2 * linux/ipc/namespace.c
3 * Copyright (C) 2006 Pavel Emelyanov <xemul@openvz.org> OpenVZ, SWsoft Inc.
8 #include <linux/ipc_namespace.h>
9 #include <linux/rcupdate.h>
10 #include <linux/nsproxy.h>
11 #include <linux/slab.h>
13 #include <linux/mount.h>
17 static struct ipc_namespace *clone_ipc_ns(struct ipc_namespace *old_ns)
19 struct ipc_namespace *ns;
22 ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
24 return ERR_PTR(-ENOMEM);
26 atomic_set(&ns->count, 1);
32 atomic_inc(&nr_ipc_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);
49 struct ipc_namespace *copy_ipcs(unsigned long flags, struct ipc_namespace *ns)
51 struct ipc_namespace *new_ns;
53 if (!(flags & CLONE_NEWIPC))
54 return get_ipc_ns(ns);
56 new_ns = clone_ipc_ns(ns);
62 * free_ipcs - free all ipcs of one type
63 * @ns: the namespace to remove the ipcs from
64 * @ids: the table of ipcs to free
65 * @free: the function called to free each individual ipc
67 * Called for each kind of ipc when an ipc_namespace exits.
69 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
70 void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
72 struct kern_ipc_perm *perm;
76 down_write(&ids->rw_mutex);
80 for (total = 0, next_id = 0; total < in_use; next_id++) {
81 perm = idr_find(&ids->ipcs_idr, next_id);
84 ipc_lock_by_ptr(perm);
88 up_write(&ids->rw_mutex);
92 * put_ipc_ns - drop a reference to an ipc namespace.
93 * @ns: the namespace to put
95 * If this is the last task in the namespace exiting, and
96 * it is dropping the refcount to 0, then it can race with
97 * a task in another ipc namespace but in a mounts namespace
98 * which has this ipcns's mqueuefs mounted, doing some action
99 * with one of the mqueuefs files. That can raise the refcount.
100 * So dropping the refcount, and raising the refcount when
101 * accessing it through the VFS, are protected with mq_lock.
103 * (Clearly, a task raising the refcount on its own ipc_ns
104 * needn't take mq_lock since it can't race with the last task
105 * in the ipcns exiting).
107 void put_ipc_ns(struct ipc_namespace *ns)
109 if (atomic_dec_and_lock(&ns->count, &mq_lock)) {
111 spin_unlock(&mq_lock);
117 void free_ipc_ns(struct ipc_namespace *ns)
120 * Unregistering the hotplug notifier at the beginning guarantees
121 * that the ipc namespace won't be freed while we are inside the
122 * callback routine. Since the blocking_notifier_chain_XXX routines
123 * hold a rw lock on the notifier list, unregister_ipcns_notifier()
124 * won't take the rw lock before blocking_notifier_call_chain() has
125 * released the rd lock.
127 unregister_ipcns_notifier(ns);
132 atomic_dec(&nr_ipc_ns);
135 * Do the ipcns removal notification after decrementing nr_ipc_ns in
136 * order to have a correct value when recomputing msgmni.
138 ipcns_notify(IPCNS_REMOVED);