Subject: Re: [PATCH net-next v3 5/6] bonding: restructure and add rcu for bond_for_each_slave_next()

From: Veaceslav Falico <[email-masked]>
Date: Thu, 5 Sep 2013 15:30:27 +0200

On Thu, Sep 05, 2013 at 03:49:01PM +0800, Ding Tianhong wrote:
>Remove the wordy int and add bond_for_each_slave_next_rcu() for future use.
>
>Suggested-by: Nikolay Aleksandrov <[email-masked]>
>Suggested-by: Veaceslav Falico <[email-masked]>
>Signed-off-by: Ding Tianhong <[email-masked]>
>Cc: Nikolay Aleksandrov <[email-masked]>
>Cc: Veaceslav Falico <[email-masked]>
>---
> drivers/net/bonding/bond_alb.c  |  3 +--
> drivers/net/bonding/bond_main.c |  6 ++----
> drivers/net/bonding/bonding.h   | 23 +++++++++++++++++++----
> 3 files changed, 22 insertions(+), 10 deletions(-)
>
>diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
>index 91f179d..c75d383 100644
>--- a/drivers/net/bonding/bond_alb.c
>+++ b/drivers/net/bonding/bond_alb.c
>@@ -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;
>diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>index 39e5b1c..4190389 100644
>--- a/drivers/net/bonding/bond_main.c
>+++ b/drivers/net/bonding/bond_main.c
>@@ -782,7 +782,6 @@ 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;
>
>@@ -801,7 +800,7 @@ 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 &&
>@@ -2756,7 +2755,6 @@ do_failover:
> static void bond_ab_arp_probe(struct bonding *bond)
> {
> 	struct slave *slave, *next_slave;
>-	int i;
>
> 	read_lock(&bond->curr_slave_lock);
>
>@@ -2788,7 +2786,7 @@ 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);
>diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
>index f013b12..48fd41a 100644
>--- a/drivers/net/bonding/bonding.h
>+++ b/drivers/net/bonding/bonding.h
>@@ -123,18 +123,33 @@
> 	(bond_is_first_slave(bond, pos) ? bond_last_slave_rcu(bond) : \
> 					  bond_to_slave_rcu((pos)->list.prev))
>
>+/* Check whether the slave is the only one in bond */
>+
> /**
>  * 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 = start; pos && &pos->list != &bond->slave_list; \
>+	    (pos = bond_next_slave(bond, pos)) != start ? pos : \
>+	    (pos = list_entry(&bond->slave_list, typeof(*pos), list)))

Do you understand the differences of these two implementations?

pos && cnt < (bond)->slave_cnt

vs

pos && &pos->list != &bond->slave_list

I'm sorry, but you should listen to comments.

>+
>+/**
>+ * 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.
>+ *
>+ * Caller must hold rcu_read_lock
>+ */
>+#define bond_for_each_slave_from_rcu(bond, pos, start) \
>+	for (pos = start; pos && &pos->list != &bond->slave_list; \
>+	    (pos = bond_next_slave_rcu(bond, pos)) != start ? pos : \
>+	    (pos = list_entry_rcu(&bond->slave_list, typeof(*pos), list)))
>
> /**
>  * bond_for_each_slave - iterate over all slaves
>-- 
>1.8.2.1
>
>
>