Message-ID: <20090918153622.GX8515@gospo.rdu.redhat.com>
Date:	Fri, 18 Sep 2009 11:36:22 -0400
From:	Andy Gospodarek <andy@...yhouse.net>
To:	Jay Vosburgh <fubar@...ibm.com>
Cc:	netdev@...r.kernel.org, bonding-devel@...ts.sourceforge.net
Subject: Re: [PATCH 2/4] bonding: make sure tx and rx hash tables stay in
	sync when using alb mode

On Wed, Sep 16, 2009 at 04:36:09PM -0700, Jay Vosburgh wrote:
> Andy Gospodarek <andy@...yhouse.net> wrote:
> 
> >
> >Subject: [PATCH] bonding: make sure tx and rx hash tables stay in sync when using alb mode
> 
> 	When testing this, I'm getting a lockdep warning.  It appears to
> be unhappy that tlb_choose_channel acquires the tx / rx hash table locks
> in the order tx then rx, but rlb_choose_channel -> alb_get_best_slave
> acquires the locks in the other order.  I applied all four patches, but
> it looks like the change that trips lockdep is in this patch (#2).
> 
> 	I haven't gotten an actual deadlock from this, although it seems
> plausible if there are two cpus in bond_alb_xmit at the same time, and
> one of them is sending an ARP.
> 
> 	One fairly straightforward fix would be to combine the rx and tx
> hash table locks into a single lock.  I suspect that wouldn't have any
> real performance penalty, since the rx hash table lock is generally not
> acquired very often (unlike the tx lock, which is taken for every packet
> that goes out).
> 
> 	Also, FYI, two of the four patches had trailing whitespace.  I
> believe it was #2 and #4.
> 
> 	Thoughts?

Jay,

This patch should address both the the deadlock and whitespace conerns.
I ran a kernel with LOCKDEP enabled and saw no warnings while passing
traffic on the bond while pulling cables and while removing the module.
Here it is....

[PATCH] bonding: make sure tx and rx hash tables stay in sync when using alb mode

I noticed that it was easy for alb (mode 6) bonding to get into a state
where the tx hash-table and rx hash-table are out of sync (there is
really nothing to keep them synchronized), and we will transmit traffic
destined for a host on one slave and send ARP frames to the same slave
from another interface using a different source MAC.

There is no compelling reason to do this, so this patch makes sure the
rx hash-table changes whenever the tx hash-table is updated based on
device load.  This patch also drops the code that does rlb re-balancing
since the balancing will not be controlled by the tx hash-table based on
transmit load.  In order to address an issue found with the initial
patch, I have also combined the rx and tx hash table lock into a single
lock.  This will facilitate moving these into a single table at some
point.
---
 drivers/net/bonding/bond_alb.c |  203 +++++++++++++++-------------------------
 drivers/net/bonding/bond_alb.h |    3 +-
 2 files changed, 75 insertions(+), 131 deletions(-)

diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
index bcf25c6..04b7055 100644
--- a/drivers/net/bonding/bond_alb.c
+++ b/drivers/net/bonding/bond_alb.c
@@ -111,6 +111,7 @@ static inline struct arp_pkt *arp_pkt(const struct sk_buff *skb)
 
 /* Forward declaration */
 static void alb_send_learning_packets(struct slave *slave, u8 mac_addr[]);
+static struct slave *alb_get_best_slave(struct bonding *bond, u32 hash_index);
 
 static inline u8 _simple_hash(const u8 *hash_start, int hash_size)
 {
@@ -124,18 +125,18 @@ static inline u8 _simple_hash(const u8 *hash_start, int hash_size)
 	return hash;
 }
 
-/*********************** tlb specific functions ***************************/
-
-static inline void _lock_tx_hashtbl(struct bonding *bond)
+/********************* hash table lock functions *************************/
+static inline void _lock_hashtbl(struct bonding *bond)
 {
-	spin_lock_bh(&(BOND_ALB_INFO(bond).tx_hashtbl_lock));
+	spin_lock_bh(&(BOND_ALB_INFO(bond).hashtbl_lock));
 }
 
