macvlan: remove one synchronize_rcu() call

When one macvlan device is dismantled, we can avoid one
synchronize_rcu() call done after deletion from hash list, since caller
will perform a synchronize_net() call after its ndo_stop() call.

Add a new netdev->dismantle field to signal this dismantle intent.

Reduces RTNL hold time.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Patrick McHardy <kaber@trash.net>
CC: Ben Greear <greearb@candelatech.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 4 deletions

diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index d7c0bc62da7f..07bcb8084d78 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -70,16 +70,17 @@ static void macvlan_hash_add(struct macvlan_dev *vlan)
         hlist_add_head_rcu(&vlan->hlist, &port->vlan_hash[addr[5]]);
 }
 
-static void macvlan_hash_del(struct macvlan_dev *vlan)
+static void macvlan_hash_del(struct macvlan_dev *vlan, bool sync)
 {
         hlist_del_rcu(&vlan->hlist);
-        synchronize_rcu();
+        if (sync)
+                synchronize_rcu();
 }
 
 static void macvlan_hash_change_addr(struct macvlan_dev *vlan,
                                         const unsigned char *addr)
 {
-        macvlan_hash_del(vlan);
+        macvlan_hash_del(vlan, true);
         /* Now that we are unhashed it is safe to change the device
          * address without confusing packet delivery.
          */
@@ -345,7 +346,7 @@ static int macvlan_stop(struct net_device *dev)
         dev_uc_del(lowerdev, dev->dev_addr);
 
 hash_del:
-        macvlan_hash_del(vlan);
+        macvlan_hash_del(vlan, !dev->dismantle);
         return 0;
 }