Before this modification, this function was quite long with many levels
of indentations.

Each case can be split in a dedicated function: fullmesh, non-fullmesh.

To remove one level of indentation, msk->pm.subflows >= subflows_max is
now checked after having added one subflow, and stops the loop if it is
no longer possible to add new subflows. This is fine to do this because
this function should only be called if msk->pm.subflows < subflows_max.

No functional changes intended.

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
v2: keep 'Reverse X-Mas Tree' order, and comments (Geliang)
---
 net/mptcp/pm_kernel.c | 116 +++++++++++++++++++++++++++++---------------------
 1 file changed, 67 insertions(+), 49 deletions(-)

diff --git a/net/mptcp/pm_kernel.c b/net/mptcp/pm_kernel.c
index 5bdcfcc26308841c49375ce35205097f30592279..7bc243c96f30e20b4da3d610d3b8211e478626e6 100644
--- a/net/mptcp/pm_kernel.c
+++ b/net/mptcp/pm_kernel.c
@@ -159,74 +159,92 @@ select_signal_address(struct pm_nl_pernet *pernet, const struct mptcp_sock *msk,
 	return found;
 }
 
-/* Fill all the remote addresses into the array addrs[],
- * and return the array size.
- */
-static unsigned int fill_remote_addresses_vec(struct mptcp_sock *msk,
-					      struct mptcp_addr_info *local,
-					      bool fullmesh,
-					      struct mptcp_addr_info *addrs)
+static unsigned int
+fill_remote_addr(struct mptcp_sock *msk, struct mptcp_addr_info *local,
+		 struct mptcp_addr_info *addrs)
 {
 	bool deny_id0 = READ_ONCE(msk->pm.remote_deny_join_id0);
+	struct mptcp_addr_info remote = { 0 };
+	struct sock *sk = (struct sock *)msk;
+
+	if (deny_id0)
+		return 0;
+
+	mptcp_remote_address((struct sock_common *)sk, &remote);
+
+	if (!mptcp_pm_addr_families_match(sk, local, &remote))
+		return 0;
+
+	msk->pm.subflows++;
+	*addrs = remote;
+
+	return 1;
+}
+
+static unsigned int
+fill_remote_addresses_fullmesh(struct mptcp_sock *msk,
+			       struct mptcp_addr_info *local,
+			       struct mptcp_addr_info *addrs)
+{
+	bool deny_id0 = READ_ONCE(msk->pm.remote_deny_join_id0);
+	DECLARE_BITMAP(unavail_id, MPTCP_PM_MAX_ADDR_ID + 1);
 	struct sock *sk = (struct sock *)msk, *ssk;
 	struct mptcp_subflow_context *subflow;
-	struct mptcp_addr_info remote = { 0 };
 	unsigned int subflows_max;
 	int i = 0;
 
 	subflows_max = mptcp_pm_get_subflows_max(msk);
-	mptcp_remote_address((struct sock_common *)sk, &remote);
 
-	/* Non-fullmesh endpoint, fill in the single entry
-	 * corresponding to the primary MPC subflow remote address
+	/* Forbid creation of new subflows matching existing ones, possibly
+	 * already created by incoming ADD_ADDR
 	 */
-	if (!fullmesh) {
-		if (deny_id0)
-			return 0;
+	bitmap_zero(unavail_id, MPTCP_PM_MAX_ADDR_ID + 1);
+	mptcp_for_each_subflow(msk, subflow)
+		if (READ_ONCE(subflow->local_id) == local->id)
+			__set_bit(subflow->remote_id, unavail_id);
 
-		if (!mptcp_pm_addr_families_match(sk, local, &remote))
-			return 0;
+	mptcp_for_each_subflow(msk, subflow) {
+		ssk = mptcp_subflow_tcp_sock(subflow);
+		mptcp_remote_address((struct sock_common *)ssk, &addrs[i]);
+		addrs[i].id = READ_ONCE(subflow->remote_id);
+		if (deny_id0 && !addrs[i].id)
+			continue;
 
+		if (test_bit(addrs[i].id, unavail_id))
+			continue;
+
+		if (!mptcp_pm_addr_families_match(sk, local, &addrs[i]))
+			continue;
+
+		/* forbid creating multiple address towards this id */
+		__set_bit(addrs[i].id, unavail_id);
 		msk->pm.subflows++;
-		addrs[i++] = remote;
-	} else {
-		DECLARE_BITMAP(unavail_id, MPTCP_PM_MAX_ADDR_ID + 1);
+		i++;
 
-		/* Forbid creation of new subflows matching existing
-		 * ones, possibly already created by incoming ADD_ADDR
-		 */
-		bitmap_zero(unavail_id, MPTCP_PM_MAX_ADDR_ID + 1);
-		mptcp_for_each_subflow(msk, subflow)
-			if (READ_ONCE(subflow->local_id) == local->id)
-				__set_bit(subflow->remote_id, unavail_id);
-
-		mptcp_for_each_subflow(msk, subflow) {
-			ssk = mptcp_subflow_tcp_sock(subflow);
-			mptcp_remote_address((struct sock_common *)ssk, &addrs[i]);
-			addrs[i].id = READ_ONCE(subflow->remote_id);
-			if (deny_id0 && !addrs[i].id)
-				continue;
-
-			if (test_bit(addrs[i].id, unavail_id))
-				continue;
-
-			if (!mptcp_pm_addr_families_match(sk, local, &addrs[i]))
-				continue;
-
-			if (msk->pm.subflows < subflows_max) {
-				/* forbid creating multiple address towards
-				 * this id
-				 */
-				__set_bit(addrs[i].id, unavail_id);
-				msk->pm.subflows++;
-				i++;
-			}
-		}
+		if (msk->pm.subflows >= subflows_max)
+			break;
 	}
 
 	return i;
 }
 
+/* Fill all the remote addresses into the array addrs[],
+ * and return the array size.
+ */
+static unsigned int
+fill_remote_addresses_vec(struct mptcp_sock *msk, struct mptcp_addr_info *local,
+			  bool fullmesh, struct mptcp_addr_info *addrs)
+{
+	/* Non-fullmesh: fill in the single entry corresponding to the primary
+	 * MPC subflow remote address, and return 1, corresponding to 1 entry.
+	 */
+	if (!fullmesh)
+		return fill_remote_addr(msk, local, addrs);
+
+	/* Fullmesh endpoint: fill all possible remote addresses */
+	return fill_remote_addresses_fullmesh(msk, local, addrs);
+}
+
 static struct mptcp_pm_addr_entry *
 __lookup_addr_by_id(struct pm_nl_pernet *pernet, unsigned int id)
 {

-- 
2.51.0