This patch defines the default packet scheduler mptcp_sched_default,
register it in mptcp_sched_init(), which is invoked in mptcp_proto_init().
Skip deleting this default scheduler in mptcp_unregister_scheduler().

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 net/mptcp/protocol.c |  9 +++++++++
 net/mptcp/protocol.h |  2 ++
 net/mptcp/sched.c    | 14 ++++++++++++++
 3 files changed, 25 insertions(+)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index b2c654992de0..0187059307d0 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2251,6 +2251,14 @@ static struct sock *mptcp_subflow_get_retrans(struct mptcp_sock *msk)
 	return min_stale_count > 1 ? backup : NULL;
 }
 
+struct sock *mptcp_get_subflow_default(struct mptcp_sock *msk, bool retrans)
+{
+	if (retrans)
+		return mptcp_subflow_get_retrans(msk);
+
+	return mptcp_subflow_get_send(msk);
+}
+
 static void mptcp_dispose_initial_subflow(struct mptcp_sock *msk)
 {
 	if (msk->subflow) {
@@ -3804,6 +3812,7 @@ void __init mptcp_proto_init(void)
 
 	mptcp_subflow_init();
 	mptcp_pm_init();
+	mptcp_sched_init();
 	mptcp_token_init();
 
 	if (proto_register(&mptcp_prot, MPTCP_USE_SLAB) != 0)
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 7cd2c1c3d25c..9ba37d0b9fcc 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -611,6 +611,8 @@ void mptcp_info2sockaddr(const struct mptcp_addr_info *info,
 struct mptcp_sched_ops *mptcp_sched_find(const char *name);
 int mptcp_register_scheduler(struct mptcp_sched_ops *sched);
 void mptcp_unregister_scheduler(struct mptcp_sched_ops *sched);
+struct sock *mptcp_get_subflow_default(struct mptcp_sock *msk, bool retrans);
+void mptcp_sched_init(void);
 
 static inline bool __mptcp_subflow_active(struct mptcp_subflow_context *subflow)
 {
diff --git a/net/mptcp/sched.c b/net/mptcp/sched.c
index c5d3bbafba71..bd0beff8cac8 100644
--- a/net/mptcp/sched.c
+++ b/net/mptcp/sched.c
@@ -13,6 +13,12 @@
 #include <linux/spinlock.h>
 #include "protocol.h"
 
+static struct mptcp_sched_ops mptcp_sched_default = {
+	.get_subflow    = mptcp_get_subflow_default,
+	.name           = "default",
+	.owner          = THIS_MODULE,
+};
+
 static DEFINE_SPINLOCK(mptcp_sched_list_lock);
 static LIST_HEAD(mptcp_sched_list);
 
@@ -50,7 +56,15 @@ int mptcp_register_scheduler(struct mptcp_sched_ops *sched)
 
 void mptcp_unregister_scheduler(struct mptcp_sched_ops *sched)
 {
+	if (sched == &mptcp_sched_default)
+		return;
+
 	spin_lock(&mptcp_sched_list_lock);
 	list_del_rcu(&sched->list);
 	spin_unlock(&mptcp_sched_list_lock);
 }
+
+void mptcp_sched_init(void)
+{
+	mptcp_register_scheduler(&mptcp_sched_default);
+}
-- 
2.34.1