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Date: Thu, 26 Sep 2013 10:33:28 +0800
From: Ding Tianhong <dingtianhong@...wei.com>
To: Veaceslav Falico <vfalico@...hat.com>
CC: Jay Vosburgh <fubar@...ibm.com>,
Andy Gospodarek <andy@...yhouse.net>,
"David S. Miller" <davem@...emloft.net>,
Nikolay Aleksandrov <nikolay@...hat.com>,
Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next v5 1/6] bonding: simplify and use RCU protection
for 3ad xmit path
On 2013/9/25 18:50, Veaceslav Falico wrote:
> On Wed, Sep 25, 2013 at 05:52:15PM +0800, Ding Tianhong wrote:
>> The commit 278b20837511776dc9d5f6ee1c7fabd5479838bb
>> (bonding: initial RCU conversion) has convert the roundrobin, active-backup,
>> broadcast and xor xmit path to rcu protection, the performance will be better
>> for these mode, so this time, convert xmit path for 3ad mode.
>>
>> Suggested-by: Nikolay Aleksandrov <nikolay@...hat.com>
>> Suggested-by: Veaceslav Falico <vfalico@...hat.com>
>> Signed-off-by: Ding Tianhong <dingtianhong@...wei.com>
>> Signed-off-by: Wang Yufen <wangyufen@...wei.com>
>> Cc: Nikolay Aleksandrov <nikolay@...hat.com>
>> Cc: Veaceslav Falico <vfalico@...hat.com>
>> ---
>> drivers/net/bonding/bond_3ad.c | 32 ++++++++++++++------------------
>> drivers/net/bonding/bonding.h | 30 +++++++++++++++++++++++++++++-
>> 2 files changed, 43 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
>> index 0d8f427..13f1deb 100644
>> --- a/drivers/net/bonding/bond_3ad.c
>> +++ b/drivers/net/bonding/bond_3ad.c
>> @@ -143,7 +143,7 @@ static inline struct bonding *__get_bond_by_port(struct port *port)
>> */
>> static inline struct port *__get_first_port(struct bonding *bond)
>> {
>> - struct slave *first_slave = bond_first_slave(bond);
>> + struct slave *first_slave = bond_first_slave_rcu(bond);
>>
>> return first_slave ? &(SLAVE_AD_INFO(first_slave).port) : NULL;
>> }
>> @@ -163,7 +163,7 @@ static inline struct port *__get_next_port(struct port *port)
>> // If there's no bond for this port, or this is the last slave
>> if (bond == NULL)
>> return NULL;
>> - slave_next = bond_next_slave(bond, slave);
>> + slave_next = bond_next_slave_rcu(bond, slave);
>> if (!slave_next || bond_is_first_slave(bond, slave_next))
>> return NULL;
>>
>> @@ -2417,16 +2417,14 @@ int bond_3ad_get_active_agg_info(struct bonding *bond, struct ad_info *ad_info)
>>
>> int bond_3ad_xmit_xor(struct sk_buff *skb, struct net_device *dev)
>> {
>> - struct slave *slave, *start_at;
>> struct bonding *bond = netdev_priv(dev);
>> + struct slave *slave;
>> int slave_agg_no;
>> int slaves_in_agg;
>> int agg_id;
>> - int i;
>> struct ad_info ad_info;
>> int res = 1;
>>
>> - read_lock(&bond->lock);
>> if (__bond_3ad_get_active_agg_info(bond, &ad_info)) {
>> pr_debug("%s: Error: __bond_3ad_get_active_agg_info failed\n",
>> dev->name);
>> @@ -2444,13 +2442,17 @@ int bond_3ad_xmit_xor(struct sk_buff *skb, struct net_device *dev)
>>
>> slave_agg_no = bond->xmit_hash_policy(skb, slaves_in_agg);
>>
>> - bond_for_each_slave(bond, slave) {
>> + bond_for_each_slave_rcu(bond, slave) {
>> struct aggregator *agg = SLAVE_AD_INFO(slave).port.aggregator;
>>
>> if (agg && (agg->aggregator_identifier == agg_id)) {
>> - slave_agg_no--;
>> - if (slave_agg_no < 0)
>> - break;
>> + if (--slave_agg_no < 0) {
>> + if (SLAVE_IS_OK(slave)) {
>> + res = bond_dev_queue_xmit(bond,
>> + skb, slave->dev);
>> + goto out;
>> + }
>> + }
>> }
>> }
>>
>> @@ -2460,23 +2462,17 @@ int bond_3ad_xmit_xor(struct sk_buff *skb, struct net_device *dev)
>> goto out;
>> }
>>
>> - start_at = slave;
>> -
>> - bond_for_each_slave_from(bond, slave, i, start_at) {
