bonding: Simplify the xmit function for modes that use xmit_hash

Earlier change to use usable slave array for TLB mode had an additional
performance advantage. So extending the same logic to all other modes
that use xmit-hash for slave selection (viz 802.3AD, and XOR modes).
Also consolidating this with the earlier TLB change.

The main idea is to build the usable slaves array in the control path
and use that array for slave selection during xmit operation.

Measured performance in a setup with a bond of 4x1G NICs with 200
instances of netperf for the modes involved (3ad, xor, tlb)
cmd: netperf -t TCP_RR -H <TargetHost> -l 60 -s 5

Mode        TPS-Before   TPS-After

802.3ad   : 468,694      493,101
TLB (lb=0): 392,583      392,965
XOR       : 475,696      484,517
Signed-off-by: Mahesh Bandewar <maheshb@google.com>
Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_alb.c

@@ -177,7 +177,6 @@ static int tlb_initialize(struct bonding *bond)
 static void tlb_deinitialize(struct bonding *bond)
 {
 	struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
-	struct tlb_up_slave *arr;
 
 	spin_lock_bh(&bond->mode_lock);
 
@@ -185,10 +184,6 @@ static void tlb_deinitialize(struct bonding *bond)
 	bond_info->tx_hashtbl = NULL;
 
 	spin_unlock_bh(&bond->mode_lock);
-
-	arr = rtnl_dereference(bond_info->slave_arr);
-	if (arr)
-		kfree_rcu(arr, rcu);
 }
 
 static long long compute_gap(struct slave *slave)
@@ -1336,39 +1331,9 @@ static int bond_do_alb_xmit(struct sk_buff *skb, struct bonding *bond,
 	return NETDEV_TX_OK;
 }
 
-static int bond_tlb_update_slave_arr(struct bonding *bond,
-				     struct slave *skipslave)
-{
-	struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
-	struct slave *tx_slave;
-	struct list_head *iter;
-	struct tlb_up_slave *new_arr, *old_arr;
-
-	new_arr = kzalloc(offsetof(struct tlb_up_slave, arr[bond->slave_cnt]),
-			  GFP_ATOMIC);
-	if (!new_arr)
-		return -ENOMEM;
-
-	bond_for_each_slave(bond, tx_slave, iter) {
-		if (!bond_slave_can_tx(tx_slave))
-			continue;
-		if (skipslave == tx_slave)
-			continue;
-		new_arr->arr[new_arr->count++] = tx_slave;
-	}
-
-	old_arr = rtnl_dereference(bond_info->slave_arr);
-	rcu_assign_pointer(bond_info->slave_arr, new_arr);
-	if (old_arr)
-		kfree_rcu(old_arr, rcu);
-
-	return 0;
-}
-
 int bond_tlb_xmit(struct sk_buff *skb, struct net_device *bond_dev)
 {
 	struct bonding *bond = netdev_priv(bond_dev);
-	struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
 	struct ethhdr *eth_data;
 	struct slave *tx_slave = NULL;
 	u32 hash_index;
@@ -1389,12 +1354,14 @@ int bond_tlb_xmit(struct sk_buff *skb, struct net_device *bond_dev)
 							      hash_index & 0xFF,
 							      skb->len);
 			} else {
-				struct tlb_up_slave *slaves;
+				struct bond_up_slave *slaves;
+				unsigned int count;
 
-				slaves = rcu_dereference(bond_info->slave_arr);
-				if (slaves && slaves->count)
+				slaves = rcu_dereference(bond->slave_arr);
+				count = slaves ? ACCESS_ONCE(slaves->count) : 0;
+				if (likely(count))
 					tx_slave = slaves->arr[hash_index %
-							       slaves->count];
+							       count];
 			}
 			break;
 		}
@@ -1641,10 +1608,6 @@ void bond_alb_deinit_slave(struct bonding *bond, struct slave *slave)
 		rlb_clear_slave(bond, slave);
 	}
 
