kernel test robot reported this Sparse warning:

  $ make C=1 net/ipv4/ipmr.o
  net/ipv4/ipmr.c:312:24: error: incompatible types in comparison expression (different address spaces):
  net/ipv4/ipmr.c:312:24:    struct mr_table [noderef] __rcu *
  net/ipv4/ipmr.c:312:24:    struct mr_table *

Let's add __rcu annotation to netns_ipv4.mrt.

Fixes: b3b6babf4751 ("ipmr: Free mr_table after RCU grace period.")
Reported-by: kernel test robot <redacted>
Closes: https://lore.kernel.org/oe-kbuild-all/202605030032.glNApko7-lkp@intel.com/ (local)
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
 include/net/netns/ipv4.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index 80ccd4dda8e0..6e27c56514df 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h

@@ -275,7 +275,7 @@ struct netns_ipv4 {
 
 #ifdef CONFIG_IP_MROUTE
 #ifndef CONFIG_IP_MROUTE_MULTIPLE_TABLES
-	struct mr_table		*mrt;
+	struct mr_table __rcu	*mrt;
 #else
 	struct list_head	mr_tables;
 	struct fib_rules_ops	*mr_rules_ops;

-- 
2.54.0.545.g6539524ca2-goog