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

[Jan Kara]

> 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 at mit.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 at suse.cz>
SuSE CR Labs