root/ipc/namespace.c

DEFINITIONS

1. clone_ipc_ns
2. copy_ipcs
3. free_ipcs
4. free_ipc_ns

/*
 * linux/ipc/namespace.c
 * Copyright (C) 2006 Pavel Emelyanov <xemul@openvz.org> OpenVZ, SWsoft Inc.
 */

#include <linux/ipc.h>
#include <linux/msg.h>
#include <linux/ipc_namespace.h>
#include <linux/rcupdate.h>
#include <linux/nsproxy.h>
#include <linux/slab.h>

#include "util.h"

static struct ipc_namespace *clone_ipc_ns(struct ipc_namespace *old_ns)
{
        struct ipc_namespace *ns;

        ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
        if (ns == NULL)
                return ERR_PTR(-ENOMEM);

        atomic_inc(&nr_ipc_ns);

        sem_init_ns(ns);
        msg_init_ns(ns);
        shm_init_ns(ns);

        /*
         * msgmni has already been computed for the new ipc ns.
         * Thus, do the ipcns creation notification before registering that
         * new ipcns in the chain.
         */
        ipcns_notify(IPCNS_CREATED);
        register_ipcns_notifier(ns);

        kref_init(&ns->kref);
        return ns;
}

struct ipc_namespace *copy_ipcs(unsigned long flags, struct ipc_namespace *ns)
{
        struct ipc_namespace *new_ns;

        BUG_ON(!ns);
        get_ipc_ns(ns);

        if (!(flags & CLONE_NEWIPC))
                return ns;

        new_ns = clone_ipc_ns(ns);

        put_ipc_ns(ns);
        return new_ns;
}

/*
 * free_ipcs - free all ipcs of one type
 * @ns:   the namespace to remove the ipcs from
 * @ids:  the table of ipcs to free
 * @free: the function called to free each individual ipc
 *
 * Called for each kind of ipc when an ipc_namespace exits.
 */
void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
               void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
{
        struct kern_ipc_perm *perm;
        int next_id;
        int total, in_use;

        down_write(&ids->rw_mutex);

        in_use = ids->in_use;

        for (total = 0, next_id = 0; total < in_use; next_id++) {
                perm = idr_find(&ids->ipcs_idr, next_id);
                if (perm == NULL)
                        continue;
                ipc_lock_by_ptr(perm);
                free(ns, perm);
                total++;
        }
        up_write(&ids->rw_mutex);
}

void free_ipc_ns(struct kref *kref)
{
        struct ipc_namespace *ns;

        ns = container_of(kref, struct ipc_namespace, kref);
        /*
         * Unregistering the hotplug notifier at the beginning guarantees
         * that the ipc namespace won't be freed while we are inside the
         * callback routine. Since the blocking_notifier_chain_XXX routines
         * hold a rw lock on the notifier list, unregister_ipcns_notifier()
         * won't take the rw lock before blocking_notifier_call_chain() has
         * released the rd lock.
         */
        unregister_ipcns_notifier(ns);
        sem_exit_ns(ns);
        msg_exit_ns(ns);
        shm_exit_ns(ns);
        kfree(ns);
        atomic_dec(&nr_ipc_ns);

        /*
         * Do the ipcns removal notification after decrementing nr_ipc_ns in
         * order to have a correct value when recomputing msgmni.
         */
        ipcns_notify(IPCNS_REMOVED);
}