-	if (bond_is_nondyn_tlb(bond))
-		if (bond_tlb_update_slave_arr(bond, slave))
-			pr_err("Failed to build slave-array for TLB mode.\n");
-
 }
 
 void bond_alb_handle_link_change(struct bonding *bond, struct slave *slave, char link)
@@ -1669,7 +1632,7 @@ void bond_alb_handle_link_change(struct bonding *bond, struct slave *slave, char
 	}
 
 	if (bond_is_nondyn_tlb(bond)) {
-		if (bond_tlb_update_slave_arr(bond, NULL))
+		if (bond_update_slave_arr(bond, NULL))
 			pr_err("Failed to build slave-array for TLB mode.\n");
 	}
 }

drivers/net/bonding/bond_alb.h

@@ -139,19 +139,11 @@ struct tlb_slave_info {
 			 */
 };
 
-struct tlb_up_slave {
-	unsigned int	count;
-	struct rcu_head rcu;
-	struct slave	*arr[0];
-};
-
 struct alb_bond_info {
 	struct tlb_client_info	*tx_hashtbl; /* Dynamically allocated */
 	u32			unbalanced_load;
 	int			tx_rebalance_counter;
 	int			lp_counter;
-	/* -------- non-dynamic tlb mode only ---------*/
-	struct tlb_up_slave __rcu *slave_arr;	  /* Up slaves */
 	/* -------- rlb parameters -------- */
 	int rlb_enabled;
 	struct rlb_client_info	*rx_hashtbl;	/* Receive hash table */

drivers/net/bonding/bond_main.c

@@ -210,6 +210,7 @@ static int bond_init(struct net_device *bond_dev);
 static void bond_uninit(struct net_device *bond_dev);
 static struct rtnl_link_stats64 *bond_get_stats(struct net_device *bond_dev,
 						struct rtnl_link_stats64 *stats);
+static void bond_slave_arr_handler(struct work_struct *work);
 
 /*---------------------------- General routines -----------------------------*/
 
@@ -1551,6 +1552,9 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
 		unblock_netpoll_tx();
 	}
 
+	if (bond_mode_uses_xmit_hash(bond))
+		bond_update_slave_arr(bond, NULL);
+
 	netdev_info(bond_dev, "Enslaving %s as %s interface with %s link\n",
 		    slave_dev->name,
 		    bond_is_active_slave(new_slave) ? "an active" : "a backup",
@@ -1668,6 +1672,9 @@ static int __bond_release_one(struct net_device *bond_dev,
 	if (BOND_MODE(bond) == BOND_MODE_8023AD)
 		bond_3ad_unbind_slave(slave);
 
+	if (bond_mode_uses_xmit_hash(bond))
+		bond_update_slave_arr(bond, slave);
+
 	netdev_info(bond_dev, "Releasing %s interface %s\n",
 		    bond_is_active_slave(slave) ? "active" : "backup",
 		    slave_dev->name);
@@ -1970,6 +1977,9 @@ static void bond_miimon_commit(struct bonding *bond)
 				bond_alb_handle_link_change(bond, slave,
 							    BOND_LINK_UP);
 
+			if (BOND_MODE(bond) == BOND_MODE_XOR)
+				bond_update_slave_arr(bond, NULL);
+
 			if (!bond->curr_active_slave || slave == primary)
 				goto do_failover;
 
@@ -1997,6 +2007,9 @@ static void bond_miimon_commit(struct bonding *bond)
 				bond_alb_handle_link_change(bond, slave,
 							    BOND_LINK_DOWN);
 
+			if (BOND_MODE(bond) == BOND_MODE_XOR)
+				bond_update_slave_arr(bond, NULL);
+
 			if (slave == rcu_access_pointer(bond->curr_active_slave))
 				goto do_failover;
 
