[Ocfs2-devel] [PATCH -v2 1/3] jbd2: Use atomic variables to avoid taking t_handle_lock in jbd2_journal_stop

[Jan Kara <jack@suse.cz>]

On Mon 09-08-10 15:05:13, Ted Ts'o wrote:
> On Mon, Aug 09, 2010 at 07:02:16PM +0200, Jan Kara wrote:
> >         spin_lock(&journal->j_state_lock);
> >         spin_lock(&transaction->t_handle_lock);
> > -       transaction->t_outstanding_credits -= handle->h_buffer_credits;
> > -       transaction->t_updates--;
> > -
> > -       if (!transaction->t_updates)
> > +       atomic_sub(handle->h_buffer_credits,
> > +                  &transaction->t_outstanding_credits);
> > +       if (atomic_dec_and_test(&transaction->t_updates))
> >
> > After this a transaction can disappear so subsequent
> > __jbd2_log_start_commit shouldn't dereference transaction->t_tid,
> > right?
> 
> I think it should be ok because we're holding j_state_lock(), so the
> transaction can't disappear until we release the j_state_lock.
  Ah, OK. You're right. I just thought we eventually want to remove the
lock but you're right that currently the code is fine. Sorry for the noise.

								Honza

-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR