linux-kernel - Re: [PATCH] sfc: ethtool: Refactor to remove fallthrough comments in case blocks

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Message-ID: <b6ad08bf-f1be-6aac-4f51-e97daa57d4aa@solarflare.com>
Date:   Thu, 12 Mar 2020 09:50:42 +0000
From:   Martin Habets <mhabets@...arflare.com>
To:     Joe Perches <joe@...ches.com>,
        Solarflare linux maintainers <linux-net-drivers@...arflare.com>,
        Edward Cree <ecree@...arflare.com>
CC:     "David S. Miller" <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sfc: ethtool: Refactor to remove fallthrough comments in
 case blocks

On 11/03/2020 02:41, Joe Perches wrote:
> Converting fallthrough comments to fallthrough; creates warnings
> in this code when compiled with gcc.
> 
> This code is overly complicated and reads rather better with a
> little refactoring and no fallthrough uses at all.
> 
> Remove the fallthrough comments and simplify the written source
> code while reducing the object code size.
> 
> Consolidate duplicated switch/case blocks for IPV4 and IPV6.
> 
> defconfig x86-64 with sfc:
> 
> $ size drivers/net/ethernet/sfc/ethtool.o*
>    text	   data	    bss	    dec	    hex	filename
>   10055	     12	      0	  10067	   2753	drivers/net/ethernet/sfc/ethtool.o.new
>   10135	     12	      0	  10147	   27a3	drivers/net/ethernet/sfc/ethtool.o.old
> 
> Signed-off-by: Joe Perches <joe@...ches.com>

Acked-by: Martin Habets <mhabets@...arflare.com>

> ---
>  drivers/net/ethernet/sfc/ethtool.c | 36 ++++++++++++++++++++----------------
>  1 file changed, 20 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/net/ethernet/sfc/ethtool.c b/drivers/net/ethernet/sfc/ethtool.c
> index 993b57..9a637cd 100644
> --- a/drivers/net/ethernet/sfc/ethtool.c
> +++ b/drivers/net/ethernet/sfc/ethtool.c
> @@ -582,6 +582,7 @@ efx_ethtool_get_rxnfc(struct net_device *net_dev,
>  
>  	case ETHTOOL_GRXFH: {
>  		struct efx_rss_context *ctx = &efx->rss_context;
> +		__u64 data;
>  
>  		mutex_lock(&efx->rss_lock);
>  		if (info->flow_type & FLOW_RSS && info->rss_context) {
> @@ -591,35 +592,38 @@ efx_ethtool_get_rxnfc(struct net_device *net_dev,
>  				goto out_unlock;
>  			}
>  		}
> -		info->data = 0;
> +
> +		data = 0;
>  		if (!efx_rss_active(ctx)) /* No RSS */
> -			goto out_unlock;
> +			goto out_setdata_unlock;
> +
>  		switch (info->flow_type & ~FLOW_RSS) {
>  		case UDP_V4_FLOW:
> -			if (ctx->rx_hash_udp_4tuple)
> -				/* fall through */
> -		case TCP_V4_FLOW:
> -				info->data |= RXH_L4_B_0_1 | RXH_L4_B_2_3;
> -			/* fall through */
> -		case SCTP_V4_FLOW:
> -		case AH_ESP_V4_FLOW:
> -		case IPV4_FLOW:
> -			info->data |= RXH_IP_SRC | RXH_IP_DST;
> -			break;
>  		case UDP_V6_FLOW:
>  			if (ctx->rx_hash_udp_4tuple)
> -				/* fall through */
> +				data = (RXH_L4_B_0_1 | RXH_L4_B_2_3 |
> +					RXH_IP_SRC | RXH_IP_DST);
> +			else
> +				data = RXH_IP_SRC | RXH_IP_DST;
> +			break;
> +		case TCP_V4_FLOW:
>  		case TCP_V6_FLOW:
> -				info->data |= RXH_L4_B_0_1 | RXH_L4_B_2_3;
> -			/* fall through */
> +			data = (RXH_L4_B_0_1 | RXH_L4_B_2_3 |
> +				RXH_IP_SRC | RXH_IP_DST);
> +			break;
> +		case SCTP_V4_FLOW:
>  		case SCTP_V6_FLOW:
> +		case AH_ESP_V4_FLOW:
>  		case AH_ESP_V6_FLOW:
> +		case IPV4_FLOW:
>  		case IPV6_FLOW:
> -			info->data |= RXH_IP_SRC | RXH_IP_DST;
> +			data = RXH_IP_SRC | RXH_IP_DST;
>  			break;
>  		default:
>  			break;
>  		}
> +out_setdata_unlock:
> +		info->data = data;
>  out_unlock:
>  		mutex_unlock(&efx->rss_lock);
>  		return rc;
> 
>