linux-kernel - Re: [PATCH] mm/huge_memory: refactor after-split (page) cache code.

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Message-ID: <7CE81DF9-7ACD-4288-A246-BF7A8206CF80@nvidia.com>
Date: Thu, 17 Jul 2025 15:27:08 -0400
From: Zi Yan <ziy@...dia.com>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 David Hildenbrand <david@...hat.com>,
 Antonio Quartulli <antonio@...delbit.com>, linux-mm@...ck.org,
 Hugh Dickins <hughd@...gle.com>, Kirill Shutemov <k.shutemov@...il.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>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/huge_memory: refactor after-split (page) cache code.

On 17 Jul 2025, at 15:22, Dan Carpenter wrote:

> On Thu, Jul 17, 2025 at 11:45:13AM -0400, Zi Yan wrote:
>>
>>>>
>>>> Since we no longer need to make new_folio->index >= end work for anon
>>>> folios, can we drop the end = -1 in the if (is_anon) { ... } branch?
>>>
>>> Sure.
>>
>> A second thought on this one. If I remove end = -1, can static analysis
>> tools understand that end is not used when a folio is anonymous?
>> Probably, I can initialize end to -1 and remove end = -1 in is_anon
>> branch.
>
> Smatch says that "if "mapping" is non-NULL then "end" is initialized"
> and it doesn't trigger a warning.  I don't know how the other checkers
> handle it.

Great. Thank you for running smatch for it.

>
> Btw, the only thing you really have to pay attention to is Clang because
> we treat build warnings as failure.  You're always free to ignore other
> checkers.

Good to know. I will compile my code using clang to get a sense on how
checkers will react to my changes. Thank you for the information.

Best Regards,
Yan, Zi