Subject: [PATCH 5/7] bonding: fix curr_active_slave/carrier with loadbalance arp monitoring

From: Nikolay Aleksandrov <[email-masked]>
Date: Tue, 18 Nov 2014 15:14:44 +0100

[ Upstream commit b8e4500f42fe4464a33a887579147050bed8fcef ]

Since commit 6fde8f037e60 ("bonding: fix locking in
bond_loadbalance_arp_mon()") we can have a stale bond carrier state and
stale curr_active_slave when using arp monitoring in loadbalance modes. The
reason is that in bond_loadbalance_arp_mon() we can't have
do_failover == true but slave_state_changed == false, whenever do_failover
is true then slave_state_changed is also true. Then the following piece
from bond_loadbalance_arp_mon():
                if (slave_state_changed) {
                        bond_slave_state_change(bond);
                        if (BOND_MODE(bond) == BOND_MODE_XOR)
                                bond_update_slave_arr(bond, NULL);
                } else if (do_failover) {
                        block_netpoll_tx();
                        bond_select_active_slave(bond);
                        unblock_netpoll_tx();
                }

will execute only the first branch, always and regardless of do_failover.
Since these two events aren't related in such way, we need to decouple and
consider them separately.

For example this issue could lead to the following result:
Bonding Mode: load balancing (round-robin)
*MII Status: down*
MII Polling Interval (ms): 0
Up Delay (ms): 0
Down Delay (ms): 0
ARP Polling Interval (ms): 100
ARP IP target/s (n.n.n.n form): 192.168.9.2

Slave Interface: ens12
*MII Status: up*
Speed: 10000 Mbps
Duplex: full
Link Failure Count: 2
Permanent HW addr: 00:0f:53:01:42:2c
Slave queue ID: 0

Slave Interface: eth1
*MII Status: up*
Speed: Unknown
Duplex: Unknown
Link Failure Count: 70
Permanent HW addr: 52:54:00:2f:0f:8e
Slave queue ID: 0

Since some interfaces are up, then the status of the bond should also be
up, but it will never change unless something invokes bond_set_carrier()
(i.e. enslave, bond_select_active_slave etc). Now, if I force the
calling of bond_select_active_slave via for example changing
primary_reselect (it can change in any mode), then the MII status goes to
"up" because it calls bond_select_active_slave() which should've been done
from bond_loadbalance_arp_mon() itself.

CC: Veaceslav Falico <[email-masked]>
CC: Jay Vosburgh <[email-masked]>
CC: Andy Gospodarek <[email-masked]>
CC: Ding Tianhong <[email-masked]>

Fixes: 6fde8f037e60 ("bonding: fix locking in bond_loadbalance_arp_mon()")
Signed-off-by: Nikolay Aleksandrov <[email-masked]>
Acked-by: Veaceslav Falico <[email-masked]>
Acked-by: Andy Gospodarek <[email-masked]>
Acked-by: Ding Tianhong <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 drivers/net/bonding/bond_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index cc38948..1537982 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -2450,9 +2450,9 @@ static void bond_loadbalance_arp_mon(struct work_struct *work)
 		if (!rtnl_trylock())
 			goto re_arm;
 
-		if (slave_state_changed) {
+		if (slave_state_changed)
 			bond_slave_state_change(bond);
-		} else if (do_failover) {
+		if (do_failover) {
 			/* the bond_select_active_slave must hold RTNL
 			 * and curr_slave_lock for write.
 			 */
-- 
1.7.11.7