[PATCH] bonding/802.3ad: fix slave initialization states race

[Aleksei Zakharov <zaharov@selectel.ru>]

Once a while, one of 802.3ad slaves fails to initialize and hangs in
BOND_LINK_FAIL state. Commit 334031219a84 ("bonding/802.3ad: fix slave
link initialization transition states") checks slave->last_link_up. But
link can still hang in weird state.
After physical link comes up it sends first two LACPDU messages and
doesn't work properly after that. It doesn't send or receive LACPDU.
Once it happens, the only message in dmesg is:
bond1: link status up again after 0 ms for interface eth2

This behavior can be reproduced (not every time):
1. Set slave link down
2. Wait for 1-3 seconds
3. Set slave link up

The fix is to check slave->link before setting it to BOND_LINK_FAIL or
BOND_LINK_DOWN state. If got invalid Speed/Dupex values and link is in
BOND_LINK_UP state, mark it as BOND_LINK_FAIL; otherwise mark it as
BOND_LINK_DOWN.

Fixes: 334031219a84 ("bonding/802.3ad: fix slave link initialization
transition states")
Signed-off-by: Aleksei Zakharov <zakharov.a.g@yandex.ru>
---
 drivers/net/bonding/bond_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 931d9d935686..a28776d8f33f 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -3135,7 +3135,7 @@ static int bond_slave_netdev_event(unsigned long event,
 		 */
 		if (bond_update_speed_duplex(slave) &&
 		    BOND_MODE(bond) == BOND_MODE_8023AD) {
-			if (slave->last_link_up)
+			if (slave->link == BOND_LINK_UP)
 				slave->link = BOND_LINK_FAIL;
 			else
 				slave->link = BOND_LINK_DOWN;
-- 
2.17.1