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

[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: OGAWA Hirofumi <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>