vhost: rcu annotation fixup

When built with rcu checks enabled, vhost triggers
bogus warnings as vhost features are read without
dev->mutex sometimes, and private pointer is read
with our kind of rcu where work serves as a
read side critical section.

Fixing it properly is not trivial.
Disable the warnings by stubbing out the checks for now.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 9b3ca10..f616cef 100644 (file)
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -128,8 +128,7 @@ static void handle_tx(struct vhost_net *net)
        size_t hdr_size;
        struct socket *sock;
 
-       /* TODO: check that we are running from vhost_worker?
-        * Not sure it's worth it, it's straight-forward enough. */
+       /* TODO: check that we are running from vhost_worker? */
        sock = rcu_dereference_check(vq->private_data, 1);
        if (!sock)
                return;
@@ -306,7 +305,8 @@ static void handle_rx_big(struct vhost_net *net)
        size_t len, total_len = 0;
        int err;
        size_t hdr_size;
-       struct socket *sock = rcu_dereference(vq->private_data);
+       /* TODO: check that we are running from vhost_worker? */
+       struct socket *sock = rcu_dereference_check(vq->private_data, 1);
        if (!sock || skb_queue_empty(&sock->sk->sk_receive_queue))
                return;
 
@@ -415,7 +415,8 @@ static void handle_rx_mergeable(struct vhost_net *net)
        int err, headcount;
        size_t vhost_hlen, sock_hlen;
        size_t vhost_len, sock_len;
-       struct socket *sock = rcu_dereference(vq->private_data);
+       /* TODO: check that we are running from vhost_worker? */
+       struct socket *sock = rcu_dereference_check(vq->private_data, 1);
        if (!sock || skb_queue_empty(&sock->sk->sk_receive_queue))
                return;
 

diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 2af44b7..b3363ae 100644 (file)
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -173,9 +173,9 @@ static inline int vhost_has_feature(struct vhost_dev *dev, int bit)
 {
        unsigned acked_features;
 
-       acked_features =
-               rcu_dereference_index_check(dev->acked_features,
-                                           lockdep_is_held(&dev->mutex));
+       /* TODO: check that we are running from vhost_worker or dev mutex is
+        * held? */
+       acked_features = rcu_dereference_index_check(dev->acked_features, 1);
        return acked_features & (1 << bit);
 }