Update not working

[eluser]Unknown[/eluser]
hi! my update function is not working because I have no idea on how to get the place the id of the record in the save function...
I have this model and controller to display the contents of the selected record in a view with text boxes:
model:

Code:

function upUser()
{
  $this->db->where('id', $this->uri->segment(3));
     $query = $this->db->get('users');
     return $query->result();
}

controller

Code:

function upUser()
{  //display in the textbox the result of the query
  $this->load->model('crudModel');
  $data['query']=
     $this->crudModel->upUser();
  $this->load->view('EditUsers',$data);
}

view

Code:

<?php echo form_open('login/updateUser'.$row->id); ?>
<?php
foreach($query as $row){
echo nl2br(" Username: ");
  echo form_input('username', set_value('username', $row->username));
    echo nl2br("\n \n Password: "); echo form_password('password', set_value('password', $row->password));
}
?>

<?php
  echo form_submit('submit', 'Save');
  echo form_close();?>

My problem is that when the SAVE button is pressed, is says that the update is successful, but it's actually not, because my save button is unable to get the current id.. how do i get it?
this is my model and controller for the save
model

Code:

function SaveupdateUsers($data)
{
  $this->db->where('id', $this->uri->segment(3));
  $this->db->update('users', $data);
}

controller

Code:

function updateUser()
{
  $data = array(
   'username' =>  $this->input->post('username'),
   'password' =>  $this->input->post('password'),
   'level' =>  $this->input->post('level')
  );
  

  $this->load->model('crudModel');
  
  $this->crudModel->updateUsers($data);
  $this->load->view('InsertUsers',$data);
}

thank you in advance for your help!