Commit a96f7a6a authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

ip6mr: convert mrt_lock to a spinlock 



mrt_lock is only held in write mode, from process context only.

We can switch to a mere spinlock, and avoid blocking BH.

Also, vif_dev_read() is always called under standard rcu_read_lock().

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 3f55211e

net/ipv6/ip6mr.c

+14 −15
Original line number Diff line number Diff line
@@ -62,12 +62,11 @@ struct ip6mr_result { 
   Note that the changes are semaphored via rtnl_lock.

 */



static DEFINE_RWLOCK(mrt_lock);

static DEFINE_SPINLOCK(mrt_lock);



static struct net_device *vif_dev_read(const struct vif_device *vif)

{

	return rcu_dereference_check(vif->dev,

				     lockdep_is_held(&mrt_lock));

	return rcu_dereference(vif->dev);

}



/* Multicast router control variables */
@@ -714,7 +713,7 @@ static int mif6_delete(struct mr_table *mrt, int vifi, int notify, 
	call_ip6mr_vif_entry_notifiers(read_pnet(&mrt->net),

				       FIB_EVENT_VIF_DEL, v, dev,

				       vifi, mrt->id);

	write_lock_bh(&mrt_lock);

	spin_lock(&mrt_lock);

	RCU_INIT_POINTER(v->dev, NULL);



#ifdef CONFIG_IPV6_PIMSM_V2
@@ -733,7 +732,7 @@ static int mif6_delete(struct mr_table *mrt, int vifi, int notify, 
		WRITE_ONCE(mrt->maxvif, tmp + 1);

	}



	write_unlock_bh(&mrt_lock);

	spin_unlock(&mrt_lock);



	dev_set_allmulti(dev, -1);
@@ -833,7 +832,7 @@ static void ipmr_expire_process(struct timer_list *t) 
	spin_unlock(&mfc_unres_lock);

}



/* Fill oifs list. It is called under write locked mrt_lock. */

/* Fill oifs list. It is called under locked mrt_lock. */



static void ip6mr_update_thresholds(struct mr_table *mrt,

				    struct mr_mfc *cache,
@@ -919,7 +918,7 @@ static int mif6_add(struct net *net, struct mr_table *mrt, 
			MIFF_REGISTER);



	/* And finish update writing critical data */

	write_lock_bh(&mrt_lock);

	spin_lock(&mrt_lock);

	rcu_assign_pointer(v->dev, dev);

	netdev_tracker_alloc(dev, &v->dev_tracker, GFP_ATOMIC);

#ifdef CONFIG_IPV6_PIMSM_V2
@@ -928,7 +927,7 @@ static int mif6_add(struct net *net, struct mr_table *mrt, 
#endif

	if (vifi + 1 > mrt->maxvif)

		WRITE_ONCE(mrt->maxvif, vifi + 1);

	write_unlock_bh(&mrt_lock);

	spin_unlock(&mrt_lock);

	call_ip6mr_vif_entry_notifiers(net, FIB_EVENT_VIF_ADD,

				       v, dev, vifi, mrt->id);

	return 0;
@@ -1442,12 +1441,12 @@ static int ip6mr_mfc_add(struct net *net, struct mr_table *mrt, 
				    &mfc->mf6cc_mcastgrp.sin6_addr, parent);

	rcu_read_unlock();

	if (c) {

		write_lock_bh(&mrt_lock);

		spin_lock(&mrt_lock);

		c->_c.mfc_parent = mfc->mf6cc_parent;

		ip6mr_update_thresholds(mrt, &c->_c, ttls);

		if (!mrtsock)

			c->_c.mfc_flags |= MFC_STATIC;

		write_unlock_bh(&mrt_lock);

		spin_unlock(&mrt_lock);

		call_ip6mr_mfc_entry_notifiers(net, FIB_EVENT_ENTRY_REPLACE,

					       c, mrt->id);

		mr6_netlink_event(mrt, c, RTM_NEWROUTE);
@@ -1565,7 +1564,7 @@ static int ip6mr_sk_init(struct mr_table *mrt, struct sock *sk) 
	struct net *net = sock_net(sk);



	rtnl_lock();

	write_lock_bh(&mrt_lock);

	spin_lock(&mrt_lock);

	if (rtnl_dereference(mrt->mroute_sk)) {

		err = -EADDRINUSE;

	} else {
@@ -1573,7 +1572,7 @@ static int ip6mr_sk_init(struct mr_table *mrt, struct sock *sk) 
		sock_set_flag(sk, SOCK_RCU_FREE);

		atomic_inc(&net->ipv6.devconf_all->mc_forwarding);

	}

	write_unlock_bh(&mrt_lock);

	spin_unlock(&mrt_lock);



	if (!err)

		inet6_netconf_notify_devconf(net, RTM_NEWNETCONF,
@@ -1603,14 +1602,14 @@ int ip6mr_sk_done(struct sock *sk) 
	rtnl_lock();

	ip6mr_for_each_table(mrt, net) {

		if (sk == rtnl_dereference(mrt->mroute_sk)) {

			write_lock_bh(&mrt_lock);

			spin_lock(&mrt_lock);

			RCU_INIT_POINTER(mrt->mroute_sk, NULL);

			/* Note that mroute_sk had SOCK_RCU_FREE set,

			 * so the RCU grace period before sk freeing

			 * is guaranteed by sk_destruct()

			 */

			atomic_dec(&devconf->mc_forwarding);

			write_unlock_bh(&mrt_lock);

			spin_unlock(&mrt_lock);

			inet6_netconf_notify_devconf(net, RTM_NEWNETCONF,

						     NETCONFA_MC_FORWARDING,

						     NETCONFA_IFINDEX_ALL,
@@ -2097,7 +2096,7 @@ static int ip6mr_forward2(struct net *net, struct mr_table *mrt, 
	return 0;

}



/* Called with mrt_lock or rcu_read_lock() */

/* Called with rcu_read_lock() */

static int ip6mr_find_vif(struct mr_table *mrt, struct net_device *dev)

{

	int ct;