Re: [PATCH] IB/core: Suppress a sparse warning

[Yann Droneaud <ydroneaud-RlY5vtjFyJ3QT0dZR+AlfA@public.gmane.org>]

Hi,

Le lundi 10 mars 2014 à 15:26 +0100, Bart Van Assche a écrit :
> On 03/10/14 14:33, Yann Droneaud wrote:
> > Le lundi 10 mars 2014 à 13:22 +0100, Bart Van Assche a écrit :
> >> Suppress the following sparse warning:
> >> include/rdma/ib_addr.h:187:24: warning: cast removes address space of expression
> > 
> > You should explain why there's a warning here, and why is it safe to
> > cast. (I believe it's related to RCU domain ?)
> 
> Hello Yann,
> 
> Now that I've had a closer look at the code in include/rdma/ib_addr.h,
> that code probably isn't safe. How about the (untested) patch below ?
> 

Thanks for investigating.

I'm not an expert in RCU, but I believe it then miss the RCU annotations
around the RCU reader section (ensure correct ordering if I recall
correctly).

Cc: "Paul E. McKenney" <paulmck-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>

> diff --git a/include/rdma/ib_addr.h b/include/rdma/ib_addr.h
> index ce55906..5a416ac 100644
> --- a/include/rdma/ib_addr.h
> +++ b/include/rdma/ib_addr.h
> @@ -184,7 +184,7 @@ static inline void iboe_addr_get_sgid(struct rdma_dev_addr *dev_addr,
>  
>  	dev = dev_get_by_index(&init_net, dev_addr->bound_dev_if);
>  	if (dev) {

+		rcu_read_lock();

> -		ip4 = (struct in_device *)dev->ip_ptr;
> +		ip4 = __in_dev_get_rcu(dev);

>  		if (ip4 && ip4->ifa_list && ip4->ifa_list->ifa_address)
>  			ipv6_addr_set_v4mapped(ip4->ifa_list->ifa_address,
>  					       (struct in6_addr *)gid);

+		rcu_read_unlock();


Regards.

-- 
Yann Droneaud
OPTEYA


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