linux-ext4 - Re: [RFC PATCH v4 2/8] jbd2: ensure abort the journal if detect IO error when writing original buffer back

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Date:   Thu, 24 Jun 2021 10:35:24 -0400
From:   "Theodore Ts'o" <tytso@....edu>
To:     Zhang Yi <yi.zhang@...wei.com>
Cc:     linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        jack@...e.cz, adilger.kernel@...ger.ca, david@...morbit.com,
        hch@...radead.org
Subject: Re: [RFC PATCH v4 2/8] jbd2: ensure abort the journal if detect IO
 error when writing original buffer back

On Thu, Jun 10, 2021 at 07:24:34PM +0800, Zhang Yi wrote:
> Although we merged c044f3d8360 ("jbd2: abort journal if free a async
> write error metadata buffer"), there is a race between
> jbd2_journal_try_to_free_buffers() and jbd2_journal_destroy(), so the
> jbd2_log_do_checkpoint() may still fail to detect the buffer write
> io error flag which may lead to filesystem inconsistency.
> 
> jbd2_journal_try_to_free_buffers()     ext4_put_super()
>                                         jbd2_journal_destroy()
>   __jbd2_journal_remove_checkpoint()
>   detect buffer write error              jbd2_log_do_checkpoint()
>                                          jbd2_cleanup_journal_tail()
>                                            <--- lead to inconsistency
>   jbd2_journal_abort()
> 
> Fix this issue by introducing a new atomic flag which only have one
> JBD2_CHECKPOINT_IO_ERROR bit now, and set it in
> __jbd2_journal_remove_checkpoint() when freeing a checkpoint buffer
> which has write_io_error flag. Then jbd2_journal_destroy() will detect
> this mark and abort the journal to prevent updating log tail.
> 
> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>
> Reviewed-by: Jan Kara <jack@...e.cz>

Applied, thanks.

					- Ted