migration: use migration_is_active to represent active state

Wrap the check into a function to make it easy to read.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Message-Id: <20190717005341.14140-1-richardw.yang@linux.intel.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
diff --git a/migration/migration.c b/migration/migration.c
index 5f7e4d1..0c51aa6 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1533,8 +1533,7 @@
         qemu_fclose(tmp);
     }
 
-    assert((s->state != MIGRATION_STATUS_ACTIVE) &&
-           (s->state != MIGRATION_STATUS_POSTCOPY_ACTIVE));
+    assert(!migration_is_active(s));
 
     if (s->state == MIGRATION_STATUS_CANCELLING) {
         migrate_set_state(&s->state, MIGRATION_STATUS_CANCELLING,
@@ -1703,6 +1702,12 @@
     return false;
 }
 
+bool migration_is_active(MigrationState *s)
+{
+    return (s->state == MIGRATION_STATUS_ACTIVE ||
+            s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE);
+}
+
 void migrate_init(MigrationState *s)
 {
     /*
@@ -3266,8 +3271,7 @@
 
     trace_migration_thread_setup_complete();
 
-    while (s->state == MIGRATION_STATUS_ACTIVE ||
-           s->state == MIGRATION_STATUS_POSTCOPY_ACTIVE) {
+    while (migration_is_active(s)) {
         int64_t current_time;
 
         if (urgent || !qemu_file_rate_limit(s->to_dst_file)) {