@@ -2453,6 +2466,8 @@ static void bond_loadbalance_arp_mon(struct work_struct *work)
 
 		if (slave_state_changed) {
 			bond_slave_state_change(bond);
+			if (BOND_MODE(bond) == BOND_MODE_XOR)
+				bond_update_slave_arr(bond, NULL);
 		} else if (do_failover) {
 			block_netpoll_tx();
 			bond_select_active_slave(bond);
@@ -2829,8 +2844,20 @@ static int bond_slave_netdev_event(unsigned long event,
 			if (old_duplex != slave->duplex)
 				bond_3ad_adapter_duplex_changed(slave);
 		}
+		/* Refresh slave-array if applicable!
+		 * If the setup does not use miimon or arpmon (mode-specific!),
+		 * then these events will not cause the slave-array to be
+		 * refreshed. This will cause xmit to use a slave that is not
+		 * usable. Avoid such situation by refeshing the array at these
+		 * events. If these (miimon/arpmon) parameters are configured
+		 * then array gets refreshed twice and that should be fine!
+		 */
+		if (bond_mode_uses_xmit_hash(bond))
+			bond_update_slave_arr(bond, NULL);
 		break;
 	case NETDEV_DOWN:
+		if (bond_mode_uses_xmit_hash(bond))
+			bond_update_slave_arr(bond, NULL);
 		break;
 	case NETDEV_CHANGEMTU:
 		/* TODO: Should slaves be allowed to
@@ -3010,6 +3037,7 @@ static void bond_work_init_all(struct bonding *bond)
 	else
 		INIT_DELAYED_WORK(&bond->arp_work, bond_loadbalance_arp_mon);
 	INIT_DELAYED_WORK(&bond->ad_work, bond_3ad_state_machine_handler);
+	INIT_DELAYED_WORK(&bond->slave_arr_work, bond_slave_arr_handler);
 }
 
 static void bond_work_cancel_all(struct bonding *bond)
@@ -3019,6 +3047,7 @@ static void bond_work_cancel_all(struct bonding *bond)
 	cancel_delayed_work_sync(&bond->alb_work);
 	cancel_delayed_work_sync(&bond->ad_work);
 	cancel_delayed_work_sync(&bond->mcast_work);
+	cancel_delayed_work_sync(&bond->slave_arr_work);
 }
 
 static int bond_open(struct net_device *bond_dev)
@@ -3068,6 +3097,9 @@ static int bond_open(struct net_device *bond_dev)
 		bond_3ad_initiate_agg_selection(bond, 1);
 	}
 
+	if (bond_mode_uses_xmit_hash(bond))
+		bond_update_slave_arr(bond, NULL);
+
 	return 0;
 }
 
@@ -3573,20 +3605,148 @@ static int bond_xmit_activebackup(struct sk_buff *skb, struct net_device *bond_d
 	return NETDEV_TX_OK;
 }
 
-/* In bond_xmit_xor() , we determine the output device by using a pre-
- * determined xmit_hash_policy(), If the selected device is not enabled,
- * find the next active slave.
+/* Use this to update slave_array when (a) it's not appropriate to update
+ * slave_array right away (note that update_slave_array() may sleep)
+ * and / or (b) RTNL is not held.
  */
-static int bond_xmit_xor(struct sk_buff *skb, struct net_device *bond_dev)
+void bond_slave_arr_work_rearm(struct bonding *bond, unsigned long delay)
 {
-	struct bonding *bond = netdev_priv(bond_dev);
-	int slave_cnt = ACCESS_ONCE(bond->slave_cnt);
+	queue_delayed_work(bond->wq, &bond->slave_arr_work, delay);
+}
 
