bootstrap: disallow upgrade from below 6.2 to current master

br/pkg/restore/snap_client/systable_restore_test.go

@@ -116,5 +116,5 @@ func TestCheckSysTableCompatibility(t *testing.T) {
 //
 // The above variables are in the file br/pkg/restore/systable_restore.go
 func TestMonitorTheSystemTableIncremental(t *testing.T) {
-	require.Equal(t, int64(216), session.CurrentBootstrapVersion)
+	require.Equal(t, int64(217), session.CurrentBootstrapVersion)
 }

pkg/session/bootstrap.go

@@ -1183,11 +1183,16 @@ const (
 	// version 216
 	//   changes variable `tidb_scatter_region` value from ON to "table" and OFF to "".
 	version216 = 216
+
+	// version 217
+	//   in this version, we disable upgrade from below v6.2.0, there are no system
+	//   table changes related to it.
+	version217 = 217
 )
 
 // currentBootstrapVersion is defined as a variable, so we can modify its value for testing.
 // please make sure this is the largest version
-var currentBootstrapVersion int64 = version216
+var currentBootstrapVersion int64 = version217
 
 // DDL owner key's expired time is ManagerSessionTTL seconds, we should wait the time and give more time to have a chance to finish it.
 var internalSQLTimeout = owner.ManagerSessionTTL + 15
@@ -1359,6 +1364,7 @@ var (
 		upgradeToVer214,
 		upgradeToVer215,
 		upgradeToVer216,
+		upgradeToVer217,
 	}
 )
 
@@ -3268,6 +3274,16 @@ func upgradeToVer216(s sessiontypes.Session, ver int64) {
 	mustExecute(s, "UPDATE mysql.global_variables SET VARIABLE_VALUE='table' WHERE VARIABLE_NAME = 'tidb_scatter_region' AND VARIABLE_VALUE = 'ON'")
 }
 
+func upgradeToVer217(_ sessiontypes.Session, ver int64) {
+	if ver >= version217 {
+		return
+	}
+	// add this function to pass linter.
+	// we disable upgrade from below v6.2.0 in this version, so we can have a version
+	// to check with if it's needed later, there are no system table changes related
+	// to it.
+}
+
 // initGlobalVariableIfNotExists initialize a global variable with specific val if it does not exist.
 func initGlobalVariableIfNotExists(s sessiontypes.Session, name string, val any) {
 	ctx := kv.WithInternalSourceType(context.Background(), kv.InternalTxnBootstrap)