linux-ext4 - Re: [PATCH RFC] jbd2: detect old record when do journal scan

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Date:   Tue, 23 Aug 2022 17:17:59 +0800
From:   yebin <yebin10@...wei.com>
To:     Jan Kara <jack@...e.cz>
CC:     <tytso@....edu>, <adilger.kernel@...ger.ca>,
        <linux-ext4@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC] jbd2: detect old record when do journal scan



On 2022/8/19 17:54, Jan Kara wrote:
> On Wed 10-08-22 09:34:42, Ye Bin wrote:
>> As https://github.com/tytso/e2fsprogs/issues/120 describe tune2fs do not update
>> j_tail_sequence when do journal recovery. This maybe recover old journal record,
>> then will lead to file system corruption.
>> To avoid file system corruption in this case, if detect current transaction's
>> commit time earlier than previous transaction's commit time when do journal
>> scan, just return error.
>>
>> Signed-off-by: Ye Bin <yebin10@...wei.com>
> Thanks for the patch! Let me see if I understand your concern right. You
> are concerned about the following scenario:
>
> 1) Kernel uses the filesystem, there's a crash.
> 2) E2fsprogs replays the journal but fails to update sb->s_sequence in the
> journal superblock.
> 3) Kernel mounts the fs again - however note that even if kernel skips
> recovery, it does scan the journal jbd2_journal_skip_recovery() and
> journal->j_transaction_sequence is set based on the last transaction found
> in the journal.
>
> So I don't think there is really possibility we will quickly reuse some
> transaction IDs and thus possibility of corruption on replay? Am I missing
> something?
>
> 								Honza
The file system corruption I encountered was indeed because e2fsprogs 
did not update
journal - > J_ transaction_ Sequence leads to replay the old transaction.
So I wonder whether the kernel should detect this kind of exception, at 
least when there
is a file system corruption, there are clues to trace.
>
>> ---
>>   fs/jbd2/recovery.c | 11 ++++++++++-
>>   1 file changed, 10 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/jbd2/recovery.c b/fs/jbd2/recovery.c
>> index f548479615c6..f3def21a96a5 100644
>> --- a/fs/jbd2/recovery.c
>> +++ b/fs/jbd2/recovery.c
>> @@ -812,8 +812,17 @@ static int do_one_pass(journal_t *journal,
>>   					break;
>>   				}
>>   			}
>> -			if (pass == PASS_SCAN)
>> +			if (pass == PASS_SCAN) {
>> +				if (commit_time < last_trans_commit_time) {
>> +					pr_err("JBD2: old journal record found "
>> +					       "in transaction %u\n",
>> +					       next_commit_ID);
>> +					err = -EFSBADCRC;
>> +					brelse(bh);
>> +					goto failed;
>> +				}
>>   				last_trans_commit_time = commit_time;
>> +			}
>>   			brelse(bh);
>>   			next_commit_ID++;
>>   			continue;
>> -- 
>> 2.31.1
>>