net/smc: Use correct buffer sizes when switching between TCP and SMC

commit 30c3c4a upstream.

Tuning of the effective buffer size through setsockopts was working for
SMC traffic only but not for TCP fall-back connections even before
commit 0227f05 ("net/smc: Unbind r/w buffer size from clcsock and
make them tunable"). That change made it apparent that TCP fall-back
connections would use net.smc.[rw]mem as buffer size instead of
net.ipv4_tcp_[rw]mem.

Amend the code that copies attributes between the (TCP) clcsock and the
SMC socket and adjust buffer sizes appropriately:
- Copy over sk_userlocks so that both sockets agree on whether tuning
  via setsockopt is active.
- When falling back to TCP use sk_sndbuf or sk_rcvbuf as specified with
  setsockopt. Otherwise, use the sysctl value for TCP/IPv4.
- Likewise, use either values from setsockopt or from sysctl for SMC
  (duplicated) on successful SMC connect.

In smc_tcp_listen_work() drop the explicit copy of buffer sizes as that
is taken care of by the attribute copy.

Fixes: 0227f05 ("net/smc: Unbind r/w buffer size from clcsock and make them tunable")
Reviewed-by: Wenjia Zhang <wenjia@linux.ibm.com>
Reviewed-by: Tony Lu <tonylu@linux.alibaba.com>
Signed-off-by: Gerd Bayer <gbayer@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

net/smc/af_smc.c

@@ -436,13 +436,60 @@ static int smc_bind(struct socket *sock, struct sockaddr *uaddr,
 	return rc;
 }
 
+/* copy only relevant settings and flags of SOL_SOCKET level from smc to
+ * clc socket (since smc is not called for these options from net/core)
+ */
+
+#define SK_FLAGS_SMC_TO_CLC ((1UL << SOCK_URGINLINE) | \
+			     (1UL << SOCK_KEEPOPEN) | \
+			     (1UL << SOCK_LINGER) | \
+			     (1UL << SOCK_BROADCAST) | \
+			     (1UL << SOCK_TIMESTAMP) | \
+			     (1UL << SOCK_DBG) | \
+			     (1UL << SOCK_RCVTSTAMP) | \
+			     (1UL << SOCK_RCVTSTAMPNS) | \
+			     (1UL << SOCK_LOCALROUTE) | \
+			     (1UL << SOCK_TIMESTAMPING_RX_SOFTWARE) | \
+			     (1UL << SOCK_RXQ_OVFL) | \
+			     (1UL << SOCK_WIFI_STATUS) | \
+			     (1UL << SOCK_NOFCS) | \
+			     (1UL << SOCK_FILTER_LOCKED) | \
+			     (1UL << SOCK_TSTAMP_NEW))
+
+/* if set, use value set by setsockopt() - else use IPv4 or SMC sysctl value */
+static void smc_adjust_sock_bufsizes(struct sock *nsk, struct sock *osk,
+				     unsigned long mask)
+{
+	struct net *nnet = sock_net(nsk);
+
+	nsk->sk_userlocks = osk->sk_userlocks;
+	if (osk->sk_userlocks & SOCK_SNDBUF_LOCK) {
+		nsk->sk_sndbuf = osk->sk_sndbuf;
+	} else {
+		if (mask == SK_FLAGS_SMC_TO_CLC)
+			WRITE_ONCE(nsk->sk_sndbuf,
+				   READ_ONCE(nnet->ipv4.sysctl_tcp_wmem[1]));
+		else
+			WRITE_ONCE(nsk->sk_sndbuf,
+				   2 * READ_ONCE(nnet->smc.sysctl_wmem));
+	}
+	if (osk->sk_userlocks & SOCK_RCVBUF_LOCK) {
+		nsk->sk_rcvbuf = osk->sk_rcvbuf;
+	} else {
+		if (mask == SK_FLAGS_SMC_TO_CLC)
+			WRITE_ONCE(nsk->sk_rcvbuf,
+				   READ_ONCE(nnet->ipv4.sysctl_tcp_rmem[1]));
+		else
+			WRITE_ONCE(nsk->sk_rcvbuf,
+				   2 * READ_ONCE(nnet->smc.sysctl_rmem));
+	}
+}
+
 static void smc_copy_sock_settings(struct sock *nsk, struct sock *osk,
 				   unsigned long mask)
 {
 	/* options we don't get control via setsockopt for */
 	nsk->sk_type = osk->sk_type;
-	nsk->sk_sndbuf = osk->sk_sndbuf;
-	nsk->sk_rcvbuf = osk->sk_rcvbuf;
 	nsk->sk_sndtimeo = osk->sk_sndtimeo;
 	nsk->sk_rcvtimeo = osk->sk_rcvtimeo;
 	nsk->sk_mark = READ_ONCE(osk->sk_mark);
@@ -453,26 +500,10 @@ static void smc_copy_sock_settings(struct sock *nsk, struct sock *osk,
 
 	nsk->sk_flags &= ~mask;
 	nsk->sk_flags |= osk->sk_flags & mask;
+
+	smc_adjust_sock_bufsizes(nsk, osk, mask);
 }
 
-#define SK_FLAGS_SMC_TO_CLC ((1UL << SOCK_URGINLINE) | \
-			     (1UL << SOCK_KEEPOPEN) | \
-			     (1UL << SOCK_LINGER) | \
-			     (1UL << SOCK_BROADCAST) | \
-			     (1UL << SOCK_TIMESTAMP) | \
-			     (1UL << SOCK_DBG) | \
-			     (1UL << SOCK_RCVTSTAMP) | \
-			     (1UL << SOCK_RCVTSTAMPNS) | \
-			     (1UL << SOCK_LOCALROUTE) | \
-			     (1UL << SOCK_TIMESTAMPING_RX_SOFTWARE) | \
-			     (1UL << SOCK_RXQ_OVFL) | \
-			     (1UL << SOCK_WIFI_STATUS) | \
-			     (1UL << SOCK_NOFCS) | \
-			     (1UL << SOCK_FILTER_LOCKED) | \
-			     (1UL << SOCK_TSTAMP_NEW))
-/* copy only relevant settings and flags of SOL_SOCKET level from smc to
- * clc socket (since smc is not called for these options from net/core)
- */
 static void smc_copy_sock_settings_to_clc(struct smc_sock *smc)
 {
 	smc_copy_sock_settings(smc->clcsock->sk, &smc->sk, SK_FLAGS_SMC_TO_CLC);
@@ -2479,8 +2510,6 @@ static void smc_tcp_listen_work(struct work_struct *work)
 		sock_hold(lsk); /* sock_put in smc_listen_work */
 		INIT_WORK(&new_smc->smc_listen_work, smc_listen_work);
 		smc_copy_sock_settings_to_smc(new_smc);
-		new_smc->sk.sk_sndbuf = lsmc->sk.sk_sndbuf;
-		new_smc->sk.sk_rcvbuf = lsmc->sk.sk_rcvbuf;
 		sock_hold(&new_smc->sk); /* sock_put in passive closing */
 		if (!queue_work(smc_hs_wq, &new_smc->smc_listen_work))
 			sock_put(&new_smc->sk);