netdev - Re: [PATCH net-next] net: ipv6: use the new fib6_nh_release_dsts helper in fib6_nh

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Date:   Mon, 29 Nov 2021 17:33:34 +0200
From:   Nikolay Aleksandrov <nikolay@...dia.com>
To:     Nikolay Aleksandrov <razor@...ckwall.org>, netdev@...r.kernel.org
Cc:     davem@...emloft.net, kuba@...nel.org, dsahern@...il.com
Subject: Re: [PATCH net-next] net: ipv6: use the new fib6_nh_release_dsts
 helper in fib6_nh_release

On 29/11/2021 14:09, Nikolay Aleksandrov wrote:
> From: Nikolay Aleksandrov <nikolay@...dia.com>
> 
> We can remove a bit of code duplication by reusing the new
> fib6_nh_release_dsts helper in fib6_nh_release. Their only difference is
> that fib6_nh_release's version doesn't use atomic operation to swap the
> pointers because it assumes the fib6_nh is no longer visible, while
> fib6_nh_release_dsts can be used anywhere.
> 
> Suggested-by: David Ahern <dsahern@...il.com>
> Signed-off-by: Nikolay Aleksandrov <nikolay@...dia.com>
> ---
>  net/ipv6/route.c | 19 ++-----------------
>  1 file changed, 2 insertions(+), 17 deletions(-)
> 
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 62f1e16eea2b..b44438b9a030 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -3656,24 +3656,9 @@ void fib6_nh_release(struct fib6_nh *fib6_nh)
>  
>  	rcu_read_unlock();
>  
> -	if (fib6_nh->rt6i_pcpu) {
> -		int cpu;
> -
> -		for_each_possible_cpu(cpu) {
> -			struct rt6_info **ppcpu_rt;
> -			struct rt6_info *pcpu_rt;
> -
> -			ppcpu_rt = per_cpu_ptr(fib6_nh->rt6i_pcpu, cpu);
> -			pcpu_rt = *ppcpu_rt;
> -			if (pcpu_rt) {
> -				dst_dev_put(&pcpu_rt->dst);
> -				dst_release(&pcpu_rt->dst);
> -				*ppcpu_rt = NULL;
> -			}
> -		}
> -
> +	fib6_nh_release_dsts(fib6_nh);
> +	if (fib6_nh->rt6i_pcpu)

Actually I can even drop the conditional here, free_percpu() is a noop
if called with NULL. Will respin in a few..