virtio_net: fix missing dma unmap for resize

For rq, we have three cases getting buffers from virtio core:

1. virtqueue_get_buf{,_ctx}
2. virtqueue_detach_unused_buf
3. callback for virtqueue_resize

But in commit 295525e("virtio_net: merge dma operations when
filling mergeable buffers"), I missed the dma unmap for the #3 case.

That will leak some memory, because I did not release the pages referred
by the unused buffers.

If we do such script, we will make the system OOM.

    while true
    do
            ethtool -G ens4 rx 128
            ethtool -G ens4 rx 256
            free -m
    done

Fixes: 295525e ("virtio_net: merge dma operations when filling mergeable buffers")
Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Link: https://lore.kernel.org/r/20231226094333.47740-1-xuanzhuo@linux.alibaba.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/virtio_net.c

@@ -334,7 +334,6 @@ struct virtio_net_common_hdr {
  };
 };
 
-static void virtnet_rq_free_unused_buf(struct virtqueue *vq, void *buf);
 static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf);
 
 static bool is_xdp_frame(void *ptr)
@@ -408,6 +407,17 @@ static struct page *get_a_page(struct receive_queue *rq, gfp_t gfp_mask)
  return p;
 }
 
+static void virtnet_rq_free_buf(struct virtnet_info *vi,
+ struct receive_queue *rq, void *buf)
+{
+ if (vi->mergeable_rx_bufs)
+ put_page(virt_to_head_page(buf));
+ else if (vi->big_packets)
+ give_pages(rq, buf);
+ else
+ put_page(virt_to_head_page(buf));
+}
+
 static void enable_delayed_refill(struct virtnet_info *vi)
 {
  spin_lock_bh(&vi->refill_lock);
@@ -634,17 +644,6 @@ static void *virtnet_rq_get_buf(struct receive_queue *rq, u32 *len, void **ctx)
  return buf;
 }
 
-static void *virtnet_rq_detach_unused_buf(struct receive_queue *rq)
-{
- void *buf;
-
- buf = virtqueue_detach_unused_buf(rq->vq);
- if (buf && rq->do_dma)
- virtnet_rq_unmap(rq, buf, 0);
-
- return buf;
-}
-
 static void virtnet_rq_init_one_sg(struct receive_queue *rq, void *buf, u32 len)
 {
  struct virtnet_rq_dma *dma;
@@ -744,6 +743,20 @@ static void virtnet_rq_set_premapped(struct virtnet_info *vi)
  }
 }
 
+static void virtnet_rq_unmap_free_buf(struct virtqueue *vq, void *buf)
+{
+ struct virtnet_info *vi = vq->vdev->priv;
+ struct receive_queue *rq;
+ int i = vq2rxq(vq);
+
+ rq = &vi->rq[i];
+
+ if (rq->do_dma)
+ virtnet_rq_unmap(rq, buf, 0);
+
+ virtnet_rq_free_buf(vi, rq, buf);
+}
+
 static void free_old_xmit_skbs(struct send_queue *sq, bool in_napi)
 {
  unsigned int len;
@@ -1764,7 +1777,7 @@ static void receive_buf(struct virtnet_info *vi, struct receive_queue *rq,
  if (unlikely(len < vi->hdr_len + ETH_HLEN)) {
  pr_debug("%s: short packet %i\n", dev->name, len);
  DEV_STATS_INC(dev, rx_length_errors);
- virtnet_rq_free_unused_buf(rq->vq, buf);
+ virtnet_rq_free_buf(vi, rq, buf);
  return;
  }
 
@@ -2392,7 +2405,7 @@ static int virtnet_rx_resize(struct virtnet_info *vi,
  if (running)
  napi_disable(&rq->napi);
 
- err = virtqueue_resize(rq->vq, ring_num, virtnet_rq_free_unused_buf);
+ err = virtqueue_resize(rq->vq, ring_num, virtnet_rq_unmap_free_buf);
  if (err)
  netdev_err(vi->dev, "resize rx fail: rx queue index: %d err: %d\n", qindex, err);
 
@@ -4031,19 +4044,6 @@ static void virtnet_sq_free_unused_buf(struct virtqueue *vq, void *buf)
  xdp_return_frame(ptr_to_xdp(buf));
 }
 
-static void virtnet_rq_free_unused_buf(struct virtqueue *vq, void *buf)
-{
- struct virtnet_info *vi = vq->vdev->priv;
- int i = vq2rxq(vq);
-
- if (vi->mergeable_rx_bufs)
- put_page(virt_to_head_page(buf));
- else if (vi->big_packets)
- give_pages(&vi->rq[i], buf);
- else
- put_page(virt_to_head_page(buf));
-}
-
 static void free_unused_bufs(struct virtnet_info *vi)
 {
  void *buf;
@@ -4057,10 +4057,10 @@ static void free_unused_bufs(struct virtnet_info *vi)
  }
 
  for (i = 0; i < vi->max_queue_pairs; i++) {
- struct receive_queue *rq = &vi->rq[i];
+ struct virtqueue *vq = vi->rq[i].vq;
 
- while ((buf = virtnet_rq_detach_unused_buf(rq)) != NULL)
- virtnet_rq_free_unused_buf(rq->vq, buf);
+ while ((buf = virtqueue_detach_unused_buf(vq)) != NULL)
+ virtnet_rq_unmap_free_buf(vq, buf);
  cond_resched();
  }
 }