virtio: support virtqueue_detach_unused_buf_ctx

Supports returning ctx while recycling unused buf, which helps to
release buf in different ways for different bufs.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>

drivers/virtio/virtio_ring.c

@@ -815,7 +815,8 @@ static bool virtqueue_enable_cb_delayed_split(struct virtqueue *_vq)
 	return true;
 }
 
-static void *virtqueue_detach_unused_buf_split(struct virtqueue *_vq)
+static void *virtqueue_detach_unused_buf_ctx_split(struct virtqueue *_vq,
+						   void **ctx)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
 	unsigned int i;
@@ -828,7 +829,7 @@ static void *virtqueue_detach_unused_buf_split(struct virtqueue *_vq)
 			continue;
 		/* detach_buf_split clears data, so grab it now. */
 		buf = vq->split.desc_state[i].data;
-		detach_buf_split(vq, i, NULL);
+		detach_buf_split(vq, i, ctx);
 		vq->split.avail_idx_shadow--;
 		vq->split.vring.avail->idx = cpu_to_virtio16(_vq->vdev,
 				vq->split.avail_idx_shadow);
@@ -1526,7 +1527,8 @@ static bool virtqueue_enable_cb_delayed_packed(struct virtqueue *_vq)
 	return true;
 }
 
-static void *virtqueue_detach_unused_buf_packed(struct virtqueue *_vq)
+static void *virtqueue_detach_unused_buf_ctx_packed(struct virtqueue *_vq,
+						    void **ctx)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
 	unsigned int i;
@@ -1539,7 +1541,7 @@ static void *virtqueue_detach_unused_buf_packed(struct virtqueue *_vq)
 			continue;
 		/* detach_buf clears data, so grab it now. */
 		buf = vq->packed.desc_state[i].data;
-		detach_buf_packed(vq, i, NULL);
+		detach_buf_packed(vq, i, ctx);
 		END_USE(vq);
 		return buf;
 	}
@@ -2018,12 +2020,18 @@ EXPORT_SYMBOL_GPL(virtqueue_enable_cb_delayed);
  * This is not valid on an active queue; it is useful only for device
  * shutdown.
  */
-void *virtqueue_detach_unused_buf(struct virtqueue *_vq)
+void *virtqueue_detach_unused_buf_ctx(struct virtqueue *_vq, void **ctx)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
 
-	return vq->packed_ring ? virtqueue_detach_unused_buf_packed(_vq) :
-				 virtqueue_detach_unused_buf_split(_vq);
+	return vq->packed_ring ?
+		virtqueue_detach_unused_buf_ctx_packed(_vq, ctx) :
+		virtqueue_detach_unused_buf_ctx_split(_vq, ctx);
+}
+
+void *virtqueue_detach_unused_buf(struct virtqueue *_vq)
+{
+	return virtqueue_detach_unused_buf_ctx(_vq, NULL);
 }
 EXPORT_SYMBOL_GPL(virtqueue_detach_unused_buf);
 

include/linux/virtio.h

@@ -78,6 +78,8 @@ bool virtqueue_poll(struct virtqueue *vq, unsigned);
 
 bool virtqueue_enable_cb_delayed(struct virtqueue *vq);
 
+void *virtqueue_detach_unused_buf_ctx(struct virtqueue *vq, void **ctx);
+
 void *virtqueue_detach_unused_buf(struct virtqueue *vq);
 
 unsigned int virtqueue_get_vring_size(struct virtqueue *vq);