linux-kernel - Re: [PATCH 2/4] mm/huge_memory: move to next folio after folio

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Message-ID: <60b6c458-e3d0-4123-9815-44e8e8ae0e60@redhat.com>
Date: Wed, 6 Aug 2025 14:47:12 +0200
From: David Hildenbrand <david@...hat.com>
To: Zi Yan <ziy@...dia.com>, linux-mm@...ck.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>, Nico Pache <npache@...hat.com>,
 Ryan Roberts <ryan.roberts@....com>, Dev Jain <dev.jain@....com>,
 Barry Song <baohua@...nel.org>, Vlastimil Babka <vbabka@...e.cz>,
 Mike Rapoport <rppt@...nel.org>, Suren Baghdasaryan <surenb@...gle.com>,
 Michal Hocko <mhocko@...e.com>, Shuah Khan <shuah@...nel.org>,
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 2/4] mm/huge_memory: move to next folio after
 folio_split() succeeds.

On 06.08.25 04:20, Zi Yan wrote:
> Current behavior is to move to next PAGE_SIZE and split, but that makes it
> hard to check after-split folio orders. This is a preparation patch to
> allow more precise split_huge_page_test check in an upcoming commit.
> 
> split_folio_to_order() part is not changed, since split_pte_mapped_thp test
> relies on its current behavior.
> 
> Signed-off-by: Zi Yan <ziy@...dia.com>
> ---

[...]

>   
> +		nr_pages = folio_nr_pages(folio);
> +
>   		if (!folio_test_anon(folio)) {
>   			mapping = folio->mapping;
>   			target_order = max(new_order,
> @@ -4385,15 +4388,16 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
>   		if (!folio_test_anon(folio) && folio->mapping != mapping)
>   			goto unlock;
>   
> -		if (in_folio_offset < 0 ||
> -		    in_folio_offset >= folio_nr_pages(folio)) {
> +		if (in_folio_offset < 0 || in_folio_offset >= nr_pages) {
>   			if (!split_folio_to_order(folio, target_order))
>   				split++;
>   		} else {
> -			struct page *split_at = folio_page(folio,
> -							   in_folio_offset);
> -			if (!folio_split(folio, target_order, split_at, NULL))
> +			struct page *split_at =
> +				folio_page(folio, in_folio_offset);

Can we add an empty line here, and just have this in a single line, 
please (feel free to exceed 80chars if it makes the code look less ugly).

> +			if (!folio_split(folio, target_order, split_at, NULL)) {
>   				split++;
> +				addr += PAGE_SIZE * nr_pages;

Hm, but won't we do another "addr += PAGE_SIZE" in the for loop?

-- 
Cheers,

David / dhildenb