netdev - Re: [PATCHv2] net: ipv4: Use BUG_ON directly instead of a if condition followed by BUG

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Date:   Thu, 13 Sep 2018 12:28:59 +0200
From:   Simon Horman <simon.horman@...ronome.com>
To:     zhong jiang <zhongjiang@...wei.com>
Cc:     davem@...emloft.net, edumazet@...gle.com, kuznet@....inr.ac.ru,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2] net: ipv4: Use BUG_ON directly instead of a if
 condition followed by BUG

On Tue, Sep 11, 2018 at 09:13:13PM +0800, zhong jiang wrote:
> The if condition can be removed if we use BUG_ON directly.
> The issule is detected with the help of Coccinelle.
> 
> Signed-off-by: zhong jiang <zhongjiang@...wei.com>
> ---
>  net/ipv4/tcp_input.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> index 62508a2..526c05e 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -4934,8 +4934,8 @@ void tcp_rbtree_insert(struct rb_root *root, struct sk_buff *skb)
>  			BUG_ON(offset < 0);
>  			if (size > 0) {
>  				size = min(copy, size);
> -				if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
> -					BUG();
> +				BUG_ON(skb_copy_bits(skb, offset,
> +						     skb_put(nskb, size), size));

Perhaps things have changed but it doesn't seem desirable to me to use
BUG_ON with statements that have side-effects in case at some point BUG_ON
gets compiled out.

>  				TCP_SKB_CB(nskb)->end_seq += size;
>  				copy -= size;
>  				start += size;
> @@ -5327,8 +5327,8 @@ static void tcp_urg(struct sock *sk, struct sk_buff *skb, const struct tcphdr *t
>  		/* Is the urgent pointer pointing into this packet? */
>  		if (ptr < skb->len) {
>  			u8 tmp;
> -			if (skb_copy_bits(skb, ptr, &tmp, 1))
> -				BUG();
> +
> +			BUG_ON(skb_copy_bits(skb, ptr, &tmp, 1));
>  			tp->urg_data = TCP_URG_VALID | tmp;
>  			if (!sock_flag(sk, SOCK_DEAD))
>  				sk->sk_data_ready(sk);
> -- 
> 1.7.12.4
>