From a239c898c12a92cb5fb74f0eb74bc5919db45b94 Mon Sep 17 00:00:00 2001
From: David Teigland <teigland@redhat.com>
Date: Dec 08 2023 23:54:12 +0000
Subject: sanlock: skip short delay in delta lease reacquire


When a host with the same host name reacquires the
same host_id, the "fast" delta lease reacquire was
still applying the short delay (default 20s) which
should not be necessary.  Reduce this further to
just 1 second when the lease is also free.

---

diff --git a/src/delta_lease.c b/src/delta_lease.c
index 9d5aafd..d36d4e0 100644
--- a/src/delta_lease.c
+++ b/src/delta_lease.c
@@ -340,6 +340,7 @@ int delta_lease_acquire(struct task *task,
 	uint32_t checksum;
 	int other_io_timeout, other_host_dead_seconds, other_id_renewal_seconds;
 	int i, error, rv, delay, delta_large_delay;
+	int fast_free_delay = 0;
 
 	log_space(sp, "delta_acquire begin %.48s:%llu",
 		  sp->space_name, (unsigned long long)host_id);
@@ -361,6 +362,19 @@ int delta_lease_acquire(struct task *task,
 			  leader.io_timeout, sp->io_timeout);
 	}
 
+	/*
+	 * This delay-free reacquire could probably be used whenever
+	 * our_host_name matches the current leader.resource_name,
+	 * regardless of wheter the lease is free (i.e. we cleanly
+	 * released the lease last time we held it.)
+	 */
+	if (!strncmp(leader.resource_name, our_host_name, NAME_ID_SIZE) &&
+	    (leader.timestamp == LEASE_FREE)) {
+		log_space(sp, "delta_acquire free fast reacquire");
+		fast_free_delay = 1;
+		goto write_new;
+	}
+
 	if (leader.timestamp == LEASE_FREE)
 		goto write_new;
 
@@ -475,7 +489,10 @@ int delta_lease_acquire(struct task *task,
 
 	memcpy(&leader1, &leader, sizeof(struct leader_record));
 
-	delay = 2 * other_io_timeout;
+	if (fast_free_delay)
+		delay = 1;
+	else
+		delay = 2 * other_io_timeout;
 	log_space(sp, "delta_acquire delta_short_delay %d", delay);
 
 	for (i = 0; i < delay; i++) {