[RFC] Subject: virtio: Add unused buffers detach from vring

Commit Message

Shirley Ma Dec. 15, 2009, 6:42 p.m. UTC

None

Patch

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index fbd2ecd..f847bc3 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -334,6 +334,29 @@  static bool vring_enable_cb(struct virtqueue *_vq)
 	return true;
 }
 
+/* This function is used to return vring unused buffers to caller for free */
+static void *vring_detach_bufs(struct virtqueue *_vq)
+{
+	struct vring_virtqueue *vq = to_vvq(_vq);
+	unsigned int i;
+
+	START_USE(vq);
+
+	for (i = 0; i < vq->vring.num; ++i) {
+		if (vq->data[i]) {
+			/* detach_buf clears data, so grab it now. */
+			detach_buf(vq, i);
+			END_USE(vq);
+			return vq->data[i];
+		}
+	}
+	/* That should have freed everything. */
+	BUG_ON(vq->num_free != vq->vring.num);
+
+	END_USE(vq);
+	return NULL;
+}
+
 irqreturn_t vring_interrupt(int irq, void *_vq)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
@@ -360,6 +383,7 @@  static struct virtqueue_ops vring_vq_ops = {
 	.kick = vring_kick,
 	.disable_cb = vring_disable_cb,
 	.enable_cb = vring_enable_cb,
+	.detach_bufs = vring_detach_bufs,
 };
 
 struct virtqueue *vring_new_virtqueue(unsigned int num,
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 057a2e0..d7da456 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -71,6 +71,7 @@  struct virtqueue_ops {
 
 	void (*disable_cb)(struct virtqueue *vq);
 	bool (*enable_cb)(struct virtqueue *vq);
+	void *(*detach_bufs)(struct virtqueue *vq);
 };
 
 /**