[PATCH vhost v8 1/6] virtio_balloon: remove the dependence where names[] is null

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

Currently, the init_vqs function within the virtio_balloon driver relies
on the condition that certain names array entries are null in order to
skip the initialization of some virtual queues (vqs). This behavior is
unique to this part of the codebase. In an upcoming commit, we plan to
eliminate this dependency by removing the function entirely. Therefore,
with this change, we are ensuring that the virtio_balloon no longer
depends on the aforementioned function.

As specification 1.0-1.2, vq indexes should not be contiguous if some
vq does not exist. But currently the virtqueue index is contiguous for
all existing devices. The Linux kernel does not implement functionality
to allow vq indexes to be discontinuous. So the current behavior of the
virtio-balloon device is different for the spec. But this commit has no
functional changes.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
---
 drivers/virtio/virtio_balloon.c | 48 ++++++++++++++-------------------
 1 file changed, 20 insertions(+), 28 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 1f5b3dd31fcf..f5ed351e31d4 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -531,49 +531,41 @@ static int init_vqs(struct virtio_balloon *vb)
 	struct virtqueue *vqs[VIRTIO_BALLOON_VQ_MAX];
 	vq_callback_t *callbacks[VIRTIO_BALLOON_VQ_MAX];
 	const char *names[VIRTIO_BALLOON_VQ_MAX];
-	int err;
+	int err, idx = 0;
 
-	/*
-	 * Inflateq and deflateq are used unconditionally. The names[]
-	 * will be NULL if the related feature is not enabled, which will
-	 * cause no allocation for the corresponding virtqueue in find_vqs.
-	 */
-	callbacks[VIRTIO_BALLOON_VQ_INFLATE] = balloon_ack;
-	names[VIRTIO_BALLOON_VQ_INFLATE] = "inflate";
-	callbacks[VIRTIO_BALLOON_VQ_DEFLATE] = balloon_ack;
-	names[VIRTIO_BALLOON_VQ_DEFLATE] = "deflate";
-	callbacks[VIRTIO_BALLOON_VQ_STATS] = NULL;
-	names[VIRTIO_BALLOON_VQ_STATS] = NULL;
-	callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
-	names[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
-	names[VIRTIO_BALLOON_VQ_REPORTING] = NULL;
+	callbacks[idx] = balloon_ack;
+	names[idx++] = "inflate";
+	callbacks[idx] = balloon_ack;
+	names[idx++] = "deflate";
 
 	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
-		names[VIRTIO_BALLOON_VQ_STATS] = "stats";
-		callbacks[VIRTIO_BALLOON_VQ_STATS] = stats_request;
+		names[idx] = "stats";
+		callbacks[idx++] = stats_request;
 	}
 
 	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT)) {
-		names[VIRTIO_BALLOON_VQ_FREE_PAGE] = "free_page_vq";
-		callbacks[VIRTIO_BALLOON_VQ_FREE_PAGE] = NULL;
+		names[idx] = "free_page_vq";
+		callbacks[idx++] = NULL;
 	}
 
 	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING)) {
-		names[VIRTIO_BALLOON_VQ_REPORTING] = "reporting_vq";
-		callbacks[VIRTIO_BALLOON_VQ_REPORTING] = balloon_ack;
+		names[idx] = "reporting_vq";
+		callbacks[idx++] = balloon_ack;
 	}
 
-	err = virtio_find_vqs(vb->vdev, VIRTIO_BALLOON_VQ_MAX, vqs,
-			      callbacks, names, NULL);
+	err = virtio_find_vqs(vb->vdev, idx, vqs, callbacks, names, NULL);
 	if (err)
 		return err;
 
-	vb->inflate_vq = vqs[VIRTIO_BALLOON_VQ_INFLATE];
-	vb->deflate_vq = vqs[VIRTIO_BALLOON_VQ_DEFLATE];
+	idx = 0;
+
+	vb->inflate_vq = vqs[idx++];
+	vb->deflate_vq = vqs[idx++];
+
 	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_STATS_VQ)) {
 		struct scatterlist sg;
 		unsigned int num_stats;
-		vb->stats_vq = vqs[VIRTIO_BALLOON_VQ_STATS];
+		vb->stats_vq = vqs[idx++];
 
 		/*
 		 * Prime this virtqueue with one buffer so the hypervisor can
@@ -593,10 +585,10 @@ static int init_vqs(struct virtio_balloon *vb)
 	}
 
 	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
-		vb->free_page_vq = vqs[VIRTIO_BALLOON_VQ_FREE_PAGE];
+		vb->free_page_vq = vqs[idx++];
 
 	if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_REPORTING))
-		vb->reporting_vq = vqs[VIRTIO_BALLOON_VQ_REPORTING];
+		vb->reporting_vq = vqs[idx++];
 
 	return 0;
 }
-- 
2.32.0.3.g01195cf9f