未定义的索引错误（Codeigniter）

My code was working fine before. But Now it is not working. I am working on codeigniter and I am uploading a file using jquery ajax. I donot know why my code stop working. If you can find the issue please let me know.

Here is the controller code

public function updatedp()
{   
    $var = $_FILES['fileUp'];
    $img=$_FILES['fileUp'];
    $config['upload_path'] = 'webim/dp_images'; 
    $config['overwrite'] = 'TRUE';
    $config["allowed_types"] = 'jpg|jpeg|png|gif';
    $config["max_size"] = '1400';
    $config["max_width"] = '1400';
    $config["max_height"] = '1400'; 
    $this->load->library('upload', $config);

    if(!$this->upload->do_upload('fileUp')) 
    {               
        $this->data['error'] = $this->upload->display_errors(); 
        echo json_encode(array("result"=>$this->data['error']));
        exit;
    } else { 
        $data=array('active'=>0);
        $this->db->where('userid','1');
        $this->db->update('music_user_dp',$data);

        $uname['uname'] =$this->session->all_userdata('uname');
        $uname['id'] =$this->session->all_userdata('id');
        $post_data = array(
            'id' => '',
            'userid' => $uname['id']['id'], 
            'profilepic'=>$var['name'], 
            'updatedate' => date("Y-m-d H:i:s"),
            'active' => '1'
        );
        $this->Userpage_model->insert_dp_to_db($post_data);
        echo json_encode(array("result"=>"Success"));
        exit;
    }
}

My jquery code which calling above function:

$("#btnupdate").click(function(event){
 if($("#fileupload2").val() != ''){
    if (typeof FormData !== 'undefined') {
      var form = $('#formname').get(0); 
      var formData = new FormData(form);  

    $.ajax({
      type: "POST",
      url: "Userpage/updatedp",
      data: formData,
      mimeType:"multipart/form-data",
      dataType: 'json',
      xhr: function() {
         return $.ajaxSettings.xhr();
      },
      cache:false,                    
      contentType: false,
      processData: false,
      success: function(result){


       toastr8.info({
         message:'Profile Picture Updated', 
         title:"New Image Uploaded",
         iconClass: "fa fa-info",
       });
      }                       
    });
     event.preventDefault();
        }  

  } else {
     toastr8.info({
       message:'Error Occured', 
       title:"Please try again",
       iconClass: "fa fa-info",
    });
  }  
});

HTML:

<div class="modal fade" id="myModal" role="dialog">
<form enctype="multipart/form-data" name="formname" id="formname"  method="post" action="">
  <div class="modal-dialog">     
    <!-- Modal content-->
    <div class="modal-content">
      <div class="modal-header "> 
        <script type="text/javascript">  
        $(document).ready(function(){
          $('#mgupload-dp').click(function(e){ 
            $('#fileupload2').click(); 
            e.preventDefault();
          });
        });
        </script>
        <button type="button" class="close" data-dismiss="modal">&times;</button>
        <h4 class="modal-title">Create profile picture</h4>
      </div>
      <div class="modal-body">
        <div class="text-center" style="width:100%"> <img src="<?php echo base_url(); ?>img/profile.png" alt="add dp" id="pop-dp" >
          <button type="button" class="btn btn-default text-center" id="mgupload-dp">Choose picture to upload</button>
          <input type="file" id="fileupload2" name="fileUp" class="hidden-dp" accept="image/*">
        </div>
        <div class="clearfix"></div>
      </div>
      <div class="modal-footer">
        <button type="button" class="btn btn-default" id="btnupdate">Update Picture</button>
      </div>
    </div>
  </div>
  </div>
</form>
</div>

Files are not uploading and I am getting this error

A PHP Error was encountered Severity: Notice Message: Undefined index: fileUp Filename: controllers/Userpage.php

1. Open the Firebug in FF.
2. Click on the ajax call URL under Console.
3. See what are passed under "Post" tab.
4. If fileUp is present there, use $this->input->post('fileUp'); to fetch the contents.