Re: [patch] KVM: return an error code in kvm_vm_ioctl_register_coalesced_mmio()

Dan Carpenter
2014-01-29T14:29:06Z

On Wed, Jan 29, 2014 at 02:57:21PM +0100, walter harms wrote:
>
>
> Am 29.01.2014 14:16, schrieb Dan Carpenter:
> > If kvm_io_bus_register_dev() fails then it returns success but it should
> > return an error code.
> >
> > I also did a little cleanup like removing an impossible NULL test.
> >
> > Fixes: 2b3c246a682c ('KVM: Make coalesced mmio use a device per zone')
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> >
> > diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c
> > index 88b2fe3ddf42..00d86427af0f 100644
> > --- a/virt/kvm/coalesced_mmio.c
> > +++ b/virt/kvm/coalesced_mmio.c
> > @@ -154,17 +154,13 @@ int kvm_vm_ioctl_register_coalesced_mmio(struct kvm *kvm,
> > list_add_tail(&dev->list, &kvm->coalesced_zones);
> > mutex_unlock(&kvm->slots_lock);
> >
> > - return ret;
> > + return 0;
> >
> > out_free_dev:
> > mutex_unlock(&kvm->slots_lock);
> > -
> > kfree(dev);
> >
> > - if (dev == NULL)
> > - return -ENXIO;
> > -
> > - return 0;
> > + return ret;
> > }
> >
> > int kvm_vm_ioctl_unregister_coalesced_mmio(struct kvm *kvm,
>
>
> I did not see the rest of the code, be careful ..
>
> You can get rid of the return 0 by protecting the free(dev) like
>
> if (ret != 0)
> kfree(dev);
>
> that will make the
> mutex_unlock(&kvm->slots_lock);
> return 0;
>
> obsolet. (simply set ret=0 if needed).

It's better to have a clean separation of success and error path. The
success path should "return 0;" and not "return ret;"

[ I spent thirty minutes here ranting about the right way to do error
paths but then I deleted it. :P ].

regards,
dan carpenter