django image upload 问题大大来帮下忙把~~

my views.py

def upload(request):
    if request.user.is_authenticated():
            user = User.objects.get(pk=request.user.id)

            if request.method == "POST":
                    form = UploadForm(request.POST, request.FILES,instance=user)
                    #print form
                    if form.is_valid():
                            #m = Upload.objects.all()
                            #print m
                            instance=Upload(image=request.FILES['image'])
                            instance.save()
                            #m = Upload(image=image)
                            #print m
                            #m.save()
            #return HttpResponseRedirect(reverse('profile_edit'))
                    else:
                            form = UploadForm(instance=user)

                    return render_to_response('upload.html', { 'form' : form })
    return render_to_response("upload.html",{"user":user},context_instance=RequestContext(request))

my models.py

class Upload(models.Model):
        user        = models.OneToOneField(User)
        #email       = models.CharField(max_length=120)
        #description = models.TextField()
        #website     = models.CharField(max_length=512)
        image       = models.ImageField('Label', upload_to='static/media/')
        user_id     = models.IntegerField()

my forms.py

class UploadForm(ModelForm):
    class Meta:
       model = Upload
       exclude = ("user")

现在的问题是我的views函数中POST得到的data save不到mysql数据库中去 ~~~