[3.16.y-ckt stable] Patch "bonding: fix curr_active_slave/carrier with loadbalance arp monitoring" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    bonding: fix curr_active_slave/carrier with loadbalance arp monitoring

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt3.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 38fd5268b3c3a7db6f16456b23b54202c42243d3 Mon Sep 17 00:00:00 2001
From: Nikolay Aleksandrov <nikolay at redhat.com>
Date: Tue, 18 Nov 2014 15:14:44 +0100
Subject: bonding: fix curr_active_slave/carrier with loadbalance arp
 monitoring

commit b8e4500f42fe4464a33a887579147050bed8fcef upstream.

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 <vfalico at gmail.com>
CC: Jay Vosburgh <j.vosburgh at gmail.com>
CC: Andy Gospodarek <andy at greyhouse.net>
CC: Ding Tianhong <dingtianhong at huawei.com>

Fixes: 6fde8f037e60 ("bonding: fix locking in bond_loadbalance_arp_mon()")
Signed-off-by: Nikolay Aleksandrov <nikolay at redhat.com>
Acked-by: Veaceslav Falico <vfalico at gmail.com>
Acked-by: Andy Gospodarek <gospo at cumulusnetworks.com>
Acked-by: Ding Tianhong <dingtianhong at huawei.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
[ luis: backported to 3.16: used davem's backport to 3.17 ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 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 5f29c9a9a316..6c795cfd6bbc 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -2505,9 +2505,9 @@ 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.
 			 */
--
2.1.0