ipc: recompute msgmni on ipc namespace creation/removal

Introduce a notification mechanism that aims at recomputing msgmni each time
an ipc namespace is created or removed.

The ipc namespace notifier chain already defined for memory hotplug management
is used for that purpose too.

Each time a new ipc namespace is allocated or an existing ipc namespace is
removed, the ipcns notifier chain is notified.  The callback routine for each
registered ipc namespace is then activated in order to recompute msgmni for
that namespace.

Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net>
Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Mingming Cao <cmm@us.ibm.com>
Cc: Pierre Peiffer <pierre.peiffer@bull.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index cfb2a08b28f5c244b4cce36e3b3f1292eefd627b..c3b1da9e5feb6e612cb8f2f18618af26e798eb0f 100644 (file)
--- 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 388e4d259f02cacc28d0eecb9157efefdd7348d6..65c384395801aa2e9f19ec318735b9dc35c44c42 100644 (file)
--- 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 0786af6ce3ecdc36c63cb998363730b2b0c7ec42..c7974609defc76ba57f96bd852f5efae68d9e870 100644 (file)
--- 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 f7a35be2e7718ce72a1510fb80f301d7a7d77832..9171d948751e72c6c0c8fa1b8e60688ba4384a0c 100644 (file)
--- 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);
 }