ipc/msg: increase MSGMNI, remove scaling

SysV can be abused to allocate locked kernel memory.  For most systems, a
small limit doesn't make sense, see the discussion with regards to SHMMAX.

Therefore: increase MSGMNI to the maximum supported.

And: If we ignore the risk of locking too much memory, then an automatic
scaling of MSGMNI doesn't make sense.  Therefore the logic can be removed.

The code preserves auto_msgmni to avoid breaking any user space applications
that expect that the value exists.

Notes:
1) If an administrator must limit the memory allocations, then he can set
MSGMNI as necessary.

Or he can disable sysv entirely (as e.g. done by Android).

2) MSGMAX and MSGMNB are intentionally not increased, as these values are used
to control latency vs. throughput:
If MSGMNB is large, then msgsnd() just returns and more messages can be queued
before a task switch to a task that calls msgrcv() is forced.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Rafael Aquini <aquini@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 0 insertions, 40 deletions

diff --git a/ipc/util.c b/ipc/util.c
index 88adc329888c..106bed0378ab 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -71,44 +71,6 @@ struct ipc_proc_iface {
         int (*show)(struct seq_file *, void *);
 };
 
-static void ipc_memory_notifier(struct work_struct *work)
-{
-        ipcns_notify(IPCNS_MEMCHANGED);
-}
-
-static int ipc_memory_callback(struct notifier_block *self,
-                                unsigned long action, void *arg)
-{
-        static DECLARE_WORK(ipc_memory_wq, ipc_memory_notifier);
-
-        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.
-                 * In order not to keep the lock on the hotplug memory chain
-                 * for too long, queue a work item that will, when waken up,
-                 * activate the ipcns notification chain.
-                 */
-                schedule_work(&ipc_memory_wq);
-                break;
-        case MEM_GOING_ONLINE:
-        case MEM_GOING_OFFLINE:
-        case MEM_CANCEL_ONLINE:
-        case MEM_CANCEL_OFFLINE:
-        default:
-                break;
-        }
-
-        return NOTIFY_OK;
-}
-
-static struct notifier_block ipc_memory_nb = {
-        .notifier_call = ipc_memory_callback,
-        .priority = IPC_CALLBACK_PRI,
-};
-
 /**
  * ipc_init - initialise ipc subsystem
  *
@@ -124,8 +86,6 @@ static int __init ipc_init(void)
         sem_init();
         msg_init();
         shm_init();
-        register_hotmemory_notifier(&ipc_memory_nb);
-        register_ipcns_notifier(&init_ipc_ns);
         return 0;
 }
 device_initcall(ipc_init);