From 86b61a5f2e39bbee254aa4d2c5445059c7656f98 Mon Sep 17 00:00:00 2001
From: Thomas Falcon <tlfalcon@linux.vnet.ibm.com>
Date: Fri, 16 Mar 2018 20:00:29 -0500
Subject: [PATCH] ibmvnic: Improve TX buffer accounting

References: bsc#1085224
patch-mainline: v4.17-rc1
Git-commit: 86b61a5f2e39bbee254aa4d2c5445059c7656f98

Improve TX pool buffer accounting to prevent the producer
index from overruning the consumer. First, set the next free
index to an invalid value if it is in use. If next buffer
to be consumed is in use, drop the packet.

Finally, if the transmit fails for some other reason, roll
back the consumer index and set the free map entry to its original
value. This should also be done if the DMA map fails.

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 | 30 +++++++++++++++++++++---------
 1 file changed, 21 insertions(+), 9 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index 672e9221d4a5..af6f8193cb67 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -1426,6 +1426,16 @@ static int ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 
 	index = tx_pool->free_map[tx_pool->consumer_index];
 
+	if (index == IBMVNIC_INVALID_MAP) {
+		dev_kfree_skb_any(skb);
+		tx_send_failed++;
+		tx_dropped++;
+		ret = NETDEV_TX_OK;
+		goto out;
+	}
+
+	tx_pool->free_map[tx_pool->consumer_index] = IBMVNIC_INVALID_MAP;
+
 	offset = index * tx_pool->buf_size;
 	dst = tx_pool->long_term_buff.buff + offset;
 	memset(dst, 0, tx_pool->buf_size);
@@ -1522,7 +1532,7 @@ static int ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 			tx_map_failed++;
 			tx_dropped++;
 			ret = NETDEV_TX_OK;
-			goto out;
+			goto tx_err_out;
 		}
 		lpar_rc = send_subcrq_indirect(adapter, handle_array[queue_num],
 					       (u64)tx_buff->indir_dma,
@@ -1534,13 +1544,6 @@ static int ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 	}
 	if (lpar_rc != H_SUCCESS) {
 		dev_err(dev, "tx failed with code %ld\n", lpar_rc);
-
-		if (tx_pool->consumer_index == 0)
-			tx_pool->consumer_index =
-				tx_pool->num_buffers - 1;
-		else
-			tx_pool->consumer_index--;
-
 		dev_kfree_skb_any(skb);
 		tx_buff->skb = NULL;
 
@@ -1556,7 +1559,7 @@ static int ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 		tx_send_failed++;
 		tx_dropped++;
 		ret = NETDEV_TX_OK;
-		goto out;
+		goto tx_err_out;
 	}
 
 	if (atomic_add_return(num_entries, &tx_scrq->used)
@@ -1569,7 +1572,16 @@ static int ibmvnic_xmit(struct sk_buff *skb, struct net_device *netdev)
 	tx_bytes += skb->len;
 	txq->trans_start = jiffies;
 	ret = NETDEV_TX_OK;
+	goto out;
 
+tx_err_out:
+	/* roll back consumer index and map array*/
+	if (tx_pool->consumer_index == 0)
+		tx_pool->consumer_index =
+			tx_pool->num_buffers - 1;
+	else
+		tx_pool->consumer_index--;
+	tx_pool->free_map[tx_pool->consumer_index] = index;
 out:
 	netdev->stats.tx_dropped += tx_dropped;
 	netdev->stats.tx_bytes += tx_bytes;
-- 
2.13.6