linux-ext4 - Re: [patch V2 6/7] fs/jbd2: Make state lock a spinlock

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Date:   Fri, 2 Aug 2019 15:31:54 +0200
From:   Jan Kara <jack@...e.cz>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Sebastian Siewior <bigeasy@...utronix.de>,
        Anna-Maria Gleixner <anna-maria@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Julia Cartwright <julia@...com>, Jan Kara <jack@...e.com>,
        Theodore Tso <tytso@....edu>, Mark Fasheh <mark@...heh.com>,
        Joseph Qi <joseph.qi@...ux.alibaba.com>,
        Joel Becker <jlbec@...lplan.org>, linux-ext4@...r.kernel.org,
        Jan Kara <jack@...e.cz>, Matthew Wilcox <willy@...radead.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org
Subject: Re: [patch V2 6/7] fs/jbd2: Make state lock a spinlock

On Thu 01-08-19 13:28:49, Peter Zijlstra wrote:
> On Thu, Aug 01, 2019 at 03:01:32AM +0200, Thomas Gleixner wrote:
> 
> > @@ -1931,7 +1932,7 @@ static void __jbd2_journal_temp_unlink_b
> >  	transaction_t *transaction;
> >  	struct buffer_head *bh = jh2bh(jh);
> >  
> > -	J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
> > +	assert_spin_locked(&jh->state_lock);
> >  	transaction = jh->b_transaction;
> >  	if (transaction)
> >  		assert_spin_locked(&transaction->t_journal->j_list_lock);
> 
> > @@ -2415,7 +2416,7 @@ void __jbd2_journal_file_buffer(struct j
> >  	int was_dirty = 0;
> >  	struct buffer_head *bh = jh2bh(jh);
> >  
> > -	J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
> > +	assert_spin_locked(&jh->state_lock);
> >  	assert_spin_locked(&transaction->t_journal->j_list_lock);
> >  
> >  	J_ASSERT_JH(jh, jh->b_jlist < BJ_Types);
> 
> > @@ -2500,7 +2501,7 @@ void __jbd2_journal_refile_buffer(struct
> >  	int was_dirty, jlist;
> >  	struct buffer_head *bh = jh2bh(jh);
> >  
> > -	J_ASSERT_JH(jh, jbd_is_locked_bh_state(bh));
> > +	assert_spin_locked(&jh->state_lock);
> >  	if (jh->b_transaction)
> >  		assert_spin_locked(&jh->b_transaction->t_journal->j_list_lock);
> >  
> 
> Do those want to be:
> 
>   lockdep_assert_held(&jh->state_lock);
> 
> instead? The difference is of course that lockdep_assert_held() requires
> the current context to hold the lock, where assert_*_locked() merely
> checks _someone_ holds it.

Yeah, jbd2 doesn't play any weird locking tricks so lockdep_assert_held()
is fine. I'll replace those when I'm updating the patch.

								Honza

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