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authorShirley Ma <mashirle@us.ibm.com>2011-07-20 10:23:12 -0700
committerMichael S. Tsirkin <mst@redhat.com>2011-07-21 10:48:27 +0300
commit9e380825ab3f5176f65306c4ac119fd23634ce03 (patch)
tree4fdf3f2609da5ee3222103682f3ce10c976353d0 /drivers/vhost
parentc047e5f3170c2595e66ed67f87cec01afd717212 (diff)
downloadlinux-linaro-stable-9e380825ab3f5176f65306c4ac119fd23634ce03.tar.gz
vhost: handle wrap around in # of bufs math
The meth for calculating the # of outstanding buffers gives incorrect results when vq->upend_idx wraps around zero. Fix that. Signed-off-by: Shirley Ma <xma@us.ibm.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'drivers/vhost')
-rw-r--r--drivers/vhost/net.c12
1 files changed, 9 insertions, 3 deletions
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 248b25008d1a..882a51fe7b3c 100644
--- a/drivers/vhost/net.c
+++ b/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;