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=-20.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,NICE_REPLY_A,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 BF26CC433E0 for ; Mon, 1 Mar 2021 03:17:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8ABD464DFF for ; Mon, 1 Mar 2021 03:17:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231229AbhCADR4 (ORCPT ); Sun, 28 Feb 2021 22:17:56 -0500 Received: from szxga05-in.huawei.com ([45.249.212.191]:13024 "EHLO szxga05-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231411AbhCADRz (ORCPT ); Sun, 28 Feb 2021 22:17:55 -0500 Received: from DGGEMS402-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4DplkJ3SWWzMgGy; Mon, 1 Mar 2021 11:15:04 +0800 (CST) Received: from [10.136.110.154] (10.136.110.154) by smtp.huawei.com (10.3.19.202) with Microsoft SMTP Server (TLS) id 14.3.498.0; Mon, 1 Mar 2021 11:17:07 +0800 Subject: Re: [f2fs-dev] [PATCH][next] f2fs: Replace one-element array with flexible-array member To: Jaegeuk Kim CC: "Gustavo A. R. Silva" , Chao Yu , , , References: <20210224190313.GA144040@embeddedor> From: Chao Yu Message-ID: Date: Mon, 1 Mar 2021 11:17:07 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.136.110.154] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org On 2021/2/28 13:00, Jaegeuk Kim wrote: > On 02/25, Chao Yu wrote: >> Hello, Gustavo, >> >> On 2021/2/25 3:03, Gustavo A. R. Silva wrote: >>> There is a regular need in the kernel to provide a way to declare having >>> a dynamically sized set of trailing elements in a structure. Kernel code >>> should always use “flexible array members”[1] for these cases. The older >>> style of one-element or zero-length arrays should no longer be used[2]. >> >> I proposal to do the similar cleanup, and I've no objection on doing this. >> >> https://lore.kernel.org/patchwork/patch/869440/ >> >> Let's ask for Jaegeuk' opinion. > > Merged, thanks. > This looks better reason than code readability. :) Agreed. Reviewed-by: Chao Yu Thanks, > >> >>> >>> Refactor the code according to the use of a flexible-array member in >>> struct f2fs_checkpoint, instead of a one-element arrays. >>> >>> Notice that a temporary pointer to void '*tmp_ptr' was used in order to >>> fix the following errors when using a flexible array instead of a one >>> element array in struct f2fs_checkpoint: >>> >>> CC [M] fs/f2fs/dir.o >>> In file included from fs/f2fs/dir.c:13: >>> fs/f2fs/f2fs.h: In function ‘__bitmap_ptr’: >>> fs/f2fs/f2fs.h:2227:40: error: invalid use of flexible array member >>> 2227 | return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32); >>> | ^ >>> fs/f2fs/f2fs.h:2227:49: error: invalid use of flexible array member >>> 2227 | return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32); >>> | ^ >>> fs/f2fs/f2fs.h:2238:40: error: invalid use of flexible array member >>> 2238 | return &ckpt->sit_nat_version_bitmap + offset; >>> | ^ >>> make[2]: *** [scripts/Makefile.build:287: fs/f2fs/dir.o] Error 1 >>> make[1]: *** [scripts/Makefile.build:530: fs/f2fs] Error 2 >>> make: *** [Makefile:1819: fs] Error 2 >>> >>> [1] https://en.wikipedia.org/wiki/Flexible_array_member >>> [2] https://www.kernel.org/doc/html/v5.9/process/deprecated.html#zero-length-and-one-element-arrays >>> >>> Link: https://github.com/KSPP/linux/issues/79 >>> Build-tested-by: kernel test robot >>> Link: https://lore.kernel.org/lkml/603647e4.DeEFbl4eqljuwAUe%25lkp@intel.com/ >>> Signed-off-by: Gustavo A. R. Silva >>> --- >>> fs/f2fs/f2fs.h | 5 +++-- >>> include/linux/f2fs_fs.h | 2 +- >>> 2 files changed, 4 insertions(+), 3 deletions(-) >>> >>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h >>> index e2d302ae3a46..3f5cb097c30f 100644 >>> --- a/fs/f2fs/f2fs.h >>> +++ b/fs/f2fs/f2fs.h >>> @@ -2215,6 +2215,7 @@ static inline block_t __cp_payload(struct f2fs_sb_info *sbi) >>> static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag) >>> { >>> struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi); >>> + void *tmp_ptr = &ckpt->sit_nat_version_bitmap; >>> int offset; >>> if (is_set_ckpt_flags(sbi, CP_LARGE_NAT_BITMAP_FLAG)) { >>> @@ -2224,7 +2225,7 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag) >>> * if large_nat_bitmap feature is enabled, leave checksum >>> * protection for all nat/sit bitmaps. >>> */ >>> - return &ckpt->sit_nat_version_bitmap + offset + sizeof(__le32); >>> + return tmp_ptr + offset + sizeof(__le32); >>> } >>> if (__cp_payload(sbi) > 0) { >>> @@ -2235,7 +2236,7 @@ static inline void *__bitmap_ptr(struct f2fs_sb_info *sbi, int flag) >>> } else { >>> offset = (flag == NAT_BITMAP) ? >>> le32_to_cpu(ckpt->sit_ver_bitmap_bytesize) : 0; >>> - return &ckpt->sit_nat_version_bitmap + offset; >>> + return tmp_ptr + offset; >>> } >>> } >>> diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h >>> index c6cc0a566ef5..5487a80617a3 100644 >>> --- a/include/linux/f2fs_fs.h >>> +++ b/include/linux/f2fs_fs.h >>> @@ -168,7 +168,7 @@ struct f2fs_checkpoint { >>> unsigned char alloc_type[MAX_ACTIVE_LOGS]; >>> /* SIT and NAT version bitmap */ >>> - unsigned char sit_nat_version_bitmap[1]; >>> + unsigned char sit_nat_version_bitmap[]; >>> } __packed; >>> #define CP_CHKSUM_OFFSET 4092 /* default chksum offset in checkpoint */ >>> > . >