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SubjectRe: [PATCH] x86: fix nommu_alloc_coherent allocation with NULL device argument
I agree with this patch in principle. It fixes the problem. But I think
we should evaluate if we can change the dma_mask of the fallback_dev to
24 bit.

On Fri, Sep 05, 2008 at 05:58:47PM +0900, FUJITA Tomonori wrote:
> We need to use __GFP_DMA for NULL device argument (fallback_dev) with
> pci-nommu. It's a hack for ISA (and some old code) so we need to use
> GFP_DMA.
>
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> ---
> arch/x86/kernel/pci-nommu.c | 5 +----
> include/asm-x86/dma-mapping.h | 2 ++
> 2 files changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kernel/pci-nommu.c b/arch/x86/kernel/pci-nommu.c
> index 73853d3..526b2db 100644
> --- a/arch/x86/kernel/pci-nommu.c
> +++ b/arch/x86/kernel/pci-nommu.c
> @@ -83,7 +83,6 @@ nommu_alloc_coherent(struct device *hwdev, size_t size,
> if (hwdev->dma_mask == NULL)
> return NULL;
>
> - gfp &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32);
> gfp |= __GFP_ZERO;
>
> dma_mask = hwdev->coherent_dma_mask;
> @@ -96,14 +95,12 @@ nommu_alloc_coherent(struct device *hwdev, size_t size,
> node = dev_to_node(hwdev);
>
> #ifdef CONFIG_X86_64
> - if (dma_mask <= DMA_32BIT_MASK)
> + if (dma_mask <= DMA_32BIT_MASK && !(gfp & GFP_DMA))
> gfp |= GFP_DMA32;
> #endif
> -
> /* No alloc-free penalty for ISA devices */
> if (dma_mask == DMA_24BIT_MASK)
> gfp |= GFP_DMA;
> -

Please leave these spare lines where they are. They increase the
readability of the code imho.

> again:
> page = alloc_pages_node(node, gfp, get_order(size));
> if (!page)
> diff --git a/include/asm-x86/dma-mapping.h b/include/asm-x86/dma-mapping.h
> index 3a9a6f5..de4495e 100644
> --- a/include/asm-x86/dma-mapping.h
> +++ b/include/asm-x86/dma-mapping.h
> @@ -246,6 +246,8 @@ dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle,
> struct dma_mapping_ops *ops = get_dma_ops(dev);
> void *memory;
>
> + gfp &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32);
> +
> if (dma_alloc_from_coherent(dev, size, dma_handle, &memory))
> return memory;
>
> --
> 1.5.4.2
>
>

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