2018-07-26 11:11 GMT+09:00 Jakub Kicinski <jakub.kicin...@netronome.com>:
> On Thu, 26 Jul 2018 00:09:50 +0900, Taehee Yoo wrote:
>> rhashtable_lookup() can return NULL. so that NULL pointer
>> check routine should be added.
>>
>> Fixes: 02b55e5657c3 ("xdp: add MEM_TYPE_ZERO_COPY")
>> Signed-off-by: Taehee Yoo <ap420...@gmail.com>
>> ---
>> V2 : add WARN_ON_ONCE when xa is NULL.
>>
>> net/core/xdp.c | 5 ++++-
>> 1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/net/core/xdp.c b/net/core/xdp.c
>> index 9d1f220..786fdbe 100644
>> --- a/net/core/xdp.c
>> +++ b/net/core/xdp.c
>> @@ -345,7 +345,10 @@ static void __xdp_return(void *data, struct
>> xdp_mem_info *mem, bool napi_direct,
>> rcu_read_lock();
>> /* mem->id is valid, checked in xdp_rxq_info_reg_mem_model() */
>> xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
>> - xa->zc_alloc->free(xa->zc_alloc, handle);
>> + if (!xa)
>> + WARN_ON_ONCE(1);
>
> nit: is compiler smart enough to figure out the fast path here?
> WARN_ON_ONCE() has the nice side effect of wrapping the condition in
> unlikely(). It could save us both LoC and potentially cycles to do:
>
> if (!WARN_ON_ONCE(!xa))
> xa->zc_alloc->free(xa->zc_alloc, handle);
>
> Although it admittedly looks a bit awkward. I'm not sure if we have
> some form of assert (i.e. positive check) in tree :S
>
Thank you for suggestion!
I like this code style and I think there is no problem because readers
are familiar with this code style.
I will send v3 patch!
Thanks!
>> + else
>> + xa->zc_alloc->free(xa->zc_alloc, handle);
>> rcu_read_unlock();
>> default:
>> /* Not possible, checked in xdp_rxq_info_reg_mem_model() */
