[PATCH 5/7] vhost: factor out the detach buf logic in SVQ

["Eugenio Pérez" <eperezma@redhat.com>]

This code path is modified to handle in order devices.  Abstract here so
we can generalize on the caller.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-shadow-virtqueue.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c
index e7e3c9155cd0..2d8fc82cc06f 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -473,11 +473,24 @@ static uint16_t vhost_svq_last_desc_of_chain(const VhostShadowVirtqueue *svq,
     return i;
 }
 
+G_GNUC_WARN_UNUSED_RESULT
+static VirtQueueElement *vhost_svq_detach_buf(VhostShadowVirtqueue *svq,
+                                              uint16_t id)
+{
+    uint16_t num = svq->desc_state[id].ndescs;
+    uint16_t last_used_chain = vhost_svq_last_desc_of_chain(svq, num, id);
+
+    svq->desc_state[last_used_chain].next = svq->free_head;
+    svq->free_head = id;
+
+    return g_steal_pointer(&svq->desc_state[id].elem);
+}
+
 G_GNUC_WARN_UNUSED_RESULT
 static VirtQueueElement *vhost_svq_get_buf(VhostShadowVirtqueue *svq,
                                            uint32_t *len)
 {
-    uint16_t last_used, last_used_chain, num;
+    uint16_t last_used;
 
     if (!vhost_svq_more_used(svq)) {
         return NULL;
@@ -500,14 +513,9 @@ static VirtQueueElement *vhost_svq_get_buf(VhostShadowVirtqueue *svq,
         return NULL;
     }
 
-    num = svq->desc_state[last_used].ndescs;
+    svq->num_free += svq->desc_state[last_used].ndescs;
     svq->desc_state[last_used].ndescs = 0;
-    last_used_chain = vhost_svq_last_desc_of_chain(svq, num, last_used);
-    svq->desc_state[last_used_chain].next = svq->free_head;
-    svq->free_head = last_used;
-    svq->num_free += num;
-
-    return g_steal_pointer(&svq->desc_state[last_used].elem);
+    return vhost_svq_detach_buf(svq, last_used);
 }
 
 /**
-- 
2.53.0