linux-kernel - Re: [PATCH v2] Updated locking documentation for journal

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Message-ID: <31c3e70b-c513-a9ac-8d94-211d80221942@tu-dortmund.de>
Date:   Wed, 17 Mar 2021 21:57:37 +0100
From:   Alexander Lochmann <alexander.lochmann@...dortmund.de>
To:     Jan Kara <jack@...e.cz>
Cc:     Horst Schirmeier <horst.schirmeier@...dortmund.de>,
        "Theodore Ts'o" <tytso@....edu>, Jan Kara <jack@...e.com>,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] Updated locking documentation for journal_t

Does this patch look good to you?
Might it be ready to be merged?

- Alex

On 11.02.21 10:51, Alexander Lochmann wrote:
> Some members of transaction_t are allowed to be read without
> any lock being held if consistency doesn't matter.
> Based on LockDoc's findings, we extended the locking
> documentation of those members.
> Each one of them is marked with a short comment:
> "no lock for quick racy checks".
> 
> Signed-off-by: Alexander Lochmann <alexander.lochmann@...dortmund.de>
> Signed-off-by: Horst Schirmeier <horst.schirmeier@...dortmund.de>
> Reviewed-by: Jan Kara <jack@...e.cz>
> ---
>  include/linux/jbd2.h | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
> index 18f77d9b1745..4dca33a063dd 100644
> --- a/include/linux/jbd2.h
> +++ b/include/linux/jbd2.h
> @@ -768,7 +768,7 @@ enum passtype {PASS_SCAN, PASS_REVOKE, PASS_REPLAY};
>  struct journal_s
>  {
>      /**
> -     * @j_flags: General journaling state flags [j_state_lock]
> +     * @j_flags: General journaling state flags [j_state_lock, no lock
> for quick racy checks]
>       */
>      unsigned long        j_flags;
> 
> @@ -808,7 +808,7 @@ struct journal_s
>      /**
>       * @j_barrier_count:
>       *
> -     * Number of processes waiting to create a barrier lock [j_state_lock]
> +     * Number of processes waiting to create a barrier lock
> [j_state_lock, no lock for quick racy checks]
>       */
>      int            j_barrier_count;
> 
> @@ -821,7 +821,7 @@ struct journal_s
>       * @j_running_transaction:
>       *
>       * Transactions: The current running transaction...
> -     * [j_state_lock] [caller holding open handle]
> +     * [j_state_lock, no lock for quick racy checks] [caller holding
> open handle]
>       */
>      transaction_t        *j_running_transaction;
> 
> @@ -1033,7 +1033,7 @@ struct journal_s
>       * @j_commit_sequence:
>       *
>       * Sequence number of the most recently committed transaction
> -     * [j_state_lock].
> +     * [j_state_lock, no lock for quick racy checks].
>       */
>      tid_t            j_commit_sequence;
> 
> @@ -1041,7 +1041,7 @@ struct journal_s
>       * @j_commit_request:
>       *
>       * Sequence number of the most recent transaction wanting commit
> -     * [j_state_lock]
> +     * [j_state_lock, no lock for quick racy checks]
>       */
>      tid_t            j_commit_request;
> 

-- 
Technische Universität Dortmund
Alexander Lochmann                PGP key: 0xBC3EF6FD
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D-44227 Dortmund                  fax:    +49.231.7556116
http://ess.cs.tu-dortmund.de/Staff/al