-static inline void _unlock_tx_hashtbl(struct bonding *bond)
+static inline void _unlock_hashtbl(struct bonding *bond)
 {
-	spin_unlock_bh(&(BOND_ALB_INFO(bond).tx_hashtbl_lock));
+	spin_unlock_bh(&(BOND_ALB_INFO(bond).hashtbl_lock));
 }
 
+/*********************** tlb specific functions ***************************/
 /* Caller must hold tx_hashtbl lock */
 static inline void tlb_init_table_entry(struct tlb_client_info *entry, int save_load)
 {
@@ -163,7 +164,7 @@ static void tlb_clear_slave(struct bonding *bond, struct slave *slave, int save_
 	struct tlb_client_info *tx_hash_table;
 	u32 index;
 
-	_lock_tx_hashtbl(bond);
+	_lock_hashtbl(bond);
 
 	/* clear slave from tx_hashtbl */
 	tx_hash_table = BOND_ALB_INFO(bond).tx_hashtbl;
@@ -180,7 +181,7 @@ static void tlb_clear_slave(struct bonding *bond, struct slave *slave, int save_
 
 	tlb_init_slave(slave);
 
-	_unlock_tx_hashtbl(bond);
+	_unlock_hashtbl(bond);
 }
 
 /* Must be called before starting the monitor timer */
@@ -191,7 +192,7 @@ static int tlb_initialize(struct bonding *bond)
 	struct tlb_client_info *new_hashtbl;
 	int i;
 
-	spin_lock_init(&(bond_info->tx_hashtbl_lock));
+	spin_lock_init(&(bond_info->hashtbl_lock));
 
 	new_hashtbl = kzalloc(size, GFP_KERNEL);
 	if (!new_hashtbl) {
@@ -200,7 +201,7 @@ static int tlb_initialize(struct bonding *bond)
 		       bond->dev->name);
 		return -1;
 	}
-	_lock_tx_hashtbl(bond);
+	_lock_hashtbl(bond);
 
 	bond_info->tx_hashtbl = new_hashtbl;
 
@@ -208,7 +209,7 @@ static int tlb_initialize(struct bonding *bond)
 		tlb_init_table_entry(&bond_info->tx_hashtbl[i], 1);
 	}
 
-	_unlock_tx_hashtbl(bond);
+	_unlock_hashtbl(bond);
 
 	return 0;
 }
@@ -218,12 +219,12 @@ static void tlb_deinitialize(struct bonding *bond)
 {
 	struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
 
-	_lock_tx_hashtbl(bond);
+	_lock_hashtbl(bond);
 
 	kfree(bond_info->tx_hashtbl);
 	bond_info->tx_hashtbl = NULL;
 
-	_unlock_tx_hashtbl(bond);
+	_unlock_hashtbl(bond);
 }
 
 /* Caller must hold bond lock for read */
@@ -264,24 +265,6 @@ static struct slave *tlb_get_least_loaded_slave(struct bonding *bond)
 	return least_loaded;
 }
 
-/* Caller must hold bond lock for read and hashtbl lock */
-static struct slave *tlb_get_best_slave(struct bonding *bond, u32 hash_index)
-{
-	struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
-	struct tlb_client_info *tx_hash_table = bond_info->tx_hashtbl;
-	struct slave *last_slave = tx_hash_table[hash_index].last_slave;
-	struct slave *next_slave = NULL;
-
-	if (last_slave && SLAVE_IS_OK(last_slave)) {
-		/* Use the last slave listed in the tx hashtbl if:
-		   the last slave currently is essentially unloaded. */
-		if (SLAVE_TLB_INFO(last_slave).load < 10)
-			next_slave = last_slave;
-	}
-
-	return next_slave ? next_slave : tlb_get_least_loaded_slave(bond);
-}
-
 /* Caller must hold bond lock for read */
 static struct slave *tlb_choose_channel(struct bonding *bond, u32 hash_index, u32 skb_len)
 {
@@ -289,13 +272,12 @@ static struct slave *tlb_choose_channel(struct bonding *bond, u32 hash_index, u3
 	struct tlb_client_info *hash_table;
 	struct slave *assigned_slave;
 
-	_lock_tx_hashtbl(bond);
+	_lock_hashtbl(bond);
 
 	hash_table = bond_info->tx_hashtbl;
 	assigned_slave = hash_table[hash_index].tx_slave;
 	if (!assigned_slave) {
-		assigned_slave = tlb_get_best_slave(bond, hash_index);
-
+		assigned_slave = alb_get_best_slave(bond, hash_index);
 		if (assigned_slave) {
 			struct tlb_slave_info *slave_info =
 				&(SLAVE_TLB_INFO(assigned_slave));
@@ -319,20 +301,52 @@ static struct slave *tlb_choose_channel(struct bonding *bond, u32 hash_index, u3
 		hash_table[hash_index].tx_bytes += skb_len;
 	}
 
-	_unlock_tx_hashtbl(bond);
+	_unlock_hashtbl(bond);
 
 	return assigned_slave;
 }
 
 /*********************** rlb specific functions ***************************/
-static inline void _lock_rx_hashtbl(struct bonding *bond)
+
+/* Caller must hold bond lock for read and hashtbl lock */
+static struct slave *rlb_update_rx_table(struct bonding *bond, struct slave *next_slave, u32 hash_index)
 {
-	spin_lock_bh(&(BOND_ALB_INFO(bond).rx_hashtbl_lock));
+	struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
+
+	/* check rlb table and correct it if wrong */
+	if (bond_info->rlb_enabled) {
+		struct rlb_client_info *rx_client_info = &(bond_info->rx_hashtbl[hash_index]);
+
+		/* if the new slave computed by tlb checks doesn't match rlb, stop rlb from using it */
+		if (next_slave && (next_slave != rx_client_info->slave))
+			rx_client_info->slave = next_slave;
+	}
+	return next_slave;
 }
 
-static inline void _unlock_rx_hashtbl(struct bonding *bond)
+/* Caller must hold bond lock for read and hashtbl lock */
+static struct slave *alb_get_best_slave(struct bonding *bond, u32 hash_index)
 {
-	spin_unlock_bh(&(BOND_ALB_INFO(bond).rx_hashtbl_lock));
+	struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
+	struct tlb_client_info *tx_hash_table = bond_info->tx_hashtbl;
+	struct slave *last_slave = tx_hash_table[hash_index].last_slave;
+	struct slave *next_slave = NULL;
+
+	/* presume the next slave will be the least loaded one */
+	next_slave = tlb_get_least_loaded_slave(bond);
+
+	if (last_slave && SLAVE_IS_OK(last_slave)) {
+		/* Use the last slave listed in the tx hashtbl if:
+		   the last slave currently is essentially unloaded. */
+		if (SLAVE_TLB_INFO(last_slave).load < 10)
+			next_slave = last_slave;
+	}
+
+	/* update the rlb hashtbl if there was a previous entry */
+	if (bond_info->rlb_enabled)
+		rlb_update_rx_table(bond, next_slave, hash_index);
+
+	return next_slave;
 }
 
 /* when an ARP REPLY is received from a client update its info
@@ -344,7 +358,7 @@ static void rlb_update_entry_from_arp(struct bonding *bond, struct arp_pkt *arp)
 	struct rlb_client_info *client_info;
 	u32 hash_index;
 
-	_lock_rx_hashtbl(bond);
+	_lock_hashtbl(bond);
 
 	hash_index = _simple_hash((u8*)&(arp->ip_src), sizeof(arp->ip_src));
 	client_info = &(bond_info->rx_hashtbl[hash_index]);
@@ -358,7 +372,7 @@ static void rlb_update_entry_from_arp(struct bonding *bond, struct arp_pkt *arp)
 		bond_info->rx_ntt = 1;
 	}
 
