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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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