On Fri, Oct 6, 2017 at 4:57 PM, 吉藤英明 <hideaki.yoshif...@miraclelinux.com> wrote: > Hi, > > 2017-10-07 4:06 GMT+09:00 Wei Wang <wei...@google.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? >
I think it doesn't really matter whether rt6_dst_from_metrics_check() is inside the table lock or not. The code looks cleaner if we put it inside the if (ip6_hold_safe()) {} block because we don't want to do rt6_dst_from_metrics_check() if ip6_hold_safe() returns false. > --yoshfuji