-	_unlock_rx_hashtbl(bond);
+	_unlock_hashtbl(bond);
 }
 
 static int rlb_arp_recv(struct sk_buff *skb, struct net_device *bond_dev, struct packet_type *ptype, struct net_device *orig_dev)
@@ -402,38 +416,6 @@ out:
 	return res;
 }
 
-/* Caller must hold bond lock for read */
-static struct slave *rlb_next_rx_slave(struct bonding *bond)
-{
-	struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
-	struct slave *rx_slave, *slave, *start_at;
-	int i = 0;
-
-	if (bond_info->next_rx_slave) {
-		start_at = bond_info->next_rx_slave;
-	} else {
-		start_at = bond->first_slave;
-	}
-
-	rx_slave = NULL;
-
-	bond_for_each_slave_from(bond, slave, i, start_at) {
-		if (SLAVE_IS_OK(slave)) {
-			if (!rx_slave) {
-				rx_slave = slave;
-			} else if (slave->speed > rx_slave->speed) {
-				rx_slave = slave;
-			}
-		}
-	}
-
-	if (rx_slave) {
-		bond_info->next_rx_slave = rx_slave->next;
-	}
-
-	return rx_slave;
-}
-
 /* teach the switch the mac of a disabled slave
  * on the primary for fault tolerance
  *
@@ -468,14 +450,14 @@ static void rlb_clear_slave(struct bonding *bond, struct slave *slave)
 	u32 index, next_index;
 
 	/* clear slave from rx_hashtbl */
-	_lock_rx_hashtbl(bond);
+	_lock_hashtbl(bond);
 
 	rx_hash_table = bond_info->rx_hashtbl;
 	index = bond_info->rx_hashtbl_head;
 	for (; index != RLB_NULL_INDEX; index = next_index) {
 		next_index = rx_hash_table[index].next;
 		if (rx_hash_table[index].slave == slave) {
-			struct slave *assigned_slave = rlb_next_rx_slave(bond);
+			struct slave *assigned_slave = alb_get_best_slave(bond, index);
 
 			if (assigned_slave) {
 				rx_hash_table[index].slave = assigned_slave;
@@ -499,7 +481,7 @@ static void rlb_clear_slave(struct bonding *bond, struct slave *slave)
 		}
 	}
 
-	_unlock_rx_hashtbl(bond);
+	_unlock_hashtbl(bond);
 
 	write_lock_bh(&bond->curr_slave_lock);
 
@@ -558,7 +540,7 @@ static void rlb_update_rx_clients(struct bonding *bond)
 	struct rlb_client_info *client_info;
 	u32 hash_index;
 
-	_lock_rx_hashtbl(bond);
+	_lock_hashtbl(bond);
 
 	hash_index = bond_info->rx_hashtbl_head;
 	for (; hash_index != RLB_NULL_INDEX; hash_index = client_info->next) {
@@ -576,7 +558,7 @@ static void rlb_update_rx_clients(struct bonding *bond)
 	 */
 	bond_info->rlb_update_delay_counter = RLB_UPDATE_DELAY;
 
-	_unlock_rx_hashtbl(bond);
+	_unlock_hashtbl(bond);
 }
 
 /* The slave was assigned a new mac address - update the clients */
@@ -587,7 +569,7 @@ static void rlb_req_update_slave_clients(struct bonding *bond, struct slave *sla
 	int ntt = 0;
 	u32 hash_index;
 
-	_lock_rx_hashtbl(bond);
+	_lock_hashtbl(bond);
 
 	hash_index = bond_info->rx_hashtbl_head;
 	for (; hash_index != RLB_NULL_INDEX; hash_index = client_info->next) {
@@ -607,7 +589,7 @@ static void rlb_req_update_slave_clients(struct bonding *bond, struct slave *sla
 		bond_info->rlb_update_retry_counter = RLB_UPDATE_RETRY;
 	}
 
