linux-kernel - Re: [PATCH *-next 01/18] mm/mmu_gather: Remove needless return in void API tlb_remove

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Message-ID: <a6dfff9c-ab0e-4308-81e7-62d8ea04d62b@icloud.com>
Date: Wed, 26 Feb 2025 19:45:34 +0800
From: Zijun Hu <zijun_hu@...oud.com>
To: David Howells <dhowells@...hat.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Will Deacon <will@...nel.org>, "Aneesh Kumar K.V" <aneesh.kumar@...nel.org>,
 Andrew Morton <akpm@...ux-foundation.org>, Nick Piggin <npiggin@...il.com>,
 Arnd Bergmann <arnd@...db.de>, Thomas Gleixner <tglx@...utronix.de>,
 Herbert Xu <herbert@...dor.apana.org.au>,
 "David S. Miller" <davem@...emloft.net>,
 "Rafael J. Wysocki" <rafael@...nel.org>, Danilo Krummrich <dakr@...nel.org>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
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 Jamal Hadi Salim <jhs@...atatu.com>, Cong Wang <xiyou.wangcong@...il.com>,
 Jiri Pirko <jiri@...nulli.us>, Jason Gunthorpe <jgg@...pe.ca>,
 Leon Romanovsky <leon@...nel.org>, Linus Walleij <linus.walleij@...aro.org>,
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 Thomas Graf <tgraf@...g.ch>, Christoph Hellwig <hch@....de>,
 Marek Szyprowski <m.szyprowski@...sung.com>,
 Robin Murphy <robin.murphy@....com>,
 Miquel Raynal <miquel.raynal@...tlin.com>,
 Richard Weinberger <richard@....at>, Vignesh Raghavendra <vigneshr@...com>,
 linux-arch@...r.kernel.org, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
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 linux-mtd@...ts.infradead.org
Subject: Re: [PATCH *-next 01/18] mm/mmu_gather: Remove needless return in
 void API tlb_remove_page()

On 2025/2/25 23:16, David Howells wrote:
> Zijun Hu <zijun_hu@...oud.com> wrote:
> 
>>>>  static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
>>>>  {
>>>> -	return tlb_remove_page_size(tlb, page, PAGE_SIZE);
>>>> +	tlb_remove_page_size(tlb, page, PAGE_SIZE);
>>>>  }
>>> So I don't mind removing it, but note that that return enforces
>>> tlb_remove_page_size() has void return type.
>>>
>>
>> tlb_remove_page_size() is void function already. (^^)
> 
> That may be true... for now.  But if that is changed in the future, then you
> will get an error indicating something you need to go and look at... so in
> that regard, it's *better* to do this ;-)
> 

i understand your point.

if the callee tlb_remove_page_size() is in the same module with the
caller tlb_remove_page. it is meaningless to watch the callee's return type.

otherwise, provided the callee is a API which is provided by other
module author. once the author changes the API's return type, he/she
must take effort to cleanup this weird and lots of usages, that is not
nice for API provider.

this is a common issue. i will list my reasons why this usage is not
good in cover letter of this series
> David
>