Den tors 26 juli 2018 kl 04:14 skrev 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
>
I'm kind of in favor of this ^^^. Hopefully, Taehee is ok with another spin.
Björn
> > + else
> > + xa->zc_alloc->free(xa->zc_alloc, handle);
> > rcu_read_unlock();
> > default:
> > /* Not possible, checked in xdp_rxq_info_reg_mem_model() */
