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 B570AC001DE for ; Sun, 30 Jul 2023 14:01:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229592AbjG3OBY (ORCPT ); Sun, 30 Jul 2023 10:01:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37528 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229472AbjG3OBW (ORCPT ); Sun, 30 Jul 2023 10:01:22 -0400 Received: from out30-98.freemail.mail.aliyun.com (out30-98.freemail.mail.aliyun.com [115.124.30.98]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9A261B1 for ; Sun, 30 Jul 2023 07:01:18 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R151e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045176;MF=hsiangkao@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0VoVu1lI_1690725672; Received: from 192.168.75.41(mailfrom:hsiangkao@linux.alibaba.com fp:SMTPD_---0VoVu1lI_1690725672) by smtp.aliyun-inc.com; Sun, 30 Jul 2023 22:01:13 +0800 Message-ID: Date: Sun, 30 Jul 2023 22:01:11 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH v2] erofs: deprecate superblock checksum feature To: =?UTF-8?Q?Thomas_Wei=c3=9fschuh?= , Jingbo Xu Cc: chao@kernel.org, huyue2@coolpad.com, linux-erofs@lists.ozlabs.org, linux-kernel@vger.kernel.org, Karel Zak References: <20230717112703.60130-1-jefflexu@linux.alibaba.com> From: Gao Xiang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Thomas, On 2023/7/30 21:31, Thomas Weißschuh wrote: > On 2023-07-17 19:27:03+0800, Jingbo Xu wrote: >> Later we're going to try the self-contained image verification. >> The current superblock checksum feature has quite limited >> functionality, instead, merkle trees can provide better protection >> for image integrity. > > The crc32c checksum is also used by libblkid to gain more confidence > in its filesystem detection. > I guess a merkle tree would be much harder to implement. > > This is for example used by the mount(8) cli program to allow mounting > of devices without explicitly needing to specify a filesystem. > > Note: libblkid tests for EROFS_FEATURE_SB_CSUM so at least it won't > break when the checksum is removed. I'm not sure if we could switch EROFS_FEATURE_SB_CSUM to a simpler checksum instead (e.g. just sum each byte up if both EROFS_FEATURE_SB_CSUM and COMPAT_XATTR_FILTER bits are set, or ignore checksums completely at least in the kernel) if the better filesystem detection by using sb chksum is needed (not sure if other filesystems have sb chksum or just do magic comparsion)? The main problem here is after xattr name filter feature is added (xxhash is generally faster than crc32c), there could be two hard-depended hashing algorithms, this increases more dependency especially for embededed devices. Thanks, Gao Xiang