From bd1bfc0fa120486d75075e6df305a6f1bdfee1f0 Mon Sep 17 00:00:00 2001
From: Shirley Ma <mashirle@us.ibm.com>
Date: Mon, 18 Jan 2010 19:15:23 +0530
Subject: [PATCH] --- yaml --- r: 180786 b: refs/heads/master c:
 c021eac4148c16bf53baa0dd14e8ebee6f39dab5 h: refs/heads/master 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 1d5805a14b93..c68e90b1615c 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 69740c8ba878f58bc3c71f74618fc2cd1da990da
+refs/heads/master: c021eac4148c16bf53baa0dd14e8ebee6f39dab5
diff --git a/trunk/drivers/virtio/virtio_ring.c b/trunk/drivers/virtio/virtio_ring.c
index 827f7e042610..782b7292a3d8 100644
--- a/trunk/drivers/virtio/virtio_ring.c
+++ b/trunk/drivers/virtio/virtio_ring.c
@@ -351,6 +351,30 @@ 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);
@@ -377,6 +401,7 @@ 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);
 };
 
 /**