linux-kernel - Re: [PATCH RFC 24/35] ata: libata-eh: drop nth

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Message-ID: <3812ed9e-2a47-4c1c-bd69-f37768e62ad3@kernel.org>
Date: Fri, 22 Aug 2025 10:59:15 +0900
From: Damien Le Moal <dlemoal@...nel.org>
To: David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org
Cc: Niklas Cassel <cassel@...nel.org>, Alexander Potapenko
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Subject: Re: [PATCH RFC 24/35] ata: libata-eh: drop nth_page() usage within SG
 entry

On 8/22/25 05:06, 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.
> 
> Cc: Damien Le Moal <dlemoal@...nel.org>
> Cc: Niklas Cassel <cassel@...nel.org>
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>  drivers/ata/libata-sff.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/ata/libata-sff.c b/drivers/ata/libata-sff.c
> index 7fc407255eb46..9f5d0f9f6d686 100644
> --- a/drivers/ata/libata-sff.c
> +++ b/drivers/ata/libata-sff.c
> @@ -614,7 +614,7 @@ static void ata_pio_sector(struct ata_queued_cmd *qc)
>  	offset = qc->cursg->offset + qc->cursg_ofs;
>  
>  	/* get the current page and offset */
> -	page = nth_page(page, (offset >> PAGE_SHIFT));
> +	page += offset / PAGE_SHIFT;

Shouldn't this be "offset >> PAGE_SHIFT" ?

>  	offset %= PAGE_SIZE;
>  
>  	/* don't overrun current sg */
> @@ -631,7 +631,7 @@ static void ata_pio_sector(struct ata_queued_cmd *qc)
>  		unsigned int split_len = PAGE_SIZE - offset;
>  
>  		ata_pio_xfer(qc, page, offset, split_len);
> -		ata_pio_xfer(qc, nth_page(page, 1), 0, count - split_len);
> +		ata_pio_xfer(qc, page + 1, 0, count - split_len);
>  	} else {
>  		ata_pio_xfer(qc, page, offset, count);
>  	}
> @@ -751,7 +751,7 @@ static int __atapi_pio_bytes(struct ata_queued_cmd *qc, unsigned int bytes)
>  	offset = sg->offset + qc->cursg_ofs;
>  
>  	/* get the current page and offset */
> -	page = nth_page(page, (offset >> PAGE_SHIFT));
> +	page += offset / PAGE_SIZE;

Same here, though this seems correct too.

>  	offset %= PAGE_SIZE;
>  
>  	/* don't overrun current sg */

-- 
Damien Le Moal
Western Digital Research