  		if (!trylock_page(page))
>  			goto next;
>  		/* split_huge_page() removes page from list on success */
>