From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751548AbdGZVtS (ORCPT ); Wed, 26 Jul 2017 17:49:18 -0400 Received: from mail-pg0-f43.google.com ([74.125.83.43]:37589 "EHLO mail-pg0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751009AbdGZVtQ (ORCPT ); Wed, 26 Jul 2017 17:49:16 -0400 Date: Wed, 26 Jul 2017 14:49:14 -0700 From: Matthias Kaehlcke To: Andrew Morton Cc: Johannes Weiner , Michal Hocko , Vladimir Davydov , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Doug Anderson Subject: Re: [PATCH] mm: memcontrol: Cast mismatched enum types passed to memcg state and event functions Message-ID: <20170726214914.GA84665@google.com> References: <20170726192356.18420-1-mka@chromium.org> <20170726142309.ac40faf5eb99568e6edb064c@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20170726142309.ac40faf5eb99568e6edb064c@linux-foundation.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org El Wed, Jul 26, 2017 at 02:23:09PM -0700 Andrew Morton ha dit: > On Wed, 26 Jul 2017 12:23:56 -0700 Matthias Kaehlcke wrote: > > > In multiple instances enum values of an incorrect type are passed to > > mod_memcg_state() and other memcg functions. Apparently this is > > intentional, however clang rightfully generates tons of warnings about > > the mismatched types. Cast the offending values to the type expected > > by the called function. The casts add noise, but this seems preferable > > over losing the typesafe interface or/and disabling the warning. > > > > ... > > > > --- a/include/linux/memcontrol.h > > +++ b/include/linux/memcontrol.h > > @@ -576,7 +576,7 @@ static inline void __mod_lruvec_state(struct lruvec *lruvec, > > if (mem_cgroup_disabled()) > > return; > > pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec); > > - __mod_memcg_state(pn->memcg, idx, val); > > + __mod_memcg_state(pn->memcg, (enum memcg_stat_item)idx, val); > > __this_cpu_add(pn->lruvec_stat->count[idx], val); > > } > > __mod_memcg_state()'s `idx' arg can be either enum memcg_stat_item or > enum memcg_stat_item. I think it would be better to just admit to > ourselves that __mod_memcg_state() is more general than it appears, and > change it to take `int idx'. I assume that this implicit cast of an > enum to an int will not trigger a clang warning? Sure, no warnings are raised for implicit casts from enum to int. __mod_memcg_state() is not the only function though, all these functions are called with conflicting types: memcg_page_state() __mod_memcg_state() mod_memcg_state() count_memcg_events() count_memcg_page_event() memcg_sum_events() Should we change all of them to reveice an int instead of an enum?