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=-13.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 1C0D6C433DF for ; Mon, 15 Jun 2020 08:38:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E6EC12067B for ; Mon, 15 Jun 2020 08:38:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728914AbgFOIiz (ORCPT ); Mon, 15 Jun 2020 04:38:55 -0400 Received: from szxga07-in.huawei.com ([45.249.212.35]:39154 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728603AbgFOIiz (ORCPT ); Mon, 15 Jun 2020 04:38:55 -0400 Received: from DGGEMS405-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id BC13CC896FF6F3D15053; Mon, 15 Jun 2020 16:38:47 +0800 (CST) Received: from [127.0.0.1] (10.166.213.7) by DGGEMS405-HUB.china.huawei.com (10.3.19.205) with Microsoft SMTP Server id 14.3.487.0; Mon, 15 Jun 2020 16:38:38 +0800 Subject: Re: [f2fs-dev] [PATCH] f2fs: Eliminate usage of uninitialized_var() macro To: Chao Yu , , , , CC: Kees Cook , References: <20200615040212.3681503-1-yanaijie@huawei.com> From: Jason Yan Message-ID: Date: Mon, 15 Jun 2020 16:38:37 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.4.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.166.213.7] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2020/6/15 16:26, Chao Yu 写道: > On 2020/6/15 12:02, Jason Yan wrote: >> This is an effort to eliminate the uninitialized_var() macro[1]. >> >> The use of this macro is the wrong solution because it forces off ANY >> analysis by the compiler for a given variable. It even masks "unused >> variable" warnings. >> >> Quoted from Linus[2]: >> >> "It's a horrible thing to use, in that it adds extra cruft to the >> source code, and then shuts up a compiler warning (even the _reliable_ >> warnings from gcc)." >> >> The gcc option "-Wmaybe-uninitialized" has been disabled and this change >> will not produce any warnnings even with "make W=1". >> >> [1] https://github.com/KSPP/linux/issues/81 >> [2] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/ >> >> Cc: Kees Cook >> Signed-off-by: Jason Yan >> --- >> fs/f2fs/data.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c >> index 326c63879ddc..e6ec61274d76 100644 >> --- a/fs/f2fs/data.c >> +++ b/fs/f2fs/data.c >> @@ -2856,7 +2856,7 @@ static int f2fs_write_cache_pages(struct address_space *mapping, >> }; >> #endif >> int nr_pages; >> - pgoff_t uninitialized_var(writeback_index); >> + pgoff_t writeback_index; > > I suggest to delete this variable directly, as we did for mm in > commit 28659cc8cc87 (mm/page-writeback.c: remove unused variable). > Good suggestion, I will send v2. Thanks, Jason > Thanks, > >> pgoff_t index; >> pgoff_t end; /* Inclusive */ >> pgoff_t done_index; >> > > . >