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Commit 70da5b5c authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by David S. Miller
Browse files

ipv6: Replace spinlock with seqlock and rcu in ip6_tunnel 



This patch uses a seqlock to ensure consistency between idst->dst and
idst->cookie.  It also makes dst freeing from fib tree to undergo a
rcu grace period.

Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 8e3d5be7

include/net/ip6_tunnel.h

+2 −2
Original line number Diff line number Diff line
@@ -33,8 +33,8 @@ struct __ip6_tnl_parm { 
};



struct ip6_tnl_dst {

	spinlock_t lock;

	struct dst_entry *dst;

	seqlock_t lock;

	struct dst_entry __rcu *dst;

	u32 cookie;

};

net/ipv6/ip6_fib.c

+7 −2
Original line number Diff line number Diff line
@@ -155,6 +155,11 @@ static void node_free(struct fib6_node *fn) 
	kmem_cache_free(fib6_node_kmem, fn);

}



static void rt6_rcu_free(struct rt6_info *rt)

{

	call_rcu(&rt->dst.rcu_head, dst_rcu_free);

}



static void rt6_free_pcpu(struct rt6_info *non_pcpu_rt)

{

	int cpu;
@@ -169,7 +174,7 @@ static void rt6_free_pcpu(struct rt6_info *non_pcpu_rt) 
		ppcpu_rt = per_cpu_ptr(non_pcpu_rt->rt6i_pcpu, cpu);

		pcpu_rt = *ppcpu_rt;

		if (pcpu_rt) {

			dst_free(&pcpu_rt->dst);

			rt6_rcu_free(pcpu_rt);

			*ppcpu_rt = NULL;

		}

	}
@@ -181,7 +186,7 @@ static void rt6_release(struct rt6_info *rt) 
{

	if (atomic_dec_and_test(&rt->rt6i_ref)) {

		rt6_free_pcpu(rt);

		dst_free(&rt->dst);

		rt6_rcu_free(rt);

	}

}

net/ipv6/ip6_tunnel.c

+27 −24
Original line number Diff line number Diff line
@@ -126,45 +126,48 @@ static struct net_device_stats *ip6_get_stats(struct net_device *dev) 
 * Locking : hash tables are protected by RCU and RTNL

 */



static void __ip6_tnl_per_cpu_dst_set(struct ip6_tnl_dst *idst,

static void ip6_tnl_per_cpu_dst_set(struct ip6_tnl_dst *idst,

				    struct dst_entry *dst)

{

	dst_release(idst->dst);

	write_seqlock_bh(&idst->lock);

	dst_release(rcu_dereference_protected(

			    idst->dst,

			    lockdep_is_held(&idst->lock.lock)));

	if (dst) {

		dst_hold(dst);

		idst->cookie = rt6_get_cookie((struct rt6_info *)dst);

	} else {

		idst->cookie = 0;

	}

	idst->dst = dst;

}



static void ip6_tnl_per_cpu_dst_set(struct ip6_tnl_dst *idst,

				    struct dst_entry *dst)

{



	spin_lock_bh(&idst->lock);

	__ip6_tnl_per_cpu_dst_set(idst, dst);

	spin_unlock_bh(&idst->lock);

	rcu_assign_pointer(idst->dst, dst);

	write_sequnlock_bh(&idst->lock);

}



struct dst_entry *ip6_tnl_dst_get(struct ip6_tnl *t)

{

	struct ip6_tnl_dst *idst;

	struct dst_entry *dst;

	unsigned int seq;

	u32 cookie;



	idst = raw_cpu_ptr(t->dst_cache);

	spin_lock_bh(&idst->lock);

	dst = idst->dst;

	if (dst) {

		if (!dst->obsolete || dst->ops->check(dst, idst->cookie)) {

			dst_hold(idst->dst);

		} else {

			__ip6_tnl_per_cpu_dst_set(idst, NULL);



	rcu_read_lock();

	do {

		seq = read_seqbegin(&idst->lock);

		dst = rcu_dereference(idst->dst);

		cookie = idst->cookie;

	} while (read_seqretry(&idst->lock, seq));



	if (dst && !atomic_inc_not_zero(&dst->__refcnt))

		dst = NULL;

	rcu_read_unlock();



	if (dst && dst->obsolete && !dst->ops->check(dst, cookie)) {

		ip6_tnl_per_cpu_dst_set(idst, NULL);

		dst_release(dst);

		dst = NULL;

	}

	}

	spin_unlock_bh(&idst->lock);

	return dst;

}

EXPORT_SYMBOL_GPL(ip6_tnl_dst_get);
@@ -204,7 +207,7 @@ int ip6_tnl_dst_init(struct ip6_tnl *t) 
		return -ENOMEM;



	for_each_possible_cpu(i)

		spin_lock_init(&per_cpu_ptr(t->dst_cache, i)->lock);

		seqlock_init(&per_cpu_ptr(t->dst_cache, i)->lock);



	return 0;

}