linux-kernel - Re: [PATCH v1 29/36] scsi: scsi_lib: drop nth

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Message-ID: <c32d351a-00f2-4929-b0c1-91aa364e681d@lucifer.local>
Date: Thu, 28 Aug 2025 19:00:27 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, Bart Van Assche <bvanassche@....org>,
        "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
        "Martin K. Petersen" <martin.petersen@...cle.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,
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        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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        linux-mmc@...r.kernel.org, linux-mm@...ck.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-scsi@...r.kernel.org, Marco Elver <elver@...gle.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Michal Hocko <mhocko@...e.com>, Mike Rapoport <rppt@...nel.org>,
        Muchun Song <muchun.song@...ux.dev>, netdev@...r.kernel.org,
        Oscar Salvador <osalvador@...e.de>, Peter Xu <peterx@...hat.com>,
        Robin Murphy <robin.murphy@....com>,
        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 29/36] scsi: scsi_lib: drop nth_page() usage within SG
 entry

On Thu, Aug 28, 2025 at 12:01:33AM +0200, David Hildenbrand wrote:
> It's no longer required to use nth_page() when iterating pages within a
> single SG entry, so let's drop the nth_page() usage.
>
> Reviewed-by: Bart Van Assche <bvanassche@....org>
> Cc: "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>
> Cc: "Martin K. Petersen" <martin.petersen@...cle.com>
> Signed-off-by: David Hildenbrand <david@...hat.com>

LGTM, so:

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

> ---
>  drivers/scsi/scsi_lib.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 0c65ecfedfbd6..d7e42293b8645 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -3148,8 +3148,7 @@ void *scsi_kmap_atomic_sg(struct scatterlist *sgl, int sg_count,
>  	/* Offset starting from the beginning of first page in this sg-entry */
>  	*offset = *offset - len_complete + sg->offset;
>
> -	/* Assumption: contiguous pages can be accessed as "page + i" */

Nice to drop this :)

> -	page = nth_page(sg_page(sg), (*offset >> PAGE_SHIFT));
> +	page = sg_page(sg) + (*offset >> PAGE_SHIFT);
>  	*offset &= ~PAGE_MASK;
>
>  	/* Bytes in this sg-entry from *offset to the end of the page */
> --
> 2.50.1
>