ip6mr: remove synchronize_rcu() in favor of SOCK_RCU_FREE
Kirill found that recently added synchronize_rcu() call in
ip6mr_sk_done()
was slowing down netns dismantle and posted a patch to use it only if
the socket
was found.
I instead suggested to get rid of this call, and use instead
SOCK_RCU_FREE
We might later change IPv4 side to use the same technique and unify
both stacks. IPv4 does not use synchronize_rcu() but has a call_rcu()
that could be replaced by SOCK_RCU_FREE.
Tested:
time for i in {1..1000}; do unshare -n /bin/false;done
Before : real 7m18.911s
After : real 10.187s
Fixes: 8571ab479a6e ("ip6mr: Make mroute_sk rcu-based")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Yuval Mintz <yuvalm@mellanox.com>
Reviewed-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
index 2a38f9d..7345bd6 100644
--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -1443,6 +1443,7 @@ static int ip6mr_sk_init(struct mr_table *mrt, struct sock *sk)
err = -EADDRINUSE;
} else {
rcu_assign_pointer(mrt->mroute_sk, sk);
+ sock_set_flag(sk, SOCK_RCU_FREE);
net->ipv6.devconf_all->mc_forwarding++;
}
write_unlock_bh(&mrt_lock);
@@ -1472,6 +1473,10 @@ int ip6mr_sk_done(struct sock *sk)
if (sk == rtnl_dereference(mrt->mroute_sk)) {
write_lock_bh(&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()
+ */
net->ipv6.devconf_all->mc_forwarding--;
write_unlock_bh(&mrt_lock);
inet6_netconf_notify_devconf(net, RTM_NEWNETCONF,
@@ -1485,7 +1490,6 @@ int ip6mr_sk_done(struct sock *sk)
}
}
rtnl_unlock();
- synchronize_rcu();
return err;
}
