netdev - RE: bonding reports interface up with 0 Mbps

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Date:	Thu, 4 Feb 2016 15:47:01 +0000
From:	"Tantilov, Emil S" <emil.s.tantilov@...el.com>
To:	Jay Vosburgh <jay.vosburgh@...onical.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"gospo@...ulusnetworks.com" <gospo@...ulusnetworks.com>,
	zhuyj <zyjzyj2000@...il.com>,
	"jiri@...lanox.com" <jiri@...lanox.com>
Subject: RE: bonding reports interface up with 0 Mbps

>-----Original Message-----
>From: Jay Vosburgh [mailto:jay.vosburgh@...onical.com]
>Sent: Wednesday, February 03, 2016 9:57 PM
>To: Tantilov, Emil S
>Cc: netdev@...r.kernel.org; gospo@...ulusnetworks.com; zhuyj;
>jiri@...lanox.com
>Subject: Re: bonding reports interface up with 0 Mbps
>
>Tantilov, Emil S <emil.s.tantilov@...el.com> wrote:
>
>>We are seeing an occasional issue where the bonding driver may report
>interface up with 0 Mbps:
>>bond0: link status definitely up for interface eth0, 0 Mbps full duplex
>>
>>So far in all the failed traces I have collected this happens on NETDEV_CHANGELOWERSTATE event:
>>
>><...>-20533 [000] .... 81811.041241: ixgbe_service_task: eth1: NIC Link is Up 10 Gbps, Flow Control: RX/TX
>><...>-20533 [000] .... 81811.041257: ixgbe_check_vf_rate_limit <-ixgbe_service_task
>><...>-20533 [000] .... 81811.041272: ixgbe_ping_all_vfs <-ixgbe_service_task
>>kworker/u48:0-7503  [010] .... 81811.041345: ixgbe_get_stats64 <-dev_get_stats
>>kworker/u48:0-7503  [010] .... 81811.041393: bond_netdev_event: eth1: event: 1b
>>kworker/u48:0-7503  [010] .... 81811.041394: bond_netdev_event: eth1: IFF_SLAVE
>>kworker/u48:0-7503  [010] .... 81811.041395: bond_netdev_event: eth1: slave->speed = ffffffff
>><...>-20533 [000] .... 81811.041407: ixgbe_ptp_overflow_check <-ixgbe_service_task
>>kworker/u48:0-7503  [010] .... 81811.041407: bond_mii_monitor: bond0: link status definitely up for interface eth1, 0 Mbps full duplex
>
>	From looking at the code that prints this, the "full" duplex is
>probably actually DUPLEX_UNKNOWN, but the netdev_info uses the
>expression slave->duplex ? "full" : "half", so DUPLEX_UNKNOWN at 0xff
>would print "full."
>
>	This is what ixgbe_get_settings returns for speed and duplex if
>it is called when carrier is off.

But in this case carrier is on and regardless - ixgbe_get_settings() is not
called as you can see from the trace, which is why speed and duplex are not set.

>>As a proof of concept I added NETDEV_CHANGELOWERSTATE in
>bond_slave_netdev_event() along with NETDEV_UP/CHANGE:
>>
>>diff --git a/drivers/net/bonding/bond_main.c
>b/drivers/net/bonding/bond_main.c
>>index 56b5605..a9dac4c 100644
>>--- a/drivers/net/bonding/bond_main.c
>>+++ b/drivers/net/bonding/bond_main.c
>>@@ -3014,6 +3014,7 @@ static int bond_slave_netdev_event(unsigned long
>event,
>> 		break;
>> 	case NETDEV_UP:
>> 	case NETDEV_CHANGE:
>>+	case NETDEV_CHANGELOWERSTATE:
>> 		bond_update_speed_duplex(slave);
>> 		if (BOND_MODE(bond) == BOND_MODE_8023AD)
>> 			bond_3ad_adapter_speed_duplex_changed(slave);
>>
>>With this change I have not seen 0 Mbps reported by the bonding driver
>(around 12 hour test up to this point
>>vs. 2-3 hours otherwise). Although I suppose it could also be some sort of
>race/timing issue with bond_mii_monitor().
>
>	This change as a fix seems kind of odd, since CHANGELOWERSTATE
>is generated by bonding itself.  Perhaps the net effect is to add a
>delay and then update the speed and duplex, masking the actual problem.

I added this case to make sure bond_update_speed_duplex() is called which
will get the speed/duplex from ixgbe_get_settings.

>	Emil, if I recall correctly, the test patch I send that uses the
>notifiers directly instead of miimon (specify miimon=0 and have bonding
>respond to the notifiers) handled everything properly, right?  If so I

Yes, but I think the code path was also different as I recall the "definitely
up" message was not displayed as often.
 
>can split that up and submit it properly; it seems more like a feature
>than a straightforward bug fix, so I'm not sure it's appropriate for
>net.
>
>	As a possibly less complex alternative for the miimon > 0 case,
>could you try the following:
>
>diff --git a/drivers/net/bonding/bond_main.c
>b/drivers/net/bonding/bond_main.c
>index 56b560558884..ac8921e65f26 100644
>--- a/drivers/net/bonding/bond_main.c
>+++ b/drivers/net/bonding/bond_main.c
>@@ -2120,6 +2120,7 @@ static void bond_miimon_commit(struct bonding *bond)
> {
> 	struct list_head *iter;
> 	struct slave *slave, *primary;
>+	int link_state;
>
> 	bond_for_each_slave(bond, slave, iter) {
> 		switch (slave->new_link) {
>@@ -2127,6 +2128,10 @@ static void bond_miimon_commit(struct bonding *bond)
> 			continue;
>
> 		case BOND_LINK_UP:
>+			link_state = bond_check_dev_link(bond, slave->dev, 0);
>+			if (!link_state)
>+				continue;
>+			bond_update_speed_duplex(slave);
> 			bond_set_slave_link_state(slave, BOND_LINK_UP,
> 						  BOND_SLAVE_NOTIFY_NOW);
> 			slave->last_link_up = jiffies;
>
>
>	This will make bonding recheck the link state and update the
>speed and duplex after it acquires RTNL to commit a link change.  This
>probably still has a race, since the change of carrier state in the
>device is not mutexed by anything bonding can acquire (so it can always
>change as soon as it's checked).

Sure, I'll give this a try, but I'm not sure this check applies in this case
as you can see from the trace link is up and carrier is on.

Thanks,
Emil