[PATCH] Fix __pfn_to_page(pfn) for CONFIG_DISCONTIGMEM=y

[Rafael J. Wysocki]

Hi Andrew,

This would be good to have in .28 IMO.

Thanks,
Rafael


---
From: Rafael J. Wysocki <rjw@xxxxxxx>
Subject: Fix __pfn_to_page(pfn) for CONFIG_DISCONTIGMEM=y

Fix macro __pfn_to_page(pfn) so that it doesn't evaluate its
argument twice in the CONFIG_DISCONTIGMEM=y case, because 'pfn' may
be a result of a funtion call having side effects.

For example, the hibernation code applies pfn_to_page(pfn) to the
result of a function returning the pfn corresponding to the next set
bit in a bitmap and the current bit position is modified on each
call.  This leads to "interesting" failures for CONFIG_DISCONTIGMEM=y
due to the current behavior of __pfn_to_page(pfn).

Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
Cc: Pavel Machek <pavel@xxxxxxx>
---
 include/asm-generic/memory_model.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6/include/asm-generic/memory_model.h
===================================================================
--- linux-2.6.orig/include/asm-generic/memory_model.h
+++ linux-2.6/include/asm-generic/memory_model.h
@@ -34,7 +34,7 @@
 
 #define __pfn_to_page(pfn)			\
 ({	unsigned long __pfn = (pfn);		\
-	unsigned long __nid = arch_pfn_to_nid(pfn);  \
+	unsigned long __nid = arch_pfn_to_nid(__pfn);  \
 	NODE_DATA(__nid)->node_mem_map + arch_local_page_offset(__pfn, __nid);\
 })
 
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