From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Wed, 6 May 2020 15:33:06 -0600
Subject: wireguard: send/receive: use explicit unlikely branch instead of
 implicit coalescing
Patch-mainline: v5.7-rc5
Git-commit: 243f2148937adc72bcaaa590d482d599c936efde
References: git-fixes

It's very unlikely that send will become true. It's nearly always false
between 0 and 120 seconds of a session, and in most cases becomes true
only between 120 and 121 seconds before becoming false again. So,
unlikely(send) is clearly the right option here.

What happened before was that we had this complex boolean expression
with multiple likely and unlikely clauses nested. Since this is
evaluated left-to-right anyway, the whole thing got converted to
unlikely. So, we can clean this up to better represent what's going on.

The generated code is the same.

Suggested-by: Sultan Alsawaf <sultan@kerneltoast.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Daniel Wagner <dwagner@suse.de>
---
 drivers/net/wireguard/receive.c |   13 ++++++-------
 drivers/net/wireguard/send.c    |   15 ++++++---------
 2 files changed, 12 insertions(+), 16 deletions(-)

--- a/drivers/net/wireguard/receive.c
+++ b/drivers/net/wireguard/receive.c
@@ -226,21 +226,20 @@ void wg_packet_handshake_receive_worker(
 static void keep_key_fresh(struct wg_peer *peer)
 {
 	struct noise_keypair *keypair;
-	bool send = false;
+	bool send;
 
 	if (peer->sent_lastminute_handshake)
 		return;
 
 	rcu_read_lock_bh();
 	keypair = rcu_dereference_bh(peer->keypairs.current_keypair);
-	if (likely(keypair && READ_ONCE(keypair->sending.is_valid)) &&
-	    keypair->i_am_the_initiator &&
-	    unlikely(wg_birthdate_has_expired(keypair->sending.birthdate,
-			REJECT_AFTER_TIME - KEEPALIVE_TIMEOUT - REKEY_TIMEOUT)))
-		send = true;
+	send = keypair && READ_ONCE(keypair->sending.is_valid) &&
+	       keypair->i_am_the_initiator &&
+	       wg_birthdate_has_expired(keypair->sending.birthdate,
+			REJECT_AFTER_TIME - KEEPALIVE_TIMEOUT - REKEY_TIMEOUT);
 	rcu_read_unlock_bh();
 
-	if (send) {
+	if (unlikely(send)) {
 		peer->sent_lastminute_handshake = true;
 		wg_packet_send_queued_handshake_initiation(peer, false);
 	}
--- a/drivers/net/wireguard/send.c
+++ b/drivers/net/wireguard/send.c
@@ -124,20 +124,17 @@ void wg_packet_send_handshake_cookie(str
 static void keep_key_fresh(struct wg_peer *peer)
 {
 	struct noise_keypair *keypair;
-	bool send = false;
+	bool send;
 
 	rcu_read_lock_bh();
 	keypair = rcu_dereference_bh(peer->keypairs.current_keypair);
-	if (likely(keypair && READ_ONCE(keypair->sending.is_valid)) &&
-	    (unlikely(atomic64_read(&keypair->sending.counter.counter) >
-		      REKEY_AFTER_MESSAGES) ||
-	     (keypair->i_am_the_initiator &&
-	      unlikely(wg_birthdate_has_expired(keypair->sending.birthdate,
-						REKEY_AFTER_TIME)))))
-		send = true;
+	send = keypair && READ_ONCE(keypair->sending.is_valid) &&
+	       (atomic64_read(&keypair->sending.counter.counter) > REKEY_AFTER_MESSAGES ||
+		(keypair->i_am_the_initiator &&
+		 wg_birthdate_has_expired(keypair->sending.birthdate, REKEY_AFTER_TIME)));
 	rcu_read_unlock_bh();
 
-	if (send)
+	if (unlikely(send))
 		wg_packet_send_queued_handshake_initiation(peer, false);
 }