From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ding Tianhong Subject: Re: [PATCH net-next v5 1/6] bonding: simplify and use RCU protection for 3ad xmit path Date: Thu, 26 Sep 2013 10:33:28 +0800 Message-ID: <52439CF8.7080209@huawei.com> References: <5242B24F.5000309@huawei.com> <20130925105000.GC23575@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Jay Vosburgh , Andy Gospodarek , "David S. Miller" , Nikolay Aleksandrov , Netdev To: Veaceslav Falico Return-path: Received: from szxga01-in.huawei.com ([119.145.14.64]:6432 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754705Ab3IZCdu (ORCPT ); Wed, 25 Sep 2013 22:33:50 -0400 In-Reply-To: <20130925105000.GC23575@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: 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 >> Suggested-by: Veaceslav Falico >> Signed-off-by: Ding Tianhong >> Signed-off-by: Wang Yufen >> Cc: Nikolay Aleksandrov >> Cc: Veaceslav Falico >> --- >> 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 >> >> >> >> -- >> To unsubscribe from this list: send the line "unsubscribe netdev" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > . >