1/*
 2 * linux/ipc/ipcns_notifier.c
 3 * Copyright (C) 2007 BULL SA. Nadia Derbey
 4 *
 5 * Notification mechanism for ipc namespaces:
 6 * The callback routine registered in the memory chain invokes the ipcns
 7 * notifier chain with the IPCNS_MEMCHANGED event.
 8 * Each callback routine registered in the ipcns namespace recomputes msgmni
 9 * for the owning namespace.
10 */
11
12#include <linux/msg.h>
13#include <linux/rcupdate.h>
14#include <linux/notifier.h>
15#include <linux/nsproxy.h>
16#include <linux/ipc_namespace.h>
17
18#include "util.h"
19
20
21
22static BLOCKING_NOTIFIER_HEAD(ipcns_chain);
23
24
25static int ipcns_callback(struct notifier_block *self,
26				unsigned long action, void *arg)
27{
28	struct ipc_namespace *ns;
29
30	switch (action) {
31	case IPCNS_MEMCHANGED:   /* amount of lowmem has changed */
32	case IPCNS_CREATED:
33	case IPCNS_REMOVED:
34		/*
35		 * It's time to recompute msgmni
36		 */
37		ns = container_of(self, struct ipc_namespace, ipcns_nb);
38		/*
39		 * No need to get a reference on the ns: the 1st job of
40		 * free_ipc_ns() is to unregister the callback routine.
41		 * blocking_notifier_chain_unregister takes the wr lock to do
42		 * it.
43		 * When this callback routine is called the rd lock is held by
44		 * blocking_notifier_call_chain.
45		 * So the ipc ns cannot be freed while we are here.
46		 */
47		recompute_msgmni(ns);
48		break;
49	default:
50		break;
51	}
52
53	return NOTIFY_OK;
54}
55
56int register_ipcns_notifier(struct ipc_namespace *ns)
57{
58	int rc;
59
60	memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb));
61	ns->ipcns_nb.notifier_call = ipcns_callback;
62	ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI;
63	rc = blocking_notifier_chain_register(&ipcns_chain, &ns->ipcns_nb);
64	if (!rc)
65		ns->auto_msgmni = 1;
66	return rc;
67}
68
69int cond_register_ipcns_notifier(struct ipc_namespace *ns)
70{
71	int rc;
72
73	memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb));
74	ns->ipcns_nb.notifier_call = ipcns_callback;
75	ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI;
76	rc = blocking_notifier_chain_cond_register(&ipcns_chain,
77							&ns->ipcns_nb);
78	if (!rc)
79		ns->auto_msgmni = 1;
80	return rc;
81}
82
83void unregister_ipcns_notifier(struct ipc_namespace *ns)
84{
85	blocking_notifier_chain_unregister(&ipcns_chain, &ns->ipcns_nb);
86	ns->auto_msgmni = 0;
87}
88
89int ipcns_notify(unsigned long val)
90{
91	return blocking_notifier_call_chain(&ipcns_chain, val, NULL);
92}