linux-kernel - Re: [PATCH v3 3/5] mm/khugepaged: Convert is_refcount

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Message-ID: <5193bc92-a2f5-496d-9625-af6c7be95d99@redhat.com>
Date:   Mon, 23 Oct 2023 09:05:09 +0200
From:   David Hildenbrand <david@...hat.com>
To:     "Vishal Moola (Oracle)" <vishal.moola@...il.com>,
        linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Subject: Re: [PATCH v3 3/5] mm/khugepaged: Convert is_refcount_suitable() to
 use folios

On 20.10.23 20:33, Vishal Moola (Oracle) wrote:
> Both callers of is_refcount_suitable() have been converted to use
> folios, so convert it to take in a folio. Both callers only operate on
> head pages of folios so mapcount/refcount conversions here are trivial.
> 
> Removes 3 calls to compound head, and removes 315 bytes of kernel text.
> 
> Signed-off-by: Vishal Moola (Oracle) <vishal.moola@...il.com>
> ---
>   mm/khugepaged.c | 14 +++++++-------
>   1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 6c4b5af43371..9efd8ff68f06 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -524,15 +524,15 @@ static void release_pte_pages(pte_t *pte, pte_t *_pte,
>   	}
>   }
>   
> -static bool is_refcount_suitable(struct page *page)
> +static bool is_refcount_suitable(struct folio *folio)
>   {
>   	int expected_refcount;
>   
> -	expected_refcount = total_mapcount(page);
> -	if (PageSwapCache(page))
> -		expected_refcount += compound_nr(page);
> +	expected_refcount = folio_mapcount(folio);
> +	if (folio_test_swapcache(folio))
> +		expected_refcount += folio_nr_pages(folio);
>   
> -	return page_count(page) == expected_refcount;
> +	return folio_ref_count(folio) == expected_refcount;
>   }
>   
>   static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
> @@ -625,7 +625,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
>   		 * but not from this process. The other process cannot write to
>   		 * the page, only trigger CoW.
>   		 */
> -		if (!is_refcount_suitable(&folio->page)) {
> +		if (!is_refcount_suitable(folio)) {
>   			folio_unlock(folio);
>   			result = SCAN_PAGE_COUNT;
>   			goto out;
> @@ -1371,7 +1371,7 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm,
>   		 * has excessive GUP pins (i.e. 512).  Anyway the same check
>   		 * will be done again later the risk seems low.
>   		 */
> -		if (!is_refcount_suitable(&folio->page)) {
> +		if (!is_refcount_suitable(folio)) {
>   			result = SCAN_PAGE_COUNT;
>   			goto out_unmap;
>   		}

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb