linux-kernel - Re: [PATCH v6 12/15] highmem: define clear

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Message-ID: <abacf7ba-f6af-40ac-b8b4-afe259546c16@redhat.com>
Date: Tue, 2 Sep 2025 22:20:05 +0200
From: David Hildenbrand <david@...hat.com>
To: Ankur Arora <ankur.a.arora@...cle.com>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, x86@...nel.org
Cc: akpm@...ux-foundation.org, bp@...en8.de, dave.hansen@...ux.intel.com,
 hpa@...or.com, mingo@...hat.com, mjguzik@...il.com, luto@...nel.org,
 peterz@...radead.org, acme@...nel.org, namhyung@...nel.org,
 tglx@...utronix.de, willy@...radead.org, raghavendra.kt@....com,
 boris.ostrovsky@...cle.com, konrad.wilk@...cle.com
Subject: Re: [PATCH v6 12/15] highmem: define clear_highpages()

On 02.09.25 10:08, Ankur Arora wrote:

subject is wrong.

Maybe call it

mm/highmem: introduce clear_user_highpages()

> Define clear_user_highpages() which clears sequentially using the
> single page variant.
> 
> With !CONFIG_HIGHMEM, pages are contiguous so use the range clearing
> primitive clear_user_pages().
> 
> Signed-off-by: Ankur Arora <ankur.a.arora@...cle.com>
> ---
>   include/linux/highmem.h | 12 ++++++++++++
>   1 file changed, 12 insertions(+)
> 
> diff --git a/include/linux/highmem.h b/include/linux/highmem.h
> index 6234f316468c..eeb0b7bc0a22 100644
> --- a/include/linux/highmem.h
> +++ b/include/linux/highmem.h
> @@ -207,6 +207,18 @@ static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
>   }
>   #endif
>   
> +#ifndef clear_user_highpages
> +static inline void clear_user_highpages(struct page *page, unsigned long vaddr,
> +					unsigned int npages)
> +{
> +	if (!IS_ENABLED(CONFIG_HIGHMEM))
> +		clear_user_pages(page_address(page), vaddr, page, npages);
> +	else
> +		for (int i = 0; i < npages; i++)
> +			clear_user_highpage(page+i, vaddr + i * PAGE_SIZE);

Maybe

if (!IS_ENABLED(CONFIG_HIGHMEM)) {
	clear_user_pages(page_address(page), vaddr, page, npages);
	return;
}

...

And maybe then the do while() pattern I suggested for the other variants.


-- 
Cheers

David / dhildenb