netdev - Re: [PATCH v2 net] net: microchip: sparx5: correctly free skb in xmit

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Date:   Thu, 1 Dec 2022 15:38:58 +0100
From:   Horatiu Vultur <horatiu.vultur@...rochip.com>
To:     Casper Andersson <casper.casan@...il.com>
CC:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Lars Povlsen <lars.povlsen@...rochip.com>,
        "Steen Hegelund" <Steen.Hegelund@...rochip.com>,
        Daniel Machon <daniel.machon@...rochip.com>,
        <UNGLinuxDriver@...rochip.com>,
        "Richard Cochran" <richardcochran@...il.com>,
        <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 net] net: microchip: sparx5: correctly free skb in xmit

The 11/29/2022 16:26, Casper Andersson wrote:
> 
> consume_skb on transmitted, kfree_skb on dropped, do not free on
> TX_BUSY.
> 
> Previously the xmit function could return -EBUSY without freeing, which
> supposedly is interpreted as a drop. And was using kfree on successfully
> transmitted packets.
> 
> sparx5_fdma_xmit and sparx5_inject returns error code, where -EBUSY
> indicates TX_BUSY and any other error code indicates dropped.
> 
> Fixes: f3cad2611a77 ("net: sparx5: add hostmode with phylink support")
> 
> Signed-off-by: Casper Andersson <casper.casan@...il.com>

Reviewed-by: Horatiu Vultur <horatiu.vultur@...rochip.com>

> ---
>  .../ethernet/microchip/sparx5/sparx5_fdma.c   |  2 +-
>  .../ethernet/microchip/sparx5/sparx5_packet.c | 41 +++++++++++--------
>  2 files changed, 25 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_fdma.c b/drivers/net/ethernet/microchip/sparx5/sparx5_fdma.c
> index 66360c8c5a38..141897dfe388 100644
> --- a/drivers/net/ethernet/microchip/sparx5/sparx5_fdma.c
> +++ b/drivers/net/ethernet/microchip/sparx5/sparx5_fdma.c
> @@ -317,7 +317,7 @@ int sparx5_fdma_xmit(struct sparx5 *sparx5, u32 *ifh, struct sk_buff *skb)
>         next_dcb_hw = sparx5_fdma_next_dcb(tx, tx->curr_entry);
>         db_hw = &next_dcb_hw->db[0];
>         if (!(db_hw->status & FDMA_DCB_STATUS_DONE))
> -               tx->dropped++;
> +               return -EINVAL;
>         db = list_first_entry(&tx->db_list, struct sparx5_db, list);
>         list_move_tail(&db->list, &tx->db_list);
>         next_dcb_hw->nextptr = FDMA_DCB_INVALID_DATA;
> diff --git a/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c b/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c
> index 83c16ca5b30f..6db6ac6a3bbc 100644
> --- a/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c
> +++ b/drivers/net/ethernet/microchip/sparx5/sparx5_packet.c
> @@ -234,9 +234,8 @@ netdev_tx_t sparx5_port_xmit_impl(struct sk_buff *skb, struct net_device *dev)
>         sparx5_set_port_ifh(ifh, port->portno);
> 
>         if (sparx5->ptp && skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) {
> -               ret = sparx5_ptp_txtstamp_request(port, skb);
> -               if (ret)
> -                       return ret;
> +               if (sparx5_ptp_txtstamp_request(port, skb) < 0)
> +                       return NETDEV_TX_BUSY;
> 
>                 sparx5_set_port_ifh_rew_op(ifh, SPARX5_SKB_CB(skb)->rew_op);
>                 sparx5_set_port_ifh_pdu_type(ifh, SPARX5_SKB_CB(skb)->pdu_type);
> @@ -250,23 +249,31 @@ netdev_tx_t sparx5_port_xmit_impl(struct sk_buff *skb, struct net_device *dev)
>         else
>                 ret = sparx5_inject(sparx5, ifh, skb, dev);
> 
> -       if (ret == NETDEV_TX_OK) {
> -               stats->tx_bytes += skb->len;
> -               stats->tx_packets++;
> +       if (ret == -EBUSY)
> +               goto busy;
> +       if (ret < 0)
> +               goto drop;
> 
> -               if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP &&
> -                   SPARX5_SKB_CB(skb)->rew_op == IFH_REW_OP_TWO_STEP_PTP)
> -                       return ret;
> +       stats->tx_bytes += skb->len;
> +       stats->tx_packets++;
> +       sparx5->tx.packets++;
> 
> -               dev_kfree_skb_any(skb);
> -       } else {
> -               stats->tx_dropped++;
> +       if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP &&
> +           SPARX5_SKB_CB(skb)->rew_op == IFH_REW_OP_TWO_STEP_PTP)
> +               return NETDEV_TX_OK;
> 
> -               if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP &&
> -                   SPARX5_SKB_CB(skb)->rew_op == IFH_REW_OP_TWO_STEP_PTP)
> -                       sparx5_ptp_txtstamp_release(port, skb);
> -       }
> -       return ret;
> +       dev_consume_skb_any(skb);
> +       return NETDEV_TX_OK;
> +drop:
> +       stats->tx_dropped++;
> +       sparx5->tx.dropped++;
> +       dev_kfree_skb_any(skb);
> +       return NETDEV_TX_OK;
> +busy:
> +       if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP &&
> +           SPARX5_SKB_CB(skb)->rew_op == IFH_REW_OP_TWO_STEP_PTP)
> +               sparx5_ptp_txtstamp_release(port, skb);
> +       return NETDEV_TX_BUSY;
>  }
> 
>  static enum hrtimer_restart sparx5_injection_timeout(struct hrtimer *tmr)
> --
> 2.34.1
> 

-- 
/Horatiu