x86: change _node_to_cpumask_ptr to return const ptr

  * Strengthen the return type for the _node_to_cpumask_ptr to be
    a const pointer.  This adds compiler checking to insure that
    node_to_cpumask_map[] is not changed inadvertently.
Signed-off-by: Mike Travis <travis@sgi.com>
Cc: "akpm@linux-foundation.org" <akpm@linux-foundation.org>
Cc: Yinghai Lu <yhlu.kernel@gmail.com>
Acked-by: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/setup_percpu.c

@@ -343,23 +343,23 @@ static const cpumask_t cpu_mask_none;
 /*
  * Returns a pointer to the bitmask of CPUs on Node 'node'.
  */
-cpumask_t *_node_to_cpumask_ptr(int node)
+const cpumask_t *_node_to_cpumask_ptr(int node)
 {
 	if (node_to_cpumask_map == NULL) {
 		printk(KERN_WARNING
 			"_node_to_cpumask_ptr(%d): no node_to_cpumask_map!\n",
 			node);
 		dump_stack();
-		return &cpu_online_map;
+		return (const cpumask_t *)&cpu_online_map;
 	}
 	if (node >= nr_node_ids) {
 		printk(KERN_WARNING
 			"_node_to_cpumask_ptr(%d): node > nr_node_ids(%d)\n",
 			node, nr_node_ids);
 		dump_stack();
-		return (cpumask_t *)&cpu_mask_none;
+		return &cpu_mask_none;
 	}
-	return (cpumask_t *)&node_to_cpumask_map[node];
+	return &node_to_cpumask_map[node];
 }
 EXPORT_SYMBOL(_node_to_cpumask_ptr);
 

include/asm-generic/topology.h

@@ -60,7 +60,8 @@
 #ifndef node_to_cpumask_ptr
 
 #define	node_to_cpumask_ptr(v, node) 					\
-		cpumask_t _##v = node_to_cpumask(node), *v = &_##v
+		cpumask_t _##v = node_to_cpumask(node);			\
+		const cpumask_t *v = &_##v
 
 #define node_to_cpumask_ptr_next(v, node)				\
 			  _##v = node_to_cpumask(node)

include/asm-x86/topology.h

@@ -82,7 +82,7 @@ DECLARE_EARLY_PER_CPU(int, x86_cpu_to_node_map);
 #ifdef CONFIG_DEBUG_PER_CPU_MAPS
 extern int cpu_to_node(int cpu);
 extern int early_cpu_to_node(int cpu);
-extern cpumask_t *_node_to_cpumask_ptr(int node);
+extern const cpumask_t *_node_to_cpumask_ptr(int node);
 extern cpumask_t node_to_cpumask(int node);
 
 #else	/* !CONFIG_DEBUG_PER_CPU_MAPS */
@@ -103,7 +103,7 @@ static inline int early_cpu_to_node(int cpu)
 }
 
 /* Returns a pointer to the cpumask of CPUs on Node 'node'. */
-static inline cpumask_t *_node_to_cpumask_ptr(int node)
+static inline const cpumask_t *_node_to_cpumask_ptr(int node)
 {
 	return &node_to_cpumask_map[node];
 }
@@ -118,7 +118,7 @@ static inline cpumask_t node_to_cpumask(int node)
 
 /* Replace default node_to_cpumask_ptr with optimized version */
 #define node_to_cpumask_ptr(v, node)		\
-		cpumask_t *v = _node_to_cpumask_ptr(node)
+		const cpumask_t *v = _node_to_cpumask_ptr(node)
 
 #define node_to_cpumask_ptr_next(v, node)	\
 			   v = _node_to_cpumask_ptr(node)
@@ -186,7 +186,7 @@ extern int __node_distance(int, int);
 #define	cpu_to_node(cpu)	0
 #define	early_cpu_to_node(cpu)	0
 
-static inline cpumask_t *_node_to_cpumask_ptr(int node)
+static inline const cpumask_t *_node_to_cpumask_ptr(int node)
 {
 	return &cpu_online_map;
 }
@@ -201,7 +201,7 @@ static inline int node_to_first_cpu(int node)
 
 /* Replace default node_to_cpumask_ptr with optimized version */
 #define node_to_cpumask_ptr(v, node)		\
-		cpumask_t *v = _node_to_cpumask_ptr(node)
+		const cpumask_t *v = _node_to_cpumask_ptr(node)
 
 #define node_to_cpumask_ptr_next(v, node)	\
 			   v = _node_to_cpumask_ptr(node)