-	_unlock_rx_hashtbl(bond);
+	_unlock_hashtbl(bond);
 }
 
 /* mark all clients using src_ip to be updated */
@@ -617,7 +599,7 @@ static void rlb_req_update_subnet_clients(struct bonding *bond, __be32 src_ip)
 	struct rlb_client_info *client_info;
 	u32 hash_index;
 
-	_lock_rx_hashtbl(bond);
+	_lock_hashtbl(bond);
 
 	hash_index = bond_info->rx_hashtbl_head;
 	for (; hash_index != RLB_NULL_INDEX; hash_index = client_info->next) {
@@ -643,7 +625,7 @@ static void rlb_req_update_subnet_clients(struct bonding *bond, __be32 src_ip)
 		}
 	}
 
-	_unlock_rx_hashtbl(bond);
+	_unlock_hashtbl(bond);
 }
 
 /* Caller must hold both bond and ptr locks for read */
@@ -655,7 +637,7 @@ static struct slave *rlb_choose_channel(struct sk_buff *skb, struct bonding *bon
 	struct rlb_client_info *client_info;
 	u32 hash_index = 0;
 
-	_lock_rx_hashtbl(bond);
+	_lock_hashtbl(bond);
 
 	hash_index = _simple_hash((u8 *)&arp->ip_dst, sizeof(arp->ip_src));
 	client_info = &(bond_info->rx_hashtbl[hash_index]);
@@ -671,7 +653,7 @@ static struct slave *rlb_choose_channel(struct sk_buff *skb, struct bonding *bon
 
 			assigned_slave = client_info->slave;
 			if (assigned_slave) {
-				_unlock_rx_hashtbl(bond);
+				_unlock_hashtbl(bond);
 				return assigned_slave;
 			}
 		} else {
@@ -687,7 +669,7 @@ static struct slave *rlb_choose_channel(struct sk_buff *skb, struct bonding *bon
 		}
 	}
 	/* assign a new slave */
-	assigned_slave = rlb_next_rx_slave(bond);
+	assigned_slave = alb_get_best_slave(bond, hash_index);
 
 	if (assigned_slave) {
 		client_info->ip_src = arp->ip_src;
@@ -723,7 +705,7 @@ static struct slave *rlb_choose_channel(struct sk_buff *skb, struct bonding *bon
 		}
 	}
 
-	_unlock_rx_hashtbl(bond);
+	_unlock_hashtbl(bond);
 
 	return assigned_slave;
 }
@@ -771,36 +753,6 @@ static struct slave *rlb_arp_xmit(struct sk_buff *skb, struct bonding *bond)
 	return tx_slave;
 }
 
-/* Caller must hold bond lock for read */
-static void rlb_rebalance(struct bonding *bond)
-{
-	struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
-	struct slave *assigned_slave;
-	struct rlb_client_info *client_info;
-	int ntt;
-	u32 hash_index;
-
-	_lock_rx_hashtbl(bond);
-
-	ntt = 0;
-	hash_index = bond_info->rx_hashtbl_head;
-	for (; hash_index != RLB_NULL_INDEX; hash_index = client_info->next) {
-		client_info = &(bond_info->rx_hashtbl[hash_index]);
-		assigned_slave = rlb_next_rx_slave(bond);
-		if (assigned_slave && (client_info->slave != assigned_slave)) {
-			client_info->slave = assigned_slave;
-			client_info->ntt = 1;
-			ntt = 1;
-		}
-	}
-
-	/* update the team's flag only after the whole iteration */
-	if (ntt) {
-		bond_info->rx_ntt = 1;
-	}
-	_unlock_rx_hashtbl(bond);
-}
-
 /* Caller must hold rx_hashtbl lock */
 static void rlb_init_table_entry(struct rlb_client_info *entry)
 {
@@ -817,8 +769,6 @@ static int rlb_initialize(struct bonding *bond)
 	int size = RLB_HASH_TABLE_SIZE * sizeof(struct rlb_client_info);
 	int i;
 
