[PATCH v6 08/26] virtio_ring: extract the logic of freeing vring

[Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>]

Introduce vring_free() to free the vring of vq.

Prevent double free by setting vq->reset.

Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
---
 drivers/virtio/virtio_ring.c | 25 ++++++++++++++++++++-----
 include/linux/virtio.h       |  8 ++++++++
 2 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 039015823c53..0b5360052ac2 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -2442,14 +2442,10 @@ struct virtqueue *vring_new_virtqueue(unsigned int index,
 }
 EXPORT_SYMBOL_GPL(vring_new_virtqueue);
 
-void vring_del_virtqueue(struct virtqueue *_vq)
+static void __vring_free(struct virtqueue *_vq)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
 
-	spin_lock(&vq->vq.vdev->vqs_list_lock);
-	list_del(&_vq->list);
-	spin_unlock(&vq->vq.vdev->vqs_list_lock);
-
 	if (vq->we_own_ring) {
 		if (vq->packed_ring) {
 			vring_free_queue(vq->vq.vdev,
@@ -2480,6 +2476,25 @@ void vring_del_virtqueue(struct virtqueue *_vq)
 		kfree(vq->split.desc_state);
 		kfree(vq->split.desc_extra);
 	}
+}
+
+static void vring_free(struct virtqueue *vq)
+{
+	__vring_free(vq);
+	vq->reset = VIRTIO_VQ_RESET_STEP_VRING_RELEASE;
+}
+
+void vring_del_virtqueue(struct virtqueue *_vq)
+{
+	struct vring_virtqueue *vq = to_vvq(_vq);
+
+	spin_lock(&vq->vq.vdev->vqs_list_lock);
+	list_del(&_vq->list);
+	spin_unlock(&vq->vq.vdev->vqs_list_lock);
+
+	if (_vq->reset != VIRTIO_VQ_RESET_STEP_VRING_RELEASE)
+		__vring_free(_vq);
+
 	kfree(vq);
 }
 EXPORT_SYMBOL_GPL(vring_del_virtqueue);
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index d59adc4be068..e3714e6db330 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -10,6 +10,13 @@
 #include <linux/mod_devicetable.h>
 #include <linux/gfp.h>
 
+enum virtio_vq_reset_step {
+	VIRTIO_VQ_RESET_STEP_NONE,
+	VIRTIO_VQ_RESET_STEP_DEVICE,
+	VIRTIO_VQ_RESET_STEP_VRING_RELEASE,
+	VIRTIO_VQ_RESET_STEP_VRING_ATTACH,
+};
+
 /**
  * virtqueue - a queue to register buffers for sending or receiving.
  * @list: the chain of virtqueues for this device
@@ -33,6 +40,7 @@ struct virtqueue {
 	unsigned int num_free;
 	unsigned int num_max;
 	void *priv;
+	enum virtio_vq_reset_step reset;
 };
 
 int virtqueue_add_outbuf(struct virtqueue *vq,
-- 
2.31.0