linux-kernel - [PATCH] net: gain ipv4 mtu when mtu is not locked

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Message-ID: <20200824113528.44193-1-linmiaohe@huawei.com>
Date:   Mon, 24 Aug 2020 07:35:28 -0400
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <davem@...emloft.net>, <kuznet@....inr.ac.ru>,
        <yoshfuji@...ux-ipv6.org>, <kuba@...nel.org>
CC:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linmiaohe@...wei.com>
Subject: [PATCH] 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@...wei.com>
---
 net/ipv4/route.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 8ca6bcab7b03..f0a0faf58267 100644
--- 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);
+	u32 old_mtu;
 	struct fib_result res;
 	bool lock = false;
 
 	if (ip_mtu_locked(dst))
 		return;
 
+	old_mtu = ipv4_mtu(dst);
 	if (old_mtu < mtu)
 		return;
 
-- 
2.19.1