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Date:   Tue, 3 Dec 2019 22:05:55 +0800
From:   "zhangyi (F)" <yi.zhang@...wei.com>
To:     Jan Kara <jack@...e.cz>
CC:     <linux-ext4@...r.kernel.org>, <jack@...e.com>, <tytso@....edu>,
        <adilger.kernel@...ger.ca>, <liangyun2@...wei.com>,
        <luoshijie1@...wei.com>
Subject: Re: [PATCH v2 3/4] Partially revert "ext4: pass -ESHUTDOWN code to
 jbd2 layer"

On 2019/12/3 20:23, Jan Kara wrote:
> On Tue 03-12-19 17:27:55, zhangyi (F) wrote:
>> This partially reverts commit fb7c02445c497943e7296cd3deee04422b63acb8.
>>
>> Commit fb7c02445c49 ("ext4: pass -ESHUTDOWN code to jbd2 layer") want to
>> allow jbd2 layer to distinguish shutdown journal abort from other error
>> cases, but this patch seems unnecessary because we distinguished those
>> cases well through a zero errno parameter when shutting down, thus the
>> jbd2 aborting peocess will not record the errno. So partially reverts
>> this commit and keep the proper locking.
>>
>> Signed-off-by: zhangyi (F) <yi.zhang@...wei.com>
> 
> Ted has written this so he'll have the definitive answer but I think the idea
> of ESHUTDOWN is that if the filesystem was shutdown, we want ESHUTDOWN to
> be recorded in the journal sb and not some other error. That's why there's
> logic in __journal_abort_soft() making sure that ESHUTDOWN takes precedence
> over any other error. Because it can happen that after EXT4_FLAGS_SHUTDOWN
> flag is set, some other place records different error in journal
> superblock before we get to jbd2_journal_abort() and record ESHUTDOWN...
> 

Thanks for the explanation, I understand now, we need to prevent record
errno in journal superblock and keep the filesystem just as it is after
EXT4_FLAGS_SHUTDOWN is set. So there is a bug now because it only
overwrite errno if it was 0, I will fix it together.

Thanks,
Yi

> 
>> ---
>>  fs/ext4/ioctl.c   |  4 ++--
>>  fs/jbd2/journal.c | 22 +++++++---------------
>>  2 files changed, 9 insertions(+), 17 deletions(-)
>>
>> diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
>> index 0b7f316fd30f..f99eeba5767d 100644
>> --- a/fs/ext4/ioctl.c
>> +++ b/fs/ext4/ioctl.c
>> @@ -597,13 +597,13 @@ static int ext4_shutdown(struct super_block *sb, unsigned long arg)
>>  		set_bit(EXT4_FLAGS_SHUTDOWN, &sbi->s_ext4_flags);
>>  		if (sbi->s_journal && !is_journal_aborted(sbi->s_journal)) {
>>  			(void) ext4_force_commit(sb);
>> -			jbd2_journal_abort(sbi->s_journal, -ESHUTDOWN);
>> +			jbd2_journal_abort(sbi->s_journal, 0);
>>  		}
>>  		break;
>>  	case EXT4_GOING_FLAGS_NOLOGFLUSH:
>>  		set_bit(EXT4_FLAGS_SHUTDOWN, &sbi->s_ext4_flags);
>>  		if (sbi->s_journal && !is_journal_aborted(sbi->s_journal))
>> -			jbd2_journal_abort(sbi->s_journal, -ESHUTDOWN);
>> +			jbd2_journal_abort(sbi->s_journal, 0);
>>  		break;
>>  	default:
>>  		return -EINVAL;
>> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
>> index a78b07841080..f3f9e0b994ef 100644
>> --- a/fs/jbd2/journal.c
>> +++ b/fs/jbd2/journal.c
>> @@ -1475,14 +1475,11 @@ static void jbd2_mark_journal_empty(journal_t *journal, int write_op)
>>  void jbd2_journal_update_sb_errno(journal_t *journal)
>>  {
>>  	journal_superblock_t *sb = journal->j_superblock;
>> -	int errcode;
>>  
>>  	lock_buffer(journal->j_sb_buffer);
>> -	errcode = journal->j_errno;
>> -	if (errcode == -ESHUTDOWN)
>> -		errcode = 0;
>> -	jbd_debug(1, "JBD2: updating superblock error (errno %d)\n", errcode);
>> -	sb->s_errno    = cpu_to_be32(errcode);
>> +	jbd_debug(1, "JBD2: updating superblock error (errno %d)\n",
>> +		  journal->j_errno);
>> +	sb->s_errno = cpu_to_be32(journal->j_errno);
>>  
>>  	jbd2_write_superblock(journal, REQ_SYNC | REQ_FUA);
>>  }
>> @@ -2100,20 +2097,15 @@ void __jbd2_journal_abort_hard(journal_t *journal)
>>   * but don't do any other IO. */
>>  static void __journal_abort_soft (journal_t *journal, int errno)
>>  {
>> -	int old_errno;
>> -
>>  	write_lock(&journal->j_state_lock);
>> -	old_errno = journal->j_errno;
>> -	if (!journal->j_errno || errno == -ESHUTDOWN)
>> -		journal->j_errno = errno;
>> -
>>  	if (journal->j_flags & JBD2_ABORT) {
>>  		write_unlock(&journal->j_state_lock);
>> -		if (!old_errno && old_errno != -ESHUTDOWN &&
>> -		    errno == -ESHUTDOWN)
>> -			jbd2_journal_update_sb_errno(journal);
>>  		return;
>>  	}
>> +
>> +	if (!journal->j_errno)
>> +		journal->j_errno = errno;
>> +
>>  	write_unlock(&journal->j_state_lock);
>>  
>>  	__jbd2_journal_abort_hard(journal);
>> -- 
>> 2.17.2
>>

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