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

From	Wei Wang <wei.w.wang@intel.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v13 5/5] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_VQ
Date	2017-08-03 15:20 +0200
Message-ID	<uaocG-rc-19@gated-at.bofh.it> (permalink)
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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

Thread

[PATCH v13 5/5] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_VQ Wei Wang <wei.w.wang@intel.com> - 2017-08-03 08:50 +0200
  Re: [PATCH v13 5/5] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_VQ Pankaj Gupta <pagupta@redhat.com> - 2017-08-03 10:20 +0200
    Re: [PATCH v13 5/5] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_VQ Wei Wang <wei.w.wang@intel.com> - 2017-08-03 14:30 +0200
      Re: [PATCH v13 5/5] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_VQ Pankaj Gupta <pagupta@redhat.com> - 2017-08-03 15:10 +0200
        Re: [PATCH v13 5/5] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_VQ Wei Wang <wei.w.wang@intel.com> - 2017-08-03 15:20 +0200
  Re: [PATCH v13 5/5] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_VQ "Michael S. Tsirkin" <mst@redhat.com> - 2017-08-03 14:40 +0200

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