linux-kernel - Re: [PATCH bpf-next v7 4/5] igc: Refactor empty packet insertion into a reusable function

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Message-ID: <Z6Hi5G0ngTnb7lb/@boxer>
Date: Tue, 4 Feb 2025 10:50:28 +0100
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: Song Yoong Siang <yoong.siang.song@...el.com>
CC: "David S . Miller" <davem@...emloft.net>, Eric Dumazet
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Subject: Re: [PATCH bpf-next v7 4/5] igc: Refactor empty packet insertion
 into a reusable function

On Tue, Feb 04, 2025 at 08:49:06AM +0800, Song Yoong Siang wrote:
> Refactor the code for inserting an empty packet into a new function
> igc_insert_empty_packet(). This change extracts the logic for inserting
> an empty packet from igc_xmit_frame_ring() into a separate function,
> allowing it to be reused in future implementations, such as the XDP
> zero copy transmit function.
> 
> This patch introduces no functional changes.
> 
> Signed-off-by: Song Yoong Siang <yoong.siang.song@...el.com>
> ---
>  drivers/net/ethernet/intel/igc/igc_main.c | 42 ++++++++++++-----------
>  1 file changed, 22 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
> index 56a35d58e7a6..c3edd8bcf633 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -1566,6 +1566,26 @@ static bool igc_request_tx_tstamp(struct igc_adapter *adapter, struct sk_buff *s
>  	return false;
>  }
>  
> +static void igc_insert_empty_packet(struct igc_ring *tx_ring)
> +{
> +	struct igc_tx_buffer *empty_info;
> +	struct sk_buff *empty;
> +	void *data;
> +
> +	empty_info = &tx_ring->tx_buffer_info[tx_ring->next_to_use];
> +	empty = alloc_skb(IGC_EMPTY_FRAME_SIZE, GFP_ATOMIC);
> +	if (!empty)
> +		return;
> +
> +	data = skb_put(empty, IGC_EMPTY_FRAME_SIZE);
> +	memset(data, 0, IGC_EMPTY_FRAME_SIZE);
> +
> +	igc_tx_ctxtdesc(tx_ring, 0, false, 0, 0, 0);
> +
> +	if (igc_init_tx_empty_descriptor(tx_ring, empty, empty_info) < 0)
> +		dev_kfree_skb_any(empty);
> +}
> +
>  static netdev_tx_t igc_xmit_frame_ring(struct sk_buff *skb,
>  				       struct igc_ring *tx_ring)
>  {
> @@ -1603,26 +1623,8 @@ static netdev_tx_t igc_xmit_frame_ring(struct sk_buff *skb,
>  	skb->tstamp = ktime_set(0, 0);
>  	launch_time = igc_tx_launchtime(tx_ring, txtime, &first_flag, &insert_empty);
>  
> -	if (insert_empty) {
> -		struct igc_tx_buffer *empty_info;
> -		struct sk_buff *empty;
> -		void *data;
> -
> -		empty_info = &tx_ring->tx_buffer_info[tx_ring->next_to_use];
> -		empty = alloc_skb(IGC_EMPTY_FRAME_SIZE, GFP_ATOMIC);
> -		if (!empty)
> -			goto done;

shouldn't this be 'goto drop' from day 1? pretty weird to silently ignore
allocation error.

> -
> -		data = skb_put(empty, IGC_EMPTY_FRAME_SIZE);
> -		memset(data, 0, IGC_EMPTY_FRAME_SIZE);
> -
> -		igc_tx_ctxtdesc(tx_ring, 0, false, 0, 0, 0);
> -
> -		if (igc_init_tx_empty_descriptor(tx_ring,
> -						 empty,
> -						 empty_info) < 0)
> -			dev_kfree_skb_any(empty);

ditto

> -	}
> +	if (insert_empty)
> +		igc_insert_empty_packet(tx_ring);
>  
>  done:
>  	/* record the location of the first descriptor for this packet */
> -- 
> 2.34.1
>