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

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Date:   Wed, 25 May 2022 19:33:59 +0800
From:   yebin <yebin10@...wei.com>
To:     Ritesh Harjani <ritesh.list@...il.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 2022/5/25 15:51, 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/
>
> With lock changes added, feel free to add -
>
> Reviewed-by: Ritesh Harjani <ritesh.list@...il.com>
Thanks for your reply.
I think there should be no concurrent  modification at this time.
So there's no need to hold buffer lock.
Am I missing something?
>
>>
>> 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
>>
> .
>