-	if (likely(slave_cnt))
-		bond_xmit_slave_id(bond, skb,
-				   bond_xmit_hash(bond, skb) % slave_cnt);
-	else
+/* Slave array work handler. Holds only RTNL */
+static void bond_slave_arr_handler(struct work_struct *work)
+{
+	struct bonding *bond = container_of(work, struct bonding,
+					    slave_arr_work.work);
+	int ret;
+
+	if (!rtnl_trylock())
+		goto err;
+
+	ret = bond_update_slave_arr(bond, NULL);
+	rtnl_unlock();
+	if (ret) {
+		pr_warn_ratelimited("Failed to update slave array from WT\n");
+		goto err;
+	}
+	return;
+
+err:
+	bond_slave_arr_work_rearm(bond, 1);
+}
+
+/* Build the usable slaves array in control path for modes that use xmit-hash
+ * to determine the slave interface -
+ * (a) BOND_MODE_8023AD
+ * (b) BOND_MODE_XOR
+ * (c) BOND_MODE_TLB && tlb_dynamic_lb == 0
+ *
+ * The caller is expected to hold RTNL only and NO other lock!
+ */
+int bond_update_slave_arr(struct bonding *bond, struct slave *skipslave)
+{
+	struct slave *slave;
+	struct list_head *iter;
+	struct bond_up_slave *new_arr, *old_arr;
+	int slaves_in_agg;
+	int agg_id = 0;
+	int ret = 0;
+
+#ifdef CONFIG_LOCKDEP
+	WARN_ON(lockdep_is_held(&bond->mode_lock));
+#endif
+
+	new_arr = kzalloc(offsetof(struct bond_up_slave, arr[bond->slave_cnt]),
+			  GFP_KERNEL);
+	if (!new_arr) {
+		ret = -ENOMEM;
+		pr_err("Failed to build slave-array.\n");
+		goto out;
+	}
+	if (BOND_MODE(bond) == BOND_MODE_8023AD) {
+		struct ad_info ad_info;
+
+		if (bond_3ad_get_active_agg_info(bond, &ad_info)) {
+			pr_debug("bond_3ad_get_active_agg_info failed\n");
+			kfree_rcu(new_arr, rcu);
+			/* No active aggragator means it's not safe to use
+			 * the previous array.
+			 */
+			old_arr = rtnl_dereference(bond->slave_arr);
+			if (old_arr) {
+				RCU_INIT_POINTER(bond->slave_arr, NULL);
+				kfree_rcu(old_arr, rcu);
+			}
+			goto out;
+		}
+		slaves_in_agg = ad_info.ports;
+		agg_id = ad_info.aggregator_id;
+	}
+	bond_for_each_slave(bond, slave, iter) {
+		if (BOND_MODE(bond) == BOND_MODE_8023AD) {
+			struct aggregator *agg;
+
+			agg = SLAVE_AD_INFO(slave)->port.aggregator;
+			if (!agg || agg->aggregator_identifier != agg_id)
+				continue;
+		}
+		if (!bond_slave_can_tx(slave))
+			continue;
+		if (skipslave == slave)
+			continue;
+		new_arr->arr[new_arr->count++] = slave;
+	}
+
+	old_arr = rtnl_dereference(bond->slave_arr);
+	rcu_assign_pointer(bond->slave_arr, new_arr);
+	if (old_arr)
+		kfree_rcu(old_arr, rcu);
+out:
+	if (ret != 0 && skipslave) {
+		int idx;
+
+		/* Rare situation where caller has asked to skip a specific
+		 * slave but allocation failed (most likely!). BTW this is
+		 * only possible when the call is initiated from
+		 * __bond_release_one(). In this situation; overwrite the
+		 * skipslave entry in the array with the last entry from the
+		 * array to avoid a situation where the xmit path may choose
+		 * this to-be-skipped slave to send a packet out.
+		 */
+		old_arr = rtnl_dereference(bond->slave_arr);
+		for (idx = 0; idx < old_arr->count; idx++) {
+			if (skipslave == old_arr->arr[idx]) {
+				old_arr->arr[idx] =
+				    old_arr->arr[old_arr->count-1];
+				old_arr->count--;
+				break;
+			}
+		}
+	}
+	return ret;
+}
+
+/* Use this Xmit function for 3AD as well as XOR modes. The current
+ * usable slave array is formed in the control path. The xmit function
+ * just calculates hash and sends the packet out.
+ */
+int bond_3ad_xor_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct bonding *bond = netdev_priv(dev);
+	struct slave *slave;
+	struct bond_up_slave *slaves;
+	unsigned int count;
+
+	slaves = rcu_dereference(bond->slave_arr);
+	count = slaves ? ACCESS_ONCE(slaves->count) : 0;
+	if (likely(count)) {
+		slave = slaves->arr[bond_xmit_hash(bond, skb) % count];
+		bond_dev_queue_xmit(bond, skb, slave->dev);
+	} else {
 		dev_kfree_skb_any(skb);
+		atomic_long_inc(&dev->tx_dropped);
+	}
 
