This patch defines the wrapper __mptcp_sched_get_retrans(), invoke
get_subflow() of msk->sched in it. Use this wrapper instead of using
mptcp_subflow_get_retrans() directly in __mptcp_retrans().

Check the subflow scheduled flags in __mptcp_retrans() to test which
subflow or subflows are picked by the scheduler, use them to send data.

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 net/mptcp/protocol.c | 53 +++++++++++++++++++++++++++-----------------
 net/mptcp/protocol.h |  2 ++
 net/mptcp/sched.c    | 25 +++++++++++++++++++++
 3 files changed, 60 insertions(+), 20 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 06192eebbd57..3ae237f89bfa 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2198,17 +2198,12 @@ static void mptcp_timeout_timer(struct timer_list *t)
  *
  * A backup subflow is returned only if that is the only kind available.
  */
-static struct sock *mptcp_subflow_get_retrans(struct mptcp_sock *msk)
+struct sock *mptcp_subflow_get_retrans(struct mptcp_sock *msk)
 {
 	struct sock *backup = NULL, *pick = NULL;
 	struct mptcp_subflow_context *subflow;
 	int min_stale_count = INT_MAX;
 
-	sock_owned_by_me((const struct sock *)msk);
-
-	if (__mptcp_check_fallback(msk))
-		return NULL;
-
 	mptcp_for_each_subflow(msk, subflow) {
 		struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
 
@@ -2452,16 +2447,17 @@ static void mptcp_check_fastclose(struct mptcp_sock *msk)
 static void __mptcp_retrans(struct sock *sk)
 {
 	struct mptcp_sock *msk = mptcp_sk(sk);
+	struct mptcp_subflow_context *subflow;
 	struct mptcp_sendmsg_info info = {};
 	struct mptcp_data_frag *dfrag;
 	size_t copied = 0;
 	struct sock *ssk;
-	int ret;
+	int err;
 
 	mptcp_clean_una_wakeup(sk);
 
 	/* first check ssk: need to kick "stale" logic */
-	ssk = mptcp_subflow_get_retrans(msk);
+	err = __mptcp_sched_get_retrans(msk);
 	dfrag = mptcp_rtx_head(sk);
 	if (!dfrag) {
 		if (mptcp_data_fin_enabled(msk)) {
@@ -2480,32 +2476,49 @@ static void __mptcp_retrans(struct sock *sk)
 		goto reset_timer;
 	}
 
-	if (!ssk)
+	if (err)
 		goto reset_timer;
 
-	lock_sock(ssk);
-
 	/* limit retransmission to the bytes already sent on some subflows */
 	info.sent = 0;
 	info.limit = READ_ONCE(msk->csum_enabled) ? dfrag->data_len : dfrag->already_sent;
 	while (info.sent < info.limit) {
-		ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
-		if (ret <= 0)
-			break;
+		int ret = 0;
+		int max = 0;
 
+		mptcp_for_each_subflow(msk, subflow) {
+			if (READ_ONCE(subflow->scheduled)) {
+				ssk = mptcp_subflow_tcp_sock(subflow);
+				if (!ssk)
+					goto reset_timer;
+
+				lock_sock(ssk);
+
+				ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
+				if (ret <= 0)
+					break;
+
+				if (ret > max)
+					max = ret;
+
+				tcp_push(ssk, 0, info.mss_now, tcp_sk(ssk)->nonagle,
+						info.size_goal);
+
+				release_sock(ssk);
+
+				msk->last_snd = ssk;
+				mptcp_subflow_set_scheduled(subflow, false);
+			}
+		}
 		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_RETRANSSEGS);
-		copied += ret;
-		info.sent += ret;
+		copied += max;
+		info.sent += max;
 	}
 	if (copied) {
 		dfrag->already_sent = max(dfrag->already_sent, info.sent);
-		tcp_push(ssk, 0, info.mss_now, tcp_sk(ssk)->nonagle,
-			 info.size_goal);
 		WRITE_ONCE(msk->allow_infinite_fallback, false);
 	}
 
-	release_sock(ssk);
-
 reset_timer:
 	mptcp_check_and_set_pending(sk);
 
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index a12507dcf1d5..4669d34f4d7c 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -632,7 +632,9 @@ void mptcp_release_sched(struct mptcp_sock *msk);
 void mptcp_subflow_set_scheduled(struct mptcp_subflow_context *subflow,
 				 bool scheduled);
 struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk);
+struct sock *mptcp_subflow_get_retrans(struct mptcp_sock *msk);
 int __mptcp_sched_get_send(struct mptcp_sock *msk);
+int __mptcp_sched_get_retrans(struct mptcp_sock *msk);
 
 static inline bool __mptcp_subflow_active(struct mptcp_subflow_context *subflow)
 {
diff --git a/net/mptcp/sched.c b/net/mptcp/sched.c
index 9427d15b4c69..70ab43c59989 100644
--- a/net/mptcp/sched.c
+++ b/net/mptcp/sched.c
@@ -146,3 +146,28 @@ int __mptcp_sched_get_send(struct mptcp_sock *msk)
 
 	return 0;
 }
+
+int __mptcp_sched_get_retrans(struct mptcp_sock *msk)
+{
+	struct mptcp_sched_data data;
+	struct sock *ssk = NULL;
+
+	sock_owned_by_me((const struct sock *)msk);
+
+	/* the following check is moved out of mptcp_subflow_get_retrans */
+	if (__mptcp_check_fallback(msk))
+		return -EINVAL;
+
+	if (!msk->sched) {
+		ssk = mptcp_subflow_get_retrans(msk);
+		if (!ssk)
+			return -EINVAL;
+		mptcp_subflow_set_scheduled(mptcp_subflow_ctx(ssk), true);
+		return 0;
+	}
+
+	mptcp_sched_data_init(msk, true, &data);
+	msk->sched->get_subflow(msk, &data);
+
+	return 0;
+}
-- 
2.34.1