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    SubjectRe: Weirdness in __alloc_bootmem_node_high
    On Tue, Apr 17, 2012 at 05:55:02PM +0200, Michal Hocko wrote:
    > Hi,
    > I just come across the following condition in __alloc_bootmem_node_high
    > which I have hard times to understand. I guess it is a bug and we need
    > something like the following. But, to be honest, I have no idea why we
    > care about those 128MB above MAX_DMA32_PFN.
    > ---
    > mm/bootmem.c | 2 +-
    > 1 file changed, 1 insertion(+), 1 deletion(-)
    >
    > diff --git a/mm/bootmem.c b/mm/bootmem.c
    > index 0131170..5adb072 100644
    > --- a/mm/bootmem.c
    > +++ b/mm/bootmem.c
    > @@ -737,7 +737,7 @@ void * __init __alloc_bootmem_node_high(pg_data_t *pgdat, unsigned long size,
    > /* update goal according ...MAX_DMA32_PFN */
    > end_pfn = pgdat->node_start_pfn + pgdat->node_spanned_pages;
    >
    > - if (end_pfn > MAX_DMA32_PFN + (128 >> (20 - PAGE_SHIFT)) &&
    > + if (end_pfn > MAX_DMA32_PFN + (128 << (20 - PAGE_SHIFT)) &&
    > (goal >> PAGE_SHIFT) < MAX_DMA32_PFN) {
    > void *ptr;
    > unsigned long new_goal;

    Regardless of x86 not using it, this is a bug fix and this code path
    seems to be used by mips at least. Michal, can you please post proper
    signed-off patch? The code is simply trying to use memory above DMA32
    limit if there seems to be enough space (128M) to avoid unnecessarily
    using DMA32 memory.

    Thanks.

    --
    tejun


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