Messages in this thread | | | Date | Fri, 20 Apr 2012 11:29:07 -0700 | From | Tejun Heo <> | Subject | Re: Weirdness in __alloc_bootmem_node_high |
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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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