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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D7BCEC433FE for ; Thu, 12 May 2022 17:10:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1356890AbiELRKo (ORCPT ); Thu, 12 May 2022 13:10:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33596 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1356888AbiELRKm (ORCPT ); Thu, 12 May 2022 13:10:42 -0400 Received: from mail.nfschina.com (unknown [IPv6:2400:dd01:100f:2:72e2:84ff:fe10:5f45]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id A036021B5 for ; Thu, 12 May 2022 10:10:40 -0700 (PDT) Received: from localhost (unknown [127.0.0.1]) by mail.nfschina.com (Postfix) with ESMTP id 35B681E80D6B; Fri, 13 May 2022 01:05:03 +0800 (CST) X-Virus-Scanned: amavisd-new at test.com Received: from mail.nfschina.com ([127.0.0.1]) by localhost (mail.nfschina.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id VMlKyIXNQHXH; Fri, 13 May 2022 01:05:00 +0800 (CST) Received: from [172.30.21.106] (unknown [180.167.10.98]) (Authenticated sender: liqiong@nfschina.com) by mail.nfschina.com (Postfix) with ESMTPA id AB25F1E80D22; Fri, 13 May 2022 01:05:00 +0800 (CST) Subject: Re: [PATCH] mm: change "char *bdi_unknown_name" to "char bdi_unknown_name[]" To: Muchun Song Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20220512082637.24649-1-liqiong@nfschina.com> From: liqiong Message-ID: Date: Fri, 13 May 2022 01:10:36 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=gbk Content-Transfer-Encoding: 8bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2022年05月12日 23:29, Muchun Song 写道: > On Thu, May 12, 2022 at 04:26:37PM +0800, liqiong wrote: >> "char bdi_unknown_nam[]" string form declares a single variable. >> It is better then "char *bdi_unknown_name" which creates two >> variables. >> > Sorry, I do not understand what you are saying here. Creating > two variables means what? > > Thanks. Hi there， The string form of "char *" creates two variables in the final assembly output, a static string, and a char pointer to the static string. Use "objdump -S -D *.o", can find out the static string occurring at "Contents of section .rodata". > >> Signed-off-by: liqiong >> --- >> mm/backing-dev.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/mm/backing-dev.c b/mm/backing-dev.c >> index 7176af65b103..4982ccc63536 100644 >> --- a/mm/backing-dev.c >> +++ b/mm/backing-dev.c >> @@ -20,7 +20,7 @@ struct backing_dev_info noop_backing_dev_info; >> EXPORT_SYMBOL_GPL(noop_backing_dev_info); >> >> static struct class *bdi_class; >> -static const char *bdi_unknown_name = "(unknown)"; >> +static const char bdi_unknown_name[] = "(unknown)"; >> >> /* >> * bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU >> -- >> 2.11.0 >> >> -- 李力琼 <13524287433> 上海市浦东新区海科路99号中科院上海高等研究院3号楼3楼