[PATCH][GIT PULL][v3.6] tracing: Don't call page_to_pfn() if pageis NULL

[Steven Rostedt]

Ingo,

I wrote a test that triggers the bug, and tested this patch which seems
to fix it as well.

Please pull the latest tip/perf/urgent tree, which can be found at:

  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
tip/perf/urgent

Head SHA1: 85f2a2ef1d0ab99523e0b947a2b723f5650ed6aa


Wen Congyang (1):
      tracing: Don't call page_to_pfn() if page is NULL

----
 include/trace/events/kmem.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---------------------------
commit 85f2a2ef1d0ab99523e0b947a2b723f5650ed6aa
Author: Wen Congyang <wency@xxxxxxxxxxxxxx>
Date:   Thu Sep 20 14:04:47 2012 +0800

    tracing: Don't call page_to_pfn() if page is NULL
    
    When allocating memory fails, page is NULL. page_to_pfn() will
    cause the kernel panicked if we don't use sparsemem vmemmap.
    
    Link: http://lkml.kernel.org/r/505AB1FF.8020104@xxxxxxxxxxxxxx
    
    Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
    Cc: Ingo Molnar <mingo@xxxxxxxxxx>
    Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
    Cc: stable <stable@xxxxxxxxxxxxxxx>
    Acked-by: Mel Gorman <mel@xxxxxxxxx>
    Reviewed-by: Minchan Kim <minchan@xxxxxxxxxx>
    Signed-off-by: Wen Congyang <wency@xxxxxxxxxxxxxx>
    Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>

diff --git a/include/trace/events/kmem.h b/include/trace/events/kmem.h
index 5f889f1..08fa272 100644
--- a/include/trace/events/kmem.h
+++ b/include/trace/events/kmem.h
@@ -214,7 +214,7 @@ TRACE_EVENT(mm_page_alloc,
 
 	TP_printk("page=%p pfn=%lu order=%d migratetype=%d gfp_flags=%s",
 		__entry->page,
-		page_to_pfn(__entry->page),
+		__entry->page ? page_to_pfn(__entry->page) : 0,
 		__entry->order,
 		__entry->migratetype,
 		show_gfp_flags(__entry->gfp_flags))
@@ -240,7 +240,7 @@ DECLARE_EVENT_CLASS(mm_page,
 
 	TP_printk("page=%p pfn=%lu order=%u migratetype=%d percpu_refill=%d",
 		__entry->page,
-		page_to_pfn(__entry->page),
+		__entry->page ? page_to_pfn(__entry->page) : 0,
 		__entry->order,
 		__entry->migratetype,
 		__entry->order == 0)


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