virtio_ballon: change stub of release_pages_by_pfn

and rename it to release_pages_balloon. The function originally takes
arrays of pfns and now it takes pointer to struct virtio_ballon.
This change is necessary to conditionally call adjust_managed_page_count
in the next patch.
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/virtio/virtio_balloon.c

@@ -166,13 +166,13 @@ static void fill_balloon(struct virtio_balloon *vb, size_t num)
 	mutex_unlock(&vb->balloon_lock);
 }
 
-static void release_pages_by_pfn(const u32 pfns[], unsigned int num)
+static void release_pages_balloon(struct virtio_balloon *vb)
 {
 	unsigned int i;
 
 	/* Find pfns pointing at start of each page, get pages and free them. */
-	for (i = 0; i < num; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
-		struct page *page = balloon_pfn_to_page(pfns[i]);
+	for (i = 0; i < vb->num_pfns; i += VIRTIO_BALLOON_PAGES_PER_PAGE) {
+		struct page *page = balloon_pfn_to_page(vb->pfns[i]);
 		adjust_managed_page_count(page, 1);
 		put_page(page); /* balloon reference */
 	}
@@ -206,7 +206,7 @@ static unsigned leak_balloon(struct virtio_balloon *vb, size_t num)
 	if (vb->num_pfns != 0)
 		tell_host(vb, vb->deflate_vq);
 	mutex_unlock(&vb->balloon_lock);
-	release_pages_by_pfn(vb->pfns, vb->num_pfns);
+	release_pages_balloon(vb);
 	return num_freed_pages;
 }