From 45e1325918e0385de07c55571a28e73fca9dac47 Mon Sep 17 00:00:00 2001
From: Shirley Ma <mashirle@us.ibm.com>
Date: Wed, 20 Jul 2011 10:23:12 -0700
Subject: [PATCH] --- yaml --- r: 256627 b: refs/heads/master c:
 9e380825ab3f5176f65306c4ac119fd23634ce03 h: refs/heads/master i:   256625:
 e3f178c80c22ac5169ccd5198fd0ed365349caee   256623:
 3089bbf8489a8fdc760851a41ffc36cf704453cf v: v3

---
 [refs]                    |  2 +-
 trunk/drivers/vhost/net.c | 12 +++++++++---
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/[refs] b/[refs]
index cfbffae4f078..b106a386dc4a 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: c047e5f3170c2595e66ed67f87cec01afd717212
+refs/heads/master: 9e380825ab3f5176f65306c4ac119fd23634ce03
diff --git a/trunk/drivers/vhost/net.c b/trunk/drivers/vhost/net.c
index 248b25008d1a..882a51fe7b3c 100644
--- a/trunk/drivers/vhost/net.c
+++ b/trunk/drivers/vhost/net.c
@@ -182,15 +182,21 @@ static void handle_tx(struct vhost_net *net)
 			break;
 		/* Nothing new?  Wait for eventfd to tell us they refilled. */
 		if (head == vq->num) {
+			int num_pends;
+
 			wmem = atomic_read(&sock->sk->sk_wmem_alloc);
 			if (wmem >= sock->sk->sk_sndbuf * 3 / 4) {
 				tx_poll_start(net, sock);
 				set_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
 				break;
 			}
-			/* If more outstanding DMAs, queue the work */
-			if (unlikely(vq->upend_idx - vq->done_idx >
-				     VHOST_MAX_PEND)) {
+			/* If more outstanding DMAs, queue the work.
+			 * Handle upend_idx wrap around
+			 */
+			num_pends = likely(vq->upend_idx >= vq->done_idx) ?
+				    (vq->upend_idx - vq->done_idx) :
+				    (vq->upend_idx + UIO_MAXIOV - vq->done_idx);
+			if (unlikely(num_pends > VHOST_MAX_PEND)) {
 				tx_poll_start(net, sock);
 				set_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
 				break;