Submitting form to itself and echoing validation errors in CodeIgniter

I had few forms in my project, they were submitted to public function's like site.com/email => site.com/validate_email, but then I realized that that's not what I want. Now I need to make them submit to themselfs ,check and display validation errors. What is the appropriate way to do this? Check for emptyness of $_POST and then call my new _validate_email(//that will return true or false) if post isn't empty? Or something else not that noobish?:)

for example:

public function login()
{
        $this->load->view('login');
}


public function login_validation()
{
        $this->load->library('form_validation');

        $this->form_validation->set_rules('email', 'Email', 'required|valid_email|trim|xss_clean|callback_validate_credentials');
        $this->form_validation->set_rules('password','Password','required|md5');

        if($this->form_validation->run())
        {
            //some stuff here
        }
        else
        {
            $this->load->view('login'); //or redirect()?
        } 

view:

<?php $this->load->view('header'); ?>


<div class="form-container">
    <?=$this->form_validation->validation_errors();?>
    <?php
    $form_atr = array(
        'id' => 'form-set'
    );
    echo form_open('main/login_validation', $form_atr);//this should be 'main/login'
    ?>
    <div class="header">
        /*
here goes other parts of form
*/
</div><!--END  form-container -->`
<?php $this->load->view('footer'); ?>

So, basicaly i need to combine login() and login_validation(), but make it so that when user`s input incorrect i get reloaded page of the same view with the same URL and get validation errors displayed.

I've tried to put code of validation into the same function that displays form, but I can't figure out how to redirect or reload the view to show val.errors if any.