cpumask: convert node_to_cpumask_map[] to cpumask_var_t

Impact: reduce kernel memory usage when CONFIG_CPUMASK_OFFSTACK=y

Straightforward conversion: done for 32 and 64 bit kernels.
node_to_cpumask_map is now a cpumask_var_t array.

64-bit used to be a dynamic cpumask_t array, and 32-bit used to be a
static cpumask_t array.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

arch/x86/include/asm/topology.h

@@ -86,15 +86,15 @@ static inline int early_cpu_to_node(int cpu)
 #endif /* CONFIG_X86_64 */
 
 /* Mappings between node number and cpus on that node. */
-extern cpumask_t *node_to_cpumask_map;
+extern cpumask_var_t node_to_cpumask_map[MAX_NUMNODES];
 
 #ifdef CONFIG_DEBUG_PER_CPU_MAPS
 extern const cpumask_t *cpumask_of_node(int node);
 #else
 /* Returns a pointer to the cpumask of CPUs on Node 'node'. */
-static inline const cpumask_t *cpumask_of_node(int node)
+static inline const struct cpumask *cpumask_of_node(int node)
 {
-	return &node_to_cpumask_map[node];
+	return node_to_cpumask_map[node];
 }
 #endif
 

arch/x86/kernel/smpboot.c

@@ -123,7 +123,7 @@ EXPORT_SYMBOL(cpu_to_node_map);
 static void map_cpu_to_node(int cpu, int node)
 {
 	printk(KERN_INFO "Mapping cpu %d to node %d\n", cpu, node);
-	cpumask_set_cpu(cpu, &node_to_cpumask_map[node]);
+	cpumask_set_cpu(cpu, node_to_cpumask_map[node]);
 	cpu_to_node_map[cpu] = node;
 }
 
@@ -134,7 +134,7 @@ static void unmap_cpu_to_node(int cpu)
 
 	printk(KERN_INFO "Unmapping cpu %d from all nodes\n", cpu);
 	for (node = 0; node < MAX_NUMNODES; node++)
-		cpumask_clear_cpu(cpu, &node_to_cpumask_map[node]);
+		cpumask_clear_cpu(cpu, node_to_cpumask_map[node]);
 	cpu_to_node_map[cpu] = 0;
 }
 #else /* !(CONFIG_NUMA && CONFIG_X86_32) */

arch/x86/mm/numa.c

@@ -12,7 +12,7 @@
 /*
  * Which logical CPUs are on which nodes
  */
-cpumask_t *node_to_cpumask_map;
+cpumask_var_t node_to_cpumask_map[MAX_NUMNODES];
 EXPORT_SYMBOL(node_to_cpumask_map);
 
 /*
@@ -25,7 +25,6 @@ EXPORT_SYMBOL(node_to_cpumask_map);
 void __init setup_node_to_cpumask_map(void)
 {
 	unsigned int node, num = 0;
-	cpumask_t *map;
 
 	/* setup nr_node_ids if not done yet */
 	if (nr_node_ids == MAX_NUMNODES) {
@@ -35,14 +34,11 @@ void __init setup_node_to_cpumask_map(void)
 	}
 
 	/* allocate the map */
-	map = alloc_bootmem_low(nr_node_ids * sizeof(cpumask_t));
+	for (node = 0; node < nr_node_ids; node++)
-	DBG("node_to_cpumask_map at %p for %d nodes\n", map, nr_node_ids);
+		alloc_bootmem_cpumask_var(&node_to_cpumask_map[node]);
 
-	pr_debug("Node to cpumask map at %p for %d nodes\n",
+	/* cpumask_of_node() will now work */
-		 map, nr_node_ids);
+	pr_debug("Node to cpumask map for %d nodes\n", nr_node_ids);
-
-	/* node_to_cpumask() will now work */
-	node_to_cpumask_map = map;
 }
 
 #ifdef CONFIG_DEBUG_PER_CPU_MAPS
@@ -51,13 +47,6 @@ void __init setup_node_to_cpumask_map(void)
  */
 const cpumask_t *cpumask_of_node(int node)
 {
-	if (node_to_cpumask_map == NULL) {
-		printk(KERN_WARNING
-			"cpumask_of_node(%d): no node_to_cpumask_map!\n",
-			node);
-		dump_stack();
-		return cpu_online_mask;
-	}
 	if (node >= nr_node_ids) {
 		printk(KERN_WARNING
 			"cpumask_of_node(%d): node > nr_node_ids(%d)\n",
@@ -65,6 +54,13 @@ const cpumask_t *cpumask_of_node(int node)
 		dump_stack();
 		return cpu_none_mask;
 	}
+	if (node_to_cpumask_map[node] == NULL) {
+		printk(KERN_WARNING
+			"cpumask_of_node(%d): no node_to_cpumask_map!\n",
+			node);
+		dump_stack();
+		return cpu_online_mask;
+	}
 	return &node_to_cpumask_map[node];
 }
 EXPORT_SYMBOL(cpumask_of_node);

arch/x86/mm/numa_64.c

@@ -681,12 +681,12 @@ void __cpuinit numa_clear_node(int cpu)
 
 void __cpuinit numa_add_cpu(int cpu)
 {
-	cpu_set(cpu, node_to_cpumask_map[early_cpu_to_node(cpu)]);
+	cpumask_set_cpu(cpu, node_to_cpumask_map[early_cpu_to_node(cpu)]);
 }
 
 void __cpuinit numa_remove_cpu(int cpu)
 {
-	cpu_clear(cpu, node_to_cpumask_map[early_cpu_to_node(cpu)]);
+	cpumask_clear_cpu(cpu, node_to_cpumask_map[early_cpu_to_node(cpu)]);
 }
 
 #else /* CONFIG_DEBUG_PER_CPU_MAPS */
@@ -700,17 +700,17 @@ static void __cpuinit numa_set_cpumask(int cpu, int enable)
 	cpumask_t *mask;
 	char buf[64];
 
-	if (node_to_cpumask_map == NULL) {
+	mask = node_to_cpumask_map[node];
-		printk(KERN_ERR "node_to_cpumask_map NULL\n");
+	if (mask == NULL) {
+		printk(KERN_ERR "node_to_cpumask_map[%i] NULL\n", node);
 		dump_stack();
 		return;
 	}
 
-	mask = &node_to_cpumask_map[node];
 	if (enable)
-		cpu_set(cpu, *mask);
+		cpumask_set_cpu(cpu, mask);
 	else
-		cpu_clear(cpu, *mask);
+		cpumask_clear_cpu(cpu, mask);
 
 	cpulist_scnprintf(buf, sizeof(buf), mask);
 	printk(KERN_DEBUG "%s cpu %d node %d: mask now %s\n",