vring_reuse_bufs_packed() checks vring.desc forward based on
last_used_idx. The resulting buffers are the order in which they were
committed.
It is beneficial to ensure the order of buffers in the process of reuse.
For example, under virtio-net, if the order is not guaranteed, it may
lead to out-of-order tcp streams.
Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
---
drivers/virtio/virtio_ring.c | 45 ++++++++++++++++++++++++++++++++++++
1 file changed, 45 insertions(+)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 8ca9985ffb4b..66f71e22ece0 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -2041,6 +2041,51 @@ static bool virtqueue_enable_cb_delayed_packed(struct virtqueue *_vq)
return true;
}
+static void vring_reuse_bufs_packed(struct vring_virtqueue *vq,
+ struct vring_virtqueue_packed *vring,
+ void (*recycle)(struct virtqueue *vq, void *buf))
+{
+ struct vring_desc_state_packed *state;
+ u32 last_used, id, desc_num = 0;
+ int err = 0;
+ void *buf;
+
+ last_used = vring->last_used_idx;
+
+ do {
+ id = le16_to_cpu(vring->vring.desc[last_used].id);
+
+ state = &vring->desc_state[id];
+
+ if (!state->data) {
+ last_used++;
+ goto next;
+ }
+
+ /* once add to vq fail, no more try add to vq. */
+ if (err >= 0) {
+ err = vring_copy_to_vq_packed(vq, vring, id);
+ if (err >= 0)
+ goto ok;
+ }
+
+ buf = state->data;
+ detach_buf_from_vring_packed(vring, vq, id, 0, NULL);
+ recycle(&vq->vq, buf);
+
+ok:
+ last_used += state->num;
+ desc_num += state->num;
+
+next:
+ if (unlikely(last_used >= vring->vring.num))
+ last_used -= vring->vring.num;
+
+ } while (last_used != vring->last_used_idx);
+
+ WARN_ON(vring->num_left != desc_num);
+}
+
static void *virtqueue_detach_unused_buf_packed(struct virtqueue *_vq)
{
struct vring_virtqueue *vq = to_vvq(_vq);
--
2.31.0
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