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SubjectRe: [PATCH 6/9] mm/page_alloc: add informative debugging message in page_outside_zone_boundaries()
On Thu, 17 Jan 2013 14:52:58 -0800
Cody P Schafer <cody@linux.vnet.ibm.com> wrote:

> Add a debug message which prints when a page is found outside of the
> boundaries of the zone it should belong to. Format is:
> "page $pfn outside zone [ $start_pfn - $end_pfn ]"
>
> Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
> ---
> mm/page_alloc.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index f8ed277..f1783cf 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -239,13 +239,20 @@ static int page_outside_zone_boundaries(struct zone *zone, struct page *page)
> int ret = 0;
> unsigned seq;
> unsigned long pfn = page_to_pfn(page);
> + unsigned long sp, start_pfn;
>
> do {
> seq = zone_span_seqbegin(zone);
> + start_pfn = zone->zone_start_pfn;
> + sp = zone->spanned_pages;
> if (!zone_spans_pfn(zone, pfn))
> ret = 1;
> } while (zone_span_seqretry(zone, seq));
>
> + if (ret)
> + pr_debug("page %lu outside zone [ %lu - %lu ]\n",
> + pfn, start_pfn, start_pfn + sp);
> +
> return ret;
> }

As this condition leads to a VM_BUG_ON(), "pr_debug" seems rather wimpy
and I doubt if we need to be concerned about flooding the console.

I'll switch it to pr_err.



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