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Date: Wed, 4 Sep 2013 14:23:51 +0800
From: Ding Tianhong <dingtianhong@...wei.com>
To: Nikolay Aleksandrov <nikolay@...hat.com>
CC: Jay Vosburgh <fubar@...ibm.com>,
Andy Gospodarek <andy@...yhouse.net>,
"David S. Miller" <davem@...emloft.net>,
Veaceslav Falico <vfalico@...hat.com>,
Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 5/6] bonding: restructure and simplify bond_for_each_slave_next()
On 2013/9/3 18:22, Nikolay Aleksandrov wrote:
> On 08/30/2013 12:05 PM, Ding Tianhong wrote:
>> remove the wordy int and add bond_for_each_slave_next_rcu() for future use.
>>
>> Signed-off-by: Ding Tianhong <dingtianhong@...wei.com>
>> Cc: Nikolay Aleksandrov <nikolay@...hat.com>
>> ---
>> 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(-)
>>
>> diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
>> index 3a5db7b..d266c56 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 4264a76..8c9902a 100644
>> --- a/drivers/net/bonding/bond_main.c
>> +++ b/drivers/net/bonding/bond_main.c
>> @@ -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);
>> diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
>> index 9898493..a3ab47f 100644
>> --- a/drivers/net/bonding/bonding.h
>> +++ b/drivers/net/bonding/bonding.h
>> @@ -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 (int cnt = 0, pos = start; pos && cnt < (bond)->slave_cnt; \
>> + cnt++, pos = bond_next_slave(bond, pos))
>> +
> Please read below the argument against using the nested cnt definition.
>
>> +/**
>> + * 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 (int cnt = 0, pos = start; pos && cnt < (bond)->slave_cnt; \
>> + cnt++, pos = bond_next_slave_rcu(bond, pos))
>>
> I don't think you can rely on slave_cnt in RCU, you may go overboard and pass
> twice over the same slave if a slave gets removed, or the opposite. Also this
> definition of cnt is troublesome because the name is quite common, I don't know
> if it's accepted, but it if it is at least change the name to something like
> __cnt or anything that is less likely to be defined.
> The cnt argument goes for bond_for_each_slave_from as well.
>
yes, more details need to think about, I modify the function to this:
#define bond_for_each_slave_from(bond, pos, start) \
for (pos = start; (pos == bond_next_slave(bond, start) ? \
&pos->list != &bond->slave_list : \
&pos->list != &start->list); \
pos = bond_next_slave(bond, pos))
I think it is fine here, or I miss something, please tell me, thanks. :)
>> /**
>> * bond_for_each_slave - iterate over all slaves
>>
>
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