linux-ext4 - Re: [PATCH v3 1/2] ext4: commit super block if fs record error when journal record without error

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Date:   Thu, 16 Feb 2023 18:31:59 +0100
From:   Jan Kara <jack@...e.cz>
To:     Ye Bin <yebin@...weicloud.com>
Cc:     tytso@....edu, adilger.kernel@...ger.ca,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        jack@...e.cz, Ye Bin <yebin10@...wei.com>
Subject: Re: [PATCH v3 1/2] ext4: commit super block if fs record error when
 journal record without error

On Tue 14-02-23 10:29:04, Ye Bin wrote:
> From: Ye Bin <yebin10@...wei.com>
> 
> Now, 'es->s_state' maybe covered by recover journal. And journal errno
> maybe not recorded in journal sb as IO error. ext4_update_super() only
> update error information when 'sbi->s_add_error_count' large than zero.
> Then 'EXT4_ERROR_FS' flag maybe lost.
> To solve above issue commit error information after recover journal.
> 
> Signed-off-by: Ye Bin <yebin10@...wei.com>
> ---
>  fs/ext4/super.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index dc3907dff13a..b94754ba8556 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -5932,6 +5932,18 @@ static int ext4_load_journal(struct super_block *sb,
>  		goto err_out;
>  	}
>  
> +	if (unlikely(es->s_error_count && !jbd2_journal_errno(journal) &&
> +		     !(le16_to_cpu(es->s_state) & EXT4_ERROR_FS))) {
> +		EXT4_SB(sb)->s_mount_state |= EXT4_ERROR_FS;
> +		es->s_state |= cpu_to_le16(EXT4_ERROR_FS);
> +		err = ext4_commit_super(sb);
> +		if (err) {
> +			ext4_msg(sb, KERN_ERR,
> +				 "Failed to commit error information, please repair fs force!");
> +			goto err_out;
> +		}
> +	}
> +

Hum, I'm not sure I follow here. If journal replay has overwritten the
superblock (and thus the stored error info), then I'd expect
es->s_error_count got overwritten (possibly to 0) as well. And this is
actually relatively realistic scenario with errors=remount-ro behavior when
the first fs error happens.

What I intended in my original suggestion was to save es->s_error_count,
es->s_state & EXT4_ERROR_FS, es->s_first_error_*, es->s_last_error_* before
doing journal replay in ext4_load_journal() and then after journal replay
merge this info back to the superblock - if EXT4_ERROR_FS was set, set it
now as well, take max of old and new s_error_count, set s_first_error_* if
it is now unset, set s_last_error_* if stored timestamp is newer than
current timestamp.

Or am I overengineering it now? :)

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR