[PATCH] bonding: various fixes for bonding, netpoll & netconsole

[PATCH] bonding: various fixes for bonding, netpoll & netconsole

[nhorman]

Grr, really sorry guys, 3rd times the charm.  netdev greylisted this and several
others pitched it because of a bad mail header.  I'm resending through tuxdriver
like I should have done before

A while ago we tried to enable netpoll on the bonding driver to enable
netconsole.  That worked well in a steady state, but deadlocked frequently in
failover conditions due to some recursive lock-taking (as well as a few other
problems).  I've gone through the driver, netconsole and netpoll code, fixed up
those deadlocks, and confirmed that, with this patch series, we can use
netconsole on bonding without deadlock in all bonding modes with all slaves,
even accross failovers.  I've also fixed up some incidental bugs that I ran
across while looking through this code, as described in individual patches

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>

[PATCH 1/5] Fix bonding drivers improper modification of netpoll structure

[nhorman]

From: Neil Horman <nhorman@tuxdriver.com>

The bonding driver currently modifies the netpoll structure in its xmit path
while sending frames from netpoll.  This is racy, as other cpus can access the
netpoll structure in parallel. Since the bonding driver points np->dev to a
slave device, other cpus can inadvertently attempt to send data directly to
slave devices, leading to improper locking with the bonding master, lost frames,
and deadlocks.  This patch fixes that up.

This patch also removes the real_dev pointer from the netpoll structure as that
data is really only used by bonding in the poll_controller, and we can emulate
its behavior by check each slave for IS_UP.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
---
 drivers/net/bonding/bond_main.c |   15 +++++++++------
 include/linux/netpoll.h         |    9 +++++++--
 net/core/netpoll.c              |    6 +++---
 3 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index a0bf35d..eb7d089 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -449,11 +449,9 @@ int bond_dev_queue_xmit(struct bonding *bond, struct sk_buff *skb,
 	if (unlikely(bond->dev->priv_flags & IFF_IN_NETPOLL)) {
 		struct netpoll *np = bond->dev->npinfo->netpoll;
 		slave_dev->npinfo = bond->dev->npinfo;
-		np->real_dev = np->dev = skb->dev;
 		slave_dev->priv_flags |= IFF_IN_NETPOLL;
-		netpoll_send_skb(np, skb);
+		netpoll_send_skb_on_dev(np, skb, slave_dev);
 		slave_dev->priv_flags &= ~IFF_IN_NETPOLL;
-		np->dev = bond->dev;
 	} else
 #endif
 		dev_queue_xmit(skb);
@@ -1332,9 +1330,14 @@ static bool slaves_support_netpoll(struct net_device *bond_dev)
 
 static void bond_poll_controller(struct net_device *bond_dev)
 {
-	struct net_device *dev = bond_dev->npinfo->netpoll->real_dev;
-	if (dev != bond_dev)
-		netpoll_poll_dev(dev);
+	struct bonding *bond = netdev_priv(bond_dev);
+	struct slave *slave;
+	int i;
+
+	bond_for_each_slave(bond, slave, i) {
+		if (slave->dev && IS_UP(slave->dev))
+			netpoll_poll_dev(slave->dev);
+	}
 }
 
 static void bond_netpoll_cleanup(struct net_device *bond_dev)
diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index 50d8009..79358bb 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -14,7 +14,6 @@
 
 struct netpoll {
 	struct net_device *dev;
-	struct net_device *real_dev;
 	char dev_name[IFNAMSIZ];
 	const char *name;
 	void (*rx_hook)(struct netpoll *, int, char *, int);
@@ -53,7 +52,13 @@ void netpoll_set_trap(int trap);
 void __netpoll_cleanup(struct netpoll *np);
 void netpoll_cleanup(struct netpoll *np);
 int __netpoll_rx(struct sk_buff *skb);
-void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb);
+void netpoll_send_skb_on_dev(struct netpoll *np, struct sk_buff *skb,
+			     struct net_device *dev);
+static inline void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
+{
+	netpoll_send_skb_on_dev(np, skb, np->dev);
+}
+
 
 
 #ifdef CONFIG_NETPOLL
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 537e01a..4e98ffa 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -288,11 +288,11 @@ static int netpoll_owner_active(struct net_device *dev)
 	return 0;
 }
 
