netdev - [PATCH v2 net-next 5/8] inet: lockless getsockopt(IP

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Date: Fri, 22 Sep 2023 03:42:18 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH v2 net-next 5/8] inet: lockless getsockopt(IP_MTU)

sk_dst_get() does not require socket lock.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reviewed-by: David Ahern <dsahern@...nel.org>
---
 net/ipv4/ip_sockglue.c | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 45d89487914a12061f05c192004ad79f0abbf756..04579e390ddd4dadb8a107ef0b5da15e7a60f1ff 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -1620,13 +1620,6 @@ int do_ip_getsockopt(struct sock *sk, int level, int optname,
 			return -EFAULT;
 		return 0;
 	}
-	}
-
-	if (needs_rtnl)
-		rtnl_lock();
-	sockopt_lock_sock(sk);
-
-	switch (optname) {
 	case IP_MTU:
 	{
 		struct dst_entry *dst;
@@ -1636,12 +1629,17 @@ int do_ip_getsockopt(struct sock *sk, int level, int optname,
 			val = dst_mtu(dst);
 			dst_release(dst);
 		}
-		if (!val) {
-			sockopt_release_sock(sk);
+		if (!val)
 			return -ENOTCONN;
-		}
-		break;
+		goto copyval;
+	}
 	}
+
+	if (needs_rtnl)
+		rtnl_lock();
+	sockopt_lock_sock(sk);
+
+	switch (optname) {
 	case IP_UNICAST_IF:
 		val = (__force int)htonl((__u32) inet->uc_index);
 		break;
-- 
2.42.0.515.g380fc7ccd1-goog