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

[Ding Tianhong <dthxman@gmail.com>]

于 2013/9/5 21:30, Veaceslav Falico 写道:
> 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 <nikolay@redhat.com>
>> Suggested-by: Veaceslav Falico <vfalico@redhat.com>
>> Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
>> Cc: Nikolay Aleksandrov <nikolay@redhat.com>
>> Cc: Veaceslav Falico <vfalico@redhat.com>
>> ---
>> 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.
>
if the slave is only one, it will run once, and out the loop, else if
the slave is more than one, it will run until reach the start again,
here I use the &bond->slave_list to control the loop, as it will not
change any time, maybe it is hard to understand first.

ok, I think they are same, just in the purpose to remove the cnt, so 
maybe it make you
unconfortable, sorry about that, if you strangly disagree, I will miss 
this patch, but
thanks again for your different opinions. :)

>> +
>> +/**
>> + * 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
>>
>>
>>
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