mptcp: drop last_snd and MPTCP_RESET_SCHEDULER

Since the burst check conditions have moved out of the function
mptcp_subflow_get_send(), it makes all msk->last_snd useless.
This patch drops them as well as the macro MPTCP_RESET_SCHEDULER.
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-v1-2-0c860fb256a8@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/pm.c

@@ -299,15 +299,8 @@ void mptcp_pm_mp_prio_received(struct sock *ssk, u8 bkup)
 
 	pr_debug("subflow->backup=%d, bkup=%d\n", subflow->backup, bkup);
 	msk = mptcp_sk(sk);
-	if (subflow->backup != bkup) {
+	if (subflow->backup != bkup)
 		subflow->backup = bkup;
-		mptcp_data_lock(sk);
-		if (!sock_owned_by_user(sk))
-			msk->last_snd = NULL;
-		else
-			__set_bit(MPTCP_RESET_SCHEDULER,  &msk->cb_flags);
-		mptcp_data_unlock(sk);
-	}
 
 	mptcp_event(MPTCP_EVENT_SUB_PRIORITY, msk, ssk, GFP_ATOMIC);
 }

net/mptcp/pm_netlink.c

@@ -472,9 +472,6 @@ static void __mptcp_pm_send_ack(struct mptcp_sock *msk, struct mptcp_subflow_con
 
 	slow = lock_sock_fast(ssk);
 	if (prio) {
-		if (subflow->backup != backup)
-			msk->last_snd = NULL;
-
 		subflow->send_mp_prio = 1;
 		subflow->backup = backup;
 		subflow->request_bkup = backup;

net/mptcp/protocol.c

@@ -1438,16 +1438,13 @@ static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
 
 	burst = min_t(int, MPTCP_SEND_BURST_SIZE, mptcp_wnd_end(msk) - msk->snd_nxt);
 	wmem = READ_ONCE(ssk->sk_wmem_queued);
-	if (!burst) {
-		msk->last_snd = NULL;
+	if (!burst)
 		return ssk;
-	}
 
 	subflow = mptcp_subflow_ctx(ssk);
 	subflow->avg_pacing_rate = div_u64((u64)subflow->avg_pacing_rate * wmem +
 					   READ_ONCE(ssk->sk_pacing_rate) * burst,
 					   burst + wmem);
-	msk->last_snd = ssk;
 	msk->snd_burst = burst;
 	return ssk;
 }
@@ -2379,9 +2376,6 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
 		WRITE_ONCE(msk->first, NULL);
 
 out:
-	if (ssk == msk->last_snd)
-		msk->last_snd = NULL;
-
 	if (need_push)
 		__mptcp_push_pending(sk, 0);
 }
@@ -3046,7 +3040,6 @@ static int mptcp_disconnect(struct sock *sk, int flags)
 	 * subflow
 	 */
 	mptcp_destroy_common(msk, MPTCP_CF_FASTCLOSE);
-	msk->last_snd = NULL;
 	WRITE_ONCE(msk->flags, 0);
 	msk->cb_flags = 0;
 	msk->push_pending = 0;
@@ -3316,8 +3309,6 @@ static void mptcp_release_cb(struct sock *sk)
 			__mptcp_set_connected(sk);
 		if (__test_and_clear_bit(MPTCP_ERROR_REPORT, &msk->cb_flags))
 			__mptcp_error_report(sk);
-		if (__test_and_clear_bit(MPTCP_RESET_SCHEDULER, &msk->cb_flags))
-			msk->last_snd = NULL;
 	}
 
 	__mptcp_update_rmem(sk);

net/mptcp/protocol.h

@@ -123,7 +123,6 @@
 #define MPTCP_RETRANSMIT	4
 #define MPTCP_FLUSH_JOIN_LIST	5
 #define MPTCP_CONNECTED		6
-#define MPTCP_RESET_SCHEDULER	7
 
 struct mptcp_skb_cb {
 	u64 map_seq;
@@ -269,7 +268,6 @@ struct mptcp_sock {
 	u64		rcv_data_fin_seq;
 	u64		bytes_retrans;
 	int		rmem_fwd_alloc;
-	struct sock	*last_snd;
 	int		snd_burst;
 	int		old_wspace;
 	u64		recovery_snd_nxt;	/* in recovery mode accept up to this seq;