ipc: scale msgmni to the number of ipc namespaces

Since all the namespaces see the same amount of memory (the total one) this
patch introduces a new variable that counts the ipc namespaces and divides
msg_ctlmni by this counter.

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>

4 files changed, 14 insertions, 3 deletions

diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index e4451d1da753..878d7ac286fa 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -33,6 +33,7 @@ struct ipc_namespace {
 };
 
 extern struct ipc_namespace init_ipc_ns;
+extern atomic_t nr_ipc_ns;
 
 #ifdef CONFIG_SYSVIPC
 #define INIT_IPC_NS(ns)         .ns             = &init_ipc_ns,
diff --git a/ipc/msg.c b/ipc/msg.c
index 9e7211122e27..be8449d48a8e 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -81,24 +81,28 @@ static int sysvipc_msg_proc_show(struct seq_file *s, void *it);
 /*
  * Scale msgmni with the available lowmem size: the memory dedicated to msg
  * queues should occupy at most 1/MSG_MEM_SCALE of lowmem.
- * This should be done staying within the (MSGMNI , IPCMNI) range.
+ * Also take into account the number of nsproxies created so far.
+ * This should be done staying within the (MSGMNI , IPCMNI/nr_ipc_ns) range.
  */
 static void recompute_msgmni(struct ipc_namespace *ns)
 {
         struct sysinfo i;
         unsigned long allowed;
+        int nb_ns;
 
         si_meminfo(&i);
         allowed = (((i.totalram - i.totalhigh) / MSG_MEM_SCALE) * i.mem_unit)
                 / MSGMNB;
+        nb_ns = atomic_read(&nr_ipc_ns);
+        allowed /= nb_ns;
 
         if (allowed < MSGMNI) {
                 ns->msg_ctlmni = MSGMNI;
                 goto out_callback;
         }
 
-        if (allowed > IPCMNI) {
-                ns->msg_ctlmni = IPCMNI;
+        if (allowed > IPCMNI / nb_ns) {
+                ns->msg_ctlmni = IPCMNI / nb_ns;
                 goto out_callback;
         }
 
diff --git a/ipc/namespace.c b/ipc/namespace.c
index 1b967655eb35..fe3c97aa99dc 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -20,6 +20,8 @@ static struct ipc_namespace *clone_ipc_ns(struct ipc_namespace *old_ns)
         if (ns == NULL)
                 return ERR_PTR(-ENOMEM);
 
+        atomic_inc(&nr_ipc_ns);
+
         sem_init_ns(ns);
         msg_init_ns(ns);
         shm_init_ns(ns);
@@ -83,4 +85,5 @@ void free_ipc_ns(struct kref *kref)
         msg_exit_ns(ns);
         shm_exit_ns(ns);
         kfree(ns);
+        atomic_dec(&nr_ipc_ns);
 }
diff --git a/ipc/util.c b/ipc/util.c
index cb017c7b9370..c27f0e92f489 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -52,6 +52,9 @@ struct ipc_namespace init_ipc_ns = {
         },
 };
 
+atomic_t nr_ipc_ns = ATOMIC_INIT(1);
+
+
 /**
  *      ipc_init        -       initialise IPC subsystem
  *