RE: [RFC 2/4] ARM: dma-mapping: IOMMU allocates pages from pool with GFP_ATOMIC

[Marek Szyprowski <m.szyprowski@samsung.com>]

Hello,

On Wednesday, August 22, 2012 12:20 PM Hiroshi Doyu wrote:

> Makes use of the same atomic pool from DMA, and skips kernel page
> mapping which can involves sleep'able operation at allocating a kernel
> page table.
> 
> Signed-off-by: Hiroshi Doyu <hdoyu@nvidia.com>
> ---
>  arch/arm/mm/dma-mapping.c |   22 ++++++++++++++++++----
>  1 files changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index aec0c06..9260107 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -1028,7 +1028,6 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_t
> size,
>  	struct page **pages;
>  	int count = size >> PAGE_SHIFT;
>  	int array_size = count * sizeof(struct page *);
> -	int err;
> 
>  	if (array_size <= PAGE_SIZE)
>  		pages = kzalloc(array_size, gfp);
> @@ -1037,9 +1036,20 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_t
> size,
>  	if (!pages)
>  		return NULL;
> 
> -	err = __alloc_fill_pages(&pages, count, gfp);
> -	if (err)
> -		goto error
> +	if (gfp & GFP_ATOMIC) {
> +		struct page *page;
> +		int i;
> +		void *addr = __alloc_from_pool(size, &page);
> +		if (!addr)
> +			goto err_out;
> +
> +		for (i = 0; i < count; i++)
> +			pages[i] = page + i;
> +	} else {
> +		int err = __alloc_fill_pages(&pages, count, gfp);
> +		if (err)
> +			goto error;
> +	}
> 
>  	return pages;
>  error:
> @@ -1055,6 +1065,10 @@ static int __iommu_free_buffer(struct device *dev, struct page **pages,
> size_t s
>  	int count = size >> PAGE_SHIFT;
>  	int array_size = count * sizeof(struct page *);
>  	int i;
> +
> +	if (__free_from_pool(page_address(pages[0]), size))
> +		return 0;

You leak memory here. pages array should be also freed.

> +
>  	for (i = 0; i < count; i++)
>  		if (pages[i])
>  			__free_pages(pages[i], 0);
> --
> 1.7.5.4


Best regards
-- 
Marek Szyprowski
Samsung Poland R&D Center