From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E06A1C433E0 for ; Tue, 14 Jul 2020 10:02:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BC961221FD for ; Tue, 14 Jul 2020 10:02:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726782AbgGNKCk (ORCPT ); Tue, 14 Jul 2020 06:02:40 -0400 Received: from mx2.suse.de ([195.135.220.15]:54808 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725906AbgGNKCk (ORCPT ); Tue, 14 Jul 2020 06:02:40 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 39D44AD12; Tue, 14 Jul 2020 10:02:41 +0000 (UTC) Subject: Re: [PATCH] mm/hugetlb: hide nr_nodes in the internal of for_each_node_mask_to_[alloc|free] To: Wei Yang Cc: mike.kravetz@oracle.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20200714073404.84863-1-richard.weiyang@linux.alibaba.com> <807a1e32-926b-2882-740b-6484b8dca2b6@suse.cz> <20200714095713.GA86690@L-31X9LVDL-1304.local> From: Vlastimil Babka Message-ID: Date: Tue, 14 Jul 2020 12:02:38 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200714095713.GA86690@L-31X9LVDL-1304.local> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/14/20 11:57 AM, Wei Yang wrote: > On Tue, Jul 14, 2020 at 11:22:03AM +0200, Vlastimil Babka wrote: >>On 7/14/20 11:13 AM, Vlastimil Babka wrote: >>> On 7/14/20 9:34 AM, Wei Yang wrote: >>>> The second parameter of for_each_node_mask_to_[alloc|free] is a loop >>>> variant, which is not used outside of loop iteration. >>>> >>>> Let's hide this. >>>> >>>> Signed-off-by: Wei Yang >>>> --- >>>> mm/hugetlb.c | 38 ++++++++++++++++++++------------------ >>>> 1 file changed, 20 insertions(+), 18 deletions(-) >>>> >>>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >>>> index 57ece74e3aae..9c3d15fb317e 100644 >>>> --- a/mm/hugetlb.c >>>> +++ b/mm/hugetlb.c >>>> @@ -1196,17 +1196,19 @@ static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed) >>>> return nid; >>>> } >>>> >>>> -#define for_each_node_mask_to_alloc(hs, nr_nodes, node, mask) \ >>>> - for (nr_nodes = nodes_weight(*mask); \ >>>> - nr_nodes > 0 && \ >>>> +#define for_each_node_mask_to_alloc(hs, node, mask) \ >>>> + int __nr_nodes; \ >>>> + for (__nr_nodes = nodes_weight(*mask); \ >>> >>> The problem with this is that if I use the macro twice in the same block, this >>> will redefine __nr_nodes and fail to compile, no? >>> In that case it's better to avoid setting up this trap, IMHO. >> >>Ah, and it will also generate the following warning, if the use of for_each* >>macro is not the first thing after variable declarations, but there's another >>statement before: >> >>warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement] >> >>Instead we should switch to C99 and declare it as "for (int __nr_nodes" :P > > Hmm... I tried what you suggested, but compiler complains. > > 'for' loop initial declarations are only allowed in C99 or C11 mode Yes, by "we should switch to C99" I meant that the kernel kbuild system would need to switch. Not a trivial change... Without that, I don't see how your patch is possible to do safely.