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Date:   Thu, 11 Feb 2021 10:53:51 +0100
From:   Alexander Lochmann <>
To:     Jan Kara <>
Cc:     Horst Schirmeier <>,
        "Theodore Ts'o" <>, Jan Kara <>,,
Subject: Re: [PATCH 1/2] Updated locking documentation for transaction_t

On 11.02.21 10:30, Jan Kara wrote:
>>   	 */
>>   	unsigned long		t_log_start;
>> -	/* Number of buffers on the t_buffers list [j_list_lock] */
>> +	/* Number of buffers on the t_buffers list [j_list_lock, no lock for quick racy checks] */
>>   	int			t_nr_buffers;
> So this case is actually somewhat different now that I audited the uses.
> There are two types of users - commit code (fs/jbd2/commit.c) and others.
> Other users properly use j_list_lock to access t_nr_buffers. Commit code
> does not use any locks because committing transaction is fully in
> ownership of the jbd2 thread and all other users need to check & wait for
> commit to be finished before doing anything with the transaction's buffers.
Mhm I see.
What about '[..., no locks needed for jbd2 thread]'?

How do the others wait for the commit to be finished?

- Alex

Technische Universit├Ąt Dortmund
Alexander Lochmann                PGP key: 0xBC3EF6FD
Otto-Hahn-Str. 16                 phone:  +49.231.7556141
D-44227 Dortmund                  fax:    +49.231.7556116

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