-void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
+void netpoll_send_skb_on_dev(struct netpoll *np, struct sk_buff *skb,
+			     struct net_device *dev)
 {
 	int status = NETDEV_TX_BUSY;
 	unsigned long tries;
-	struct net_device *dev = np->dev;
 	const struct net_device_ops *ops = dev->netdev_ops;
 	/* It is up to the caller to keep npinfo alive. */
 	struct netpoll_info *npinfo = np->dev->npinfo;
@@ -346,7 +346,7 @@ void netpoll_send_skb(struct netpoll *np, struct sk_buff *skb)
 		schedule_delayed_work(&npinfo->tx_work,0);
 	}
 }
-EXPORT_SYMBOL(netpoll_send_skb);
+EXPORT_SYMBOL(netpoll_send_skb_on_dev);
 
 void netpoll_send_udp(struct netpoll *np, const char *msg, int len)
 {
-- 
1.7.2.3

[PATCH 2/5] Fix deadlock in bonding driver resulting from internal locking when using netpoll

[nhorman]

From: Neil Horman <nhorman@tuxdriver.com>

The monitoring paths in the bonding driver take write locks that are shared by
the tx path.  If netconsole is in use, these paths can call printk which puts us
in the netpoll tx path, which, if netconsole is attached to the bonding driver,
result in deadlock (the xmit_lock guards are useless in netpoll_send_skb, as the
monitor paths in the bonding driver don't claim the xmit_lock, nor should they).
The solution is to use a per cpu flag internal to the driver to indicate when a
cpu is holding the lock in a path that might recusrse into the tx path for the
driver via netconsole.  By checking this flag on transmit, we can defer the
sending of the netconsole frames until a later time using the retransmit feature
of netpoll_send_skb that is triggered on the return code NETDEV_TX_BUSY.  I've
tested this and am able to transmit via netconsole while causing failover
conditions on the bond slave links.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
---
 drivers/net/bonding/bond_main.c |   67 ++++++++++++++++++++++++++++++++++++--
 1 files changed, 63 insertions(+), 4 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index eb7d089..1d0d8c5 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -76,6 +76,7 @@
 #include <linux/if_vlan.h>
 #include <linux/if_bonding.h>
 #include <linux/jiffies.h>
+#include <linux/preempt.h>
 #include <net/route.h>
 #include <net/net_namespace.h>
 #include <net/netns/generic.h>
@@ -169,6 +170,35 @@ MODULE_PARM_DESC(resend_igmp, "Number of IGMP membership reports to send on link
 
 /*----------------------------- Global variables ----------------------------*/
 
+#ifdef CONFIG_NET_POLL_CONTROLLER
+static cpumask_var_t netpoll_block_tx;
+
+static inline void block_netpoll_tx(void
+{
+	preempt_disable();
+	BUG_ON(cpumask_test_and_set_cpu(smp_processor_id(),
+					netpoll_block_tx));
+}
+
+static inline void unblock_netpoll_tx(void)
+{
+	BUG_ON(!cpumask_test_and_clear_cpu(smp_processor_id(),
+					  netpoll_block_tx));
+	preempt_enable();
+}
+
+static inline int is_netpoll_tx_blocked(struct net_device *dev)
+{
+	if (unlikely(dev->priv_flags & IFF_IN_NETPOLL))
+		return cpumask_test_cpu(smp_processor_id(), netpoll_block_tx);
+	return 0;
+}
+#else
+#define block_netpoll_tx()
+#define unblock_netpoll_tx()
+#define is_netpoll_tx_blocked(dev)
+#endif
+
 static const char * const version =
 	DRV_DESCRIPTION ": v" DRV_VERSION " (" DRV_RELDATE ")\n";
 
@@ -310,6 +340,7 @@ static int bond_del_vlan(struct bonding *bond, unsigned short vlan_id)
 
 	pr_debug("bond: %s, vlan id %d\n", bond->dev->name, vlan_id);
 
+	block_netpoll_tx();
 	write_lock_bh(&bond->lock);
 
 	list_for_each_entry(vlan, &bond->vlan_list, vlan_list) {
@@ -344,6 +375,7 @@ static int bond_del_vlan(struct bonding *bond, unsigned short vlan_id)
 
 out:
 	write_unlock_bh(&bond->lock);
+	unblock_netpoll_tx();
 	return res;
 }
 
@@ -1804,10 +1836,6 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
 	bond_set_carrier(bond);
 
