From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750976AbcIBE3W (ORCPT ); Fri, 2 Sep 2016 00:29:22 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:48665 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750791AbcIBE3V (ORCPT ); Fri, 2 Sep 2016 00:29:21 -0400 X-IBM-Helo: d23dlp01.au.ibm.com X-IBM-MailFrom: khandual@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org Date: Fri, 02 Sep 2016 09:59:12 +0530 From: Anshuman Khandual User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Andrew Morton CC: linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] mm: Move definition of 'zone_names' array into mmzone.h References: <1472613950-16867-1-git-send-email-khandual@linux.vnet.ibm.com> <20160831141033.8f617b6000bf129bbc40bda7@linux-foundation.org> In-Reply-To: <20160831141033.8f617b6000bf129bbc40bda7@linux-foundation.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16090204-0008-0000-0000-000000B90B3C X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16090204-0009-0000-0000-000007FAE645 Message-Id: <57C90018.70507@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-09-02_02:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1604210000 definitions=main-1609020058 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/01/2016 02:40 AM, Andrew Morton wrote: > On Wed, 31 Aug 2016 08:55:49 +0530 Anshuman Khandual wrote: > >> zone_names[] is used to identify any zone given it's index which >> can be used in many other places. So moving the definition into >> include/linux/mmzone.h for broader access. >> >> ... >> >> --- a/include/linux/mmzone.h >> +++ b/include/linux/mmzone.h >> @@ -341,6 +341,23 @@ enum zone_type { >> >> }; >> >> +static char * const zone_names[__MAX_NR_ZONES] = { >> +#ifdef CONFIG_ZONE_DMA >> + "DMA", >> +#endif >> +#ifdef CONFIG_ZONE_DMA32 >> + "DMA32", >> +#endif >> + "Normal", >> +#ifdef CONFIG_HIGHMEM >> + "HighMem", >> +#endif >> + "Movable", >> +#ifdef CONFIG_ZONE_DEVICE >> + "Device", >> +#endif >> +}; >> + >> #ifndef __GENERATING_BOUNDS_H >> >> struct zone { >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 3fbe73a..8e2261c 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -207,23 +207,6 @@ int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1] = { >> >> EXPORT_SYMBOL(totalram_pages); >> >> -static char * const zone_names[MAX_NR_ZONES] = { >> -#ifdef CONFIG_ZONE_DMA >> - "DMA", >> -#endif >> -#ifdef CONFIG_ZONE_DMA32 >> - "DMA32", >> -#endif >> - "Normal", >> -#ifdef CONFIG_HIGHMEM >> - "HighMem", >> -#endif >> - "Movable", >> -#ifdef CONFIG_ZONE_DEVICE >> - "Device", >> -#endif >> -}; >> - >> char * const migratetype_names[MIGRATE_TYPES] = { >> "Unmovable", >> "Movable", > > This is worrisome. On some (ancient) compilers, this will produce a > copy of that array into each compilation unit which includes mmzone.h. > > On smarter compilers, it will produce a copy of the array in each > compilation unit which *uses* zone_names[]. > > On even smarter compilers (and linkers!), only one copy of zone_names[] > will exist in vmlinux. > > I don't know if gcc is an "even smarter compiler" and I didn't check, > and I didn't check which gcc versions are even smarter. I'd rather not > have to ;) It is risky. > > So, let's just make it non-static and add a declaration into mmzone.h, > please. > I understand your concern, will change it.