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

From: Wei Wang
Date: Thu Aug 03 2017 - 09:18:47 EST


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