linux-kernel - Re: [PATCH] dma_declare_coherent

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Message-Id: <20070421000817.124e917b.akpm@linux-foundation.org>
Date:	Sat, 21 Apr 2007 00:08:17 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Guennadi Liakhovetski <g.liakhovetski@....de>
Cc:	James Bottomley <James.Bottomley@...elEye.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dma_declare_coherent_memory wrong allocation

On Fri, 13 Apr 2007 20:08:28 +0200 (CEST) Guennadi Liakhovetski <g.liakhovetski@....de> wrote:

> Hi
> 
> Either I've finally gone blind on this Friday 13th or... Looks like this 
> almost 3 year old function has a bug. Patch below compile-tested... in a 
> way.
> 
> Thanks
> Guennadi
> ---
> Guennadi Liakhovetski
> 
> dma_declare_coherent_memory() allocates a bitmap 1 bit per page, it 
> calculates the bitmap size based on size of long, but allocates bytes...
> 
> Signed-off-by: G. Liakhovetski <g.liakhovetski@....de>
> 
> diff --git a/arch/i386/kernel/pci-dma.c b/arch/i386/kernel/pci-dma.c
> index 3ebcea0..3d55226 100644
> --- a/arch/i386/kernel/pci-dma.c
> +++ b/arch/i386/kernel/pci-dma.c
> @@ -77,7 +77,7 @@ int dma_declare_coherent_memory(struct device *dev, dma_addr_t bus_addr,
>  {
>  	void __iomem *mem_base = NULL;
>  	int pages = size >> PAGE_SHIFT;
> -	int bitmap_size = (pages + 31)/32;
> +	int bitmap_size = DIV_ROUND_UP(pages, 8);
>  
>  	if ((flags & (DMA_MEMORY_MAP | DMA_MEMORY_IO)) == 0)
>  		goto out;

Looks that way to me, too.

It also hopes like hell that `size' was a multiple of PAGE_SIZE.
-
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