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Date: Tue, 15 Apr 2008 17:32:46 -0700
From: "Yinghai Lu" <yhlu.kernel@gmail.com>
To: "Ingo Molnar" <mingo@elte.hu>
Subject: Re: [patch] mm: sparsemem memory_present() memory corruption fix
Cc: "Linus Torvalds" <torvalds@linux-foundation.org>,
       "Pekka Enberg" <penberg@cs.helsinki.fi>,
       "Christoph Lameter" <clameter@sgi.com>, linux-kernel@vger.kernel.org,
       "Mel Gorman" <mel@csn.ul.ie>, "Nick Piggin" <npiggin@suse.de>,
       "Andrew Morton" <akpm@linux-foundation.org>,
       "Rafael J. Wysocki" <rjw@sisk.pl>, apw@shadowen.org,
       "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@jp.fujitsu.com>
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On Tue, Apr 15, 2008 at 5:18 PM, Ingo Molnar <mingo@elte.hu> wrote:
>
>  * Ingo Molnar <mingo@elte.hu> 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