netdev - Re: [PATCH net-next 11/16] ipv6: replace dst_hold() with dst_hold

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Date:   Sat, 7 Oct 2017 08:57:49 +0900
From:   吉藤英明 <hideaki.yoshifuji@...aclelinux.com>
To:     Wei Wang <weiwan@...gle.com>
Cc:     David Miller <davem@...emloft.net>,
        network dev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Martin KaFai Lau <kafai@...com>,
        吉藤英明 <hideaki.yoshifuji@...aclelinux.com>,
        YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>
Subject: Re: [PATCH net-next 11/16] ipv6: replace dst_hold() with
 dst_hold_safe() in routing code

Hi,

2017-10-07 4:06 GMT+09:00 Wei Wang <weiwan@...gle.com>:
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 941c062389d2..aeb349aea429 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
:
> @@ -1625,12 +1643,17 @@ struct rt6_info *ip6_pol_route(struct net *net, struct fib6_table *table,
>         if (rt_cache)
>                 rt = rt_cache;
>
> -       if (rt == net->ipv6.ip6_null_entry || (rt->rt6i_flags & RTF_CACHE)) {
> -               dst_use(&rt->dst, jiffies);
> +       if (rt == net->ipv6.ip6_null_entry) {
> +               read_unlock_bh(&table->tb6_lock);
> +               dst_hold(&rt->dst);
> +               trace_fib6_table_lookup(net, rt, table->tb6_id, fl6);
> +               return rt;
> +       } else if (rt->rt6i_flags & RTF_CACHE) {
> +               if (ip6_hold_safe(net, &rt, true)) {
> +                       dst_use_noref(&rt->dst, jiffies);
> +                       rt6_dst_from_metrics_check(rt);
> +               }
>                 read_unlock_bh(&table->tb6_lock);
> -
> -               rt6_dst_from_metrics_check(rt);
> -
>                 trace_fib6_table_lookup(net, rt, table->tb6_id, fl6);
>                 return rt;
>         } else if (unlikely((fl6->flowi6_flags & FLOWI_FLAG_KNOWN_NH) &&

Is it intended to move rt6_dst_from_metrics_check() inside the table lock?

--yoshfuji