• Nadia Derbey's avatar
    ipc: recompute msgmni on ipc namespace creation/removal · e2c284d8
    Nadia Derbey authored
    
    Introduce a notification mechanism that aims at recomputing msgmni each time
    an ipc namespace is created or removed.
    
    The ipc namespace notifier chain already defined for memory hotplug management
    is used for that purpose too.
    
    Each time a new ipc namespace is allocated or an existing ipc namespace is
    removed, the ipcns notifier chain is notified.  The callback routine for each
    registered ipc namespace is then activated in order to recompute msgmni for
    that namespace.
    Signed-off-by: default avatarNadia Derbey <Nadia.Derbey@bull.net>
    Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
    Cc: Matt Helsley <matthltc@us.ibm.com>
    Cc: Mingming Cao <cmm@us.ibm.com>
    Cc: Pierre Peiffer <pierre.peiffer@bull.net>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
    e2c284d8
namespace.c 2.54 KB
/*
 * 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);
}