From ecba616e041e64840d14e294b089ca355614b7fb Mon Sep 17 00:00:00 2001
From: Thomas Falcon <tlfalcon@linux.vnet.ibm.com>
Date: Mon, 26 Feb 2018 18:10:55 -0600
Subject: [PATCH] ibmvnic: Fix TX descriptor tracking again

References: bsc#1082993
Patch-mainline: v4.17-rc1
Git-commit: ecba616e041e64840d14e294b089ca355614b7fb

Sorry, the previous change introduced a race condition between
transmit completion processing and tracking TX descriptors. If a
completion is received before the number of descriptors is logged,
the number of descriptors will be add but not removed. After enough
times, this could halt the transmit queue forever.

Log the number of descriptors used by a transmit before sending.
I stress tested the fix on two different systems running over the
weekend without any issues.

Signed-off-by: Thomas Falcon <tlfalcon@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
 drivers/net/ethernet/ibm/ibmvnic.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index 5a86a916492c..32ee202de13a 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -1482,6 +1482,7 @@ static int ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 	if ((*hdrs >> 7) & 1) {
 		build_hdr_descs_arr(tx_buff, &num_entries, *hdrs);
 		tx_crq.v1.n_crq_elem = num_entries;
+		tx_buff->num_entries = num_entries;
 		tx_buff->indir_arr[0] = tx_crq;
 		tx_buff->indir_dma = dma_map_single(dev, tx_buff->indir_arr,
 						    sizeof(tx_buff->indir_arr),
@@ -1500,6 +1501,7 @@ static int ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 					       (u64)tx_buff->indir_dma,
 					       (u64)num_entries);
 	} else {
+		tx_buff->num_entries = num_entries;
 		lpar_rc = send_subcrq(adapter, handle_array[queue_num],
 				      &tx_crq);
 	}
@@ -1536,7 +1538,6 @@ static int ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 		netif_stop_subqueue(netdev, queue_num);
 	}
 
-	tx_buff->num_entries = num_entries;
 	tx_packets++;
 	tx_bytes += skb->len;
 	txq->trans_start = jiffies;
-- 
2.13.6