[PATCH net-next] vxlan: reduce usage of synchronize_net in ndo_stop

[Hannes Frederic Sowa]

We only need to do the synchronize_net dance once for both, ipv4 and
ipv6 sockets, thus removing one synchronize_net in case both sockets get
dismantled.

Signed-off-by: Hannes Frederic Sowa <han...@stressinduktion.org>
---
Based on patch: [net-next,v2] vxlan: synchronously and race-free destruction of 
vxlan sockets

 drivers/net/vxlan.c | 28 ++++++++++++++++++++--------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
index 77ba31a0e44f97..c417bbfa3ab49f 100644
--- a/drivers/net/vxlan.c
+++ b/drivers/net/vxlan.c
@@ -1037,14 +1037,14 @@ static bool vxlan_group_used(struct vxlan_net *vn, 
struct vxlan_dev *dev)
        return false;
 }
 
-static void __vxlan_sock_release(struct vxlan_sock *vs)
+static bool __vxlan_sock_release_prep(struct vxlan_sock *vs)
 {
        struct vxlan_net *vn;
 
        if (!vs)
-               return;
+               return false;
        if (!atomic_dec_and_test(&vs->refcnt))
-               return;
+               return false;
 
        vn = net_generic(sock_net(vs->sock->sk), vxlan_net_id);
        spin_lock(&vn->sock_lock);
@@ -1052,16 +1052,28 @@ static void __vxlan_sock_release(struct vxlan_sock *vs)
        vxlan_notify_del_rx_port(vs);
        spin_unlock(&vn->sock_lock);
 
-       synchronize_net();
-       udp_tunnel_sock_release(vs->sock);
-       kfree(vs);
+       return true;
 }
 
 static void vxlan_sock_release(struct vxlan_dev *vxlan)
 {
-       __vxlan_sock_release(vxlan->vn4_sock);
+       bool ipv4 = __vxlan_sock_release_prep(vxlan->vn4_sock);
 #if IS_ENABLED(CONFIG_IPV6)
-       __vxlan_sock_release(vxlan->vn6_sock);
+       bool ipv6 = __vxlan_sock_release_prep(vxlan->vn6_sock);
+#endif
+
+       synchronize_net();
+
+       if (ipv4) {
+               udp_tunnel_sock_release(vxlan->vn4_sock->sock);
+               kfree(vxlan->vn4_sock);
+       }
+
+#if IS_ENABLED(CONFIG_IPV6)
+       if (ipv6) {
+               udp_tunnel_sock_release(vxlan->vn6_sock->sock);
+               kfree(vxlan->vn6_sock);
+       }
 #endif
 }
 
-- 
2.5.5