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    Subject[PATCH] ppc highmem fix
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    I've noticed that the calculations for seg_size and nr_segs in
    __dma_sync_page_highmem() (arch/ppc/kernel/dma-mapping.c) are wrong.
    The incorrect calculations can result in either an oops or a panic when
    running fsck depending on the size of the partition. The problem with
    the
    seg_size calculation is that it can result in a negative number if size
    is offset > size. The problem with the nr_segs caculation is returns
    the
    wrong number of segments, e.g. it returns 1 when size is 200 and offset
    is 4095, when it should return 2 or more.

    Here is the patch to fix the problem.

    --- linux-2.6.14-rc3-git8/arch/ppc/kernel/dma-mapping.c 2005-10-10
    13:55:37.000000000 -0700
    +++ linux-2.6.14/arch/ppc/kernel/dma-mapping.c 2005-10-10
    13:57:51.000000000 -0700
    @@ -401,10 +401,10 @@
    static inline void __dma_sync_page_highmem(struct page *page,
    unsigned long offset, size_t size, int direction)
    {
    - size_t seg_size = min((size_t)PAGE_SIZE, size) - offset;
    + size_t seg_size = min((size_t)(PAGE_SIZE - offset), size);
    size_t cur_size = seg_size;
    unsigned long flags, start, seg_offset = offset;
    - int nr_segs = PAGE_ALIGN(size + (PAGE_SIZE - offset))/PAGE_SIZE;
    + int nr_segs = 1 + ((size - seg_size) + PAGE_SIZE - 1)/PAGE_SIZE;
    int seg_nr = 0;

    local_irq_save(flags);

    Paolo Galtieri (pgaltieri@mvista.com)


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