linux-kernel - Re: [PATCH -next] ext4: fix super block checksum incorrect after mount

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Message-ID: <20220525075123.rx5v7fe6ocn354wn@riteshh-domain>
Date:   Wed, 25 May 2022 13:21:23 +0530
From:   Ritesh Harjani <ritesh.list@...il.com>
To:     Ye Bin <yebin10@...wei.com>
Cc:     tytso@....edu, adilger.kernel@...ger.ca,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        jack@...e.cz
Subject: Re: [PATCH -next] ext4: fix super block checksum incorrect after
 mount

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/

With lock changes added, feel free to add -

Reviewed-by: Ritesh Harjani <ritesh.list@...il.com>


>
>
> Signed-off-by: Ye Bin <yebin10@...wei.com>
> ---
>  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
>