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
22 static BLOCKING_NOTIFIER_HEAD(ipcns_chain);
23
24
25 static 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
56 int 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
69 int 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
83 void 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
89 int ipcns_notify(unsigned long val)
90 {
91 return blocking_notifier_call_chain(&ipcns_chain, val, NULL);
92 }
93
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