netdev - Re: [PATCH net-next] net/ipv6: prefer rcu_access_pointer() over rcu

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Message-ID: <2e26b615-65e9-96b3-d1fa-e72116320030@gmail.com>
Date:   Fri, 15 Feb 2019 15:13:06 -0700
From:   David Ahern <dsahern@...il.com>
To:     Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH net-next] net/ipv6: prefer rcu_access_pointer() over
 rcu_dereference()

On 2/15/19 10:15 AM, Paolo Abeni wrote:
> rt6_cache_allowed_for_pmtu() checks for rt->from presence, but
> it does not access the RCU protected pointer. We can use
> rcu_access_pointer() and clean-up the code a bit. No functional
> changes intended.
> 
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>
> ---
>  net/ipv6/route.c | 8 +-------
>  1 file changed, 1 insertion(+), 7 deletions(-)
> 
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index dc066fdf7e46..87a0561136dd 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -2277,14 +2277,8 @@ static void rt6_do_update_pmtu(struct rt6_info *rt, u32 mtu)
>  
>  static bool rt6_cache_allowed_for_pmtu(const struct rt6_info *rt)
>  {
> -	bool from_set;
> -
> -	rcu_read_lock();
> -	from_set = !!rcu_dereference(rt->from);
> -	rcu_read_unlock();
> -
>  	return !(rt->rt6i_flags & RTF_CACHE) &&
> -		(rt->rt6i_flags & RTF_PCPU || from_set);
> +		(rt->rt6i_flags & RTF_PCPU || rcu_access_pointer(rt->from));
>  }
>  
>  static void __ip6_rt_update_pmtu(struct dst_entry *dst, const struct sock *sk,
> 

good cleanup

Reviewed-by: David Ahern <dsahern@...il.com>