From 5399d20f20f2ede800fe205c13305de4d73cb6eb Mon Sep 17 00:00:00 2001
From: Shirley Ma <mashirle@us.ibm.com>
Date: Fri, 29 Jan 2010 03:19:05 +0000
Subject: [PATCH] --- yaml --- r: 183781 b: refs/heads/master c:
 f9bfbebf34eab707b065116cdc9699d25ba4252a h: refs/heads/master i:   183779:
 dad13e2d2dd793868908a60714c679e36271a8b0 v: v3

---
 [refs]                             |  2 +-
 trunk/drivers/virtio/virtio_ring.c | 25 +++++++++++++++++++++++++
 trunk/include/linux/virtio.h       |  4 ++++
 3 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 13a87082568f..d491d36154f7 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 28aecb9d7728dc26bf03ce7925fe622023a83a2a
+refs/heads/master: f9bfbebf34eab707b065116cdc9699d25ba4252a
diff --git a/trunk/drivers/virtio/virtio_ring.c b/trunk/drivers/virtio/virtio_ring.c
index fbd2ecde93e4..71929ee00d69 100644
--- a/trunk/drivers/virtio/virtio_ring.c
+++ b/trunk/drivers/virtio/virtio_ring.c
@@ -334,6 +334,30 @@ static bool vring_enable_cb(struct virtqueue *_vq)
 	return true;
 }
 
+static void *vring_detach_unused_buf(struct virtqueue *_vq)
+{
+	struct vring_virtqueue *vq = to_vvq(_vq);
+	unsigned int i;
+	void *buf;
+
+	START_USE(vq);
+
+	for (i = 0; i < vq->vring.num; i++) {
+		if (!vq->data[i])
+			continue;
+		/* detach_buf clears data, so grab it now. */
+		buf = vq->data[i];
+		detach_buf(vq, i);
+		END_USE(vq);
+		return buf;
+	}
+	/* 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 +384,7 @@ static struct virtqueue_ops vring_vq_ops = {
 	.kick = vring_kick,
 	.disable_cb = vring_disable_cb,
 	.enable_cb = vring_enable_cb,
+	.detach_unused_buf = vring_detach_unused_buf,
 };
 
 struct virtqueue *vring_new_virtqueue(unsigned int num,
diff --git a/trunk/include/linux/virtio.h b/trunk/include/linux/virtio.h
index 057a2e010758..f508c651e53d 100644
--- a/trunk/include/linux/virtio.h
+++ b/trunk/include/linux/virtio.h
@@ -51,6 +51,9 @@ struct virtqueue {
  *	This re-enables callbacks; it returns "false" if there are pending
  *	buffers in the queue, to detect a possible race between the driver
  *	checking for more work, and enabling callbacks.
+ * @detach_unused_buf: detach first unused buffer
+ * 	vq: the struct virtqueue we're talking about.
+ * 	Returns NULL or the "data" token handed to add_buf
  *
  * Locking rules are straightforward: the driver is responsible for
  * locking.  No two operations may be invoked simultaneously, with the exception
@@ -71,6 +74,7 @@ struct virtqueue_ops {
 
 	void (*disable_cb)(struct virtqueue *vq);
 	bool (*enable_cb)(struct virtqueue *vq);
+	void *(*detach_unused_buf)(struct virtqueue *vq);
 };
 
 /**