1 files changed, 33 insertions, 0 deletions

diff --git a/ipc/util.c b/ipc/util.c
index c27f0e92f489..2d545d7144a7 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -33,6 +33,7 @@
 #include <linux/audit.h>
 #include <linux/nsproxy.h>
 #include <linux/rwsem.h>
+#include <linux/memory.h>
 #include <linux/ipc_namespace.h>
 
 #include <asm/unistd.h>
@@ -55,11 +56,41 @@ struct ipc_namespace init_ipc_ns = {
 atomic_t nr_ipc_ns = ATOMIC_INIT(1);
 
 
+#ifdef CONFIG_MEMORY_HOTPLUG
+
+static int ipc_memory_callback(struct notifier_block *self,
+                                unsigned long action, void *arg)
+{
+        switch (action) {
+        case MEM_ONLINE:    /* memory successfully brought online */
+        case MEM_OFFLINE:   /* or offline: it's time to recompute msgmni */
+                /*
+                 * This is done by invoking the ipcns notifier chain with the
+                 * IPC_MEMCHANGED event.
+                 */
+                ipcns_notify(IPCNS_MEMCHANGED);
+                break;
+        case MEM_GOING_ONLINE:
+        case MEM_GOING_OFFLINE:
+        case MEM_CANCEL_ONLINE:
+        case MEM_CANCEL_OFFLINE:
+        default:
+                break;
+        }
+
+        return NOTIFY_OK;
+}
+
+#endif /* CONFIG_MEMORY_HOTPLUG */
+
 /**
  *      ipc_init        -       initialise IPC subsystem
  *
  *      The various system5 IPC resources (semaphores, messages and shared
  *      memory) are initialised
+ *      A callback routine is registered into the memory hotplug notifier
+ *      chain: since msgmni scales to lowmem this callback routine will be
+ *      called upon successful memory add / remove to recompute msmgni.
  */
  
 static int __init ipc_init(void)
@@ -67,6 +98,8 @@ static int __init ipc_init(void)
         sem_init();
         msg_init();
         shm_init();
+        hotplug_memory_notifier(ipc_memory_callback, IPC_CALLBACK_PRI);
+        register_ipcns_notifier(&init_ipc_ns);
         return 0;
 }
 __initcall(ipc_init);