From: Michal Nazarewicz <mina86@mina86.com>
To: Danesh Petigara <dpetigara@broadcom.com>, akpm@linux-foundation.org
Cc: m.szyprowski@samsung.com, iamjoonsoo.kim@lge.com,
        aneesh.kumar@linux.vnet.ibm.com,
        laurent.pinchart+renesas@ideasonboard.com, gregory.0xf0@gmail.com,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Danesh Petigara <dpetigara@broadcom.com>, stable@vger.kernel.org
Subject: Re: [PATCH] mm: cma: fix CMA aligned offset calculation
In-Reply-To: <1424807759-23311-1-git-send-email-dpetigara@broadcom.com>
Organization: http://mina86.com/
References: <1424807759-23311-1-git-send-email-dpetigara@broadcom.com>
User-Agent: Notmuch/0.19+53~g2e63a09 (http://notmuchmail.org) Emacs/25.0.50.1 (x86_64-unknown-linux-gnu)
Face: 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
Date: Tue, 24 Feb 2015 22:10:28 +0100
Message-ID: <xa1twq37ow1n.fsf@mina86.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8BIT
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1972
Lines: 59

On Tue, Feb 24 2015, Danesh Petigara <dpetigara@broadcom.com> wrote:
> The CMA aligned offset calculation is incorrect for
> non-zero order_per_bit values.
>
> For example, if cma->order_per_bit=1, cma->base_pfn=
> 0x2f800000 and align_order=12, the function returns
> a value of 0x17c00 instead of 0x400.
>
> This patch fixes the CMA aligned offset calculation.
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Danesh Petigara <dpetigara@broadcom.com>
> Reviewed-by: Gregory Fong <gregory.0xf0@gmail.com>

Acked-by: Michal Nazarewicz <mina86@mina86.com>

> ---
>  mm/cma.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/mm/cma.c b/mm/cma.c
> index 75016fd..58f37bd 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -70,9 +70,13 @@ static unsigned long cma_bitmap_aligned_offset(struct cma *cma, int align_order)
>  
>  	if (align_order <= cma->order_per_bit)
>  		return 0;
> -	alignment = 1UL << (align_order - cma->order_per_bit);
> -	return ALIGN(cma->base_pfn, alignment) -
> -		(cma->base_pfn >> cma->order_per_bit);
> +
> +	/*
> +	 * Find a PFN aligned to the specified order and return
> +	 * an offset represented in order_per_bits.
> +	 */

It probably makes sense to move this comment outside of the function as
function documentation.

> +	return (ALIGN(cma->base_pfn, (1UL << align_order))
> +		- cma->base_pfn) >> cma->order_per_bit;
>  }
>  
>  static unsigned long cma_bitmap_maxno(struct cma *cma)
> -- 
> 1.9.1
>

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
ooo +--<mpn@google.com>--<xmpp:mina86@jabber.org>--ooO--(_)--Ooo--
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/