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

Tuning of the effective buffer size through setsockopts was working for
SMC traffic only but not for TCP fall-back connections even before
commit 0227f058aa ("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: 0227f058aa ("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>

net/smc/af_smc.c

@@ -436,24 +436,9 @@ out:
 	return rc;
 }
 
-static void smc_copy_sock_settings(struct sock *nsk, struct sock *osk,
+/* copy only relevant settings and flags of SOL_SOCKET level from smc to
-				   unsigned long mask)
+ * clc socket (since smc is not called for these options from net/core)
-{
+ */
-	/* 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);
-	nsk->sk_priority = osk->sk_priority;
-	nsk->sk_rcvlowat = osk->sk_rcvlowat;
-	nsk->sk_bound_dev_if = osk->sk_bound_dev_if;
-	nsk->sk_err = osk->sk_err;
-
-	nsk->sk_flags &= ~mask;
-	nsk->sk_flags |= osk->sk_flags & mask;
-}
 
 #define SK_FLAGS_SMC_TO_CLC ((1UL << SOCK_URGINLINE) | \
 			     (1UL << SOCK_KEEPOPEN) | \
@@ -470,9 +455,55 @@ static void smc_copy_sock_settings(struct sock *nsk, struct sock *osk,
 			     (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)
+/* 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_sndtimeo = osk->sk_sndtimeo;
+	nsk->sk_rcvtimeo = osk->sk_rcvtimeo;
+	nsk->sk_mark = READ_ONCE(osk->sk_mark);
+	nsk->sk_priority = osk->sk_priority;
+	nsk->sk_rcvlowat = osk->sk_rcvlowat;
+	nsk->sk_bound_dev_if = osk->sk_bound_dev_if;
+	nsk->sk_err = osk->sk_err;
+
+	nsk->sk_flags &= ~mask;
+	nsk->sk_flags |= osk->sk_flags & mask;
+
+	smc_adjust_sock_bufsizes(nsk, osk, mask);
+}
+
 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);