fed up with those stupid warnings
[mmotm.git] / ipc / namespace.c
bloba1094ff0befa2775c5e9023c44c1520ff813ad04
1 /*
2 * linux/ipc/namespace.c
3 * Copyright (C) 2006 Pavel Emelyanov <xemul@openvz.org> OpenVZ, SWsoft Inc.
4 */
6 #include <linux/ipc.h>
7 #include <linux/msg.h>
8 #include <linux/ipc_namespace.h>
9 #include <linux/rcupdate.h>
10 #include <linux/nsproxy.h>
11 #include <linux/slab.h>
12 #include <linux/fs.h>
13 #include <linux/mount.h>
15 #include "util.h"
17 static struct ipc_namespace *create_ipc_ns(void)
19 struct ipc_namespace *ns;
20 int err;
22 ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
23 if (ns == NULL)
24 return ERR_PTR(-ENOMEM);
26 atomic_set(&ns->count, 1);
27 err = mq_init_ns(ns);
28 if (err) {
29 kfree(ns);
30 return ERR_PTR(err);
32 atomic_inc(&nr_ipc_ns);
34 sem_init_ns(ns);
35 msg_init_ns(ns);
36 shm_init_ns(ns);
39 * msgmni has already been computed for the new ipc ns.
40 * Thus, do the ipcns creation notification before registering that
41 * new ipcns in the chain.
43 ipcns_notify(IPCNS_CREATED);
44 register_ipcns_notifier(ns);
46 return ns;
49 struct ipc_namespace *copy_ipcs(unsigned long flags, struct ipc_namespace *ns)
51 if (!(flags & CLONE_NEWIPC))
52 return get_ipc_ns(ns);
53 return create_ipc_ns();
57 * free_ipcs - free all ipcs of one type
58 * @ns: the namespace to remove the ipcs from
59 * @ids: the table of ipcs to free
60 * @free: the function called to free each individual ipc
62 * Called for each kind of ipc when an ipc_namespace exits.
64 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
65 void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
67 struct kern_ipc_perm *perm;
68 int next_id;
69 int total, in_use;
71 down_write(&ids->rw_mutex);
73 in_use = ids->in_use;
75 for (total = 0, next_id = 0; total < in_use; next_id++) {
76 perm = idr_find(&ids->ipcs_idr, next_id);
77 if (perm == NULL)
78 continue;
79 ipc_lock_by_ptr(perm);
80 free(ns, perm);
81 total++;
83 up_write(&ids->rw_mutex);
86 static void free_ipc_ns(struct ipc_namespace *ns)
89 * Unregistering the hotplug notifier at the beginning guarantees
90 * that the ipc namespace won't be freed while we are inside the
91 * callback routine. Since the blocking_notifier_chain_XXX routines
92 * hold a rw lock on the notifier list, unregister_ipcns_notifier()
93 * won't take the rw lock before blocking_notifier_call_chain() has
94 * released the rd lock.
96 unregister_ipcns_notifier(ns);
97 sem_exit_ns(ns);
98 msg_exit_ns(ns);
99 shm_exit_ns(ns);
100 kfree(ns);
101 atomic_dec(&nr_ipc_ns);
104 * Do the ipcns removal notification after decrementing nr_ipc_ns in
105 * order to have a correct value when recomputing msgmni.
107 ipcns_notify(IPCNS_REMOVED);
111 * put_ipc_ns - drop a reference to an ipc namespace.
112 * @ns: the namespace to put
114 * If this is the last task in the namespace exiting, and
115 * it is dropping the refcount to 0, then it can race with
116 * a task in another ipc namespace but in a mounts namespace
117 * which has this ipcns's mqueuefs mounted, doing some action
118 * with one of the mqueuefs files. That can raise the refcount.
119 * So dropping the refcount, and raising the refcount when
120 * accessing it through the VFS, are protected with mq_lock.
122 * (Clearly, a task raising the refcount on its own ipc_ns
123 * needn't take mq_lock since it can't race with the last task
124 * in the ipcns exiting).
126 void put_ipc_ns(struct ipc_namespace *ns)
128 if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
129 mq_clear_sbinfo(ns);
130 spin_unlock(&mq_lock);
131 mq_put_mnt(ns);
132 free_ipc_ns(ns);