ipc: recompute msgmni on memory add / remove

[mv-sheeva.git] / ipc / ipcns_notifier.c

diff --git a/ipc/ipcns_notifier.c b/ipc/ipcns_notifier.c
new file mode 100644 (file)
index 0000000..0786af6
--- /dev/null
+++ b/ipc/ipcns_notifier.c
@@ -0,0 +1,71 @@
+/*
+ * 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 */
+               /*
+                * 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)
+{
+       memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb));
+       ns->ipcns_nb.notifier_call = ipcns_callback;
+       ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI;
+       return blocking_notifier_chain_register(&ipcns_chain, &ns->ipcns_nb);
+}
+
+int unregister_ipcns_notifier(struct ipc_namespace *ns)
+{
+       return blocking_notifier_chain_unregister(&ipcns_chain,
+                                               &ns->ipcns_nb);
+}
+
+int ipcns_notify(unsigned long val)
+{
+       return blocking_notifier_call_chain(&ipcns_chain, val, NULL);
+}