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From:   Gerd Bayer <gbayer@linux.ibm.com>
To:     Wenjia Zhang <wenjia@linux.ibm.com>,
        Jan Karcher <jaka@linux.ibm.com>,
        Tony Lu <tonylu@linux.alibaba.com>,
        Paolo Abeni <pabeni@redhat.com>
Cc:     Karsten Graul <kgraul@linux.ibm.com>,
        "D . Wythe" <alibuda@linux.alibaba.com>,
        Wen Gu <guwen@linux.alibaba.com>,
        "David S . Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>, linux-s390@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH net 2/2] net/smc: Use correct buffer sizes when switching between TCP and SMC
Date:   Wed,  2 Aug 2023 11:33:13 +0200
Message-ID: <20230802093313.1501605-3-gbayer@linux.ibm.com>
In-Reply-To: <20230802093313.1501605-1-gbayer@linux.ibm.com>
References: <20230802093313.1501605-1-gbayer@linux.ibm.com>
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Tuning of the effective buffer size through setsockopts was working for
SMC traffic only but not for TCP fall-back connections even before
commit 0227f058aa29 ("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: 0227f058aa29 ("net/smc: Unbind r/w buffer size from clcsock and make them tunable")
Signed-off-by: Gerd Bayer <gbayer@linux.ibm.com>
Reviewed-by: Wenjia Zhang <wenjia@linux.ibm.com>
Reviewed-by: Jan Karcher <jaka@linux.ibm.com>

---
 net/smc/af_smc.c | 76 ++++++++++++++++++++++++++++++++++--------------
 1 file changed, 54 insertions(+), 22 deletions(-)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 1fcf1e42474a..1c8ed19041d7 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -436,13 +436,63 @@ 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;
+
+	nnet = nsk->sk_net.net;
+
+	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 = osk->sk_mark;
@@ -453,26 +503,10 @@ 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 +2513,6 @@ 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);
-- 
2.41.0