net: core: rcu-ify rtnl af_ops

rtnl af_ops currently rely on rtnl mutex: unregister (called from module
exit functions) takes the rtnl mutex and all users that do af_ops lookup
also take the rtnl mutex. IOW, parallel rmmod will block until doit()
callback is done.

As none of the af_ops implementation sleep we can use rcu instead.

doit functions that need the af_ops can now use rcu instead of the
rtnl mutex provided the mutex isn't needed for other reasons.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 2 deletions

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 7ce22a2c07ce..6d9b072d903b 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1757,7 +1757,7 @@ static int inet_validate_link_af(const struct net_device *dev,
         struct nlattr *a, *tb[IFLA_INET_MAX+1];
         int err, rem;
 
-        if (dev && !__in_dev_get_rtnl(dev))
+        if (dev && !__in_dev_get_rcu(dev))
                 return -EAFNOSUPPORT;
 
         err = nla_parse_nested(tb, IFLA_INET_MAX, nla, inet_af_policy, NULL);
@@ -1781,7 +1781,7 @@ static int inet_validate_link_af(const struct net_device *dev,
 
 static int inet_set_link_af(struct net_device *dev, const struct nlattr *nla)
 {
-        struct in_device *in_dev = __in_dev_get_rtnl(dev);
+        struct in_device *in_dev = __in_dev_get_rcu(dev);
         struct nlattr *a, *tb[IFLA_INET_MAX+1];
         int rem;