 #ifdef CONFIG_NET_POLL_CONTROLLER
-	/*
-	 * Netpoll and bonding is broken, make sure it is not initialized
-	 * until it is fixed.
-	 */
 	if (disable_netpoll) {
 		bond_dev->priv_flags |= IFF_DISABLE_NETPOLL;
 	} else {
@@ -1892,6 +1920,7 @@ int bond_release(struct net_device *bond_dev, struct net_device *slave_dev)
 		return -EINVAL;
 	}
 
+	block_netpoll_tx();
 	netdev_bonding_change(bond_dev, NETDEV_BONDING_DESLAVE);
 	write_lock_bh(&bond->lock);
 
@@ -1901,6 +1930,7 @@ int bond_release(struct net_device *bond_dev, struct net_device *slave_dev)
 		pr_info("%s: %s not enslaved\n",
 			bond_dev->name, slave_dev->name);
 		write_unlock_bh(&bond->lock);
+		unblock_netpoll_tx();
 		return -EINVAL;
 	}
 
@@ -1994,6 +2024,7 @@ int bond_release(struct net_device *bond_dev, struct net_device *slave_dev)
 	}
 
 	write_unlock_bh(&bond->lock);
+	unblock_netpoll_tx();
 
 	/* must do this from outside any spinlocks */
 	bond_destroy_slave_symlinks(bond_dev, slave_dev);
@@ -2085,6 +2116,7 @@ static int bond_release_all(struct net_device *bond_dev)
 	struct net_device *slave_dev;
 	struct sockaddr addr;
 
+	block_netpoll_tx();
 	write_lock_bh(&bond->lock);
 
 	netif_carrier_off(bond_dev);
@@ -2183,6 +2215,7 @@ static int bond_release_all(struct net_device *bond_dev)
 
 out:
 	write_unlock_bh(&bond->lock);
+	unblock_netpoll_tx();
 
 	return 0;
 }
@@ -2232,9 +2265,11 @@ static int bond_ioctl_change_active(struct net_device *bond_dev, struct net_devi
 	    (old_active) &&
 	    (new_active->link == BOND_LINK_UP) &&
 	    IS_UP(new_active->dev)) {
+		block_netpoll_tx();
 		write_lock_bh(&bond->curr_slave_lock);
 		bond_change_active_slave(bond, new_active);
 		write_unlock_bh(&bond->curr_slave_lock);
+		unblock_netpoll_tx();
 	} else
 		res = -EINVAL;
 
@@ -2466,9 +2501,11 @@ static void bond_miimon_commit(struct bonding *bond)
 
 do_failover:
 		ASSERT_RTNL();
+		block_netpoll_tx();
 		write_lock_bh(&bond->curr_slave_lock);
 		bond_select_active_slave(bond);
 		write_unlock_bh(&bond->curr_slave_lock);
+		unblock_netpoll_tx();
 	}
 
 	bond_set_carrier(bond);
@@ -2911,11 +2948,13 @@ void bond_loadbalance_arp_mon(struct work_struct *work)
 	}
 
 	if (do_failover) {
+		block_netpoll_tx();
 		write_lock_bh(&bond->curr_slave_lock);
 
 		bond_select_active_slave(bond);
 
 		write_unlock_bh(&bond->curr_slave_lock);
+		unblock_netpoll_tx();
 	}
 
 re_arm:
@@ -3074,9 +3113,11 @@ static void bond_ab_arp_commit(struct bonding *bond, int delta_in_ticks)
 
 do_failover:
 		ASSERT_RTNL();
+		block_netpoll_tx();
 		write_lock_bh(&bond->curr_slave_lock);
 		bond_select_active_slave(bond);
 		write_unlock_bh(&bond->curr_slave_lock);
+		unblock_netpoll_tx();
 	}
 
 	bond_set_carrier(bond);
@@ -4564,6 +4605,13 @@ static netdev_tx_t bond_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct bonding *bond = netdev_priv(dev);
 
