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SubjectRe: [BUG] sysrq-m oops
Bob Picco wrote:
> john stultz wrote: [Thu Jun 07 2007, 03:54:41PM EDT]
> [snip]
> john you are welcome.
>
> We aren't sampling for holes in memory. Thus we encounter a section hole with
> empty section map pointer for SPARSEMEM and OOPs for show_mem. This issue
> has been seen in 2.6.21, current git and current mm. The patch below
> is for mainline and mm. It was boot tested for SPARSEMEM, current
> VMEMMAP of Andy's in mm ml and DISCONTIGMEM. A slightly different patch
> will be posted to stable for 2.6.21.
>
> Previous to commit f0a5a58aa812b31fd9f197c4ba48245942364eae memory_present
> was called for node_start_pfn to node_end_pfn. This would cover the hole(s)
> with reserved pages and valid sections. Most SPARSEMEM supported arches
> do a pfn_valid check in show_mem before computing the page structure address.
>
> This issue was brought to my attention on IRC by Arnaldo Carvalho de Melo at
> acme@redhat.com. Thanks to Arnaldo for testing.
>
> Signed-off-by: Bob Picco <bob.picco@hp.com>
>
> arch/x86_64/mm/init.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> Index: linux-2.6.22-rc4-mm1/arch/x86_64/mm/init.c
> ===================================================================
> --- linux-2.6.22-rc4-mm1.orig/arch/x86_64/mm/init.c 2007-06-06 12:59:26.000000000 -0400
> +++ linux-2.6.22-rc4-mm1/arch/x86_64/mm/init.c 2007-06-07 11:14:31.000000000 -0400
> @@ -79,6 +79,8 @@ void show_mem(void)
> if (unlikely(i % MAX_ORDER_NR_PAGES == 0)) {
> touch_nmi_watchdog();
> }
> + if (!pfn_valid(pgdat->node_start_pfn + i))
> + continue;
> page = pfn_to_page(pgdat->node_start_pfn + i);
> total++;
> if (PageReserved(page))

Yes this is required with SPARSEMEM. Good spot.

Acked-by: Andy Whitcroft <apw@shadowen.org>

-apw
-
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