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Date:   Tue, 3 Dec 2019 13:23:12 +0100
From:   Jan Kara <jack@suse.cz>
To:     "zhangyi (F)" <yi.zhang@huawei.com>
Cc:     linux-ext4@vger.kernel.org, jack@suse.com, tytso@mit.edu,
        adilger.kernel@dilger.ca, liangyun2@huawei.com,
        luoshijie1@huawei.com
Subject: Re: [PATCH v2 3/4] Partially revert "ext4: pass -ESHUTDOWN code to
 jbd2 layer"
Message-ID: <20191203122312.GD8206@quack2.suse.cz>
References: <20191203092756.26129-1-yi.zhang@huawei.com>
 <20191203092756.26129-4-yi.zhang@huawei.com>
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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@huawei.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...

								Honza

> ---
>  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
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR