2018-07-26 21:07 GMT+09:00 Björn Töpel <bjorn.to...@gmail.com>: > 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. >
I like this code style and I think it has performance benefit. So I will send v3 patch! Thanks! > Björn > >> > + else >> > + xa->zc_alloc->free(xa->zc_alloc, handle); >> > rcu_read_unlock(); >> > default: >> > /* Not possible, checked in xdp_rxq_info_reg_mem_model() */