Subject: [PATCH 47/48] vhost_net: add missing lock nesting notation

From: Jason Wang <[email-masked]>
Date: Mon, 26 Mar 2018 16:10:23 +0800

[ Upstream commit aaa3149bbee9ba9b4e6f0bd6e3e7d191edeae942 ]

We try to hold TX virtqueue mutex in vhost_net_rx_peek_head_len()
after RX virtqueue mutex is held in handle_rx(). This requires an
appropriate lock nesting notation to calm down deadlock detector.

Fixes: 0308813724606 ("vhost_net: basic polling support")
Reported-by: [email-masked]
Signed-off-by: Jason Wang <[email-masked]>
Acked-by: Michael S. Tsirkin <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 drivers/vhost/net.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 5636c7ca8eba..0020ae906bf9 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -618,7 +618,7 @@ static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk)
 
 	if (!len && vq->busyloop_timeout) {
 		/* Both tx vq and rx socket were polled here */
-		mutex_lock(&vq->mutex);
+		mutex_lock_nested(&vq->mutex, 1);
 		vhost_disable_notify(&net->dev, vq);
 
 		preempt_disable();
@@ -751,7 +751,7 @@ static void handle_rx(struct vhost_net *net)
 	struct iov_iter fixup;
 	__virtio16 num_buffers;
 
-	mutex_lock(&vq->mutex);
+	mutex_lock_nested(&vq->mutex, 0);
 	sock = vq->private_data;
 	if (!sock)
 		goto out;
-- 
2.14.3