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

[KyongHo Cho]

Hi.

vzalloc() call in __iommu_alloc_buffer() also causes BUG() in atomic
context.


On Wed, Aug 22, 2012 at 7:20 PM, Hiroshi Doyu <hdoyu at nvidia.com> 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 at 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;
> +
>         for (i = 0; i < count; i++)
>                 if (pages[i])
>                         __free_pages(pages[i], 0);
> --
> 1.7.5.4
>
> --
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