Revert "macvlan: simplify the structure port"

This reverts commit a188a54d.

It causes crashes

====================
[   80.643286] BUG: unable to handle kernel NULL pointer dereference at 0000000000000878
[   80.670103] IP: [<ffffffff810832e4>] try_to_grab_pending+0x64/0x1f0
[   80.691289] PGD 22c102067 PUD 235bf0067 PMD 0
[   80.706611] Oops: 0002 [#1] SMP
[   80.717836] Modules linked in: macvlan nfsd lockd nfs_acl exportfs auth_rpcgss sunrpc oid_registry ioatdma ixgbe(-) mdio igb dca
[   80.757935] CPU: 37 PID: 6724 Comm: rmmod Not tainted 3.16.0-net-next-08-12-2014-FCoE+ #1
[   80.785688] Hardware name: Intel Corporation S2600CO/S2600CO, BIOS SE5C600.86B.02.03.0003.041920141333 04/19/2014
[   80.820310] task: ffff880235a9eae0 ti: ffff88022e844000 task.ti: ffff88022e844000
[   80.845770] RIP: 0010:[<ffffffff810832e4>]  [<ffffffff810832e4>] try_to_grab_pending+0x64/0x1f0
[   80.875326] RSP: 0018:ffff88022e847b28  EFLAGS: 00010046
[   80.893251] RAX: 0000000000037a6a RBX: 0000000000000878 RCX: 0000000000000000
[   80.917187] RDX: ffff880235a9eae0 RSI: 0000000000000001 RDI: ffffffff810832db
[   80.941125] RBP: ffff88022e847b58 R08: 0000000000000000 R09: 0000000000000000
[   80.965056] R10: 0000000000000001 R11: 0000000000000001 R12: ffff88022e847b70
[   80.988994] R13: 0000000000000000 R14: ffff88022e847be8 R15: ffffffff81ebe440
[   81.012929] FS:  00007fab90b07700(0000) GS:ffff88043f7a0000(0000) knlGS:0000000000000000
[   81.040400] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   81.059757] CR2: 0000000000000878 CR3: 0000000235a42000 CR4: 00000000001407e0
[   81.083689] Stack:
[   81.090739]  ffff880235a9eae0 0000000000000878 ffff88022e847b70 0000000000000000
[   81.116253]  ffff88022e847be8 ffffffff81ebe440 ffff88022e847b98 ffffffff810847f1
[   81.141766]  ffff88022e847b78 0000000000000286 ffff880234200000 0000000000000000
[   81.167282] Call Trace:
[   81.175768]  [<ffffffff810847f1>] __cancel_work_timer+0x31/0x170
[   81.195985]  [<ffffffff8108494b>] cancel_work_sync+0xb/0x10
[   81.214769]  [<ffffffffa015ae68>] macvlan_port_destroy+0x28/0x60 [macvlan]
[   81.237844]  [<ffffffffa015b930>] macvlan_uninit+0x40/0x50 [macvlan]
[   81.259209]  [<ffffffff816bf6e2>] rollback_registered_many+0x1a2/0x2c0
[   81.281140]  [<ffffffff816bf81a>] unregister_netdevice_many+0x1a/0xb0
[   81.302786]  [<ffffffffa015a4ff>] macvlan_device_event+0x1ef/0x240 [macvlan]
[   81.326439]  [<ffffffff8108a13d>] notifier_call_chain+0x4d/0x70
[   81.346366]  [<ffffffff8108a201>] raw_notifier_call_chain+0x11/0x20
[   81.367439]  [<ffffffff816bf25b>] call_netdevice_notifiers_info+0x3b/0x70
[   81.390228]  [<ffffffff816bf2a1>] call_netdevice_notifiers+0x11/0x20
[   81.411587]  [<ffffffff816bf6bd>] rollback_registered_many+0x17d/0x2c0
[   81.433518]  [<ffffffff816bf925>] unregister_netdevice_queue+0x75/0x110
[   81.455735]  [<ffffffff816bfb2b>] unregister_netdev+0x1b/0x30
[   81.475094]  [<ffffffffa0039b50>] ixgbe_remove+0x170/0x1d0 [ixgbe]
[   81.495886]  [<ffffffff813512a2>] pci_device_remove+0x32/0x60
[   81.515246]  [<ffffffff814c75c4>] __device_release_driver+0x64/0xd0
[   81.536321]  [<ffffffff814c76f8>] driver_detach+0xc8/0xd0
[   81.554530]  [<ffffffff814c656e>] bus_remove_driver+0x4e/0xa0
[   81.573888]  [<ffffffff814c828b>] driver_unregister+0x2b/0x60
[   81.593246]  [<ffffffff8135143e>] pci_unregister_driver+0x1e/0xa0
[   81.613749]  [<ffffffffa005db18>] ixgbe_exit_module+0x1c/0x2e [ixgbe]
[   81.635401]  [<ffffffff810e738b>] SyS_delete_module+0x15b/0x1e0
[   81.655334]  [<ffffffff8187a395>] ? sysret_check+0x22/0x5d
[   81.673833]  [<ffffffff810abd2d>] ? trace_hardirqs_on_caller+0x11d/0x1e0
[   81.696339]  [<ffffffff8132bfde>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[   81.717985]  [<ffffffff8187a369>] system_call_fastpath+0x16/0x1b
[   81.738199] Code: 00 48 83 3d 6e bb da 00 00 48 89 c2 0f 84 67 01 00 00 fa 66 0f 1f 44 00 00 49 89 14 24 e8 b5 4b 02 00 45 84 ed 0f 85 ac 00 00 00 <f0> 0f ba 2b 00 72 1d 31 c0 48 8b 5d d8 4c 8b 65 e0 4c 8b 6d e8
[   81.807026] RIP  [<ffffffff810832e4>] try_to_grab_pending+0x64/0x1f0
[   81.828468]  RSP <ffff88022e847b28>
[   81.840384] CR2: 0000000000000878
[   81.851731] ---[ end trace 9f6c7232e3464e11 ]---
====================

