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

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Date:	Tue, 15 Apr 2008 17:56:41 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Pekka Enberg" <penberg@...helsinki.fi>,
	"Christoph Lameter" <clameter@....com>,
	linux-kernel@...r.kernel.org, "Mel Gorman" <mel@....ul.ie>,
	"Nick Piggin" <npiggin@...e.de>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, apw@...dowen.org,
	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [patch] mm: sparsemem memory_present() memory corruption fix

On Tue, Apr 15, 2008 at 5:44 PM, Ingo Molnar <mingo@...e.hu> wrote:
>
>  * Yinghai Lu <yhlu.kernel@...il.com> wrote:
>
>  > >  +       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.
>  >
>
> > can you check why find_max_pfn() e820_32.c need to call
>  > memory_present? wonder if it can be removed.
>
>  this is the only call to memory_present() we do in 32-bit arch setup, so
>  it's required.
>
>  (the function find_max_pfn() is woefully misnamed, but that's a cleanup
>  - i just fixed this in x86.git.)

64 bit is calling that via paging_init
==>sparse_memory_present_with_active_regions(MAX_NUMNODES).

and
void __init sparse_memory_present_with_active_regions(int nid)
{
        int i;

        for_each_active_range_index_in_nid(i, nid)
                memory_present(early_node_map[i].nid,
                                early_node_map[i].start_pfn,
                                early_node_map[i].end_pfn);
}

that is some late than 32 bit.

YH
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