linux-kernel - Re: [PATCH v1 14/36] mm/mm/percpu-km: drop nth

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Message-ID: <2ee63b0d-f5d8-41ee-ae7a-0e917638cebc@lucifer.local>
Date: Thu, 28 Aug 2025 16:43:55 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, 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>,
        linux-arm-kernel@...s.com, linux-arm-kernel@...ts.infradead.org,
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        Suren Baghdasaryan <surenb@...gle.com>, Tejun Heo <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 v1 14/36] mm/mm/percpu-km: drop nth_page() usage within
 single allocation

On Thu, Aug 28, 2025 at 12:01:18AM +0200, David Hildenbrand wrote:
> We're allocating a higher-order page from the buddy. For these pages
> (that are guaranteed to not exceed a single memory section) there is no
> need to use nth_page().
>
> Signed-off-by: David Hildenbrand <david@...hat.com>

Oh hello! Now it all comes together :)

nth_tag():

LGTM, so:

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

> ---
>  mm/percpu-km.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/percpu-km.c b/mm/percpu-km.c
> index fe31aa19db81a..4efa74a495cb6 100644
> --- a/mm/percpu-km.c
> +++ b/mm/percpu-km.c
> @@ -69,7 +69,7 @@ static struct pcpu_chunk *pcpu_create_chunk(gfp_t gfp)
>  	}
>
>  	for (i = 0; i < nr_pages; i++)
> -		pcpu_set_page_chunk(nth_page(pages, i), chunk);
> +		pcpu_set_page_chunk(pages + i, chunk);
>
>  	chunk->data = pages;
>  	chunk->base_addr = page_address(pages);
> --
> 2.50.1
>