netdev - Re: [PATCH net] bonding: fix curr_active_slave/carrier with loadbalance arp monitoring

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Date:	Tue, 18 Nov 2014 10:28:47 -0500
From:	Andy Gospodarek <gospo@...ulusnetworks.com>
To:	Veaceslav Falico <vfalico@...il.com>
Cc:	Nikolay Aleksandrov <nikolay@...hat.com>, netdev@...r.kernel.org,
	davem@...emloft.net, Jay Vosburgh <j.vosburgh@...il.com>,
	Andy Gospodarek <andy@...yhouse.net>,
	Ding Tianhong <dingtianhong@...wei.com>
Subject: Re: [PATCH net] bonding: fix curr_active_slave/carrier with
 loadbalance arp monitoring

On Tue, Nov 18, 2014 at 03:37:27PM +0100, Veaceslav Falico wrote:
> On Tue, Nov 18, 2014 at 03:14:44PM +0100, Nikolay Aleksandrov wrote:
> >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) {
> 
> Ouch, must have been a big PITA to track :).

Agreed!

> 
> >                       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@...il.com>
> 
> Acked-by: Veaceslav Falico <vfalico@...il.com>

Acked-by: Andy Gospodarek <gospo@...ulusnetworks.com>

> 
> >CC: Jay Vosburgh <j.vosburgh@...il.com>
> >CC: Andy Gospodarek <andy@...yhouse.net>
> >CC: Ding Tianhong <dingtianhong@...wei.com>
> >
> >Fixes: 6fde8f037e60 ("bonding: fix locking in bond_loadbalance_arp_mon()")
> >Signed-off-by: Nikolay Aleksandrov <nikolay@...hat.com>
> >---
> >Note: I left the parent if() the same even though we can shorten it. I think
> >     it's better this way since it shows that any of the two events can cause
> >     it to enter even though currently we can't have do_failover without
> >     slave_state_changed, that may also change in the future.
> >
> >drivers/net/bonding/bond_main.c | 3 ++-
> >1 file changed, 2 insertions(+), 1 deletion(-)
> >
> >diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> >index c9ac06cfe6b7..a5115fb7cf33 100644
> >--- a/drivers/net/bonding/bond_main.c
> >+++ b/drivers/net/bonding/bond_main.c
> >@@ -2471,7 +2471,8 @@ static void bond_loadbalance_arp_mon(struct work_struct *work)
> >			bond_slave_state_change(bond);
> >			if (BOND_MODE(bond) == BOND_MODE_XOR)
> >				bond_update_slave_arr(bond, NULL);
> >-		} else if (do_failover) {
> >+		}
> >+		if (do_failover) {
> >			block_netpoll_tx();
> >			bond_select_active_slave(bond);
> >			unblock_netpoll_tx();
> >-- 
> >1.9.3
> >
> --
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