netdev - [PATCH net] ibmvnic: device remove has higher precedence over reset

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Message-Id: <20210121062005.53271-1-ljp@linux.ibm.com>
Date:   Thu, 21 Jan 2021 00:20:05 -0600
From:   Lijun Pan <ljp@...ux.ibm.com>
To:     netdev@...r.kernel.org
Cc:     linuxppc-dev@...ts.ozlabs.org, drt@...ux.ibm.com,
        sukadev@...ux.ibm.com, mpe@...erman.id.au,
        julietk@...ux.vnet.ibm.com, benh@...nel.crashing.org,
        paulus@...ba.org, davem@...emloft.net, kuba@...nel.org,
        gregkh@...uxfoundation.org, kernel@...gutronix.de,
        Lijun Pan <ljp@...ux.ibm.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Subject: [PATCH net] ibmvnic: device remove has higher precedence over reset

Returning -EBUSY in ibmvnic_remove() does not actually hold the
removal procedure since driver core doesn't care for the return
value (see __device_release_driver() in drivers/base/dd.c
calling dev->bus->remove()) though vio_bus_remove
(in arch/powerpc/platforms/pseries/vio.c) records the
return value and passes it on. [1]

During the device removal precedure, we should not schedule
any new reset (ibmvnic_reset check for REMOVING and exit),
and should rely on the flush_work and flush_delayed_work
to complete the pending resets, specifically we need to
let __ibmvnic_reset() keep running while in REMOVING state since
flush_work and flush_delayed_work shall call __ibmvnic_reset finally.
So we skip the checking for REMOVING in __ibmvnic_reset.

[1] https://lore.kernel.org/linuxppc-dev/20210117101242.dpwayq6wdgfdzirl@pengutronix.de/T/#m48f5befd96bc9842ece2a3ad14f4c27747206a53
Reported-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Fixes: 7d7195a026ba ("ibmvnic: Do not process device remove during device reset")
Signed-off-by: Lijun Pan <ljp@...ux.ibm.com>
---
v1 versus RFC: 
  1/ articulate why remove the REMOVING checking in __ibmvnic_reset
  and why keep the current checking for REMOVING in ibmvnic_reset.
  2/ The locking issue mentioned by Uwe are being addressed separately 
     by	https://lists.openwall.net/netdev/2021/01/08/89
  3/ This patch does not have merge conflict with 2/

 drivers/net/ethernet/ibm/ibmvnic.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index aed985e08e8a..11f28fd03057 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -2235,8 +2235,7 @@ static void __ibmvnic_reset(struct work_struct *work)
 	while (rwi) {
 		spin_lock_irqsave(&adapter->state_lock, flags);
 
-		if (adapter->state == VNIC_REMOVING ||
-		    adapter->state == VNIC_REMOVED) {
+		if (adapter->state == VNIC_REMOVED) {
 			spin_unlock_irqrestore(&adapter->state_lock, flags);
 			kfree(rwi);
 			rc = EBUSY;
@@ -5372,11 +5371,6 @@ static int ibmvnic_remove(struct vio_dev *dev)
 	unsigned long flags;
 
 	spin_lock_irqsave(&adapter->state_lock, flags);
-	if (test_bit(0, &adapter->resetting)) {
-		spin_unlock_irqrestore(&adapter->state_lock, flags);
-		return -EBUSY;
-	}
-
 	adapter->state = VNIC_REMOVING;
 	spin_unlock_irqrestore(&adapter->state_lock, flags);
 
-- 
2.22.0