bonding: restructure and simplify bond_for_each_slave_next()

remove the wordy int and add bond_for_each_slave_next_rcu().

Signed-off-by Ding Tianhong <[email protected]>

---
 drivers/net/bonding/bond_alb.c  |  3 +--
 drivers/net/bonding/bond_main.c |  6 ++----
 drivers/net/bonding/bonding.h   | 19 +++++++++++++++----
 3 files changed, 18 insertions(+), 10 deletions(-)

drivers/net/bonding/bond_alb.c +1 -2

index 3a5db7b..d266c56 100644
@@ -383,7 +383,6 @@ 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;

@@ -392,7 +391,7 @@ static struct slave *rlb_next_rx_slave(struct bonding *bond)
 
 	rx_slave = NULL;
 
-	bond_for_each_slave_from(bond, slave, i, start_at) {
+	bond_for_each_slave_from(bond, slave, start_at) {
 		if (SLAVE_IS_OK(slave)) {
 			if (!rx_slave) {
 				rx_slave = slave;

drivers/net/bonding/bond_main.c +2 -4

index 4264a76..8c9902a 100644
@@ -904,7 +904,6 @@ static struct slave *bond_find_best_slave(struct bonding *bond)
 	struct slave *new_active, *old_active;
 	struct slave *bestslave = NULL;
 	int mintime = bond->params.updelay;
-	int i;
 
 	new_active = bond->curr_active_slave;
 

@@ -923,7 +922,7 @@ static struct slave *bond_find_best_slave(struct bonding *bond)
 	/* remember where to stop iterating over the slaves */
 	old_active = new_active;
 
-	bond_for_each_slave_from(bond, new_active, i, old_active) {
+	bond_for_each_slave_from(bond, new_active, old_active) {
 		if (new_active->link == BOND_LINK_UP) {
 			return new_active;
 		} else if (new_active->link == BOND_LINK_BACK &&

@@ -2891,7 +2890,6 @@ do_failover:
 static void bond_ab_arp_probe(struct bonding *bond)
 {
 	struct slave *slave, *next_slave;
-	int i;
 
 	read_lock(&bond->curr_slave_lock);
 

@@ -2923,7 +2921,7 @@ static void bond_ab_arp_probe(struct bonding *bond)
 
 	/* search for next candidate */
 	next_slave = bond_next_slave(bond, bond->current_arp_slave);
-	bond_for_each_slave_from(bond, slave, i, next_slave) {
+	bond_for_each_slave_from(bond, slave, next_slave) {
 		if (IS_UP(slave->dev)) {
 			slave->link = BOND_LINK_BACK;
 			bond_set_slave_active_flags(slave);

drivers/net/bonding/bonding.h +6 -4

index ecb5d1d..7670584 100644
@@ -119,14 +119,25 @@
  * bond_for_each_slave_from - iterate the slaves list from a starting point
  * @bond:	the bond holding this list.
  * @pos:	current slave.
- * @cnt:	counter for max number of moves
  * @start:	starting point.
  *
  * Caller must hold bond->lock
  */
-#define bond_for_each_slave_from(bond, pos, cnt, start) \
-	for (cnt = 0, pos = start; pos && cnt < (bond)->slave_cnt; \
-	     cnt++, pos = bond_next_slave(bond, pos))
+#define bond_for_each_slave_from(bond, pos, start) \
+	for (pos = bond_next_slave(bond, start); pos && pos != start; \
+			pos = bond_next_slave(bond, pos))
+
+/**
+ * bond_for_each_slave_from_rcu - iterate the slaves list from a starting point

drivers/net/bonding/bonding.h +0 -0

 /**
  * bond_for_each_slave - iterate over all slaves

Quoted 29 lines

drivers/net/bonding/bond_main.c +0 -0

 			slave->link = BOND_LINK_BACK;
 			bond_set_slave_active_flags(slave);

drivers/net/bonding/bonding.h +10 -4

index ecb5d1d..7670584 100644
@@ -119,14 +119,25 @@
  * bond_for_each_slave_from - iterate the slaves list from a starting point
  * @bond:	the bond holding this list.
  * @pos:	current slave.
- * @cnt:	counter for max number of moves
  * @start:	starting point.
  *
  * Caller must hold bond->lock
  */
-#define bond_for_each_slave_from(bond, pos, cnt, start) \
-	for (cnt = 0, pos = start; pos && cnt < (bond)->slave_cnt; \
-	     cnt++, pos = bond_next_slave(bond, pos))
+#define bond_for_each_slave_from(bond, pos, start) \
+	for (pos = bond_next_slave(bond, start); pos && pos != start; \
+			pos = bond_next_slave(bond, pos))
+
+/**
+ * bond_for_each_slave_from_rcu - iterate the slaves list from a starting point
+ * @bond:	the bond holding this list.
+ * @pos:	current slave.
+ * @start:	starting point.
+ *

drivers/net/bonding/bonding.h line 141

Quoted 6 lines

drivers/net/bonding/bonding.h +5 -0

+ * Caller must hold rcu_read_lock
+ */
+#define bond_for_each_slave_from_rcu(bond, pos, start) \
+	for (pos = bond_next_slave_rcu(bond, start); pos && pos != start; \
+			pos = bond_next_slave_rcu(bond, pos))
 

One question here: what if "start" gets deleted while we're traversing the list, could this lead to an infinite loop ?

drivers/net/bonding/bonding.h line 143

Quoted 3 lines

drivers/net/bonding/bonding.h +0 -0

 /**
  * bond_for_each_slave - iterate over all slaves

.