introduce MIG_STATE_CANCELLING state

Introduce MIG_STATE_CANCELLING state to avoid starting a new migration task while the previous one still exist.
Signed-off-by: Zeng Junliang <zengjunliang@huawei.com>
Signed-off-by: Zhang Haoyu <haoyu.zhang@huawei.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

migration.c

@@ -40,6 +40,7 @@ enum {
     MIG_STATE_ERROR = -1,
     MIG_STATE_NONE,
     MIG_STATE_SETUP,
+    MIG_STATE_CANCELLING,
     MIG_STATE_CANCELLED,
     MIG_STATE_ACTIVE,
     MIG_STATE_COMPLETED,
@@ -196,6 +197,7 @@ MigrationInfo *qmp_query_migrate(Error **errp)
         info->has_total_time = false;
         break;
     case MIG_STATE_ACTIVE:
+    case MIG_STATE_CANCELLING:
         info->has_status = true;
         info->status = g_strdup("active");
         info->has_total_time = true;
@@ -282,6 +284,13 @@ void qmp_migrate_set_capabilities(MigrationCapabilityStatusList *params,
 
 /* shared migration helpers */
 
+static void migrate_set_state(MigrationState *s, int old_state, int new_state)
+{
+    if (atomic_cmpxchg(&s->state, old_state, new_state) == new_state) {
+        trace_migrate_set_state(new_state);
+    }
+}
+
 static void migrate_fd_cleanup(void *opaque)
 {
     MigrationState *s = opaque;
@@ -303,18 +312,14 @@ static void migrate_fd_cleanup(void *opaque)
 
     if (s->state != MIG_STATE_COMPLETED) {
         qemu_savevm_state_cancel();
+        if (s->state == MIG_STATE_CANCELLING) {
+            migrate_set_state(s, MIG_STATE_CANCELLING, MIG_STATE_CANCELLED);
+        }
     }
 
     notifier_list_notify(&migration_state_notifiers, s);
 }
 
-static void migrate_set_state(MigrationState *s, int old_state, int new_state)
-{
-    if (atomic_cmpxchg(&s->state, old_state, new_state) == new_state) {
-        trace_migrate_set_state(new_state);
-    }
-}
-
 void migrate_fd_error(MigrationState *s)
 {
     DPRINTF("setting error state\n");
@@ -334,8 +339,8 @@ static void migrate_fd_cancel(MigrationState *s)
         if (old_state != MIG_STATE_SETUP && old_state != MIG_STATE_ACTIVE) {
             break;
         }
-        migrate_set_state(s, old_state, MIG_STATE_CANCELLED);
-    } while (s->state != MIG_STATE_CANCELLED);
+        migrate_set_state(s, old_state, MIG_STATE_CANCELLING);
+    } while (s->state != MIG_STATE_CANCELLING);
 }
 
 void add_migration_state_change_notifier(Notifier *notify)
@@ -412,7 +417,8 @@ void qmp_migrate(const char *uri, bool has_blk, bool blk,
     params.blk = has_blk && blk;
     params.shared = has_inc && inc;
 
-    if (s->state == MIG_STATE_ACTIVE || s->state == MIG_STATE_SETUP) {
+    if (s->state == MIG_STATE_ACTIVE || s->state == MIG_STATE_SETUP ||
+        s->state == MIG_STATE_CANCELLING) {
         error_set(errp, QERR_MIGRATION_ACTIVE);
         return;
     }