net/smc: smc_poll improvements

Increase the socket refcount during poll wait.
Take the socket lock before checking socket state.
For a listening socket return a mask independent of state SMC_ACTIVE and
cover errors or closed state as well.
Get rid of the accept_q loop in smc_accept_poll().
Signed-off-by: Ursula Braun <ubraun@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/smc/af_smc.c

@@ -1122,21 +1122,15 @@ static int smc_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 
 static unsigned int smc_accept_poll(struct sock *parent)
 {
-	struct smc_sock *isk;
-	struct sock *sk;
-
-	lock_sock(parent);
-	list_for_each_entry(isk, &smc_sk(parent)->accept_q, accept_q) {
-		sk = (struct sock *)isk;
+	struct smc_sock *isk = smc_sk(parent);
+	int mask = 0;
 
-		if (sk->sk_state == SMC_ACTIVE) {
-			release_sock(parent);
-			return POLLIN | POLLRDNORM;
-		}
-	}
-	release_sock(parent);
+	spin_lock(&isk->accept_q_lock);
+	if (!list_empty(&isk->accept_q))
+		mask = POLLIN | POLLRDNORM;
+	spin_unlock(&isk->accept_q_lock);
 
-	return 0;
+	return mask;
 }
 
 static unsigned int smc_poll(struct file *file, struct socket *sock,
@@ -1147,9 +1141,15 @@ static unsigned int smc_poll(struct file *file, struct socket *sock,
 	struct smc_sock *smc;
 	int rc;
 
+	if (!sk)
+		return POLLNVAL;
+
 	smc = smc_sk(sock->sk);
+	sock_hold(sk);
+	lock_sock(sk);
 	if ((sk->sk_state == SMC_INIT) || smc->use_fallback) {
 		/* delegate to CLC child sock */
+		release_sock(sk);
 		mask = smc->clcsock->ops->poll(file, smc->clcsock, wait);
 		/* if non-blocking connect finished ... */
 		lock_sock(sk);
@@ -1161,21 +1161,27 @@ static unsigned int smc_poll(struct file *file, struct socket *sock,
 				rc = smc_connect_rdma(smc);
 				if (rc < 0)
 					mask |= POLLERR;
-				else
 				/* success cases including fallback */
 				mask |= POLLOUT | POLLWRNORM;
 			}
 		}
-		release_sock(sk);
 	} else {
+		if (sk->sk_state != SMC_CLOSED) {
+			release_sock(sk);
 			sock_poll_wait(file, sk_sleep(sk), wait);
-		if (sk->sk_state == SMC_LISTEN)
-			/* woken up by sk_data_ready in smc_listen_work() */
-			mask |= smc_accept_poll(sk);
+			lock_sock(sk);
+		}
 		if (sk->sk_err)
 			mask |= POLLERR;
+		if ((sk->sk_shutdown == SHUTDOWN_MASK) ||
+		    (sk->sk_state == SMC_CLOSED))
+			mask |= POLLHUP;
+		if (sk->sk_state == SMC_LISTEN) {
+			/* woken up by sk_data_ready in smc_listen_work() */
+			mask = smc_accept_poll(sk);
+		} else {
 			if (atomic_read(&smc->conn.sndbuf_space) ||
-		    (sk->sk_shutdown & SEND_SHUTDOWN)) {
+			    sk->sk_shutdown & SEND_SHUTDOWN) {
 				mask |= POLLOUT | POLLWRNORM;
 			} else {
 				sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
@@ -1183,15 +1189,15 @@ static unsigned int smc_poll(struct file *file, struct socket *sock,
 			}
 			if (atomic_read(&smc->conn.bytes_to_rcv))
 				mask |= POLLIN | POLLRDNORM;
-		if ((sk->sk_shutdown == SHUTDOWN_MASK) ||
-		    (sk->sk_state == SMC_CLOSED))
-			mask |= POLLHUP;
 			if (sk->sk_shutdown & RCV_SHUTDOWN)
 				mask |= POLLIN | POLLRDNORM | POLLRDHUP;
 			if (sk->sk_state == SMC_APPCLOSEWAIT1)
 				mask |= POLLIN;
+		}
 
 	}
+	release_sock(sk);
+	sock_put(sk);
 
 	return mask;
 }