+	/*
+	 * If we risk deadlock from transmitting this in the
+	 * netpoll path, tell netpoll to queue the frame for later tx
+	 */
+	if (is_netpoll_tx_blocked(dev))
+		return NETDEV_TX_BUSY;
+
 	if (TX_QUEUE_OVERRIDE(bond->params.mode)) {
 		if (!bond_slave_override(bond, skb))
 			return NETDEV_TX_OK;
@@ -5295,6 +5343,13 @@ static int __init bonding_init(void)
 	if (res)
 		goto err;
 
+#ifdef CONFIG_NET_POLL_CONTROLLER
+	if (!alloc_cpumask_var(&netpoll_block_tx, GFP_KERNEL)) {
+		res = -ENOMEM;
+		bond_destroy_sysfs();
+		goto err;
+	}
+#endif
 	register_netdevice_notifier(&bond_netdev_notifier);
 	register_inetaddr_notifier(&bond_inetaddr_notifier);
 	bond_register_ipv6_notifier();
@@ -5316,6 +5371,10 @@ static void __exit bonding_exit(void)
 
 	bond_destroy_sysfs();
 
+#ifdef CONFIG_NET_POLL_CONTROLLER
+	free_cpumask_var(netpoll_block_tx);
+#endif
+
 	rtnl_link_unregister(&bond_link_ops);
 	unregister_pernet_subsys(&bond_net_ops);
 }
-- 
1.7.2.3

Re: [PATCH 2/5] Fix deadlock in bonding driver resulting from internal locking when using netpoll

[Cong Wang]

On 10/13/10 05:55, nhorman@tuxdriver.com wrote:
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -76,6 +76,7 @@
>   #include<linux/if_vlan.h>
>   #include<linux/if_bonding.h>
>   #include<linux/jiffies.h>
> +#include<linux/preempt.h>
>   #include<net/route.h>
>   #include<net/net_namespace.h>
>   #include<net/netns/generic.h>
> @@ -169,6 +170,35 @@ MODULE_PARM_DESC(resend_igmp, "Number of IGMP membership reports to send on link
>
>   /*----------------------------- Global variables ----------------------------*/
>
> +#ifdef CONFIG_NET_POLL_CONTROLLER
> +static cpumask_var_t netpoll_block_tx;
> +
> +static inline void block_netpoll_tx(void
> +{
> +	preempt_disable();
> +	BUG_ON(cpumask_test_and_set_cpu(smp_processor_id(),
> +					netpoll_block_tx));
> +}
> +
> +static inline void unblock_netpoll_tx(void)
> +{
> +	BUG_ON(!cpumask_test_and_clear_cpu(smp_processor_id(),
> +					  netpoll_block_tx));
> +	preempt_enable();
> +}
> +
> +static inline int is_netpoll_tx_blocked(struct net_device *dev)
> +{
> +	if (unlikely(dev->priv_flags&  IFF_IN_NETPOLL))
> +		return cpumask_test_cpu(smp_processor_id(), netpoll_block_tx);
> +	return 0;
> +}
> +#else
> +#define block_netpoll_tx()
> +#define unblock_netpoll_tx()
> +#define is_netpoll_tx_blocked(dev)
> +#endif
> +

These should go to netpoll.h, IMHO.

Re: [PATCH 2/5] Fix deadlock in bonding driver resulting from internal locking when using netpoll

[Neil Horman]

On Wed, Oct 13, 2010 at 10:44:55AM +0800, Cong Wang wrote:
> On 10/13/10 05:55, nhorman@tuxdriver.com wrote:
> >--- a/drivers/net/bonding/bond_main.c
> >+++ b/drivers/net/bonding/bond_main.c
> >@@ -76,6 +76,7 @@
> >  #include<linux/if_vlan.h>
> >  #include<linux/if_bonding.h>
> >  #include<linux/jiffies.h>
> >+#include<linux/preempt.h>
> >  #include<net/route.h>
> >  #include<net/net_namespace.h>
> >  #include<net/netns/generic.h>
> >@@ -169,6 +170,35 @@ MODULE_PARM_DESC(resend_igmp, "Number of IGMP membership reports to send on link
> >
> >  /*----------------------------- Global variables ----------------------------*/
> >
> >+#ifdef CONFIG_NET_POLL_CONTROLLER
> >+static cpumask_var_t netpoll_block_tx;
> >+
> >+static inline void block_netpoll_tx(void
> >+{
> >+	preempt_disable();
> >+	BUG_ON(cpumask_test_and_set_cpu(smp_processor_id(),
> >+					netpoll_block_tx));
> >+}
> >+
> >+static inline void unblock_netpoll_tx(void)
> >+{
> >+	BUG_ON(!cpumask_test_and_clear_cpu(smp_processor_id(),
> >+					  netpoll_block_tx));
> >+	preempt_enable();
> >+}
> >+
> >+static inline int is_netpoll_tx_blocked(struct net_device *dev)
> >+{
> >+	if (unlikely(dev->priv_flags&  IFF_IN_NETPOLL))
> >+		return cpumask_test_cpu(smp_processor_id(), netpoll_block_tx);
> >+	return 0;
> >+}
> >+#else
> >+#define block_netpoll_tx()
> >+#define unblock_netpoll_tx()
> >+#define is_netpoll_tx_blocked(dev)
> >+#endif
> >+
> 
> These should go to netpoll.h, IMHO.
> 

Doh, you're right, they should.  Particularly because I just noticed there are
a few paths through sysfs for bonding that can recurse the same way the
monitoring code can.  I'll respin this shortly, thanks.
Neil

[PATCH 3/5] Fix napi poll for bonding driver

[nhorman]

From: Neil Horman <nhorman@tuxdriver.com>

Usually the netpoll path, when preforming a napi poll can get away with just
polling all the napi instances of the configured device.  Thats not the case for
the bonding driver however, as the napi instances which may wind up getting
flagged as needing polling after the poll_controller call don't belong to the
bonded device, but rather to the slave devices.  Fix this by checking the device
in question for the IFF_MASTER flag, if set, we know we need to check the full
poll list for this cpu, rather than just the devices napi instance list.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
---
 net/core/netpoll.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 4e98ffa..d79d221 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -156,8 +156,15 @@ static void poll_napi(struct net_device *dev)
 {
 	struct napi_struct *napi;
 	int budget = 16;
+	struct softnet_data *sd = &__get_cpu_var(softnet_data);
+	struct list_head *nlist;
 
-	list_for_each_entry(napi, &dev->napi_list, dev_list) {
+	if (dev->flags & IFF_MASTER)
+		nlist = &sd->poll_list;
+	else
+		nlist = &dev->napi_list;
+
+	list_for_each_entry(napi, nlist, dev_list) {
 		if (napi->poll_owner != smp_processor_id() &&
 		    spin_trylock(&napi->poll_lock)) {
 			budget = poll_one_napi(dev->npinfo, napi, budget);
-- 
1.7.2.3

[PATCH 4/5] Fix netconsole to not deadlock on rmmod

[nhorman]

From: Neil Horman <nhorman@tuxdriver.com>

Netconsole calls netpoll_cleanup on receipt of a NETDEVICE_UNREGISTER event.
The notifier subsystem calls these event handlers with rtnl_lock held, which
netpoll_cleanup also takes, resulting in deadlock.  Fix this by calling the
__netpoll_cleanup interior function instead, and fixing up the additional
pointers.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
---
 drivers/net/netconsole.c |    9 ++++++++-
 1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index ca142c4..94255f0 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -678,7 +678,14 @@ static int netconsole_netdev_event(struct notifier_block *this,
 				strlcpy(nt->np.dev_name, dev->name, IFNAMSIZ);
 				break;
 			case NETDEV_UNREGISTER:
-				netpoll_cleanup(&nt->np);
+				/*
+				 * rtnl_lock already held
+				 */
+				if (nt->np.dev) {
+					__netpoll_cleanup(&nt->np);
+					dev_put(nt->np.dev);
+					nt->np.dev = NULL;
+				}
 				/* Fall through */
 			case NETDEV_GOING_DOWN:
 			case NETDEV_BONDING_DESLAVE:
-- 
1.7.2.3

[PATCH 5/5] Re-enable netpoll over bonding

[nhorman]

