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

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@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@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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