[PATCH net-next v2 2/5] virtio_ring: add 'flushed' as an argument to virtqueue_resize()

[Koichiro Den <koichiro.den@xxxxxxxxxxxxx>]

When virtqueue_resize() has actually recycled all unused buffers,
additional work may be required in some cases. Relying solely on its
return status is fragile, so introduce a new argument 'flushed' to
explicitly indicate whether it has really occurred.

Signed-off-by: Koichiro Den <koichiro.den@xxxxxxxxxxxxx>
---
 drivers/net/virtio_net.c     | 6 ++++--
 drivers/virtio/virtio_ring.c | 7 ++++++-
 include/linux/virtio.h       | 3 ++-
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 48ce8b3881b6..df9bfe31aa6d 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -3326,12 +3326,13 @@ static int virtnet_rx_resize(struct virtnet_info *vi,
 			     struct receive_queue *rq, u32 ring_num)
 {
 	int err, qindex;
+	bool flushed;
 
 	qindex = rq - vi->rq;
 
 	virtnet_rx_pause(vi, rq);
 
-	err = virtqueue_resize(rq->vq, ring_num, virtnet_rq_unmap_free_buf);
+	err = virtqueue_resize(rq->vq, ring_num, virtnet_rq_unmap_free_buf, &flushed);
 	if (err)
 		netdev_err(vi->dev, "resize rx fail: rx queue index: %d err: %d\n", qindex, err);
 
@@ -3389,12 +3390,13 @@ static int virtnet_tx_resize(struct virtnet_info *vi, struct send_queue *sq,
 			     u32 ring_num)
 {
 	int qindex, err;
+	bool flushed;
 
 	qindex = sq - vi->sq;
 
 	virtnet_tx_pause(vi, sq);
 
-	err = virtqueue_resize(sq->vq, ring_num, virtnet_sq_free_unused_buf);
+	err = virtqueue_resize(sq->vq, ring_num, virtnet_sq_free_unused_buf, &flushed);
 	if (err)
 		netdev_err(vi->dev, "resize tx fail: tx queue index: %d err: %d\n", qindex, err);
 
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 82a7d2cbc704..34a068d401ec 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -2772,6 +2772,7 @@ EXPORT_SYMBOL_GPL(vring_create_virtqueue_dma);
  * @_vq: the struct virtqueue we're talking about.
  * @num: new ring num
  * @recycle: callback to recycle unused buffers
+ * @flushed: whether or not unused buffers are all flushed
  *
  * When it is really necessary to create a new vring, it will set the current vq
  * into the reset state. Then call the passed callback to recycle the buffer
@@ -2792,11 +2793,14 @@ EXPORT_SYMBOL_GPL(vring_create_virtqueue_dma);
  *
  */
 int virtqueue_resize(struct virtqueue *_vq, u32 num,
-		     void (*recycle)(struct virtqueue *vq, void *buf))
+		     void (*recycle)(struct virtqueue *vq, void *buf),
+		     bool *flushed)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
 	int err;
 
+	*flushed = false;
+
 	if (num > vq->vq.num_max)
 		return -E2BIG;
 
@@ -2809,6 +2813,7 @@ int virtqueue_resize(struct virtqueue *_vq, u32 num,
 	err = virtqueue_disable_and_recycle(_vq, recycle);
 	if (err)
 		return err;
+	*flushed = true;
 
 	if (vq->packed_ring)
 		err = virtqueue_resize_packed(_vq, num);
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 57cc4b07fd17..878feda08af9 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -109,7 +109,8 @@ dma_addr_t virtqueue_get_avail_addr(const struct virtqueue *vq);
 dma_addr_t virtqueue_get_used_addr(const struct virtqueue *vq);
 
 int virtqueue_resize(struct virtqueue *vq, u32 num,
-		     void (*recycle)(struct virtqueue *vq, void *buf));
+		     void (*recycle)(struct virtqueue *vq, void *buf),
+		     bool *flushed);
 int virtqueue_reset(struct virtqueue *vq,
 		    void (*recycle)(struct virtqueue *vq, void *buf));
 
-- 
2.43.0