linux-kernel - Re: [PATCH v1 22/36] dma-remap: drop nth_page() in dma_common_contiguous

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Message-ID: <7cfdbb15-72c1-47e7-b5e0-b8a243f2a516@lucifer.local>
Date: Thu, 28 Aug 2025 18:29:12 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, Marek Szyprowski <m.szyprowski@...sung.com>,
        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 Zhou <dennis@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>, dri-devel@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, iommu@...ts.linux.dev,
        io-uring@...r.kernel.org, Jason Gunthorpe <jgg@...dia.com>,
        Jens Axboe <axboe@...nel.dk>, Johannes Weiner <hannes@...xchg.org>,
        John Hubbard <jhubbard@...dia.com>, kasan-dev@...glegroups.com,
        kvm@...r.kernel.org, "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
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        virtualization@...ts.linux.dev, Vlastimil Babka <vbabka@...e.cz>,
        wireguard@...ts.zx2c4.com, x86@...nel.org, Zi Yan <ziy@...dia.com>
Subject: Re: [PATCH v1 22/36] dma-remap: drop nth_page() in
 dma_common_contiguous_remap()

On Thu, Aug 28, 2025 at 12:01:26AM +0200, 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.
>
> Acked-by: Marek Szyprowski <m.szyprowski@...sung.com>
> Cc: Marek Szyprowski <m.szyprowski@...sung.com>
> Cc: Robin Murphy <robin.murphy@....com>
> Signed-off-by: David Hildenbrand <david@...hat.com>

Nice!

LGTM, so:

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.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);
>
> --
> 2.50.1
>