[PATCH] net: udp_unhash() can test if sk is hashed

[Eric Dumazet <dada1@cosmosbay.com>]

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Impact: Optimization

Like done in inet_unhash(), we can avoid taking a chain lock if
socket is not hashed in udp_unhash()

Triggered by close(socket(AF_INET, SOCK_DGRAM, 0));

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
---
 net/ipv4/udp.c |   18 ++++++++++--------
 1 files changed, 10 insertions(+), 8 deletions(-)

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diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index da869ce..e2ab258 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -970,16 +970,18 @@ int udp_disconnect(struct sock *sk, int flags)
 
 void udp_lib_unhash(struct sock *sk)
 {
-	struct udp_table *udptable = sk->sk_prot->h.udp_table;
-	unsigned int hash = udp_hashfn(sock_net(sk), sk->sk_hash);
-	struct udp_hslot *hslot = &udptable->hash[hash];
+	if (sk_hashed(sk)) {
+		struct udp_table *udptable = sk->sk_prot->h.udp_table;
+		unsigned int hash = udp_hashfn(sock_net(sk), sk->sk_hash);
+		struct udp_hslot *hslot = &udptable->hash[hash];
 
-	spin_lock_bh(&hslot->lock);
-	if (sk_nulls_del_node_init_rcu(sk)) {
-		inet_sk(sk)->num = 0;
-		sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
+		spin_lock_bh(&hslot->lock);
+		if (sk_nulls_del_node_init_rcu(sk)) {
+			inet_sk(sk)->num = 0;
+			sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
+		}
+		spin_unlock_bh(&hslot->lock);
 	}
-	spin_unlock_bh(&hslot->lock);
 }
 EXPORT_SYMBOL(udp_lib_unhash);