Re: [kvm-devel] [PATCH] kvm balloon guest driver (v2)

[Akio T. <tak...@jp...>]

Hi, Marcelo

>+struct balloon_buf *alloc_balloon_buf(struct virtio_device *vdev, gfp_t 
>flags)
>+{
>+	struct balloon_buf *buf;
>+
>+	buf = kzalloc(sizeof(struct balloon_buf), flags);
>+	if (!buf)
>+		dev_printk(KERN_ERR, &vdev->dev, "%s: alloc fail\n", __func__);
>+
>+	return buf;
>+}
>+
[snip..]
>+static int kvm_balloon_inflate(struct virtballoon *v, int32_t npages)
>+{
>+	LIST_HEAD(tmp_list);
>+	struct page *page, *tmp;
>+	struct balloon_buf *buf;
>+	u32 *pfn;
>+	int allocated = 0;
>+	int i, r = -ENOMEM;
>+
>+	buf = alloc_balloon_buf(v->vdev, GFP_KERNEL);
When does balloon driver free the buf?

>+	if (!buf)
>+		return r;
>+
>+	pfn = (u32 *)&buf->data;
>+	*pfn++ = (u32)npages;
>+
>+	for (i = 0; i < npages; i++) {
>+		page = alloc_page(GFP_HIGHUSER | __GFP_NORETRY);
>+		if (!page)
>+			goto out_free;
>+		list_add(&page->lru, &tmp_list);
>+		allocated++;
>+		*pfn = page_to_pfn(page);
>+		pfn++;
>+	}
>+
>+	r = send_balloon_buf(v, CMD_BALLOON_INFLATE, buf);
>+	if (r)
>+		goto out_free;
>+
>+	spin_lock(&v->plist_lock);
>+	list_splice(&tmp_list, &v->balloon_plist);
>+	v->balloon_size += allocated;
>+	totalram_pages -= allocated;
>+	dprintk(&v->vdev->dev, "%s: current balloon size=%d\n", __func__,
>+		v->balloon_size);
>+	spin_unlock(&v->plist_lock);
>+	return allocated;
>+
>+out_free:
>+	list_for_each_entry_safe(page, tmp, &tmp_list, lru) {
>+		list_del(&page->lru);
>+		__free_page(page);
>+	}
>+	return r;
>+}
>+
>+static int kvm_balloon_deflate(struct virtballoon *v, int32_t npages)
>+{
>+	LIST_HEAD(tmp_list);
>+	struct page *page, *tmp;
>+	struct balloon_buf *buf;
>+	u32 *pfn;
>+	int deallocated = 0;
>+	int r = 0;
>+
>+	buf = alloc_balloon_buf(v->vdev, GFP_KERNEL);
ditto.

>+	if (!buf)
>+		return r;
>+
>+	spin_lock(&v->plist_lock);
>+
>+	if (v->balloon_size < npages) {
>+		dev_printk(KERN_INFO, &v->vdev->dev,
>+			   "%s: balloon=%d with deflate rq=%d\n",
>+			   __func__, v->balloon_size, npages);
>+		npages = v->balloon_size;
>+		if (!npages)
>+			goto out;
>+	}
>+
>+	pfn = (u32 *)&buf->data;
>+	*pfn++ = (u32)-npages;
>+
>+	/*
>+	 * Move the balloon pages to tmp list before issuing 
>+	 * the virtio buffer
>+	 */
>+	list_for_each_entry_safe(page, tmp, &v->balloon_plist, lru) {
>+		*pfn++ = page_to_pfn(page);
>+		list_move(&page->lru, &tmp_list);
>+		if (++deallocated == npages)
>+			break;
>+	}
>+
>+	r = send_balloon_buf(v, CMD_BALLOON_DEFLATE, buf);
>+	if (r)
>+		goto out;
>+
>+	list_for_each_entry_safe(page, tmp, &tmp_list, lru)
>+		list_del_init(&page->lru);
>+
>+	v->balloon_size -= npages;
>+	totalram_pages += npages;
>+	dprintk(&v->vdev->dev, "%s: current balloon size=%d\n", __func__,
>+	       v->balloon_size);
>+
>+	spin_unlock(&v->plist_lock);
>+	return deallocated;
>+
>+out:
>+	list_splice(&tmp_list, &v->balloon_plist);
>+	spin_unlock(&v->plist_lock);
>+	return r;
>+}
>+

Best Regards,

Akio Takebe