ipv6: fix sparse warning on rt6i_node

commit 4e587ea71bf924f7dac621f1351653bd41e446cb upstream.

Commit c5cff8561d2d adds rcu grace period before freeing fib6_node. This
generates a new sparse warning on rt->rt6i_node related code:
  net/ipv6/route.c:1394:30: error: incompatible types in comparison
  expression (different address spaces)
  ./include/net/ip6_fib.h:187:14: error: incompatible types in comparison
  expression (different address spaces)

This commit adds "__rcu" tag for rt6i_node and makes sure corresponding
rcu API is used for it.
After this fix, sparse no longer generates the above warning.

Fixes: c5cff8561d2d ("ipv6: add rcu grace period before freeing fib6_node")
Signed-off-by: Wei Wang <weiwan@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2:
 - fib6_add_rt2node() has only one assignment to update
 - Drop changes in rt6_cache_allowed_for_pmtu()
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
index 039e026..852f2ce 100644 (file)
--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -96,7 +96,7 @@ struct rt6_info {
         * the same cache line.
         */
        struct fib6_table               *rt6i_table;
-       struct fib6_node                *rt6i_node;
+       struct fib6_node __rcu          *rt6i_node;
 
        struct in6_addr                 rt6i_gateway;
 

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index cd4f45b..9d74f44 100644 (file)
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -4284,7 +4284,7 @@ static void __ipv6_ifa_notify(int event, struct inet6_ifaddr *ifp)
                 * our DAD process, so we don't need
                 * to do it again
                 */
-               if (!(ifp->rt->rt6i_node))
+               if (!rcu_access_pointer(ifp->rt->rt6i_node))
                        ip6_ins_rt(ifp->rt);
                if (ifp->idev->cnf.forwarding)
                        addrconf_join_anycast(ifp);

diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 96d4d1c..8b1f0f9 100644 (file)
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -670,7 +670,7 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct rt6_info *rt,
 
        rt->dst.rt6_next = iter;
        *ins = rt;
-       rt->rt6i_node = fn;
+       rcu_assign_pointer(rt->rt6i_node, fn);
        atomic_inc(&rt->rt6i_ref);
        inet6_rt_notify(RTM_NEWROUTE, rt, info);
        info->nl_net->ipv6.rt6_stats->fib_rt_entries++;
@@ -1181,8 +1181,9 @@ static void fib6_del_route(struct fib6_node *fn, struct rt6_info **rtp,
 
 int fib6_del(struct rt6_info *rt, struct nl_info *info)
 {
+       struct fib6_node *fn = rcu_dereference_protected(rt->rt6i_node,
+                                   lockdep_is_held(&rt->rt6i_table->tb6_lock));
        struct net *net = info->nl_net;
-       struct fib6_node *fn = rt->rt6i_node;
        struct rt6_info **rtp;
 
 #if RT6_DEBUG >= 2
@@ -1360,7 +1361,10 @@ static int fib6_clean_node(struct fib6_walker_t *w)
                        res = fib6_del(rt, &info);
                        if (res) {
 #if RT6_DEBUG >= 2
-                               printk(KERN_DEBUG "fib6_clean_node: del failed: rt=%p@%p err=%d\n", rt, rt->rt6i_node, res);
+                               pr_debug("%s: del failed: rt=%p@%p err=%d\n",
+                                        __func__, rt,
+                                        rcu_access_pointer(rt->rt6i_node),
+                                        res);
 #endif
                                continue;
                        }