netdev - Re: [PATCH 3/7] net: stmmac: Check for DMA mapping errors

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Date:   Mon, 27 Feb 2017 11:37:24 +0200
From:   Mikko Perttunen <cyndis@...si.fi>
To:     Thierry Reding <thierry.reding@...il.com>,
        "David S . Miller" <davem@...emloft.net>
Cc:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        Alexandre Courbot <gnurou@...il.com>,
        Jon Hunter <jonathanh@...dia.com>, netdev@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/7] net: stmmac: Check for DMA mapping errors

On 23.02.2017 19:24, Thierry Reding wrote:
> From: Thierry Reding <treding@...dia.com>
>
> When DMA mapping an SKB fragment, the mapping must be checked for
> errors, otherwise the DMA debug code will complain upon unmap.
>
> Signed-off-by: Thierry Reding <treding@...dia.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 6b7a5ce19589..d7387919bdb6 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -2072,6 +2072,8 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev)
>  		des = skb_frag_dma_map(priv->device, frag, 0,
>  				       skb_frag_size(frag),
>  				       DMA_TO_DEVICE);
> +		if (dma_mapping_error(priv->device, des))
> +			goto dma_map_err;

If this map fails, we should also unmap the previously mapped fragments 
and the separate mapping made using dma_map_single.

>
>  		stmmac_tso_allocator(priv, des, skb_frag_size(frag),
>  				     (i == nfrags - 1));
>