django update 错误

def issue_save(request):
    action = "/jira/issue/s/"
    user = request.user
    data = request.POST.copy()
    id = request.POST.get('id')
    if id != '' and int(id)>0:
      o = Issue.objects.get(pk=int(id))
      u = IssueForm(data,instance=o)
    else:
      data['issue_reportor'] = user.id
      data['status'] = -1
      u = IssueForm(data)
    if u.is_valid():
      u.save()
      return HttpResponseRedirect('/jira/issue/?status=-1')
    else:
      return render_to_response('jira/issue_edit.html',{'form':u,'action':action})

在更新的时候，一些隐藏的字段需要列出来，否则值丢失。
<div style="display:none">
  {{ form.issue_reportor }}
  {{ form.issue_reason}}
  {{ form.issue_reason_detail}}
  {{ form.issue_creator}}
  {{ form.issue_dep}}
  {{ form.service_level}}
  {{ form.pre_end_date}}
  {{ form.finished_date}}
  {{ form.status}}
</div>