[PATCH net] net/mlx4_en: fix spurious timestamping callbacks

[Eric Dumazet]

From: Eric Dumazet <eduma...@google.com>

When multiple skb are TX-completed in a row, we might incorrectly keep
a timestamp of a prior skb and cause extra work.

Fixes: ec693d47010e8 ("net/mlx4_en: Add HW timestamping (TS) support")
Signed-off-by: Eric Dumazet <eduma...@google.com>
Willem de Bruijn <will...@google.com>
---
 drivers/net/ethernet/mellanox/mlx4/en_tx.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_tx.c 
b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
index c0d7b7296236..a386f047c1af 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_tx.c
@@ -405,7 +405,6 @@ static bool mlx4_en_process_tx_cq(struct net_device *dev,
        u32 packets = 0;
        u32 bytes = 0;
        int factor = priv->cqe_factor;
-       u64 timestamp = 0;
        int done = 0;
        int budget = priv->tx_work_limit;
        u32 last_nr_txbb;
@@ -445,9 +444,12 @@ static bool mlx4_en_process_tx_cq(struct net_device *dev,
                new_index = be16_to_cpu(cqe->wqe_index) & size_mask;
 
                do {
+                       u64 timestamp = 0;
+
                        txbbs_skipped += last_nr_txbb;
                        ring_index = (ring_index + last_nr_txbb) & size_mask;
-                       if (ring->tx_info[ring_index].ts_requested)
+
+                       if (unlikely(ring->tx_info[ring_index].ts_requested))
                                timestamp = mlx4_en_get_cqe_ts(cqe);
 
                        /* free next descriptor */