mptcp: pm: remove mptcp_pm_remove_subflow()

This helper is confusing. It is in pm.c, but it is specific to the
in-kernel PM and it cannot be used by the userspace one. Also, it simply
calls one in-kernel specific function with the PM lock, while the
similar mptcp_pm_remove_addr() helper requires the PM lock.

What's left is the pr_debug(), which is not that useful, because a
similar one is present in the only function called by this helper:

  mptcp_pm_nl_rm_subflow_received()

After these modifications, this helper can be marked as 'static', and
the lock can be taken only once in mptcp_pm_flush_addrs_and_subflows().

Note that it is not a bug fix, but it will help backporting the
following commits.

Fixes: 0ee4261 ("mptcp: implement mptcp_pm_remove_subflow")
Cc: stable@vger.kernel.org
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20240819-net-mptcp-pm-reusing-id-v1-7-38035d40de5b@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/pm.c

@@ -60,16 +60,6 @@ int mptcp_pm_remove_addr(struct mptcp_sock *msk, const struct mptcp_rm_list *rm_
 	return 0;
 }
 
-int mptcp_pm_remove_subflow(struct mptcp_sock *msk, const struct mptcp_rm_list *rm_list)
-{
-	pr_debug("msk=%p, rm_list_nr=%d", msk, rm_list->nr);
-
-	spin_lock_bh(&msk->pm.lock);
-	mptcp_pm_nl_rm_subflow_received(msk, rm_list);
-	spin_unlock_bh(&msk->pm.lock);
-	return 0;
-}
-
 /* path manager event handlers */
 
 void mptcp_pm_new_connection(struct mptcp_sock *msk, const struct sock *ssk, int server_side)

net/mptcp/pm_netlink.c

@@ -857,8 +857,8 @@ static void mptcp_pm_nl_rm_addr_received(struct mptcp_sock *msk)
 	mptcp_pm_nl_rm_addr_or_subflow(msk, &msk->pm.rm_list_rx, MPTCP_MIB_RMADDR);
 }
 
-void mptcp_pm_nl_rm_subflow_received(struct mptcp_sock *msk,
-				     const struct mptcp_rm_list *rm_list)
+static void mptcp_pm_nl_rm_subflow_received(struct mptcp_sock *msk,
+					    const struct mptcp_rm_list *rm_list)
 {
 	mptcp_pm_nl_rm_addr_or_subflow(msk, rm_list, MPTCP_MIB_RMSUBFLOW);
 }
@@ -1471,7 +1471,9 @@ static int mptcp_nl_remove_subflow_and_signal_addr(struct net *net,
 					  !(entry->flags & MPTCP_PM_ADDR_FLAG_IMPLICIT));
 
 		if (remove_subflow) {
-			mptcp_pm_remove_subflow(msk, &list);
+			spin_lock_bh(&msk->pm.lock);
+			mptcp_pm_nl_rm_subflow_received(msk, &list);
+			spin_unlock_bh(&msk->pm.lock);
 		} else if (entry->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW) {
 			/* If the subflow has been used, but now closed */
 			spin_lock_bh(&msk->pm.lock);
@@ -1617,18 +1619,14 @@ static void mptcp_pm_remove_addrs_and_subflows(struct mptcp_sock *msk,
 			alist.ids[alist.nr++] = entry->addr.id;
 	}
 
+	spin_lock_bh(&msk->pm.lock);
 	if (alist.nr) {
-		spin_lock_bh(&msk->pm.lock);
 		msk->pm.add_addr_signaled -= alist.nr;
 		mptcp_pm_remove_addr(msk, &alist);
-		spin_unlock_bh(&msk->pm.lock);
 	}
-
 	if (slist.nr)
-		mptcp_pm_remove_subflow(msk, &slist);
-
+		mptcp_pm_nl_rm_subflow_received(msk, &slist);
 	/* Reset counters: maybe some subflows have been removed before */
-	spin_lock_bh(&msk->pm.lock);
 	bitmap_fill(msk->pm.id_avail_bitmap, MPTCP_PM_MAX_ADDR_ID + 1);
 	msk->pm.local_addr_used = 0;
 	spin_unlock_bh(&msk->pm.lock);

net/mptcp/protocol.h

@@ -1026,7 +1026,6 @@ int mptcp_pm_announce_addr(struct mptcp_sock *msk,
 			   const struct mptcp_addr_info *addr,
 			   bool echo);
 int mptcp_pm_remove_addr(struct mptcp_sock *msk, const struct mptcp_rm_list *rm_list);
-int mptcp_pm_remove_subflow(struct mptcp_sock *msk, const struct mptcp_rm_list *rm_list);
 void mptcp_pm_remove_addrs(struct mptcp_sock *msk, struct list_head *rm_list);
 
 void mptcp_free_local_addr_list(struct mptcp_sock *msk);
@@ -1133,8 +1132,6 @@ static inline u8 subflow_get_local_id(const struct mptcp_subflow_context *subflo
 
 void __init mptcp_pm_nl_init(void);
 void mptcp_pm_nl_work(struct mptcp_sock *msk);
-void mptcp_pm_nl_rm_subflow_received(struct mptcp_sock *msk,
-				     const struct mptcp_rm_list *rm_list);
 unsigned int mptcp_pm_get_add_addr_signal_max(const struct mptcp_sock *msk);
 unsigned int mptcp_pm_get_add_addr_accept_max(const struct mptcp_sock *msk);
 unsigned int mptcp_pm_get_subflows_max(const struct mptcp_sock *msk);