Re: [PATCH v2 net 2/4] igb: Fix passing 0 to ERR_PTR in igb_run_xdp()

[Maciej Fijalkowski <maciej.fijalkowski@intel.com>]

On Fri, Oct 18, 2024 at 10:37:32AM +0800, Yue Haibing wrote:
> igb_run_xdp() converts customed xdp action to a negative error code
> with the sk_buff pointer type which be checked with IS_ERR in
> igb_clean_rx_irq(). Remove this error pointer handing instead use plain
> int return value.
> 
> Fixes: 9cbc948b5a20 ("igb: add XDP support")
> Signed-off-by: Yue Haibing <yuehaibing@huawei.com>

Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>

> ---
>  drivers/net/ethernet/intel/igb/igb_main.c | 22 ++++++++--------------
>  1 file changed, 8 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
> index f1d088168723..50c23dfcf304 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -8584,9 +8584,8 @@ static struct sk_buff *igb_build_skb(struct igb_ring *rx_ring,
>  	return skb;
>  }
>  
> -static struct sk_buff *igb_run_xdp(struct igb_adapter *adapter,
> -				   struct igb_ring *rx_ring,
> -				   struct xdp_buff *xdp)
> +static int igb_run_xdp(struct igb_adapter *adapter, struct igb_ring *rx_ring,
> +		       struct xdp_buff *xdp)
>  {
>  	int err, result = IGB_XDP_PASS;
>  	struct bpf_prog *xdp_prog;
> @@ -8626,7 +8625,7 @@ static struct sk_buff *igb_run_xdp(struct igb_adapter *adapter,
>  		break;
>  	}
>  xdp_out:
> -	return ERR_PTR(-result);
> +	return result;
>  }
>  
>  static unsigned int igb_rx_frame_truesize(struct igb_ring *rx_ring,
> @@ -8752,10 +8751,6 @@ static bool igb_cleanup_headers(struct igb_ring *rx_ring,
>  				union e1000_adv_rx_desc *rx_desc,
>  				struct sk_buff *skb)
>  {
> -	/* XDP packets use error pointer so abort at this point */
> -	if (IS_ERR(skb))
> -		return true;
> -
>  	if (unlikely((igb_test_staterr(rx_desc,
>  				       E1000_RXDEXT_ERR_FRAME_ERR_MASK)))) {
>  		struct net_device *netdev = rx_ring->netdev;
> @@ -8879,6 +8874,7 @@ static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
>  	struct xdp_buff xdp;
>  	u32 frame_sz = 0;
>  	int rx_buf_pgcnt;
> +	int xdp_res = 0;
>  
>  	/* Frame size depend on rx_ring setup when PAGE_SIZE=4K */
>  #if (PAGE_SIZE < 8192)
> @@ -8936,12 +8932,10 @@ static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
>  			/* At larger PAGE_SIZE, frame_sz depend on len size */
>  			xdp.frame_sz = igb_rx_frame_truesize(rx_ring, size);
>  #endif
> -			skb = igb_run_xdp(adapter, rx_ring, &xdp);
> +			xdp_res = igb_run_xdp(adapter, rx_ring, &xdp);
>  		}
>  
> -		if (IS_ERR(skb)) {
> -			unsigned int xdp_res = -PTR_ERR(skb);
> -
> +		if (xdp_res) {
>  			if (xdp_res & (IGB_XDP_TX | IGB_XDP_REDIR)) {
>  				xdp_xmit |= xdp_res;
>  				igb_rx_buffer_flip(rx_ring, rx_buffer, size);
> @@ -8960,7 +8954,7 @@ static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
>  						&xdp, timestamp);
>  
>  		/* exit if we failed to retrieve a buffer */
> -		if (!skb) {
> +		if (!xdp_res && !skb) {
>  			rx_ring->rx_stats.alloc_failed++;
>  			rx_buffer->pagecnt_bias++;
>  			break;
> @@ -8974,7 +8968,7 @@ static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
>  			continue;
>  
>  		/* verify the packet layout is correct */
> -		if (igb_cleanup_headers(rx_ring, rx_desc, skb)) {
> +		if (xdp_res || igb_cleanup_headers(rx_ring, rx_desc, skb)) {
>  			skb = NULL;
>  			continue;
>  		}
> -- 
> 2.34.1
> 
>