Two helpers of setting/getting used len were introduced to avoid
explicitly manipulating vhost_used_elem in zerocopy code. This will be
used to hide used_elem internals and simplify packed ring
implementation.

Signed-off-by: Jason Wang <jasow...@redhat.com>
---
 drivers/vhost/net.c   | 11 +++++------
 drivers/vhost/vhost.c | 12 ++++++++++--
 drivers/vhost/vhost.h |  5 +++++
 3 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 3826f1f..30273ad 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -341,9 +341,10 @@ static void vhost_zerocopy_signal_used(struct vhost_net 
*net,
        int j = 0;
 
        for (i = nvq->done_idx; i != nvq->upend_idx; i = (i + 1) % UIO_MAXIOV) {
-               if (vq->heads[i].elem.len == VHOST_DMA_FAILED_LEN)
+               if (vhost_get_used_len(vq, &vq->heads[i]) ==
+                   VHOST_DMA_FAILED_LEN)
                        vhost_net_tx_err(net);
-               if (VHOST_DMA_IS_DONE(vq->heads[i].elem.len)) {
+               if (VHOST_DMA_IS_DONE(vhost_get_used_len(vq, &vq->heads[i]))) {
                        vq->heads[i].elem.len = VHOST_DMA_CLEAR_LEN;
                        ++j;
                } else
@@ -542,10 +543,8 @@ static void handle_tx(struct vhost_net *net)
                        struct ubuf_info *ubuf;
                        ubuf = nvq->ubuf_info + nvq->upend_idx;
 
-                       vq->heads[nvq->upend_idx].elem.id =
-                               cpu_to_vhost32(vq, used.elem.id);
-                       vq->heads[nvq->upend_idx].elem.len =
-                               VHOST_DMA_IN_PROGRESS;
+                       vhost_set_used_len(vq, &used, VHOST_DMA_IN_PROGRESS);
+                       vq->heads[nvq->upend_idx] = used;
                        ubuf->callback = vhost_zerocopy_callback;
                        ubuf->ctx = nvq->ubufs;
                        ubuf->desc = nvq->upend_idx;
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 2b2a776..e0fcfec 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -2067,11 +2067,19 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
 }
 EXPORT_SYMBOL_GPL(vhost_get_vq_desc);
 
-static void vhost_set_used_len(struct vhost_virtqueue *vq,
-                              struct vhost_used_elem *used, int len)
+void vhost_set_used_len(struct vhost_virtqueue *vq,
+                       struct vhost_used_elem *used, int len)
 {
        used->elem.len = cpu_to_vhost32(vq, len);
 }
+EXPORT_SYMBOL_GPL(vhost_set_used_len);
+
+int vhost_get_used_len(struct vhost_virtqueue *vq,
+                      struct vhost_used_elem *used)
+{
+       return vhost32_to_cpu(vq, used->elem.len);
+}
+EXPORT_SYMBOL_GPL(vhost_get_used_len);
 
 /* This is a multi-buffer version of vhost_get_desc, that works if
  *     vq has read descriptors only.
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 8dea44b..604821b 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -198,6 +198,11 @@ int vhost_get_bufs(struct vhost_virtqueue *vq,
                   unsigned *log_num,
                   unsigned int quota,
                   s16 *count);
+void vhost_set_used_len(struct vhost_virtqueue *vq,
+                       struct vhost_used_elem *used,
+                       int len);
+int vhost_get_used_len(struct vhost_virtqueue *vq,
+                      struct vhost_used_elem *used);
 void vhost_discard_vq_desc(struct vhost_virtqueue *, int n);
 
 int vhost_vq_init_access(struct vhost_virtqueue *);
-- 
2.7.4

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