 	return NETDEV_TX_OK;
 }
@@ -3682,12 +3842,11 @@ static netdev_tx_t __bond_start_xmit(struct sk_buff *skb, struct net_device *dev
 		return bond_xmit_roundrobin(skb, dev);
 	case BOND_MODE_ACTIVEBACKUP:
 		return bond_xmit_activebackup(skb, dev);
+	case BOND_MODE_8023AD:
 	case BOND_MODE_XOR:
-		return bond_xmit_xor(skb, dev);
+		return bond_3ad_xor_xmit(skb, dev);
 	case BOND_MODE_BROADCAST:
 		return bond_xmit_broadcast(skb, dev);
-	case BOND_MODE_8023AD:
-		return bond_3ad_xmit_xor(skb, dev);
 	case BOND_MODE_ALB:
 		return bond_alb_xmit(skb, dev);
 	case BOND_MODE_TLB:
@@ -3861,6 +4020,7 @@ static void bond_uninit(struct net_device *bond_dev)
 	struct bonding *bond = netdev_priv(bond_dev);
 	struct list_head *iter;
 	struct slave *slave;
+	struct bond_up_slave *arr;
 
 	bond_netpoll_cleanup(bond_dev);
 
@@ -3869,6 +4029,12 @@ static void bond_uninit(struct net_device *bond_dev)
 		__bond_release_one(bond_dev, slave->dev, true);
 	netdev_info(bond_dev, "Released all slaves\n");
 
+	arr = rtnl_dereference(bond->slave_arr);
+	if (arr) {
+		RCU_INIT_POINTER(bond->slave_arr, NULL);
+		kfree_rcu(arr, rcu);
+	}
+
 	list_del(&bond->bond_list);
 
 	bond_debug_unregister(bond);

drivers/net/bonding/bonding.h

@@ -179,6 +179,12 @@ struct slave {
 	struct rtnl_link_stats64 slave_stats;
 };
 
+struct bond_up_slave {
+	unsigned int	count;
+	struct rcu_head rcu;
+	struct slave	*arr[0];
+};
+
 /*
  * Link pseudo-state only used internally by monitors
  */
@@ -193,6 +199,7 @@ struct bonding {
 	struct   slave __rcu *curr_active_slave;
 	struct   slave __rcu *current_arp_slave;
 	struct   slave __rcu *primary_slave;
+	struct   bond_up_slave __rcu *slave_arr; /* Array of usable slaves */
 	bool     force_primary;
 	s32      slave_cnt; /* never change this value outside the attach/detach wrappers */
 	int     (*recv_probe)(const struct sk_buff *, struct bonding *,
@@ -222,6 +229,7 @@ struct bonding {
 	struct   delayed_work alb_work;
 	struct   delayed_work ad_work;
 	struct   delayed_work mcast_work;
+	struct   delayed_work slave_arr_work;
 #ifdef CONFIG_DEBUG_FS
 	/* debugging support via debugfs */
 	struct	 dentry *debug_dir;
@@ -534,6 +542,8 @@ const char *bond_slave_link_status(s8 link);
 struct bond_vlan_tag *bond_verify_device_path(struct net_device *start_dev,
 					      struct net_device *end_dev,
 					      int level);
+int bond_update_slave_arr(struct bonding *bond, struct slave *skipslave);
+void bond_slave_arr_work_rearm(struct bonding *bond, unsigned long delay);
 
 #ifdef CONFIG_PROC_FS
 void bond_create_proc_entry(struct bonding *bond);