-	spin_lock_init(&(bond_info->rx_hashtbl_lock));
-
 	new_hashtbl = kmalloc(size, GFP_KERNEL);
 	if (!new_hashtbl) {
 		printk(KERN_ERR DRV_NAME
@@ -826,7 +776,7 @@ static int rlb_initialize(struct bonding *bond)
 		       bond->dev->name);
 		return -1;
 	}
-	_lock_rx_hashtbl(bond);
+	_lock_hashtbl(bond);
 
 	bond_info->rx_hashtbl = new_hashtbl;
 
@@ -836,7 +786,7 @@ static int rlb_initialize(struct bonding *bond)
 		rlb_init_table_entry(bond_info->rx_hashtbl + i);
 	}
 
-	_unlock_rx_hashtbl(bond);
+	_unlock_hashtbl(bond);
 
 	/*initialize packet type*/
 	pk_type->type = cpu_to_be16(ETH_P_ARP);
@@ -855,13 +805,13 @@ static void rlb_deinitialize(struct bonding *bond)
 
 	dev_remove_pack(&(bond_info->rlb_pkt_type));
 
-	_lock_rx_hashtbl(bond);
+	_lock_hashtbl(bond);
 
 	kfree(bond_info->rx_hashtbl);
 	bond_info->rx_hashtbl = NULL;
 	bond_info->rx_hashtbl_head = RLB_NULL_INDEX;
 
-	_unlock_rx_hashtbl(bond);
+	_unlock_hashtbl(bond);
 }
 
 static void rlb_clear_vlan(struct bonding *bond, unsigned short vlan_id)
@@ -869,7 +819,7 @@ static void rlb_clear_vlan(struct bonding *bond, unsigned short vlan_id)
 	struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
 	u32 curr_index;
 
-	_lock_rx_hashtbl(bond);
+	_lock_hashtbl(bond);
 
 	curr_index = bond_info->rx_hashtbl_head;
 	while (curr_index != RLB_NULL_INDEX) {
@@ -894,7 +844,7 @@ static void rlb_clear_vlan(struct bonding *bond, unsigned short vlan_id)
 		curr_index = next_index;
 	}
 
-	_unlock_rx_hashtbl(bond);
+	_unlock_hashtbl(bond);
 }
 
 /*********************** tlb/rlb shared functions *********************/
@@ -1521,11 +1471,6 @@ void bond_alb_monitor(struct work_struct *work)
 			read_lock(&bond->lock);
 		}
 
-		if (bond_info->rlb_rebalance) {
-			bond_info->rlb_rebalance = 0;
-			rlb_rebalance(bond);
-		}
-
 		/* check if clients need updating */
 		if (bond_info->rx_ntt) {
 			if (bond_info->rlb_update_delay_counter) {
diff --git a/drivers/net/bonding/bond_alb.h b/drivers/net/bonding/bond_alb.h
index b65fd29..09d755a 100644
--- a/drivers/net/bonding/bond_alb.h
+++ b/drivers/net/bonding/bond_alb.h
@@ -90,7 +90,7 @@ struct tlb_slave_info {
 struct alb_bond_info {
 	struct timer_list	alb_timer;
 	struct tlb_client_info	*tx_hashtbl; /* Dynamically allocated */
-	spinlock_t		tx_hashtbl_lock;
+	spinlock_t		hashtbl_lock; /* lock for both tables */
 	u32			unbalanced_load;
 	int			tx_rebalance_counter;
 	int			lp_counter;
@@ -98,7 +98,6 @@ struct alb_bond_info {
 	int rlb_enabled;
 	struct packet_type	rlb_pkt_type;
 	struct rlb_client_info	*rx_hashtbl;	/* Receive hash table */
-	spinlock_t		rx_hashtbl_lock;
 	u32			rx_hashtbl_head;
 	u8			rx_ntt;	/* flag - need to transmit
 					 * to all rx clients
-- 
1.5.5.6


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