[PATCH 3.17 008/141] net: mv643xx_eth: reclaim TX skbs only when released by the HW

Greg Kroah-Hartman
2014-11-19T22:29:07Z

From: Karl Beldan <karl.beldan@rivierawaves.com>

[ Upstream commit 2c2a9cbd64387d6b70ac5db013e9bfe9412c7354 ]

ATM, txq_reclaim will dequeue and free an skb for each tx desc released
by the hw that has TX_LAST_DESC set. However, in case of TSO, each
hw desc embedding the last part of a segment has TX_LAST_DESC set,
losing the one-to-one 'last skb frag'/'TX_LAST_DESC set' correspondance,
which causes data corruption.

Fix this by checking TX_ENABLE_INTERRUPT instead of TX_LAST_DESC, and
warn when trying to dequeue from an empty txq (which can be symptomatic
of releasing skbs prematurely).

Fixes: 3ae8f4e0b98 ('net: mv643xx_eth: Implement software TSO')
Reported-by: Slawomir Gajzner <slawomir.gajzner@gmail.com>
Reported-by: Julien D'Ascenzio <jdascenzio@yahoo.fr>
Signed-off-by: Karl Beldan <karl.beldan@rivierawaves.com>
Cc: Ian Campbell <ijc@hellion.org.uk>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Cc: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/ethernet/marvell/mv643xx_eth.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)

--- a/drivers/net/ethernet/marvell/mv643xx_eth.c
+++ b/drivers/net/ethernet/marvell/mv643xx_eth.c
@@ -1047,7 +1047,6 @@ static int txq_reclaim(struct tx_queue *
int tx_index;
struct tx_desc *desc;
u32 cmd_sts;
- struct sk_buff *skb;

tx_index = txq->tx_used_desc;
desc = &txq->tx_desc_area[tx_index];
@@ -1066,19 +1065,22 @@ static int txq_reclaim(struct tx_queue *
reclaimed++;
txq->tx_desc_count--;

- skb = NULL;
- if (cmd_sts & TX_LAST_DESC)
- skb = __skb_dequeue(&txq->tx_skb);
+ if (!IS_TSO_HEADER(txq, desc->buf_ptr))
+ dma_unmap_single(mp->dev->dev.parent, desc->buf_ptr,
+ desc->byte_cnt, DMA_TO_DEVICE);
+
+ if (cmd_sts & TX_ENABLE_INTERRUPT) {
+ struct sk_buff *skb = __skb_dequeue(&txq->tx_skb);
+
+ if (!WARN_ON(!skb))
+ dev_kfree_skb(skb);
+ }

if (cmd_sts & ERROR_SUMMARY) {
netdev_info(mp->dev, "tx error\n");
mp->dev->stats.tx_errors++;
}

- if (!IS_TSO_HEADER(txq, desc->buf_ptr))
- dma_unmap_single(mp->dev->dev.parent, desc->buf_ptr,
- desc->byte_cnt, DMA_TO_DEVICE);
- dev_kfree_skb(skb);
}

__netif_tx_unlock_bh(nq);