Re: [patch] mm: sparsemem memory_present() memory corruption fix

From: Yinghai Lu
Date: Tue Apr 15 2008 - 20:33:21 EST


On Tue, Apr 15, 2008 at 5:18 PM, Ingo Molnar <mingo@xxxxxxx> wrote:
>
> * Ingo Molnar <mingo@xxxxxxx> wrote:
>
> > finally found it ... the patch below solves the sparsemem crash and
> > the testsystem boots up fine now:
> >
> > mars:~> uname -a
> > Linux mars 2.6.25-rc9-sched-devel.git-x86-latest.git #985 SMP Wed Apr 16
> > 01:37:37 CEST 2008 i686 i686 i386 GNU/Linux
>
> i re-checked the original SLAB config too and that boots fine as well
> now - so i'm confident that the regression has been sufficiently cured.
>
> it's getting quite late here (or rather, it's getting early :-/ ) so it
> would be nice if others could double-check this calculation (with an eye
> on all possible architectures):
>
> + unsigned long max_arch_pfn = 1ULL << (MAX_PHYSMEM_BITS-PAGE_SHIFT);
>
> and also check my analysis whether it is correct and whether it matches
> the reported bug patterns. But otherwise the fix looks like a safe fix
> for v2.6.25-final to me - it only filters out values from sparsemem
> input that are nonsensical in the sparsemem framework anyway.
>
> Ingo
>

can you check why find_max_pfn() e820_32.c need to call memory_present?
wonder if it can be removed.

YH
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