From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751753AbdGZVXM (ORCPT ); Wed, 26 Jul 2017 17:23:12 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:60508 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751622AbdGZVXL (ORCPT ); Wed, 26 Jul 2017 17:23:11 -0400 Date: Wed, 26 Jul 2017 14:23:09 -0700 From: Andrew Morton To: Matthias Kaehlcke 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: <20170726142309.ac40faf5eb99568e6edb064c@linux-foundation.org> In-Reply-To: <20170726192356.18420-1-mka@chromium.org> References: <20170726192356.18420-1-mka@chromium.org> X-Mailer: Sylpheed 3.4.1 (GTK+ 2.24.23; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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?