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, 92 deletions

diff --git a/ipc/ipcns_notifier.c b/ipc/ipcns_notifier.c
deleted file mode 100644
index b9b31a4f77e1..000000000000
--- a/ipc/ipcns_notifier.c
+++ /dev/null
@@ -1,92 +0,0 @@
-/*
- * linux/ipc/ipcns_notifier.c
- * Copyright (C) 2007 BULL SA. Nadia Derbey
- *
- * Notification mechanism for ipc namespaces:
- * The callback routine registered in the memory chain invokes the ipcns
- * notifier chain with the IPCNS_MEMCHANGED event.
- * Each callback routine registered in the ipcns namespace recomputes msgmni
- * for the owning namespace.
- */
-
-#include <linux/msg.h>
-#include <linux/rcupdate.h>
-#include <linux/notifier.h>
-#include <linux/nsproxy.h>
-#include <linux/ipc_namespace.h>
-
-#include "util.h"
-
-
-
-static BLOCKING_NOTIFIER_HEAD(ipcns_chain);
-
-
-static int ipcns_callback(struct notifier_block *self,
-				unsigned long action, void *arg)
-{
-	struct ipc_namespace *ns;
-
-	switch (action) {
-	case IPCNS_MEMCHANGED:   /* amount of lowmem has changed */
-	case IPCNS_CREATED:
-	case IPCNS_REMOVED:
-		/*
-		 * It's time to recompute msgmni
-		 */
-		ns = container_of(self, struct ipc_namespace, ipcns_nb);
-		/*
-		 * No need to get a reference on the ns: the 1st job of
-		 * free_ipc_ns() is to unregister the callback routine.
-		 * blocking_notifier_chain_unregister takes the wr lock to do
-		 * it.
-		 * When this callback routine is called the rd lock is held by
-		 * blocking_notifier_call_chain.
-		 * So the ipc ns cannot be freed while we are here.
-		 */
-		recompute_msgmni(ns);
-		break;
-	default:
-		break;
-	}
-
-	return NOTIFY_OK;
-}
-
-int register_ipcns_notifier(struct ipc_namespace *ns)
-{
-	int rc;
-
-	memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb));
-	ns->ipcns_nb.notifier_call = ipcns_callback;
-	ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI;
-	rc = blocking_notifier_chain_register(&ipcns_chain, &ns->ipcns_nb);
-	if (!rc)
-		ns->auto_msgmni = 1;
-	return rc;
-}
-
-int cond_register_ipcns_notifier(struct ipc_namespace *ns)
-{
-	int rc;
-
-	memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb));
-	ns->ipcns_nb.notifier_call = ipcns_callback;
-	ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI;
-	rc = blocking_notifier_chain_cond_register(&ipcns_chain,
-							&ns->ipcns_nb);
-	if (!rc)
-		ns->auto_msgmni = 1;
-	return rc;
-}
-
-void unregister_ipcns_notifier(struct ipc_namespace *ns)
-{
-	blocking_notifier_chain_unregister(&ipcns_chain, &ns->ipcns_nb);
-	ns->auto_msgmni = 0;
-}
-
-int ipcns_notify(unsigned long val)
-{
-	return blocking_notifier_call_chain(&ipcns_chain, val, NULL);
-}