2 files changed, 48 insertions, 3 deletions

diff --git a/include/linux/msg.h b/include/linux/msg.h
index 10a3d5a1abff..6f3b8e79a991 100644
--- a/include/linux/msg.h
+++ b/include/linux/msg.h
@@ -49,16 +49,26 @@ struct msginfo {
         unsigned short  msgseg; 
 };
 
+/*
+ * Scaling factor to compute msgmni:
+ * the memory dedicated to msg queues (msgmni * msgmnb) should occupy
+ * at most 1/MSG_MEM_SCALE of the lowmem (see the formula in ipc/msg.c):
+ * up to 8MB       : msgmni = 16 (MSGMNI)
+ * 4 GB            : msgmni = 8K
+ * more than 16 GB : msgmni = 32K (IPCMNI)
+ */
+#define MSG_MEM_SCALE 32
+
 #define MSGMNI    16   /* <= IPCMNI */     /* max # of msg queue identifiers */
 #define MSGMAX  8192   /* <= INT_MAX */   /* max size of message (bytes) */
 #define MSGMNB 16384   /* <= INT_MAX */   /* default max size of a message queue */
 
 /* unused */
-#define MSGPOOL (MSGMNI*MSGMNB/1024)  /* size in kilobytes of message pool */
+#define MSGPOOL (MSGMNI * MSGMNB) /* size in bytes of message pool */
 #define MSGTQL  MSGMNB            /* number of system message headers */
 #define MSGMAP  MSGMNB            /* number of entries in message map */
 #define MSGSSZ  16                /* message segment size */
-#define __MSGSEG ((MSGPOOL*1024)/ MSGSSZ) /* max no. of segments */
+#define __MSGSEG (MSGPOOL / MSGSSZ) /* max no. of segments */
 #define MSGSEG (__MSGSEG <= 0xffff ? __MSGSEG : 0xffff)
 
 #ifdef __KERNEL__
diff --git a/ipc/msg.c b/ipc/msg.c
index 805ee08ec8bb..9e7211122e27 100644
--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -27,6 +27,7 @@
 #include <linux/msg.h>
 #include <linux/spinlock.h>
 #include <linux/init.h>
+#include <linux/mm.h>
 #include <linux/proc_fs.h>
 #include <linux/list.h>
 #include <linux/security.h>
@@ -77,11 +78,45 @@ static int newque(struct ipc_namespace *, struct ipc_params *);
 static int sysvipc_msg_proc_show(struct seq_file *s, void *it);
 #endif
 
+/*
+ * 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.
+ */
+static void recompute_msgmni(struct ipc_namespace *ns)
+{
+        struct sysinfo i;
+        unsigned long allowed;
+
+        si_meminfo(&i);
+        allowed = (((i.totalram - i.totalhigh) / MSG_MEM_SCALE) * i.mem_unit)
+                / MSGMNB;
+
+        if (allowed < MSGMNI) {
+                ns->msg_ctlmni = MSGMNI;
+                goto out_callback;
+        }
+
+        if (allowed > IPCMNI) {
+                ns->msg_ctlmni = IPCMNI;
+                goto out_callback;
+        }
+
+        ns->msg_ctlmni = allowed;
+
+out_callback:
+
+        printk(KERN_INFO "msgmni has been set to %d for ipc namespace %p\n",
+                ns->msg_ctlmni, ns);
+}
+
 void msg_init_ns(struct ipc_namespace *ns)
 {
         ns->msg_ctlmax = MSGMAX;
         ns->msg_ctlmnb = MSGMNB;
-        ns->msg_ctlmni = MSGMNI;
+
+        recompute_msgmni(ns);
+
         atomic_set(&ns->msg_bytes, 0);
         atomic_set(&ns->msg_hdrs, 0);
         ipc_init_ids(&ns->ids[IPC_MSG_IDS]);