[PATCH] ext3/4: fix J_ASSERT(transaction->t_updates > 0) in journal_stop()

A disk generated some I/O error, after it, I hitted
J_ASSERT(transaction->t_updates > 0) in journal_stop().

It seems to happened on ext3_truncate() path from stack trace. Then,
maybe the following case may trigger J_ASSERT(transaction->t_updates > 0).

ext3_truncate()
    -> ext3_free_branches()
        -> ext3_journal_test_restart()
	    -> ext3_journal_restart()
                -> journal_restart()
                transaction->t_updates--;
                /* another process aborted journal */
                    -> start_this_handle()
		    returns -EROFS without transaction->t_updates++;

    -> ext3_journal_stop()
        -> journal_stop()
	J_ASSERT(transaction->t_updates > 0)

If journal was aborted in middle of journal_restart(), ext3_truncate()
may trigger J_ASSERT().
Signed-off-by: NOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

fs/jbd/transaction.c

@@ -1314,13 +1314,14 @@ int journal_stop(handle_t *handle)
 	int old_handle_count, err;
 	pid_t pid;
 
-	J_ASSERT(transaction->t_updates > 0);
 	J_ASSERT(journal_current_handle() == handle);
 
 	if (is_handle_aborted(handle))
 		err = -EIO;
-	else
+	else {
+		J_ASSERT(transaction->t_updates > 0);
 		err = 0;
+	}
 
 	if (--handle->h_ref > 0) {
 		jbd_debug(4, "h_ref %d -> %d\n", handle->h_ref + 1,

fs/jbd2/transaction.c

@@ -1314,13 +1314,14 @@ int jbd2_journal_stop(handle_t *handle)
 	int old_handle_count, err;
 	pid_t pid;
 
-	J_ASSERT(transaction->t_updates > 0);
 	J_ASSERT(journal_current_handle() == handle);
 
 	if (is_handle_aborted(handle))
 		err = -EIO;
-	else
+	else {
+		J_ASSERT(transaction->t_updates > 0);
 		err = 0;
+	}
 
 	if (--handle->h_ref > 0) {
 		jbd_debug(4, "h_ref %d -> %d\n", handle->h_ref + 1,