[PATCH v2 net-next 1/6] bonding: add rcu to vlan_uses_dev() and make bond_vlan_used() use it

[Veaceslav Falico <vfalico@redhat.com>]

RFC -> v1: don't add vlan_uses_dev_rcu() and change vlan_uses_dev() instead
v1  -> v2: remove the ASSERT_RTNL(), cause we can now be called under rcu.

Currently, bond_vlan_used() looks for any vlan, including the pseudo-vlan
id 0, and always returns true if 8021q is loaded. This creates several bad
situations - some warnings in __bond_release_one() because it thinks that
we still have vlans while removing, sending LB packets with vlan id 0 and,
possibly, other caused by vlan id 0.

Fix it by changing vlan_uses_dev() to use rcu_dereference_rtnl() instead of
rtnl_dereference(), and thus it can already be used in bond_vlan_used()
under rcu_read_lock().

By the time vlan_uses_dev() returns we cannot be sure if there were no
vlans added/removed, so it's basicly an optimization function.

Also, use the vlan_uses_dev() in __bond_release_one() cause the rtnl lock
is held there.

For this call to be visible in bonding.h, add include <linux/if_vlan.h>,
and also remove it from any other bonding file, cause they all include
bonding.h, and thus linux/if_vlan.h.

CC: Jay Vosburgh <fubar@us.ibm.com>
CC: Andy Gospodarek <andy@greyhouse.net>
CC: Patrick McHardy <kaber@trash.net>
CC: "David S. Miller" <davem@davemloft.net>
CC: Nikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: Veaceslav Falico <vfalico@redhat.com>
---
 drivers/net/bonding/bond_alb.c  |    1 -
 drivers/net/bonding/bond_main.c |    3 +--
 drivers/net/bonding/bonding.h   |   10 +++++++++-
 net/8021q/vlan_core.c           |    5 ++---
 4 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
index 3a5db7b..2684329 100644
--- a/drivers/net/bonding/bond_alb.c
+++ b/drivers/net/bonding/bond_alb.c
@@ -34,7 +34,6 @@
 #include <linux/if_arp.h>
 #include <linux/if_ether.h>
 #include <linux/if_bonding.h>
-#include <linux/if_vlan.h>
 #include <linux/in.h>
 #include <net/ipx.h>
 #include <net/arp.h>
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 4264a76..9d1045d 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -69,7 +69,6 @@
 #include <net/arp.h>
 #include <linux/mii.h>
 #include <linux/ethtool.h>
-#include <linux/if_vlan.h>
 #include <linux/if_bonding.h>
 #include <linux/jiffies.h>
 #include <linux/preempt.h>
@@ -1953,7 +1952,7 @@ static int __bond_release_one(struct net_device *bond_dev,
 		bond_set_carrier(bond);
 		eth_hw_addr_random(bond_dev);
 
-		if (bond_vlan_used(bond)) {
+		if (vlan_uses_dev(bond_dev)) {
 			pr_warning("%s: Warning: clearing HW address of %s while it still has VLANs.\n",
 				   bond_dev->name, bond_dev->name);
 			pr_warning("%s: When re-adding slaves, make sure the bond's HW address matches its VLANs'.\n",
diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
index 4bf52d5..9c4539e 100644
--- a/drivers/net/bonding/bonding.h
+++ b/drivers/net/bonding/bonding.h
@@ -23,6 +23,7 @@
 #include <linux/netpoll.h>
 #include <linux/inetdevice.h>
 #include <linux/etherdevice.h>
+#include <linux/if_vlan.h>
 #include "bond_3ad.h"
 #include "bond_alb.h"
 
@@ -267,9 +268,16 @@ struct bonding {
 #endif /* CONFIG_DEBUG_FS */
 };
 
+/* use vlan_uses_dev() if under rtnl */
 static inline bool bond_vlan_used(struct bonding *bond)
 {
-	return !list_empty(&bond->vlan_list);
+	bool ret;
+
+	rcu_read_lock();
+	ret = vlan_uses_dev(bond->dev);
+	rcu_read_unlock();
+
+	return ret;
 }
 
 #define bond_slave_get_rcu(dev) \
diff --git a/net/8021q/vlan_core.c b/net/8021q/vlan_core.c
index 4a78c4d..361c97b 100644
--- a/net/8021q/vlan_core.c
+++ b/net/8021q/vlan_core.c
@@ -387,13 +387,12 @@ void vlan_vids_del_by_dev(struct net_device *dev,
 }
 EXPORT_SYMBOL(vlan_vids_del_by_dev);
 
+/* Must hold either rtnl or rcu_read_lock */
 bool vlan_uses_dev(const struct net_device *dev)
 {
 	struct vlan_info *vlan_info;
 
-	ASSERT_RTNL();
-
-	vlan_info = rtnl_dereference(dev->vlan_info);
+	vlan_info = rcu_dereference_rtnl(dev->vlan_info);
 	if (!vlan_info)
 		return false;
 	return vlan_info->grp.nr_vlan_devs ? true : false;
-- 
1.7.1