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 738C5C433EF for ; Fri, 27 May 2022 09:16:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245100AbiE0JQr (ORCPT ); Fri, 27 May 2022 05:16:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39700 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242737AbiE0JQq (ORCPT ); Fri, 27 May 2022 05:16:46 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F1BE36AA6B; Fri, 27 May 2022 02:16:44 -0700 (PDT) Received: from canpemm500010.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4L8fHT1mF3zRhS6; Fri, 27 May 2022 17:13:41 +0800 (CST) Received: from [10.174.178.185] (10.174.178.185) by canpemm500010.china.huawei.com (7.192.105.118) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Fri, 27 May 2022 17:16:42 +0800 Subject: Re: [PATCH -next] ext4: fix super block checksum incorrect after mount To: Jan Kara , Ritesh Harjani References: <20220525012904.1604737-1-yebin10@huawei.com> <20220525075123.rx5v7fe6ocn354wn@riteshh-domain> <20220525115400.kr3urpp3cf3hybvi@quack3.lan> CC: , , , From: yebin Message-ID: <629096FA.6030801@huawei.com> Date: Fri, 27 May 2022 17:16:42 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <20220525115400.kr3urpp3cf3hybvi@quack3.lan> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.178.185] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To canpemm500010.china.huawei.com (7.192.105.118) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On 2022/5/25 19:54, Jan Kara wrote: > On Wed 25-05-22 13:21:23, Ritesh Harjani wrote: >> On 22/05/25 09:29AM, Ye Bin wrote: >>> We got issue as follows: >>> [home]# mount /dev/sda test >>> EXT4-fs (sda): warning: mounting fs with errors, running e2fsck is recommended >>> [home]# dmesg >>> EXT4-fs (sda): warning: mounting fs with errors, running e2fsck is recommended >>> EXT4-fs (sda): Errors on filesystem, clearing orphan list. >>> EXT4-fs (sda): recovery complete >>> EXT4-fs (sda): mounted filesystem with ordered data mode. Quota mode: none. >>> [home]# debugfs /dev/sda >>> debugfs 1.46.5 (30-Dec-2021) >>> Checksum errors in superblock! Retrying... >>> >>> Reason is ext4_orphan_cleanup will reset ‘s_last_orphan’ but not update >>> super block checksum. >>> To solve above issue, defer update super block checksum after ext4_orphan_cleanup. >> I agree with the analysis. However after [1], I think all updates to superblock >> (including checksum computation) should be done within buffer lock. >> (lock_buffer(), unlock_buffer()). >> >> [1]: https://lore.kernel.org/all/20201216101844.22917-4-jack@suse.cz/ > So technically you're right that we should hold buffer lock all the time > from before we modify superblock buffer until we recompute the checksum (so > that we avoid writing superblock with mismatched checksum). To do this we'd > have to put checksum recomputations and superblock buffer locking into > ext4_orphan_cleanup() around setting of es->s_last_orphan (in three places > there AFAICS). A bit tedious but it would actually also fix a (theoretical) > race that someone decides to write out superblock after we set > s_last_orphan but before we set the checksum. > > Overall I'm not convinced this is really necessary so I'd be OK even with > what Ye suggested. That is IMHO better than mostly pointless locking just > around checksum computation because that just makes reader wonder why is it > needed... > > Honza Thanks for your reply. Does my patch need to be adjusted? >> With lock changes added, feel free to add - >> >> Reviewed-by: Ritesh Harjani >> >> >>> >>> Signed-off-by: Ye Bin >>> --- >>> fs/ext4/super.c | 16 ++++++++-------- >>> 1 file changed, 8 insertions(+), 8 deletions(-) >>> >>> diff --git a/fs/ext4/super.c b/fs/ext4/super.c >>> index f9a3ad683b4a..c47204029429 100644 >>> --- a/fs/ext4/super.c >>> +++ b/fs/ext4/super.c >>> @@ -5300,14 +5300,6 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb) >>> err = percpu_counter_init(&sbi->s_freeinodes_counter, freei, >>> GFP_KERNEL); >>> } >>> - /* >>> - * Update the checksum after updating free space/inode >>> - * counters. Otherwise the superblock can have an incorrect >>> - * checksum in the buffer cache until it is written out and >>> - * e2fsprogs programs trying to open a file system immediately >>> - * after it is mounted can fail. >>> - */ >>> - ext4_superblock_csum_set(sb); >>> if (!err) >>> err = percpu_counter_init(&sbi->s_dirs_counter, >>> ext4_count_dirs(sb), GFP_KERNEL); >>> @@ -5365,6 +5357,14 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb) >>> EXT4_SB(sb)->s_mount_state |= EXT4_ORPHAN_FS; >>> ext4_orphan_cleanup(sb, es); >>> EXT4_SB(sb)->s_mount_state &= ~EXT4_ORPHAN_FS; >>> + /* >>> + * Update the checksum after updating free space/inode counters and >>> + * ext4_orphan_cleanup. Otherwise the superblock can have an incorrect >>> + * checksum in the buffer cache until it is written out and >>> + * e2fsprogs programs trying to open a file system immediately >>> + * after it is mounted can fail. >>> + */ >>> + ext4_superblock_csum_set(sb); >>> if (needs_recovery) { >>> ext4_msg(sb, KERN_INFO, "recovery complete"); >>> err = ext4_mark_recovery_complete(sb, es); >>> -- >>> 2.31.1 >>>