linux-kernel - Re: [PATCH v2 5/7] ext4: correct behavior under errors=remount-ro mode

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Message-ID: <v4k7pgwfeaa2drgkdpkyzl2qyemicnwyhvo3zcyn53frj3b2w5@3wpniv2edlfk>
Date: Tue, 11 Feb 2025 15:31:09 +0100
From: Jan Kara <jack@...e.cz>
To: libaokun@...weicloud.com
Cc: linux-ext4@...r.kernel.org, tytso@....edu, adilger.kernel@...ger.ca, 
	jack@...e.cz, linux-kernel@...r.kernel.org, yi.zhang@...wei.com, 
	yangerkun@...wei.com, Baokun Li <libaokun1@...wei.com>
Subject: Re: [PATCH v2 5/7] ext4: correct behavior under errors=remount-ro
 mode

On Wed 22-01-25 19:41:28, libaokun@...weicloud.com wrote:
> From: Baokun Li <libaokun1@...wei.com>
> 
> And after commit 95257987a638 ("ext4: drop EXT4_MF_FS_ABORTED flag") in
> v6.6-rc1, the EXT4_FLAGS_SHUTDOWN bit is set in ext4_handle_error() under
> errors=remount-ro mode. This causes the read to fail even when the error
> is triggered in errors=remount-ro mode.
> 
> To correct the behavior under errors=remount-ro, EXT4_FLAGS_SHUTDOWN is
> replaced by the newly introduced EXT4_FLAGS_EMERGENCY_RO. This new flag
> only prevents writes, matching the previous behavior with SB_RDONLY.
> 
> Fixes: 95257987a638 ("ext4: drop EXT4_MF_FS_ABORTED flag")
> Closes: https://lore.kernel.org/all/22d652f6-cb3c-43f5-b2fe-0a4bb6516a04@huawei.com/
> Suggested-by: Jan Kara <jack@...e.cz>
> Signed-off-by: Baokun Li <libaokun1@...wei.com>
> Reviewed-by: Zhang Yi <yi.zhang@...wei.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/ext4/super.c | 19 ++++++++-----------
>  1 file changed, 8 insertions(+), 11 deletions(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index d8116c9c2bd0..098e62727aec 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -708,11 +708,8 @@ static void ext4_handle_error(struct super_block *sb, bool force_ro, int error,
>  	if (test_opt(sb, WARN_ON_ERROR))
>  		WARN_ON_ONCE(1);
>  
> -	if (!continue_fs && !sb_rdonly(sb)) {
> -		set_bit(EXT4_FLAGS_SHUTDOWN, &EXT4_SB(sb)->s_ext4_flags);
> -		if (journal)
> -			jbd2_journal_abort(journal, -EIO);
> -	}
> +	if (!continue_fs && !ext4_emergency_ro(sb) && journal)
> +		jbd2_journal_abort(journal, -EIO);
>  
>  	if (!bdev_read_only(sb->s_bdev)) {
>  		save_error_info(sb, error, ino, block, func, line);
> @@ -738,17 +735,17 @@ static void ext4_handle_error(struct super_block *sb, bool force_ro, int error,
>  			sb->s_id);
>  	}
>  
> -	if (sb_rdonly(sb) || continue_fs)
> +	if (ext4_emergency_ro(sb) || continue_fs)
>  		return;
>  
>  	ext4_msg(sb, KERN_CRIT, "Remounting filesystem read-only");
>  	/*
> -	 * EXT4_FLAGS_SHUTDOWN was set which stops all filesystem
> -	 * modifications. We don't set SB_RDONLY because that requires
> -	 * sb->s_umount semaphore and setting it without proper remount
> -	 * procedure is confusing code such as freeze_super() leading to
> -	 * deadlocks and other problems.
> +	 * We don't set SB_RDONLY because that requires sb->s_umount
> +	 * semaphore and setting it without proper remount procedure is
> +	 * confusing code such as freeze_super() leading to deadlocks
> +	 * and other problems.
>  	 */
> +	set_bit(EXT4_FLAGS_EMERGENCY_RO, &EXT4_SB(sb)->s_ext4_flags);
>  }
>  
>  static void update_super_work(struct work_struct *work)
> -- 
> 2.39.2
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR