[PATCH net-next 0/5] bonding: locking simplifications and cleanup

[PATCH net-next 0/5] bonding: locking simplifications and cleanup

[Nikolay Aleksandrov]

Hello,
This small patchset aims to remove some use cases of bond->lock for mutual
exclusion which will help in the RCUfication of the function users. It also
does some small style cleanups and fixes.

Patch 01 - Drops the use of bond->lock as mutual exclusion for peer
notification and relies on RTNL being held when send_peer_notif is modified
Patch 02 - trivial outdated comment removal
Patch 03 - Drops the use of bond->lock as mutual exclusion for lacp rate
update and relies on RTNL, also fixes possible races with mode change
Patch 04 - Drops read_lock in bond_fix_features because RTNL is held
Patch 05 - Drops read_lock in bond_compute_features because RTNL is held
whenever it's called

Best regards,
 Nikolay Aleksandrov

Nikolay Aleksandrov (5):
  bonding: simplify and fix peer notification
  bonding: trivial: remove outdated comment and braces
  bonding: simplify bond_3ad_update_lacp_rate and use RTNL for sync
  bonding: drop read_lock in bond_fix_features
  bonding: drop read_lock in bond_compute_features

 drivers/net/bonding/bond_3ad.c   |  8 +------
 drivers/net/bonding/bond_main.c  | 48 ++++++++++++----------------------------
 drivers/net/bonding/bond_sysfs.c |  7 +++++-
 3 files changed, 21 insertions(+), 42 deletions(-)

-- 
1.8.1.4

[PATCH net-next 1/5] bonding: simplify and fix peer notification

[Nikolay Aleksandrov]

This patch aims to remove a use of the bond->lock for mutual exclusion
which will later allow easier migration to RCU of the users of this
functionality. We use RTNL as a synchronizing mechanism since it's
always held when send_peer_notif is set, and when it is decremented from
the notifier function. We can also drop some locking, and fix the
leakage of the send_peer_notif counter.

Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
---
 drivers/net/bonding/bond_main.c | 22 +++++++---------------
 1 file changed, 7 insertions(+), 15 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index c50679f..05e638b 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -828,7 +828,6 @@ static bool bond_should_notify_peers(struct bonding *bond)
 	    test_bit(__LINK_STATE_LINKWATCH_PENDING, &slave->dev->state))
 		return false;
 
-	bond->send_peer_notif--;
 	return true;
 }
 
@@ -2259,12 +2258,8 @@ re_arm:
 	read_unlock(&bond->lock);
 
 	if (should_notify_peers) {
-		if (!rtnl_trylock()) {
-			read_lock(&bond->lock);
-			bond->send_peer_notif++;
-			read_unlock(&bond->lock);
+		if (!rtnl_trylock())
 			return;
-		}
 		call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, bond->dev);
 		rtnl_unlock();
 	}
@@ -2876,12 +2871,8 @@ re_arm:
 	read_unlock(&bond->lock);
 
 	if (should_notify_peers) {
-		if (!rtnl_trylock()) {
-			read_lock(&bond->lock);
-			bond->send_peer_notif++;
-			read_unlock(&bond->lock);
+		if (!rtnl_trylock())
 			return;
-		}
 		call_netdevice_notifiers(NETDEV_NOTIFY_PEERS, bond->dev);
 		rtnl_unlock();
 	}
@@ -2916,6 +2907,10 @@ static int bond_master_netdev_event(unsigned long event,
 	case NETDEV_REGISTER:
 		bond_create_proc_entry(event_bond);
 		break;
+	case NETDEV_NOTIFY_PEERS:
+		if (event_bond->send_peer_notif)
+			event_bond->send_peer_notif--;
+		break;
 	default:
 		break;
 	}
@@ -3213,11 +3208,8 @@ static int bond_close(struct net_device *bond_dev)
 {
 	struct bonding *bond = netdev_priv(bond_dev);
 
-	write_lock_bh(&bond->lock);
-	bond->send_peer_notif = 0;
-	write_unlock_bh(&bond->lock);
-
 	bond_work_cancel_all(bond);
+	bond->send_peer_notif = 0;
 	if (bond_is_lb(bond)) {
 		/* Must be called only after all
 		 * slaves have been released
-- 
1.8.1.4

[PATCH net-next 2/5] bonding: trivial: remove outdated comment and braces

[Nikolay Aleksandrov]

We don't have to release all slaves when closing the bond dev, so remove
the outdated comment and the braces around the left single statement.

Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
---
 drivers/net/bonding/bond_main.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 05e638b..486e041 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -3210,12 +3210,8 @@ static int bond_close(struct net_device *bond_dev)
 
 	bond_work_cancel_all(bond);
 	bond->send_peer_notif = 0;
-	if (bond_is_lb(bond)) {
-		/* Must be called only after all
-		 * slaves have been released
-		 */
+	if (bond_is_lb(bond))
 		bond_alb_deinitialize(bond);
-	}
 	bond->recv_probe = NULL;
 
 	return 0;
-- 
1.8.1.4

[PATCH net-next 3/5] bonding: simplify bond_3ad_update_lacp_rate and use RTNL for sync

[Nikolay Aleksandrov]

We can drop the use of bond->lock for mutual exclusion in
bond_3ad_update_lacp_rate and use RTNL in the sysfs store function
instead. This way we'll prevent races with mode change and interface
up/down as well as simplify update_lacp_rate by removing the check for
port->slave because it'll always be initialized (done while enslaving
with RTNL). This change will also help in the future removal of reader
bond->lock from bond_enslave.

Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
---
 drivers/net/bonding/bond_3ad.c   | 8 +-------
 drivers/net/bonding/bond_sysfs.c | 7 ++++++-
 2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
index 9010265..0d8f427 100644
--- a/drivers/net/bonding/bond_3ad.c
+++ b/drivers/net/bonding/bond_3ad.c
@@ -2514,17 +2514,13 @@ int bond_3ad_lacpdu_recv(const struct sk_buff *skb, struct bonding *bond,
  */
 void bond_3ad_update_lacp_rate(struct bonding *bond)
 {
-	struct slave *slave;
 	struct port *port = NULL;
+	struct slave *slave;
 	int lacp_fast;
 
-	write_lock_bh(&bond->lock);
 	lacp_fast = bond->params.lacp_fast;
-
 	bond_for_each_slave(bond, slave) {
 		port = &(SLAVE_AD_INFO(slave).port);
-		if (port->slave == NULL)
-			continue;
 		__get_state_machine_lock(port);
 		if (lacp_fast)
 			port->actor_oper_port_state |= AD_STATE_LACP_TIMEOUT;
@@ -2532,6 +2528,4 @@ void bond_3ad_update_lacp_rate(struct bonding *bond)
 			port->actor_oper_port_state &= ~AD_STATE_LACP_TIMEOUT;
 		__release_state_machine_lock(port);
 	}
-
-	write_unlock_bh(&bond->lock);
 }
diff --git a/drivers/net/bonding/bond_sysfs.c b/drivers/net/bonding/bond_sysfs.c
index 0f539de..ce46776 100644
--- a/drivers/net/bonding/bond_sysfs.c
+++ b/drivers/net/bonding/bond_sysfs.c
@@ -852,8 +852,11 @@ static ssize_t bonding_store_lacp(struct device *d,
 				  struct device_attribute *attr,
 				  const char *buf, size_t count)
 {
-	int new_value, ret = count;
 	struct bonding *bond = to_bond(d);
+	int new_value, ret = count;
+
+	if (!rtnl_trylock())
+		return restart_syscall();
 
 	if (bond->dev->flags & IFF_UP) {
 		pr_err("%s: Unable to update LACP rate because interface is up.\n",
@@ -883,6 +886,8 @@ static ssize_t bonding_store_lacp(struct device *d,
 		ret = -EINVAL;
 	}
 out:
+	rtnl_unlock();
+
 	return ret;
 }
 static DEVICE_ATTR(lacp_rate, S_IRUGO | S_IWUSR,
-- 
1.8.1.4

[PATCH net-next 4/5] bonding: drop read_lock in bond_fix_features

[Nikolay Aleksandrov]

We're protected by RTNL so nothing can happen and we can safely drop the
read bond->lock.

Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
---
 drivers/net/bonding/bond_main.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 486e041..c5ebdc5 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1084,18 +1084,16 @@ static void bond_netpoll_cleanup(struct net_device *bond_dev)
 /*---------------------------------- IOCTL ----------------------------------*/
 
 static netdev_features_t bond_fix_features(struct net_device *dev,
-	netdev_features_t features)
+					   netdev_features_t features)
 {
-	struct slave *slave;
 	struct bonding *bond = netdev_priv(dev);
 	netdev_features_t mask;
-
-	read_lock(&bond->lock);
+	struct slave *slave;
 
 	if (list_empty(&bond->slave_list)) {
 		/* Disable adding VLANs to empty bond. But why? --mq */
 		features |= NETIF_F_VLAN_CHALLENGED;
-		goto out;
+		return features;
 	}
 
 	mask = features;
@@ -1109,8 +1107,6 @@ static netdev_features_t bond_fix_features(struct net_device *dev,
 	}
 	features = netdev_add_tso_features(features, mask);
 
-out:
-	read_unlock(&bond->lock);
 	return features;
 }
 
-- 
1.8.1.4

[PATCH net-next 5/5] bonding: drop read_lock in bond_compute_features

[Nikolay Aleksandrov]

bond_compute_features is always called with RTNL held, so we can safely
drop the read bond->lock.

Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
---
 drivers/net/bonding/bond_main.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index c5ebdc5..39e5b1c 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -1116,15 +1116,13 @@ static netdev_features_t bond_fix_features(struct net_device *dev,
 
 static void bond_compute_features(struct bonding *bond)
 {
-	struct slave *slave;
-	struct net_device *bond_dev = bond->dev;
+	unsigned int flags, dst_release_flag = IFF_XMIT_DST_RELEASE;
 	netdev_features_t vlan_features = BOND_VLAN_FEATURES;
 	unsigned short max_hard_header_len = ETH_HLEN;
 	unsigned int gso_max_size = GSO_MAX_SIZE;
+	struct net_device *bond_dev = bond->dev;
 	u16 gso_max_segs = GSO_MAX_SEGS;
-	unsigned int flags, dst_release_flag = IFF_XMIT_DST_RELEASE;
-
-	read_lock(&bond->lock);
+	struct slave *slave;
 
 	if (list_empty(&bond->slave_list))
 		goto done;
@@ -1150,8 +1148,6 @@ done:
 	flags = bond_dev->priv_flags & ~IFF_XMIT_DST_RELEASE;
 	bond_dev->priv_flags = flags | dst_release_flag;
 
-	read_unlock(&bond->lock);
-
 	netdev_change_features(bond_dev);
 }
 
-- 
1.8.1.4

Re: [PATCH net-next 0/5] bonding: locking simplifications and cleanup

[Ding Tianhong]

On 2013/9/2 19:51, Nikolay Aleksandrov wrote:
> Hello,
> This small patchset aims to remove some use cases of bond->lock for mutual
> exclusion which will help in the RCUfication of the function users. It also
> does some small style cleanups and fixes.
> 
> Patch 01 - Drops the use of bond->lock as mutual exclusion for peer
> notification and relies on RTNL being held when send_peer_notif is modified
> Patch 02 - trivial outdated comment removal
> Patch 03 - Drops the use of bond->lock as mutual exclusion for lacp rate
> update and relies on RTNL, also fixes possible races with mode change
> Patch 04 - Drops read_lock in bond_fix_features because RTNL is held
> Patch 05 - Drops read_lock in bond_compute_features because RTNL is held
> whenever it's called
> 
> Best regards,
>  Nikolay Aleksandrov
> 
> Nikolay Aleksandrov (5):
>   bonding: simplify and fix peer notification
>   bonding: trivial: remove outdated comment and braces
>   bonding: simplify bond_3ad_update_lacp_rate and use RTNL for sync
>   bonding: drop read_lock in bond_fix_features
>   bonding: drop read_lock in bond_compute_features
> 
>  drivers/net/bonding/bond_3ad.c   |  8 +------
>  drivers/net/bonding/bond_main.c  | 48 ++++++++++++----------------------------
>  drivers/net/bonding/bond_sysfs.c |  7 +++++-
>  3 files changed, 21 insertions(+), 42 deletions(-)
> 

Reviewed-by: Ding Tianhong <dingtianhong@huawei.com>

Re: [PATCH net-next 0/5] bonding: locking simplifications and cleanup

[David Miller]

From: Nikolay Aleksandrov <nikolay@redhat.com>
Date: Mon,  2 Sep 2013 13:51:37 +0200

> This small patchset aims to remove some use cases of bond->lock for mutual
> exclusion which will help in the RCUfication of the function users. It also
> does some small style cleanups and fixes.

Series applied.