net: gain ipv4 mtu when mtu is not locked

When mtu is locked, we should not obtain ipv4 mtu as we return immediately
in this case and leave acquired ipv4 mtu unused.

Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 8ca6bcab7b03d9204fc0de3adca2cdd0c8e0672d..18c8baf32de563ea21174f145ca21e4d06d35286 100644 (file)
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1013,13 +1013,14 @@ out:    kfree_skb(skb);
 static void __ip_rt_update_pmtu(struct rtable *rt, struct flowi4 *fl4, u32 mtu)
 {
        struct dst_entry *dst = &rt->dst;
-       u32 old_mtu = ipv4_mtu(dst);
        struct fib_result res;
        bool lock = false;
+       u32 old_mtu;
 
        if (ip_mtu_locked(dst))
                return;
 
+       old_mtu = ipv4_mtu(dst);
        if (old_mtu < mtu)
                return;