mptcp: drop *_max fields in mptcp_pm_data

This patch drops the per-msk values add_addr_signal_max,
add_addr_accept_max, local_addr_max and subflows_max fields in struct
mptcp_pm_data, uses the pernet *_max values instead. And adds four new
helpers to get the pernet *_max values separately.

Co-developed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
index 0a6ebd0..01a846b 100644
--- a/net/mptcp/pm.c
+++ b/net/mptcp/pm.c
@@ -78,10 +78,13 @@ void mptcp_pm_new_connection(struct mptcp_sock *msk, int server_side)
 bool mptcp_pm_allow_new_subflow(struct mptcp_sock *msk)
 {
 	struct mptcp_pm_data *pm = &msk->pm;
+	unsigned int subflows_max;
 	int ret = 0;
 
+	subflows_max = mptcp_pm_get_subflows_max(msk);
+
 	pr_debug("msk=%p subflows=%d max=%d allow=%d", msk, pm->subflows,
-		 pm->subflows_max, READ_ONCE(pm->accept_subflow));
+		 subflows_max, READ_ONCE(pm->accept_subflow));
 
 	/* try to avoid acquiring the lock below */
 	if (!READ_ONCE(pm->accept_subflow))
@@ -89,8 +92,8 @@ bool mptcp_pm_allow_new_subflow(struct mptcp_sock *msk)
 
 	spin_lock_bh(&pm->lock);
 	if (READ_ONCE(pm->accept_subflow)) {
-		ret = pm->subflows < pm->subflows_max;
-		if (ret && ++pm->subflows == pm->subflows_max)
+		ret = pm->subflows < subflows_max;
+		if (ret && ++pm->subflows == subflows_max)
 			WRITE_ONCE(pm->accept_subflow, false);
 	}
 	spin_unlock_bh(&pm->lock);