linux-ext4 - Re: [PATCH v4] jbd2: Fix data missing when reusing bh which is ready to be checkpointed

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Message-Id: <167678522172.2723470.1837475559242554356.b4-ty@mit.edu>
Date:   Sun, 19 Feb 2023 00:40:43 -0500
From:   "Theodore Ts'o" <tytso@....edu>
To:     jack@...e.com, Zhihao Cheng <chengzhihao1@...wei.com>
Cc:     "Theodore Ts'o" <tytso@....edu>, linux-ext4@...r.kernel.org,
        zhanchengbin1@...wei.com, libaokun1@...wei.com,
        linux-kernel@...r.kernel.org, yi.zhang@...wei.com
Subject: Re: [PATCH v4] jbd2: Fix data missing when reusing bh which is ready to be checkpointed

On Tue, 10 Jan 2023 09:53:27 +0800, Zhihao Cheng wrote:
> Following process will make data lost and could lead to a filesystem
> corrupted problem:
> 
> 1. jh(bh) is inserted into T1->t_checkpoint_list, bh is dirty, and
>    jh->b_transaction = NULL
> 2. T1 is added into journal->j_checkpoint_transactions.
> 3. Get bh prepare to write while doing checkpoing:
>            PA				    PB
>    do_get_write_access             jbd2_log_do_checkpoint
>     spin_lock(&jh->b_state_lock)
>      if (buffer_dirty(bh))
>       clear_buffer_dirty(bh)   // clear buffer dirty
>        set_buffer_jbddirty(bh)
> 				    transaction =
> 				    journal->j_checkpoint_transactions
> 				    jh = transaction->t_checkpoint_list
> 				    if (!buffer_dirty(bh))
> 		                      __jbd2_journal_remove_checkpoint(jh)
> 				      // bh won't be flushed
> 		                    jbd2_cleanup_journal_tail
>     __jbd2_journal_file_buffer(jh, transaction, BJ_Reserved)
> 4. Aborting journal/Power-cut before writing latest bh on journal area.
> 
> [...]

Applied, thanks!

[1/1] jbd2: Fix data missing when reusing bh which is ready to be checkpointed
      commit: e6b9bd7290d334451ce054e98e752abc055e0034

Best regards,
-- 
Theodore Ts'o <tytso@....edu>