mptcp: add scheduled in mptcp_subflow_context

This patch adds a new member scheduled in struct mptcp_subflow_context,
which will be set in the MPTCP scheduler context when the scheduler
picks this subflow to send data.

Add a new helper mptcp_subflow_set_scheduled() to set this flag using
WRITE_ONCE().
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Geliang Tang <geliang.tang@suse.com>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Link: https://lore.kernel.org/r/20230821-upstream-net-next-20230818-v1-6-0c860fb256a8@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/protocol.h

@@ -491,6 +491,7 @@ struct mptcp_subflow_context {
 		is_mptfo : 1,	    /* subflow is doing TFO */
 		__unused : 9;
 	enum mptcp_data_avail data_avail;
+	bool	scheduled;
 	u32	remote_nonce;
 	u64	thmac;
 	u32	local_nonce;
@@ -663,6 +664,8 @@ void mptcp_unregister_scheduler(struct mptcp_sched_ops *sched);
 int mptcp_init_sched(struct mptcp_sock *msk,
 		     struct mptcp_sched_ops *sched);
 void mptcp_release_sched(struct mptcp_sock *msk);
+void mptcp_subflow_set_scheduled(struct mptcp_subflow_context *subflow,
+				 bool scheduled);
 
 static inline bool __tcp_can_send(const struct sock *ssk)
 {

net/mptcp/sched.c

@@ -87,3 +87,9 @@ void mptcp_release_sched(struct mptcp_sock *msk)
 
 	bpf_module_put(sched, sched->owner);
 }
+
+void mptcp_subflow_set_scheduled(struct mptcp_subflow_context *subflow,
+				 bool scheduled)
+{
+	WRITE_ONCE(subflow->scheduled, scheduled);
+}