[PATCH net-next 2/3] bonding: fix __get_first_agg RCU usage

[Veaceslav Falico <vfalico@redhat.com>]

Currently, the RCU read lock usage is just wrong - it gets the slave struct
under RCU and continues to use it when RCU lock is released.

However, it's still safe to do this cause we didn't need the
rcu_read_lock() initially - all of the __get_first_agg() callers are either
holding RCU read lock or the RTNL lock, so that we can't sync while in it.

So, remove the useless rcu locking and add a comment.

Fixes: be79bd048 ("bonding: add RCU for bond_3ad_state_machine_handler()")
CC: dingtianhong@huawei.com
CC: Jay Vosburgh <fubar@us.ibm.com>
CC: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: Veaceslav Falico <vfalico@redhat.com>
---
 drivers/net/bonding/bond_3ad.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
index 6330beb..70e72d7 100644
--- a/drivers/net/bonding/bond_3ad.c
+++ b/drivers/net/bonding/bond_3ad.c
@@ -143,6 +143,7 @@ static inline struct bonding *__get_bond_by_port(struct port *port)
  *
  * Return the aggregator of the first slave in @bond, or %NULL if it can't be
  * found.
+ * The caller must either hold RCU or RTNL lock.
  */
 static inline struct aggregator *__get_first_agg(struct port *port)
 {
@@ -153,9 +154,7 @@ static inline struct aggregator *__get_first_agg(struct port *port)
 	if (bond == NULL)
 		return NULL;
 
-	rcu_read_lock();
 	first_slave = bond_first_slave_rcu(bond);
-	rcu_read_unlock();
 
 	return first_slave ? &(SLAVE_AD_INFO(first_slave).aggregator) : NULL;
 }
-- 
1.8.4