From: Neil Horman <nhorman@tuxdriver.com>

With the inclusion of previous fixup patches, netpoll over bonding apears to
work reliably with failover conditions.  This reverts Gospos previous commit
c22d7ac844f1cb9c6a5fd20f89ebadc2feef891b, and allows access again to the netpoll
functionality in the bonding driver.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
---
 drivers/net/bonding/bond_main.c |   31 +++++++++++--------------------
 1 files changed, 11 insertions(+), 20 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 1d0d8c5..3b53360 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -173,7 +173,7 @@ MODULE_PARM_DESC(resend_igmp, "Number of IGMP membership reports to send on link
 #ifdef CONFIG_NET_POLL_CONTROLLER
 static cpumask_var_t netpoll_block_tx;
 
-static inline void block_netpoll_tx(void
+static inline void block_netpoll_tx(void)
 {
 	preempt_disable();
 	BUG_ON(cpumask_test_and_set_cpu(smp_processor_id(),
@@ -209,9 +209,6 @@ static int arp_ip_count;
 static int bond_mode	= BOND_MODE_ROUNDROBIN;
 static int xmit_hashtype = BOND_XMIT_POLICY_LAYER2;
 static int lacp_fast;
-#ifdef CONFIG_NET_POLL_CONTROLLER
-static int disable_netpoll = 1;
-#endif
 
 const struct bond_parm_tbl bond_lacp_tbl[] = {
 {	"slow",		AD_LACP_SLOW},
@@ -1836,19 +1833,15 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
 	bond_set_carrier(bond);
 
 #ifdef CONFIG_NET_POLL_CONTROLLER
-	if (disable_netpoll) {
+	if (slaves_support_netpoll(bond_dev)) {
+		bond_dev->priv_flags &= ~IFF_DISABLE_NETPOLL;
+		if (bond_dev->npinfo)
+			slave_dev->npinfo = bond_dev->npinfo;
+	} else if (!(bond_dev->priv_flags & IFF_DISABLE_NETPOLL)) {
 		bond_dev->priv_flags |= IFF_DISABLE_NETPOLL;
-	} else {
-		if (slaves_support_netpoll(bond_dev)) {
-			bond_dev->priv_flags &= ~IFF_DISABLE_NETPOLL;
-			if (bond_dev->npinfo)
-				slave_dev->npinfo = bond_dev->npinfo;
-		} else if (!(bond_dev->priv_flags & IFF_DISABLE_NETPOLL)) {
-			bond_dev->priv_flags |= IFF_DISABLE_NETPOLL;
-			pr_info("New slave device %s does not support netpoll\n",
-				slave_dev->name);
-			pr_info("Disabling netpoll support for %s\n", bond_dev->name);
-		}
+		pr_info("New slave device %s does not support netpoll\n",
+			slave_dev->name);
+		pr_info("Disabling netpoll support for %s\n", bond_dev->name);
 	}
 #endif
 	read_unlock(&bond->lock);
@@ -2055,10 +2048,8 @@ int bond_release(struct net_device *bond_dev, struct net_device *slave_dev)
 #ifdef CONFIG_NET_POLL_CONTROLLER
 	read_lock_bh(&bond->lock);
 
-	 /* Make sure netpoll over stays disabled until fixed. */
-	if (!disable_netpoll)
-		if (slaves_support_netpoll(bond_dev))
-				bond_dev->priv_flags &= ~IFF_DISABLE_NETPOLL;
+	if (slaves_support_netpoll(bond_dev))
+		bond_dev->priv_flags &= ~IFF_DISABLE_NETPOLL;
 	read_unlock_bh(&bond->lock);
 	if (slave_dev->netdev_ops->ndo_netpoll_cleanup)
 		slave_dev->netdev_ops->ndo_netpoll_cleanup(slave_dev);
-- 
1.7.2.3

[PATCH] bonding: various fixes for bonding, netpoll & netconsole

[nhorman]

Sorry if this is a resend for some, a bad git-send-email config caused some
rejections, so I'm resending.

A few months back, an attempt was made to enable netpoll over bonding, so that
netconsole could be used over bonded interfaces.  This worked in the steady
state, but had several deadlocks in various failover conditions.  I've gone
through the bonding code, and fixed up those deadlocks, along with several other
problems noted along the way, which caused other issues with netpoll+bonding.
With this patch series, netpoll works with bonding in all modes accross all
slaves during failover conditions.  It also allows fixes some deadlock
conditions in the netconsole code itself.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>