netdev - Re: [PATCH net] bonding/802.3ad: fix slave link initialization transition states

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Date:   Fri, 24 May 2019 14:16:56 -0700
From:   Jay Vosburgh <jay.vosburgh@...onical.com>
To:     Jarod Wilson <jarod@...hat.com>
cc:     linux-kernel@...r.kernel.org, Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Heesoon Kim <Heesoon.Kim@...atus.com>
Subject: Re: [PATCH net] bonding/802.3ad: fix slave link initialization transition states

Jarod Wilson <jarod@...hat.com> wrote:

>Once in a while, with just the right timing, 802.3ad slaves will fail to
>properly initialize, winding up in a weird state, with a partner system
>mac address of 00:00:00:00:00:00. This started happening after a fix to
>properly track link_failure_count tracking, where an 802.3ad slave that
>reported itself as link up in the miimon code, but wasn't able to get a
>valid speed/duplex, started getting set to BOND_LINK_FAIL instead of
>BOND_LINK_DOWN. That was the proper thing to do for the general "my link
>went down" case, but has created a link initialization race that can put
>the interface in this odd state.

	Reading back in the git history, the ultimate cause of this
"weird state" appears to be devices that assert NETDEV_UP prior to
actually being able to supply sane speed/duplex values, correct?

	Presuming that this is the case, I don't see that there's much
else to be done here, and so:

Acked-by: Jay Vosburgh <jay.vosburgh@...onical.com>

>The simple fix is to instead set the slave link to BOND_LINK_DOWN again,
>if the link has never been up (last_link_up == 0), so the link state
>doesn't bounce from BOND_LINK_DOWN to BOND_LINK_FAIL -- it hasn't failed
>in this case, it simply hasn't been up yet, and this prevents the
>unnecessary state change from DOWN to FAIL and getting stuck in an init
>failure w/o a partner mac.
>
>Fixes: ea53abfab960 ("bonding/802.3ad: fix link_failure_count tracking")
>CC: Jay Vosburgh <j.vosburgh@...il.com>
>CC: Veaceslav Falico <vfalico@...il.com>
>CC: Andy Gospodarek <andy@...yhouse.net>
>CC: "David S. Miller" <davem@...emloft.net>
>CC: netdev@...r.kernel.org
>Tested-by: Heesoon Kim <Heesoon.Kim@...atus.com>
>Signed-off-by: Jarod Wilson <jarod@...hat.com>



>---
> drivers/net/bonding/bond_main.c | 15 ++++++++++-----
> 1 file changed, 10 insertions(+), 5 deletions(-)
>
>diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>index 062fa7e3af4c..407f4095a37a 100644
>--- a/drivers/net/bonding/bond_main.c
>+++ b/drivers/net/bonding/bond_main.c
>@@ -3122,13 +3122,18 @@ static int bond_slave_netdev_event(unsigned long event,
> 	case NETDEV_CHANGE:
> 		/* For 802.3ad mode only:
> 		 * Getting invalid Speed/Duplex values here will put slave
>-		 * in weird state. So mark it as link-fail for the time
>-		 * being and let link-monitoring (miimon) set it right when
>-		 * correct speeds/duplex are available.
>+		 * in weird state. Mark it as link-fail if the link was
>+		 * previously up or link-down if it hasn't yet come up, and
>+		 * let link-monitoring (miimon) set it right when correct
>+		 * speeds/duplex are available.
> 		 */
> 		if (bond_update_speed_duplex(slave) &&
>-		    BOND_MODE(bond) == BOND_MODE_8023AD)
>-			slave->link = BOND_LINK_FAIL;
>+		    BOND_MODE(bond) == BOND_MODE_8023AD) {
>+			if (slave->last_link_up)
>+				slave->link = BOND_LINK_FAIL;
>+			else
>+				slave->link = BOND_LINK_DOWN;
>+		}
> 
> 		if (BOND_MODE(bond) == BOND_MODE_8023AD)
> 			bond_3ad_adapter_speed_duplex_changed(slave);
>-- 
>2.20.1
>