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: <20100809170216.GB31969@atrey.karlin.mff.cuni.cz>
Date:	Mon, 9 Aug 2010 19:02:16 +0200
From:	Jan Kara <jack@...e.cz>
To:	Theodore Ts'o <tytso@....edu>
Cc:	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

> By using an atomic_t for t_updates and t_outstanding credits, this
> should allow us to not need to take transaction t_handle_lock in
> jbd2_journal_stop().
> 
> Signed-off-by: "Theodore Ts'o" <tytso@....edu>
  The patch looks OK to me besides:
@@ -426,15 +429,14 @@ int jbd2__journal_restart(handle_t *handle, int nblocks, int gfp_mask)
         * First unlink the handle from its current transaction, and start the
         * commit on that.
         */
-       J_ASSERT(transaction->t_updates > 0);
+       J_ASSERT(atomic_read(&transaction->t_updates) > 0);
        J_ASSERT(journal_current_handle() == handle);

        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?

										Honza
-- 
Jan Kara <jack@...e.cz>
SuSE CR Labs
--
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