Subject: Re: [PATCH] net: dont use __netdev_alloc_skb for bounce buffer

From: Stefan Bader <[email-masked]>
Date: Mon, 02 Jul 2012 22:03:42 +0200

I can confirm that, with the below patch applied, at least the b44 regression is
fixed and network is usable again.

-Stefan

On 02.07.2012 20:36, Eric Dumazet wrote:
> From: Eric Dumazet <[email-masked]>
> 
> commit a1c7fff7e1 (net: netdev_alloc_skb() use build_skb()) broke b44 on
> some 64bit machines.
> 
> It appears b44 and b43 use __netdev_alloc_skb() instead of alloc_skb()
> for their bounce buffers.
> 
> There is no need to add an extra NET_SKB_PAD reservation for bounce
> buffers :
> 
> - In TX path, NET_SKB_PAD is useless
> 
> - In RX path in b44, we force a copy of incoming frames if
>   GFP_DMA allocations were needed.
> 
> Reported-and-bisected-by: Stefan Bader <[email-masked]>
> Signed-off-by: Eric Dumazet <[email-masked]>
> ---
>  drivers/net/ethernet/broadcom/b44.c  |    4 ++--
>  drivers/net/wireless/b43legacy/dma.c |    2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/broadcom/b44.c b/drivers/net/ethernet/broadcom/b44.c
> index 46b8b7d..d09c6b5 100644
> --- a/drivers/net/ethernet/broadcom/b44.c
> +++ b/drivers/net/ethernet/broadcom/b44.c
> @@ -656,7 +656,7 @@ static int b44_alloc_rx_skb(struct b44 *bp, int src_idx, u32 dest_idx_unmasked)
>  			dma_unmap_single(bp->sdev->dma_dev, mapping,
>  					     RX_PKT_BUF_SZ, DMA_FROM_DEVICE);
>  		dev_kfree_skb_any(skb);
> -		skb = __netdev_alloc_skb(bp->dev, RX_PKT_BUF_SZ, GFP_ATOMIC|GFP_DMA);
> +		skb = alloc_skb(RX_PKT_BUF_SZ, GFP_ATOMIC | GFP_DMA);
>  		if (skb == NULL)
>  			return -ENOMEM;
>  		mapping = dma_map_single(bp->sdev->dma_dev, skb->data,
> @@ -967,7 +967,7 @@ static netdev_tx_t b44_start_xmit(struct sk_buff *skb, struct net_device *dev)
>  			dma_unmap_single(bp->sdev->dma_dev, mapping, len,
>  					     DMA_TO_DEVICE);
>  
> -		bounce_skb = __netdev_alloc_skb(dev, len, GFP_ATOMIC | GFP_DMA);
> +		bounce_skb = alloc_skb(len, GFP_ATOMIC | GFP_DMA);
>  		if (!bounce_skb)
>  			goto err_out;
>  
> diff --git a/drivers/net/wireless/b43legacy/dma.c b/drivers/net/wireless/b43legacy/dma.c
> index f1f8bd0..c8baf02 100644
> --- a/drivers/net/wireless/b43legacy/dma.c
> +++ b/drivers/net/wireless/b43legacy/dma.c
> @@ -1072,7 +1072,7 @@ static int dma_tx_fragment(struct b43legacy_dmaring *ring,
>  	meta->dmaaddr = map_descbuffer(ring, skb->data, skb->len, 1);
>  	/* create a bounce buffer in zone_dma on mapping failure. */
>  	if (b43legacy_dma_mapping_error(ring, meta->dmaaddr, skb->len, 1)) {
> -		bounce_skb = __dev_alloc_skb(skb->len, GFP_ATOMIC | GFP_DMA);
> +		bounce_skb = alloc_skb(skb->len, GFP_ATOMIC | GFP_DMA);
>  		if (!bounce_skb) {
>  			ring->current_slot = old_top_slot;
>  			ring->used_slots = old_used_slots;
> 
>