Re: [PATCH V4] mm: fix kernel crash in khugepaged thread

[Hillf Danton]

> 
> Instead of the condition, we could have:
> 
> 	__entry->pfn = page ? page_to_pfn(page) : -1;
> 
> 
> But if there's no reason to do the tracepoint if page is NULL, then
> this patch is fine. I'm just throwing out this idea.
> 
we trace only if page is valid

--- linux-next/mm/huge_memory.c	Fri Nov 13 16:00:22 2015
+++ b/mm/huge_memory.c	Fri Nov 13 16:26:19 2015
@@ -1987,7 +1987,8 @@ static int __collapse_huge_page_isolate(
 
 out:
 	release_pte_pages(pte, _pte);
-	trace_mm_collapse_huge_page_isolate(page_to_pfn(page), none_or_zero,
+	if (page)
+		trace_mm_collapse_huge_page_isolate(page_to_pfn(page), none_or_zero,
 					    referenced, writable, result);
 	return 0;
 }
--



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