2 files changed, 52 insertions, 10 deletions

diff --git a/drivers/base/node.c b/drivers/base/node.c
index 9e218a6d4a5b..54e5d8eaf70e 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -186,11 +186,14 @@ static SYSDEV_ATTR(distance, S_IRUGO, node_read_distance, NULL);
 static node_registration_func_t __hugetlb_register_node;
 static node_registration_func_t __hugetlb_unregister_node;
 
-static inline void hugetlb_register_node(struct node *node)
+static inline bool hugetlb_register_node(struct node *node)
 {
         if (__hugetlb_register_node &&
-                        node_state(node->sysdev.id, N_HIGH_MEMORY))
+                        node_state(node->sysdev.id, N_HIGH_MEMORY)) {
                 __hugetlb_register_node(node);
+                return true;
+        }
+        return false;
 }
 
 static inline void hugetlb_unregister_node(struct node *node)
@@ -387,10 +390,31 @@ static int link_mem_sections(int nid)
         return err;
 }
 
+#ifdef CONFIG_HUGETLBFS
 /*
  * Handle per node hstate attribute [un]registration on transistions
  * to/from memoryless state.
  */
+static void node_hugetlb_work(struct work_struct *work)
+{
+        struct node *node = container_of(work, struct node, node_work);
+
+        /*
+         * We only get here when a node transitions to/from memoryless state.
+         * We can detect which transition occurred by examining whether the
+         * node has memory now.  hugetlb_register_node() already check this
+         * so we try to register the attributes.  If that fails, then the
+         * node has transitioned to memoryless, try to unregister the
+         * attributes.
+         */
+        if (!hugetlb_register_node(node))
+                hugetlb_unregister_node(node);
+}
+
+static void init_node_hugetlb_work(int nid)
+{
+        INIT_WORK(&node_devices[nid].node_work, node_hugetlb_work);
+}
 
 static int node_memory_callback(struct notifier_block *self,
                                 unsigned long action, void *arg)
@@ -399,14 +423,16 @@ static int node_memory_callback(struct notifier_block *self,
         int nid = mnb->status_change_nid;
 
         switch (action) {
-        case MEM_ONLINE:    /* memory successfully brought online */
+        case MEM_ONLINE:
+        case MEM_OFFLINE:
+                /*
+                 * offload per node hstate [un]registration to a work thread
+                 * when transitioning to/from memoryless state.
+                 */
                 if (nid != NUMA_NO_NODE)
-                        hugetlb_register_node(&node_devices[nid]);
-                break;
-        case MEM_OFFLINE:   /* or offline */
-                if (nid != NUMA_NO_NODE)
-                        hugetlb_unregister_node(&node_devices[nid]);
+                        schedule_work(&node_devices[nid].node_work);
                 break;
+
         case MEM_GOING_ONLINE:
         case MEM_GOING_OFFLINE:
         case MEM_CANCEL_ONLINE:
@@ -417,15 +443,23 @@ static int node_memory_callback(struct notifier_block *self,
 
         return NOTIFY_OK;
 }
-#else
+#endif  /* CONFIG_HUGETLBFS */
+#else   /* !CONFIG_MEMORY_HOTPLUG_SPARSE */
+
 static int link_mem_sections(int nid) { return 0; }
+#endif  /* CONFIG_MEMORY_HOTPLUG_SPARSE */
 
+#if !defined(CONFIG_MEMORY_HOTPLUG_SPARSE) || \
+    !defined(CONFIG_HUGETLBFS)
 static inline int node_memory_callback(struct notifier_block *self,
                                 unsigned long action, void *arg)
 {
         return NOTIFY_OK;
 }
-#endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
+
+static void init_node_hugetlb_work(int nid) { }
+
+#endif
 
 int register_one_node(int nid)
 {
@@ -449,6 +483,9 @@ int register_one_node(int nid)
 
                 /* link memory sections under this node */
                 error = link_mem_sections(nid);
+
+                /* initialize work queue for memory hot plug */
+                init_node_hugetlb_work(nid);
         }
 
         return error;
diff --git a/include/linux/node.h b/include/linux/node.h
index dae1521e1f05..06292dac3eab 100644
--- a/include/linux/node.h
+++ b/include/linux/node.h
@@ -21,9 +21,14 @@
 
 #include <linux/sysdev.h>
 #include <linux/cpumask.h>
+#include <linux/workqueue.h>
 
 struct node {
         struct sys_device       sysdev;
+
+#if defined(CONFIG_MEMORY_HOTPLUG_SPARSE) && defined(CONFIG_HUGETLBFS)
+        struct work_struct      node_work;
+#endif
 };
 
 struct memory_block;