fix volume placement validating

fix https://github.com/chrislusf/seaweedfs/issues/1626

weed/shell/command_volume_balance.go

@@ -306,16 +306,16 @@ func isGoodMove(placement *super_block.ReplicaPlacement, existingReplicas []*Vol
 	dcs[targetNode.dc] = true
 	racks[fmt.Sprintf("%s %s", targetNode.dc, targetNode.rack)]++
 
-	if len(dcs) > placement.DiffDataCenterCount+1 {
+	if len(dcs) != placement.DiffDataCenterCount+1 {
 		return false
 	}
 
-	if len(racks) > placement.DiffRackCount+placement.DiffDataCenterCount+1 {
+	if len(racks) != placement.DiffRackCount+placement.DiffDataCenterCount+1 {
 		return false
 	}
 
 	for _, sameRackCount := range racks {
-		if sameRackCount > placement.SameRackCount+1 {
+		if sameRackCount != placement.SameRackCount+1 {
 			return false
 		}
 	}

weed/shell/command_volume_balance_test.go

@@ -20,6 +20,22 @@ func TestIsGoodMove(t *testing.T) {
 
 	var tests = []testMoveCase{
 
+		{
+			name:        "test 100 move to wrong data centers",
+			replication: "100",
+			replicas: []*VolumeReplica{
+				{
+					location: &location{"dc1", "r1", &master_pb.DataNodeInfo{Id: "dn1"}},
+				},
+				{
+					location: &location{"dc2", "r2", &master_pb.DataNodeInfo{Id: "dn2"}},
+				},
+			},
+			sourceLocation: location{"dc1", "r1", &master_pb.DataNodeInfo{Id: "dn1"}},
+			targetLocation: location{"dc2", "r3", &master_pb.DataNodeInfo{Id: "dn3"}},
+			expected:       false,
+		},
+
 		{
 			name:        "test 100 move to spread into proper data centers",
 			replication: "100",