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Message-ID: <52A2D22F.1000902@huawei.com>
Date: Sat, 7 Dec 2013 15:45:51 +0800
From: Ding Tianhong <dingtianhong@...wei.com>
To: Jay Vosburgh <fubar@...ibm.com>,
Andy Gospodarek <andy@...yhouse.net>,
"David S. Miller" <davem@...emloft.net>,
Nikolay Aleksandrov <nikolay@...hat.com>,
Veaceslav Falico <vfalico@...hat.com>,
Netdev <netdev@...r.kernel.org>
Subject: [PATCH net-next v4 6/11] bonding: rebuild the lock use for bond_activebackup_arp_mon()
The bond_activebackup_arp_mon() use the bond lock for read to
protect the slave list, it is no effect, and the RTNL is only
called for bond_ab_arp_commit() and peer notify, for the performance
better, use RCU to replace with the bond lock, to the bond slave
list need to called in RCU, add a new bond_first_slave_rcu()
to get the first slave in RCU protection.
In bond_ab_arp_probe(), the bond->current_arp_slave may changd
if bond release slave, just like:
bond_ab_arp_probe() bond_release()
cpu 0 cpu 1
...
if (bond->current_arp_slave...) ...
... bond->current_arp_slave = NULl
bond->current_arp_slave->dev->name ...
So the current_arp_slave need to dereference in the section.
When bond_ab_arp_inspect() and should_notify_peers is true, the
RTNL will called twice, it is a loss of performance, so make the
two RTNL together to avoid performance loss.
Suggested-by: Nikolay Aleksandrov <nikolay@...hat.com>
Suggested-by: Jay Vosburgh <fubar@...ibm.com>
Suggested-by: Veaceslav Falico <vfalico@...hat.com>
Signed-off-by: Ding Tianhong <dingtianhong@...wei.com>
---
drivers/net/bonding/bond_main.c | 49 +++++++++++++++++++++--------------------
1 file changed, 25 insertions(+), 24 deletions(-)
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 1f5e709..d9bb5ee 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -2521,7 +2521,7 @@ re_arm:
* place for the slave. Returns 0 if no changes are found, >0 if changes
* to link states must be committed.
*
- * Called with bond->lock held for read.
+ * Called with rcu_read_lock hold.
*/
static int bond_ab_arp_inspect(struct bonding *bond)
{
@@ -2530,7 +2530,7 @@ static int bond_ab_arp_inspect(struct bonding *bond)
struct slave *slave;
int commit = 0;
- bond_for_each_slave(bond, slave, iter) {
+ bond_for_each_slave_rcu(bond, slave, iter) {
slave->new_link = BOND_LINK_NOCHANGE;
last_rx = slave_last_rx(bond, slave);
@@ -2592,7 +2592,7 @@ static int bond_ab_arp_inspect(struct bonding *bond)
* Called to commit link state changes noted by inspection step of
* active-backup mode ARP monitor.
*
- * Called with RTNL and bond->lock for read.
+ * Called with RTNL hold.
*/
static void bond_ab_arp_commit(struct bonding *bond)
{
@@ -2667,19 +2667,20 @@ do_failover:
/*
* Send ARP probes for active-backup mode ARP monitor.
*
- * Called with bond->lock held for read.
+ * Called with rcu_read_lock hold.
*/
static void bond_ab_arp_probe(struct bonding *bond)
{
- struct slave *slave, *before = NULL, *new_slave = NULL;
+ struct slave *slave, *before = NULL, *new_slave = NULL,
+ *curr_arp_slave = rcu_dereference(bond->current_arp_slave);
struct list_head *iter;
bool found = false;
read_lock(&bond->curr_slave_lock);
- if (bond->current_arp_slave && bond->curr_active_slave)
+ if (curr_arp_slave && bond->curr_active_slave)
pr_info("PROBE: c_arp %s && cas %s BAD\n",
- bond->current_arp_slave->dev->name,
+ curr_arp_slave->dev->name,
bond->curr_active_slave->dev->name);
if (bond->curr_active_slave) {
@@ -2695,15 +2696,15 @@ static void bond_ab_arp_probe(struct bonding *bond)
* for becoming the curr_active_slave
*/
- if (!bond->current_arp_slave) {
- bond->current_arp_slave = bond_first_slave(bond);
- if (!bond->current_arp_slave)
+ if (!curr_arp_slave) {
+ curr_arp_slave = bond_first_slave_rcu(bond);
+ if (!curr_arp_slave)
return;
}
- bond_set_slave_inactive_flags(bond->current_arp_slave);
+ bond_set_slave_inactive_flags(curr_arp_slave);
- bond_for_each_slave(bond, slave, iter) {
+ bond_for_each_slave_rcu(bond, slave, iter) {
if (!found && !before && IS_UP(slave->dev))
before = slave;
@@ -2726,7 +2727,7 @@ static void bond_ab_arp_probe(struct bonding *bond)
pr_info("%s: backup interface %s is now down.\n",
bond->dev->name, slave->dev->name);
}
- if (slave == bond->current_arp_slave)
+ if (slave == curr_arp_slave)
found = true;
}
@@ -2740,8 +2741,7 @@ static void bond_ab_arp_probe(struct bonding *bond)
bond_set_slave_active_flags(new_slave);
bond_arp_send_all(bond, new_slave);
new_slave->jiffies = jiffies;
- bond->current_arp_slave = new_slave;
-
+ rcu_assign_pointer(bond->current_arp_slave, new_slave);
}
void bond_activebackup_arp_mon(struct work_struct *work)
@@ -2751,17 +2751,17 @@ void bond_activebackup_arp_mon(struct work_struct *work)
bool should_notify_peers = false;
int delta_in_ticks;
- read_lock(&bond->lock);
-
delta_in_ticks = msecs_to_jiffies(bond->params.arp_interval);
if (!bond_has_slaves(bond))
goto re_arm;
+ rcu_read_lock();
+
should_notify_peers = bond_should_notify_peers(bond);
if (bond_ab_arp_inspect(bond)) {
- read_unlock(&bond->lock);
+ rcu_read_unlock();
/* Race avoidance with bond_close flush of workqueue */
if (!rtnl_trylock()) {
@@ -2771,23 +2771,24 @@ void bond_activebackup_arp_mon(struct work_struct *work)
goto re_arm;
}
- read_lock(&bond->lock);
-
bond_ab_arp_commit(bond);
+ if (should_notify_peers) {
+ call_netdevice_notifiers(NETDEV_NOTIFY_PEERS,
+ bond->dev);
+ should_notify_peers = false;
+ }
- read_unlock(&bond->lock);
rtnl_unlock();
- read_lock(&bond->lock);
+ rcu_read_lock();
}
bond_ab_arp_probe(bond);
+ rcu_read_unlock();
re_arm:
if (bond->params.arp_interval)
queue_delayed_work(bond->wq, &bond->arp_work, delta_in_ticks);
- read_unlock(&bond->lock);
-
if (should_notify_peers) {
if (!rtnl_trylock())
return;
--
1.8.2.1
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