linux-kernel - RE: [PATCH] arm: dma: Drop GFP_COMP for DMA memory allocations

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Date:	Wed, 9 Nov 2011 10:03:46 -0800
From:	Stephen Warren <swarren@...dia.com>
To:	Russell King <linux@....linux.org.uk>
CC:	Jon Medhurst <tixy@...t.co.uk>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Sumit Bhattacharya <sumitb@...dia.com>
Subject: RE: [PATCH] arm: dma:  Drop GFP_COMP for DMA memory allocations

Stephen Warren wrote at Friday, November 04, 2011 3:36 PM:
> dma_alloc_coherent wants to split pages after allocation in order to
> reduce the memory footprint. This does not work well with GFP_COMP
> pages, so drop this flag before allocation.
> 
> This patch is ported from arch/avr32
> (commit 3611553ef985ef7c5863c8a94641738addd04cff).
> 
> Signed-off-by: Sumit Bhattacharya <sumitb@...dia.com>
> Tested-by: Varun Colbert <vcolbert@...dia.com>
> [swarren: s/HUGETLB_PAGE/HUGETLBFS/ in comment, minor comment cleanup]
> Signed-off-by: Stephen Warren <swarren@...dia.com>

Russell, does this look good to go in the patch system now?

> ---
>  arch/arm/mm/dma-mapping.c |    9 +++++++++
>  1 files changed, 9 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index e4e7f6c..68d64b4 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -332,6 +332,15 @@ __dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp,
>  	struct page *page;
>  	void *addr;
> 
> +	/*
> +	 * Following is a work-around (a.k.a. hack) to prevent pages
> +	 * with __GFP_COMP being passed to split_page() which cannot
> +	 * handle them.  The real problem is that this flag probably
> +	 * should be 0 on ARM as it is not supported on this
> +	 * platform; see CONFIG_HUGETLBFS.
> +	 */
> +	gfp &= ~(__GFP_COMP);
> +
>  	*handle = ~0;
>  	size = PAGE_ALIGN(size);
> 
> --
> 1.7.0.4

-- 
nvpublic

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