This patch defines a wrapper named mptcp_sched_get_retrans(), invoke
mptcp_subflow_get_retrans() or get_subflow() of msk->sched in it.

Move sock_owned_by_me() and the fallback check code from
mptcp_subflow_get_retans() into this wrapper.

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 net/mptcp/protocol.c |  7 +------
 net/mptcp/protocol.h |  2 ++
 net/mptcp/sched.c    | 25 +++++++++++++++++++++++++
 3 files changed, 28 insertions(+), 6 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 257b04315271..3bb3445c1eaf 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2241,17 +2241,12 @@ 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);
 
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index a5a6e8aed5c7..c4ce576458a2 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -633,7 +633,9 @@ 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);
 struct sock *mptcp_sched_get_send(struct mptcp_sock *msk, int *err);
+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 527ea07982c5..0ac80eb9a428 100644
--- a/net/mptcp/sched.c
+++ b/net/mptcp/sched.c
@@ -164,3 +164,28 @@ struct sock *mptcp_sched_get_send(struct mptcp_sock *msk, int *err)
 
 	return ssk;
 }
+
+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;
+}
-- 
2.35.3