bonding: alb: remove curr_slave_lock

First in rlb_teach_disabled_mac_on_primary() it's okay to remove
curr_slave_lock as all callers except bond_alb_monitor() already hold
RTNL, and in case bond_alb_monitor() is executing we can at most have a
period with bad throughput (very unlikely though).
In bond_alb_monitor() it's okay to remove the read_lock as the slave
list is walked with RCU and the worst that could happen is another
transmitter at the same time and thus for a period which currently is 10
seconds (bond_alb.h: BOND_ALB_LP_TICKS).
And bond_alb_handle_active_change() is okay because it's always called
with RTNL. Removed the ASSERT_RTNL() because it'll be inserted in the
parent function in a following patch.

Signed-off-by: Nikolay Aleksandrov <nikolay@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 36 deletions

diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
index 028496205f39..cf4ede8594ff 100644
--- a/drivers/net/bonding/bond_alb.c
+++ b/drivers/net/bonding/bond_alb.c
@@ -447,7 +447,7 @@ static struct slave *__rlb_next_rx_slave(struct bonding *bond)
 /* teach the switch the mac of a disabled slave
  * on the primary for fault tolerance
  *
- * Caller must hold bond->curr_slave_lock for write or bond lock for write
+ * Caller must hold RTNL
  */
 static void rlb_teach_disabled_mac_on_primary(struct bonding *bond, u8 addr[])
 {
@@ -512,12 +512,8 @@ static void rlb_clear_slave(struct bonding *bond, struct slave *slave)
 
         _unlock_rx_hashtbl_bh(bond);
 
-        write_lock_bh(&bond->curr_slave_lock);
-
         if (slave != bond_deref_active_protected(bond))
                 rlb_teach_disabled_mac_on_primary(bond, slave->dev->dev_addr);
-
-        write_unlock_bh(&bond->curr_slave_lock);
 }
 
 static void rlb_update_client(struct rlb_client_info *client_info)
@@ -1595,13 +1591,6 @@ void bond_alb_monitor(struct work_struct *work)
         if (bond_info->lp_counter >= BOND_ALB_LP_TICKS(bond)) {
                 bool strict_match;
 
-                /* change of curr_active_slave involves swapping of mac addresses.
-                 * in order to avoid this swapping from happening while
-                 * sending the learning packets, the curr_slave_lock must be held for
-                 * read.
-                 */
-                read_lock(&bond->curr_slave_lock);
-
                 bond_for_each_slave_rcu(bond, slave, iter) {
                         /* If updating current_active, use all currently
                          * user mac addreses (!strict_match).  Otherwise, only
@@ -1613,17 +1602,11 @@ void bond_alb_monitor(struct work_struct *work)
                         alb_send_learning_packets(slave, slave->dev->dev_addr,
                                                   strict_match);
                 }
-
-                read_unlock(&bond->curr_slave_lock);
-
                 bond_info->lp_counter = 0;
         }
 
         /* rebalance tx traffic */
         if (bond_info->tx_rebalance_counter >= BOND_TLB_REBALANCE_TICKS) {
-
-                read_lock(&bond->curr_slave_lock);
-
                 bond_for_each_slave_rcu(bond, slave, iter) {
                         tlb_clear_slave(bond, slave, 1);
                         if (slave == rcu_access_pointer(bond->curr_active_slave)) {
@@ -1633,9 +1616,6 @@ void bond_alb_monitor(struct work_struct *work)
                                 bond_info->unbalanced_load = 0;
                         }
                 }
-
-                read_unlock(&bond->curr_slave_lock);
-
                 bond_info->tx_rebalance_counter = 0;
         }
 
@@ -1775,21 +1755,14 @@ void bond_alb_handle_link_change(struct bonding *bond, struct slave *slave, char
  * Set the bond->curr_active_slave to @new_slave and handle
  * mac address swapping and promiscuity changes as needed.
  *
- * If new_slave is NULL, caller must hold curr_slave_lock for write
- *
- * If new_slave is not NULL, caller must hold RTNL, curr_slave_lock
- * for write.  Processing here may sleep, so no other locks may be held.
+ * Caller must hold RTNL
  */
 void bond_alb_handle_active_change(struct bonding *bond, struct slave *new_slave)
-        __releases(&bond->curr_slave_lock)
-        __acquires(&bond->curr_slave_lock)
 {
         struct slave *swap_slave;
         struct slave *curr_active;
 
-        curr_active = rcu_dereference_protected(bond->curr_active_slave,
-                                                !new_slave ||
-                                                lockdep_is_held(&bond->curr_slave_lock));
+        curr_active = rtnl_dereference(bond->curr_active_slave);
         if (curr_active == new_slave)
                 return;
 
@@ -1820,10 +1793,6 @@ void bond_alb_handle_active_change(struct bonding *bond, struct slave *new_slave
                 tlb_clear_slave(bond, swap_slave, 1);
         tlb_clear_slave(bond, new_slave, 1);
 
-        write_unlock_bh(&bond->curr_slave_lock);
-
-        ASSERT_RTNL();
-
         /* in TLB mode, the slave might flip down/up with the old dev_addr,
          * and thus filter bond->dev_addr's packets, so force bond's mac
          */
@@ -1852,8 +1821,6 @@ void bond_alb_handle_active_change(struct bonding *bond, struct slave *new_slave
                 alb_send_learning_packets(new_slave, bond->dev->dev_addr,
                                           false);
         }
-
-        write_lock_bh(&bond->curr_slave_lock);
 }
 
 /* Called with RTNL */