>> - int slave_agg_id = 0;
>> + bond_for_each_slave_rcu(bond, slave) {
>> struct aggregator *agg = SLAVE_AD_INFO(slave).port.aggregator;
>>
>> - if (agg)
>> - slave_agg_id = agg->aggregator_identifier;
>> -
>> - if (SLAVE_IS_OK(slave) && agg && (slave_agg_id == agg_id)) {
>> + if (SLAVE_IS_OK(slave) && agg &&
>> + agg->aggregator_identifier == agg_id) {
>> res = bond_dev_queue_xmit(bond, skb, slave->dev);
>> break;
>> }
>> }
>>
>> out:
>> - read_unlock(&bond->lock);
>> if (res) {
>> /* no suitable interface, frame not sent */
>> kfree_skb(skb);
>> diff --git a/drivers/net/bonding/bonding.h b/drivers/net/bonding/bonding.h
>> index 03cf3fd..eb36f57 100644
>> --- a/drivers/net/bonding/bonding.h
>> +++ b/drivers/net/bonding/bonding.h
>> @@ -74,13 +74,31 @@
>> /* slave list primitives */
>> #define bond_to_slave(ptr) list_entry(ptr, struct slave, list)
>>
>> +/* slave list primitives, Caller must hold rcu_read_lock */
>> +#define bond_to_slave_rcu(ptr) list_entry_rcu(ptr, struct slave, list)
>> +
>> +/* bond_is_empty return NULL if slave list is empty*/
>> +#define bond_is_empty(bond) \
>> + (list_empty(&(bond)->slave_list))
>> +
>> +/* bond_is_empty_rcu return NULL if slave list is empty*/
>> +#define bond_is_empty_rcu(bond) \
>> + (!list_first_or_null_rcu(&(bond)->slave_list, struct slave, list))
>
> Useless/dangerous function. It's not used in this patch and there can be no
> constructs like:
>
> 1 if (!bond_is_empty_rcu(bond)) {
> 2 slave = bond_first_slave_rcu(bond);
> 3 do_something(slave);
>
agree, forgot to remove it.
> because between 1) and 2) the slave can go away, and we'll end up with
> slave == NULL.
>
>> +
>> /* IMPORTANT: bond_first/last_slave can return NULL in case of an empty list */
>> #define bond_first_slave(bond) \
>> list_first_entry_or_null(&(bond)->slave_list, struct slave, list)
>> #define bond_last_slave(bond) \
>> - (list_empty(&(bond)->slave_list) ? NULL : \
>> + (bond_is_empty(bond) ? NULL : \
>> bond_to_slave((bond)->slave_list.prev))
>>
>> +/**
>> + * IMPORTANT: bond_first/last_slave_rcu can return NULL in case of an empty list
>> + * Caller must hold rcu_read_lock
>> + */
>> +#define bond_first_slave_rcu(bond) \
>> + list_first_or_null_rcu(&(bond)->slave_list, struct slave, list);
>
> bond_first_slave_or_null_rcu() ?
>
both is suitable.
>> +
>> #define bond_is_first_slave(bond, pos) ((pos)->list.prev == &(bond)->slave_list)
>> #define bond_is_last_slave(bond, pos) ((pos)->list.next == &(bond)->slave_list)
>>
>> @@ -93,6 +111,16 @@
>> (bond_is_first_slave(bond, pos) ? bond_last_slave(bond) : \
>> bond_to_slave((pos)->list.prev))
>>
>> +/* Since bond_first/last_slave_rcu can return NULL, these can return NULL too */
>> +#define bond_next_slave_rcu(bond, pos) \
>> + ({struct list_head *__slave_list = &(bond)->slave_list; \
>> + struct list_head __rcu *__next = list_next_rcu(__slave_list); \
>> + struct list_head __rcu *__pos_next = list_next_rcu(&(pos)->list); \
>> + likely(__pos_next != __slave_list) ? \
>> + container_of(__pos_next, struct slave, list) : \
>> + container_of(__next, struct slave, list); \
>> + })
>
> And if bond has no slaves, whilst pos being the slave that has just
> detached? Then bond->slave_list->next == pos->list->next ==
> &bond->slave_list, and we'll return the container_of(bond->slave_list),
> which is garbage, but not NULL.
>
>> +
>> /**
>> * bond_for_each_slave_from - iterate the slaves list from a starting point
>> * @bond: the bond holding this list.
>> --
>> 1.8.0
>>
>>
>>
>> --
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>
> .
>
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