linux-kernel - Re: [PATCH v2 4/4] mm/huge_memory: fix folio split stats counting

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Message-ID: <a4bdd286-ebbf-49a2-9b98-fa5197e1a6f3@kernel.org>
Date: Mon, 24 Nov 2025 11:45:18 +0100
From: "David Hildenbrand (Red Hat)" <david@...nel.org>
To: Zi Yan <ziy@...dia.com>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 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>, Lance Yang <lance.yang@...ux.dev>,
 Miaohe Lin <linmiaohe@...wei.com>, Naoya Horiguchi
 <nao.horiguchi@...il.com>, Wei Yang <richard.weiyang@...il.com>,
 Balbir Singh <balbirs@...dia.com>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/4] mm/huge_memory: fix folio split stats counting

On 11/22/25 03:55, Zi Yan wrote:
> The "return <error code>" statements for error checks at the beginning of
> __folio_split() skip necessary count_vm_event() and count_mthp_stat() at
> the end of the function. Fix these by replacing them with
> "ret = <error code>; goto out;".
> 
> Signed-off-by: Zi Yan <ziy@...dia.com>
> ---
>   mm/huge_memory.c | 14 +++++++++-----
>   1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index ebc3ba0907fd..a42c4f29ce4f 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -3954,16 +3954,20 @@ static int __folio_split(struct folio *folio, unsigned int new_order,
>   	VM_WARN_ON_ONCE_FOLIO(!folio_test_locked(folio), folio);
>   	VM_WARN_ON_ONCE_FOLIO(!folio_test_large(folio), folio);
>   
> -	if (folio != page_folio(split_at) || folio != page_folio(lock_at))
> -		return -EINVAL;
> +	if (folio != page_folio(split_at) || folio != page_folio(lock_at)) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
>   
> -	if (new_order >= old_order)
> -		return -EINVAL;
> +	if (new_order >= old_order) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
>   
>   	ret = folio_check_splittable(folio, new_order, split_type,
>   				     /* warn = */ true);
>   	if (ret)
> -		return ret;
> +		goto out;
>   
>   	if (is_anon) {
>   		/*

I guess this is not Fixes:/stable material. Wonder if such early (mostly 
-EINVAL etc) checks were at some point not intended to be counted.

In any case

Acked-by: David Hildenbrand (Red Hat) <david@...nel.org>

-- 
Cheers

David