hv_netvsc: use RCU to protect vf_netdev

The vf_netdev pointer in the netvsc device context can simply be protected
by RCU because network device destruction is already RCU synchronized.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
index 284b97b6b258f6b823abd4db91683673dd16c832..6b794876444396d5bc2c7c6e2f80f1b58e3136c8 100644 (file)
--- a/drivers/net/hyperv/hyperv_net.h
+++ b/drivers/net/hyperv/hyperv_net.h
@@ -695,7 +695,7 @@ struct net_device_context {
        bool start_remove;
 
        /* State to manage the associated VF interface. */
-       struct net_device *vf_netdev;
+       struct net_device __rcu *vf_netdev;
        bool vf_inject;
        atomic_t vf_use_cnt;
        /* 1: allocated, serial number is valid. 0: not allocated */

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 87682198ff73e945fea7c400a4fa265963405220..dde17c0faf9f1eb502d13a97623838055e77c8d2 100644 (file)
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -667,8 +667,8 @@ int netvsc_recv_callback(struct hv_device *device_obj,
 {
        struct net_device *net = hv_get_drvdata(device_obj);
        struct net_device_context *net_device_ctx = netdev_priv(net);
+       struct net_device *vf_netdev;
        struct sk_buff *skb;
-       struct sk_buff *vf_skb;
        struct netvsc_stats *rx_stats;
        u32 bytes_recvd = packet->total_data_buflen;
        int ret = 0;
@@ -676,9 +676,12 @@ int netvsc_recv_callback(struct hv_device *device_obj,
        if (!net || net->reg_state != NETREG_REGISTERED)
                return NVSP_STAT_FAIL;
 
-       if (READ_ONCE(net_device_ctx->vf_inject)) {
+       vf_netdev = rcu_dereference(net_device_ctx->vf_netdev);
+       if (vf_netdev) {
+               struct sk_buff *vf_skb;
+
                atomic_inc(&net_device_ctx->vf_use_cnt);
-               if (!READ_ONCE(net_device_ctx->vf_inject)) {
+               if (!net_device_ctx->vf_inject) {
                        /*
                         * We raced; just move on.
                         */
@@ -694,13 +697,12 @@ int netvsc_recv_callback(struct hv_device *device_obj,
                 * the host). Deliver these via the VF interface
                 * in the guest.
                 */
-               vf_skb = netvsc_alloc_recv_skb(net_device_ctx->vf_netdev,
+               vf_skb = netvsc_alloc_recv_skb(vf_netdev,
                                               packet, csum_info, *data,
                                               vlan_tci);
                if (vf_skb != NULL) {
-                       ++net_device_ctx->vf_netdev->stats.rx_packets;
-                       net_device_ctx->vf_netdev->stats.rx_bytes +=
-                               bytes_recvd;
+                       ++vf_netdev->stats.rx_packets;
+                       vf_netdev->stats.rx_bytes += bytes_recvd;
                        netif_receive_skb(vf_skb);
                } else {
                        ++net->stats.rx_dropped;
@@ -1232,7 +1234,7 @@ static struct net_device *get_netvsc_bymac(const u8 *mac)
        return NULL;
 }
 
-static struct net_device *get_netvsc_byref(const struct net_device *vf_netdev)
+static struct net_device *get_netvsc_byref(struct net_device *vf_netdev)
 {
        struct net_device *dev;
 
@@ -1248,7 +1250,7 @@ static struct net_device *get_netvsc_byref(const struct net_device *vf_netdev)
                if (net_device_ctx->nvdev == NULL)
                        continue;       /* device is removed */
 
-               if (net_device_ctx->vf_netdev == vf_netdev)
+               if (rtnl_dereference(net_device_ctx->vf_netdev) == vf_netdev)
                        return dev;     /* a match */
        }
 
@@ -1275,7 +1277,7 @@ static int netvsc_register_vf(struct net_device *vf_netdev)
 
        net_device_ctx = netdev_priv(ndev);
        netvsc_dev = net_device_ctx->nvdev;
-       if (!netvsc_dev || net_device_ctx->vf_netdev)
+       if (!netvsc_dev || rtnl_dereference(net_device_ctx->vf_netdev))
                return NOTIFY_DONE;
 
        netdev_info(ndev, "VF registering: %s\n", vf_netdev->name);
@@ -1285,7 +1287,7 @@ static int netvsc_register_vf(struct net_device *vf_netdev)
        try_module_get(THIS_MODULE);
 
        dev_hold(vf_netdev);
-       net_device_ctx->vf_netdev = vf_netdev;
+       rcu_assign_pointer(net_device_ctx->vf_netdev, vf_netdev);
        return NOTIFY_OK;
 }
 
@@ -1379,7 +1381,8 @@ static int netvsc_unregister_vf(struct net_device *vf_netdev)
 
        netdev_info(ndev, "VF unregistering: %s\n", vf_netdev->name);
        netvsc_inject_disable(net_device_ctx);
-       net_device_ctx->vf_netdev = NULL;
+
+       RCU_INIT_POINTER(net_device_ctx->vf_netdev, NULL);
        dev_put(vf_netdev);
        module_put(THIS_MODULE);
        return NOTIFY_OK;
@@ -1433,8 +1436,6 @@ static int netvsc_probe(struct hv_device *dev,
        INIT_LIST_HEAD(&net_device_ctx->reconfig_events);
 
        atomic_set(&net_device_ctx->vf_use_cnt, 0);
-       net_device_ctx->vf_netdev = NULL;
-       net_device_ctx->vf_inject = false;
 
        net->netdev_ops = &device_ops;