[PULL 16/18] migration: Allow migrate-recover to run multiple times

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: Peter Xu <peterx@redhat.com>

Previously migration didn't have an easy way to cleanup the listening
transport, migrate recovery only allows to execute once.  That's done with a
trick flag in postcopy_recover_triggered.

Now the facility is already there.

Drop postcopy_recover_triggered and instead allows a new migrate-recover to
release the previous listener transport.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20220331150857.74406-8-peterx@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 migration/migration.c | 13 ++-----------
 migration/migration.h |  1 -
 migration/savevm.c    |  3 ---
 3 files changed, 2 insertions(+), 15 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index b1659b7092..cc00b344a9 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -2162,11 +2162,8 @@ void qmp_migrate_recover(const char *uri, Error **errp)
         return;
     }
 
-    if (qatomic_cmpxchg(&mis->postcopy_recover_triggered,
-                       false, true) == true) {
-        error_setg(errp, "Migrate recovery is triggered already");
-        return;
-    }
+    /* If there's an existing transport, release it */
+    migration_incoming_transport_cleanup(mis);
 
     /*
      * Note that this call will never start a real migration; it will
@@ -2174,12 +2171,6 @@ void qmp_migrate_recover(const char *uri, Error **errp)
      * to continue using that newly established channel.
      */
     qemu_start_incoming_migration(uri, errp);
-
-    /* Safe to dereference with the assert above */
-    if (*errp) {
-        /* Reset the flag so user could still retry */
-        qatomic_set(&mis->postcopy_recover_triggered, false);
-    }
 }
 
 void qmp_migrate_pause(Error **errp)
diff --git a/migration/migration.h b/migration/migration.h
index f17ccc657c..a863032b71 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -139,7 +139,6 @@ struct MigrationIncomingState {
     struct PostcopyBlocktimeContext *blocktime_ctx;
 
     /* notify PAUSED postcopy incoming migrations to try to continue */
-    bool postcopy_recover_triggered;
     QemuSemaphore postcopy_pause_sem_dst;
     QemuSemaphore postcopy_pause_sem_fault;
 
diff --git a/migration/savevm.c b/migration/savevm.c
index 02ed94c180..d9076897b8 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2589,9 +2589,6 @@ static bool postcopy_pause_incoming(MigrationIncomingState *mis)
 
     assert(migrate_postcopy_ram());
 
-    /* Clear the triggered bit to allow one recovery */
-    mis->postcopy_recover_triggered = false;
-
     /*
      * Unregister yank with either from/to src would work, since ioc behind it
      * is the same
-- 
2.35.1