Rusty Russell [off-list ref] writes:

Jason Wang [off-list ref] writes:

quoted

It looks like there's no need for those two fields:

- Unless there's a failure for the first refill try, rq->max should be always
  equal to the vring size.
- rq->num is only used to determine the condition that we need to do the refill,
  we could check vq->num_free instead.
- rq->num was required to be increased or decreased explicitly after each
  get/put which results a bad API.

So this patch removes them both to make the code simpler.

Nice.  These fields date from when the vq struct was opaque.

Applied,
Rusty.

Oops, this doesn't require any core virtio changes, so it's for DaveM:

Acked-by: Rusty Russell <redacted>

Thanks,
Rusty.

quoted

Cc: Rusty Russell <redacted>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 drivers/net/virtio_net.c | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index c51a988..4e1bce3 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c

@@ -72,9 +72,6 @@ struct receive_queue {
 
 	struct napi_struct napi;
 
-	/* Number of input buffers, and max we've ever had. */
-	unsigned int num, max;
-
 	/* Chain pages by the private ptr. */
 	struct page *pages;
 

@@ -360,7 +357,6 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 		}
 
 		page = virt_to_head_page(buf);
-		--rq->num;
 
 		num_skb_frags = skb_shinfo(curr_skb)->nr_frags;
 		if (unlikely(num_skb_frags == MAX_SKB_FRAGS)) {

@@ -406,7 +402,6 @@ err_skb:
 		}
 		page = virt_to_head_page(buf);
 		put_page(page);
-		--rq->num;
 	}
 err_buf:
 	dev->stats.rx_dropped++;

@@ -628,10 +623,7 @@ static bool try_fill_recv(struct receive_queue *rq, gfp_t gfp)
 		oom = err == -ENOMEM;
 		if (err)
 			break;
-		++rq->num;
 	} while (rq->vq->num_free);
-	if (unlikely(rq->num > rq->max))
-		rq->max = rq->num;
 	if (unlikely(!virtqueue_kick(rq->vq)))
 		return false;
 	return !oom;

@@ -699,11 +691,10 @@ again:
 	while (received < budget &&
 	       (buf = virtqueue_get_buf(rq->vq, &len)) != NULL) {
 		receive_buf(rq, buf, len);
-		--rq->num;
 		received++;
 	}
 
-	if (rq->num < rq->max / 2) {
+	if (rq->vq->num_free > virtqueue_get_vring_size(rq->vq) / 2) {
 		if (!try_fill_recv(rq, GFP_ATOMIC))
 			schedule_delayed_work(&vi->refill, 0);
 	}

@@ -1398,9 +1389,7 @@ static void free_unused_bufs(struct virtnet_info *vi)
 				give_pages(&vi->rq[i], buf);
 			else
 				dev_kfree_skb(buf);
-			--vi->rq[i].num;
 		}
-		BUG_ON(vi->rq[i].num != 0);
 	}
 }
 

@@ -1671,7 +1660,8 @@ static int virtnet_probe(struct virtio_device *vdev)
 		try_fill_recv(&vi->rq[i], GFP_KERNEL);
 
 		/* If we didn't even get one input buffer, we're useless. */
-		if (vi->rq[i].num == 0) {
+		if (vi->rq[i].vq->num_free ==
+		    virtqueue_get_vring_size(vi->rq[i].vq)) {
 			free_unused_bufs(vi);
 			err = -ENOMEM;
 			goto free_recv_bufs;

-- 
1.8.3.2

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