linux-ext4 - Re: [PATCH -v2 1/3] jbd2: Use atomic variables to avoid taking t_handle_lock in jbd2_journal

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20100809194554.GB5356@quack.suse.cz>
Date:	Mon, 9 Aug 2010 21:45:55 +0200
From:	Jan Kara <jack@...e.cz>
To:	Ted Ts'o <tytso@....edu>
Cc:	Jan Kara <jack@...e.cz>,
	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	ocfs2-devel@....oracle.com, John Stultz <johnstul@...ibm.com>,
	Keith Maanthey <kmannth@...ibm.com>,
	Eric Whitney <eric.whitney@...com>
Subject: Re: [PATCH -v2 1/3] jbd2: Use atomic variables to avoid taking
 t_handle_lock in jbd2_journal_stop

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@...e.cz>
SUSE Labs, CR
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html