linux-kernel - Re: Weirdness in __alloc_bootmem_node

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Message-ID: <20120417173203.GA32482@tiehlicka.suse.cz>
Date:	Tue, 17 Apr 2012 19:32:03 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: Weirdness in __alloc_bootmem_node_high

On Tue 17-04-12 10:12:30, Yinghai Lu wrote:
> On Tue, Apr 17, 2012 at 8:55 AM, Michal Hocko <mhocko@...e.cz> 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;
> > --
> 
> We are not using bootmem with x86 now, so could remove those workaround now.

Could you be more specific about what the workaround is used for?

Thanks

> 
> Thanks
> 
> Yinghai
> 
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-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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