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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: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Martin KaFai Lau 2015-09-15 14:30:09 -07:00 committed by David S. Miller
parent 8e3d5be736
commit 70da5b5c53
3 changed files with 36 additions and 28 deletions
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4
include/net/ip6_tunnel.h
View File

@ -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;
};

9
net/ipv6/ip6_fib.c
View File

@ -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);
}
}

51
net/ipv6/ip6_tunnel.c
View File

@ -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,
struct dst_entry *dst)
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);
dst = 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;
}