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
*create_ipc_ns(void)
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 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
;
71 down_write(&ids
->rw_mutex
);
75 for (total
= 0, next_id
= 0; total
< in_use
; next_id
++) {
76 perm
= idr_find(&ids
->ipcs_idr
, next_id
);
79 ipc_lock_by_ptr(perm
);
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
);
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
)) {
130 spin_unlock(&mq_lock
);
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