3 files changed, 49 insertions, 0 deletions

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 35b07b773e6c..864035fb8f8a 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -202,6 +202,7 @@ static inline int is_mem_section_removable(unsigned long pfn,
 }
 #endif /* CONFIG_MEMORY_HOTREMOVE */
 
+extern int mem_online_node(int nid);
 extern int add_memory(int nid, u64 start, u64 size);
 extern int arch_add_memory(int nid, u64 start, u64 size);
 extern int remove_memory(u64 start, u64 size);
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 545777574779..a3fbcc0a0abc 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -326,6 +326,12 @@ out_notify:
 int __cpuinit cpu_up(unsigned int cpu)
 {
         int err = 0;
+
+#ifdef  CONFIG_MEMORY_HOTPLUG
+        int nid;
+        pg_data_t       *pgdat;
+#endif
+
         if (!cpu_possible(cpu)) {
                 printk(KERN_ERR "can't online cpu %d because it is not "
                         "configured as may-hotadd at boot time\n", cpu);
@@ -336,6 +342,25 @@ int __cpuinit cpu_up(unsigned int cpu)
                 return -EINVAL;
         }
 
+#ifdef  CONFIG_MEMORY_HOTPLUG
+        nid = cpu_to_node(cpu);
+        if (!node_online(nid)) {
+                err = mem_online_node(nid);
+                if (err)
+                        return err;
+        }
+
+        pgdat = NODE_DATA(nid);
+        if (!pgdat) {
+                printk(KERN_ERR
+                        "Can't online cpu %d due to NULL pgdat\n", cpu);
+                return -ENOMEM;
+        }
+
+        if (pgdat->node_zonelists->_zonerefs->zone == NULL)
+                build_all_zonelists();
+#endif
+
         cpu_maps_update_begin();
 
         if (cpu_hotplug_disabled) {
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index be211a582930..85eb4d342ac5 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -482,6 +482,29 @@ static void rollback_node_hotadd(int nid, pg_data_t *pgdat)
 }
 
 
+/*
+ * called by cpu_up() to online a node without onlined memory.
+ */
+int mem_online_node(int nid)
+{
+        pg_data_t       *pgdat;
+        int     ret;
+
+        lock_system_sleep();
+        pgdat = hotadd_new_pgdat(nid, 0);
+        if (pgdat) {
+                ret = -ENOMEM;
+                goto out;
+        }
+        node_set_online(nid);
+        ret = register_one_node(nid);
+        BUG_ON(ret);
+
+out:
+        unlock_system_sleep();
+        return ret;
+}
+
 /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
 int __ref add_memory(int nid, u64 start, u64 size)
 {