[PATCH 4.19 19/31] ibmvnic: Properly dispose of all skbs during a failover.

Greg Kroah-Hartman
2022-07-11T09:13:40Z

From: Rick Lindsley <ricklind@us.ibm.com>

[ Upstream commit 1b18f09d31cfa7148df15a7d5c5e0e86f105f7d1 ]

During a reset, there may have been transmits in flight that are no
longer valid and cannot be fulfilled. Resetting and clearing the
queues is insufficient; each skb also needs to be explicitly freed
so that upper levels are not left waiting for confirmation of a
transmit that will never happen. If this happens frequently enough,
the apparent backlog will cause TCP to begin "congestion control"
unnecessarily, culminating in permanently decreased throughput.

Fixes: d7c0ef36bde03 ("ibmvnic: Free and re-allocate scrqs when tx/rx scrqs change")
Tested-by: Nick Child <nnac123@linux.ibm.com>
Reviewed-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Rick Lindsley <ricklind@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/ibm/ibmvnic.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index ae3eea4a4213..1463cf4321a8 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -4691,6 +4691,15 @@ static int ibmvnic_reset_init(struct ibmvnic_adapter *adapter)
release_sub_crqs(adapter, 0);
rc = init_sub_crqs(adapter);
} else {
+ /* no need to reinitialize completely, but we do
+ * need to clean up transmits that were in flight
+ * when we processed the reset. Failure to do so
+ * will confound the upper layer, usually TCP, by
+ * creating the illusion of transmits that are
+ * awaiting completion.
+ */
+ clean_tx_pools(adapter);
+
rc = reset_sub_crq_queues(adapter);
}
} else {
--
2.35.1