linux-ext4 - Re: [PATCH v2 0/6] fix error flag covered by journal recovery

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Date:   Fri, 10 Feb 2023 20:47:10 +0800
From:   Zhang Yi <yi.zhang@...wei.com>
To:     Jan Kara <jack@...e.cz>, Ye Bin <yebin@...weicloud.com>
CC:     <tytso@....edu>, <adilger.kernel@...ger.ca>,
        <linux-ext4@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Ye Bin <yebin10@...wei.com>
Subject: Re: [PATCH v2 0/6] fix error flag covered by journal recovery

On 2023/2/10 19:56, Jan Kara wrote:
> Hello!
> 
> On Fri 10-02-23 11:20:38, Ye Bin wrote:
>> From: Ye Bin <yebin10@...wei.com>
>>
>> Diff v2 vs v1:
>> Move call 'j_replay_prepare_callback' and 'j_replay_end_callback' from
>> ext4_load_journal() to jbd2_journal_recover().
>>
>> When do fault injection test, got issue as follows:
>> EXT4-fs (dm-5): warning: mounting fs with errors, running e2fsck is recommended
>> EXT4-fs (dm-5): Errors on filesystem, clearing orphan list.
>> EXT4-fs (dm-5): recovery complete
>> EXT4-fs (dm-5): mounted filesystem with ordered data mode. Opts: data_err=abort,errors=remount-ro
>>
>> EXT4-fs (dm-5): recovery complete
>> EXT4-fs (dm-5): mounted filesystem with ordered data mode. Opts: data_err=abort,errors=remount-ro
>>
>> Without do file system check, file system is clean when do second mount.
>> Theoretically, the kernel will not clear fs error flag. In errors=remount-ro
>> mode the last super block is commit directly. So super block in journal is
>> not uptodate. When do jounral recovery, the uptodate super block will be
>> covered by jounral data. If super block submit all failed after recover
>> journal, then file system error flag is lost. When do "fsck -a" couldn't
>> repair file system deeply.
>> To solve above issue we need to do extra handle when do super block journal
>> recovery.
> 
> Thanks for the patches. Looking through the patches, I think this is a bit
> of an overengineering for the problem at hand. The only thing that is
> really worth preserving so that it is not lost after journal replay is the
> error information. So in ext4_load_journal() I would just save that if
> EXT4_ERROR_FS is set in es->s_state before journal replay and restore it
> after journal replay. Sure if the superblock write during journal replay
> succeeds but the write restoring the error information fails, we will loose
> the error information but that is so unlikely in practice that I don't
> think it is really worth complicating the code for it. Also the only
> downside is we will loose the information there is some error in the
> filesystem - we'll soon find that out again anyway :).
> 

I think so, also add a error message if we failed to restoring the error
information, it could let us know what happened.

Thanks,
Yi.