linux-kernel - Re: [PATCH RFC 22/35] dma-remap: drop nth_page() in dma_common_contiguous

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Message-ID: <debc61e1-683c-4fcc-9040-d55324f096f7@samsung.com>
Date: Fri, 22 Aug 2025 10:15:01 +0200
From: Marek Szyprowski <m.szyprowski@...sung.com>
To: David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org
Cc: Robin Murphy <robin.murphy@....com>, Alexander Potapenko
	<glider@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, Brendan
	Jackman <jackmanb@...gle.com>, Christoph Lameter <cl@...two.org>, Dennis
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	dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
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	<hannes@...xchg.org>, John Hubbard <jhubbard@...dia.com>,
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	<Liam.Howlett@...cle.com>, Linus Torvalds <torvalds@...ux-foundation.org>,
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	<tj@...nel.org>, virtualization@...ts.linux.dev, Vlastimil Babka
	<vbabka@...e.cz>, wireguard@...ts.zx2c4.com, x86@...nel.org, Zi Yan
	<ziy@...dia.com>
Subject: Re: [PATCH RFC 22/35] dma-remap: drop nth_page() in
 dma_common_contiguous_remap()

On 21.08.2025 22:06, David Hildenbrand wrote:
> dma_common_contiguous_remap() is used to remap an "allocated contiguous
> region". Within a single allocation, there is no need to use nth_page()
> anymore.
>
> Neither the buddy, nor hugetlb, nor CMA will hand out problematic page
> ranges.
>
> Cc: Marek Szyprowski <m.szyprowski@...sung.com>
> Cc: Robin Murphy <robin.murphy@....com>
> Signed-off-by: David Hildenbrand <david@...hat.com>
Acked-by: Marek Szyprowski <m.szyprowski@...sung.com>
> ---
>   kernel/dma/remap.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/dma/remap.c b/kernel/dma/remap.c
> index 9e2afad1c6152..b7c1c0c92d0c8 100644
> --- a/kernel/dma/remap.c
> +++ b/kernel/dma/remap.c
> @@ -49,7 +49,7 @@ void *dma_common_contiguous_remap(struct page *page, size_t size,
>   	if (!pages)
>   		return NULL;
>   	for (i = 0; i < count; i++)
> -		pages[i] = nth_page(page, i);
> +		pages[i] = page++;
>   	vaddr = vmap(pages, count, VM_DMA_COHERENT, prot);
>   	kvfree(pages);
>   

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland