Re: [PATCH v13 5/5] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_VQ

[Wei Wang]

On 08/03/2017 09:05 PM, Pankaj Gupta wrote:
> > On 08/03/2017 04:13 PM, Pankaj Gupta wrote:
> > > > +        /* Allocate space for find_vqs parameters */
> > > > +        vqs = kcalloc(nvqs, sizeof(*vqs), GFP_KERNEL);
> > > > +        if (!vqs)
> > > > +                goto err_vq;
> > > > +        callbacks = kmalloc_array(nvqs, sizeof(*callbacks), GFP_KERNEL);
> > > > +        if (!callbacks)
> > > > +                goto err_callback;
> > > > +        names = kmalloc_array(nvqs, sizeof(*names), GFP_KERNEL);
> > >                       
> > >          is size here (integer) intentional?
> >
> > Sorry, I didn't get it. Could you please elaborate more?
> This is okay
>
> > > > +        if (!names)
> > > > +                goto err_names;
> > > > +
> > > > +        callbacks[0] = balloon_ack;
> > > > +        names[0] = "inflate";
> > > > +        callbacks[1] = balloon_ack;
> > > > +        names[1] = "deflate";
> > > > +
> > > > +        i = 2;
> > > > +        if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
> > > > +                callbacks[i] = stats_request;
> > > just thinking if memory for callbacks[3] & names[3] is allocated?
> >
> > Yes, the above kmalloc_array allocated them.
> I mean we have created callbacks array for two entries 0,1?
>
> callbacks = kmalloc_array(nvqs, sizeof(*callbacks), GFP_KERNEL);
>
> But we are trying to access location '2' which is third:
>
>           i = 2;
> +        if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
> +                callbacks[i] = stats_request;      <---- callbacks[2]
> +                names[i] = "stats";                <----- names[2]
> +                i++;
> +        }
>
> I am missing anything obvious here?


Yes.
if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ) is true
nvqs will be 3, that is, callbacks[2] is allocated.

Best,
Wei