This bug could be triggered by these steps:

modprobe ixgbe ; modprobe macvlan
ip link add link p96p1 address 00:1B:21:6E:06:00 macvlan0 type macvlan
ip link add link p96p1 address 00:1B:21:6E:06:01 macvlan1 type macvlan
ip link add link p96p1 address 00:1B:21:6E:06:02 macvlan2 type macvlan
ip link add link p96p1 address 00:1B:21:6E:06:03 macvlan3 type macvlan
rmmod ixgbe
Reported-by: "Keller, Jacob E" <jacob.e.keller@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/macvlan.c

@@ -45,10 +45,9 @@ struct macvlan_port {
 	struct sk_buff_head	bc_queue;
 	struct work_struct	bc_work;
 	bool 			passthru;
+	int			count;
 };
 
-#define MACVLAN_PORT_IS_EMPTY(port)    list_empty(&port->vlans)
-
 struct macvlan_skb_cb {
 	const struct macvlan_dev *src;
 };
@@ -667,7 +666,8 @@ static void macvlan_uninit(struct net_device *dev)
 
 	free_percpu(vlan->pcpu_stats);
 
-	if (MACVLAN_PORT_IS_EMPTY(port))
+	port->count -= 1;
+	if (!port->count)
 		macvlan_port_destroy(port->dev);
 }
 
@@ -1020,12 +1020,13 @@ int macvlan_common_newlink(struct net *src_net, struct net_device *dev,
 		vlan->flags = nla_get_u16(data[IFLA_MACVLAN_FLAGS]);
 
 	if (vlan->mode == MACVLAN_MODE_PASSTHRU) {
-		if (!MACVLAN_PORT_IS_EMPTY(port))
+		if (port->count)
 			return -EINVAL;
 		port->passthru = true;
 		eth_hw_addr_inherit(dev, lowerdev);
 	}
 
+	port->count += 1;
 	err = register_netdevice(dev);
 	if (err < 0)
 		goto destroy_port;
@@ -1043,7 +1044,8 @@ int macvlan_common_newlink(struct net *src_net, struct net_device *dev,
 unregister_netdev:
 	unregister_netdevice(dev);
 destroy_port:
-	if (MACVLAN_PORT_IS_EMPTY(port))
+	port->count -= 1;
+	if (!port->count)
 		macvlan_port_destroy(lowerdev);
 
 	return err;