4 files changed, 17 insertions, 25 deletions

diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index cfb2a08b28f5..c3b1da9e5feb 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -4,14 +4,14 @@
 #include <linux/err.h>
 #include <linux/idr.h>
 #include <linux/rwsem.h>
-#ifdef CONFIG_MEMORY_HOTPLUG
 #include <linux/notifier.h>
-#endif /* CONFIG_MEMORY_HOTPLUG */
 
 /*
  * ipc namespace events
  */
 #define IPCNS_MEMCHANGED   0x00000001   /* Notify lowmem size changed */
+#define IPCNS_CREATED  0x00000002   /* Notify new ipc namespace created */
+#define IPCNS_REMOVED  0x00000003   /* Notify ipc namespace removed */
 
 #define IPCNS_CALLBACK_PRI 0
 
@@ -42,9 +42,7 @@ struct ipc_namespace {
         int             shm_ctlmni;
         int             shm_tot;
 
-#ifdef CONFIG_MEMORY_HOTPLUG
         struct notifier_block ipcns_nb;
-#endif
 };
 
 extern struct ipc_namespace init_ipc_ns;
@@ -53,29 +51,10 @@ extern atomic_t nr_ipc_ns;
 #ifdef CONFIG_SYSVIPC
 #define INIT_IPC_NS(ns)         .ns             = &init_ipc_ns,
 
-#ifdef CONFIG_MEMORY_HOTPLUG
-
 extern int register_ipcns_notifier(struct ipc_namespace *);
 extern int unregister_ipcns_notifier(struct ipc_namespace *);
 extern int ipcns_notify(unsigned long);
 
-#else /* CONFIG_MEMORY_HOTPLUG */
-
-static inline int register_ipcns_notifier(struct ipc_namespace *ipcns)
-{
-        return 0;
-}
-static inline int unregister_ipcns_notifier(struct ipc_namespace *ipcns)
-{
-        return 0;
-}
-static inline int ipcns_notify(unsigned long ev)
-{
-        return 0;
-}
-
-#endif /* CONFIG_MEMORY_HOTPLUG */
-
 #else /* CONFIG_SYSVIPC */
 #define INIT_IPC_NS(ns)
 #endif /* CONFIG_SYSVIPC */
diff --git a/ipc/Makefile b/ipc/Makefile
index 388e4d259f02..65c384395801 100644
--- a/ipc/Makefile
+++ b/ipc/Makefile
@@ -3,8 +3,7 @@
 #
 
 obj-$(CONFIG_SYSVIPC_COMPAT) += compat.o
-obj_mem-$(CONFIG_MEMORY_HOTPLUG) += ipcns_notifier.o
-obj-$(CONFIG_SYSVIPC) += util.o msgutil.o msg.o sem.o shm.o $(obj_mem-y)
+obj-$(CONFIG_SYSVIPC) += util.o msgutil.o msg.o sem.o shm.o ipcns_notifier.o
 obj-$(CONFIG_SYSVIPC_SYSCTL) += ipc_sysctl.o
 obj_mq-$(CONFIG_COMPAT) += compat_mq.o
 obj-$(CONFIG_POSIX_MQUEUE) += mqueue.o msgutil.o $(obj_mq-y)
diff --git a/ipc/ipcns_notifier.c b/ipc/ipcns_notifier.c
index 0786af6ce3ec..c7974609defc 100644
--- a/ipc/ipcns_notifier.c
+++ b/ipc/ipcns_notifier.c
@@ -29,6 +29,8 @@ static int ipcns_callback(struct notifier_block *self,
 
         switch (action) {
         case IPCNS_MEMCHANGED:   /* amount of lowmem has changed */
+        case IPCNS_CREATED:
+        case IPCNS_REMOVED:
                 /*
                  * It's time to recompute msgmni
                  */
diff --git a/ipc/namespace.c b/ipc/namespace.c
index f7a35be2e771..9171d948751e 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -26,6 +26,12 @@ static struct ipc_namespace *clone_ipc_ns(struct ipc_namespace *old_ns)
         msg_init_ns(ns);
         shm_init_ns(ns);
 
+        /*
+         * msgmni has already been computed for the new ipc ns.
+         * Thus, do the ipcns creation notification before registering that
+         * new ipcns in the chain.
+         */
+        ipcns_notify(IPCNS_CREATED);
         register_ipcns_notifier(ns);
 
         kref_init(&ns->kref);
@@ -97,4 +103,10 @@ void free_ipc_ns(struct kref *kref)
         shm_exit_ns(ns);
         kfree(ns);
         atomic_dec(&nr_ipc_ns);
+
+        /*
+         * Do the ipcns removal notification after decrementing nr_ipc_ns in
+         * order to have a correct value when recomputing msgmni.
+         */
+        ipcns_notify(IPCNS_REMOVED);
 }