cpqarray broken since 2.5.19

[Adam Kropelin]

The cpqarray driver seems to have been broken around 2.5.19 with the
blk_start_queue/blk_stop_queue changes. As-is, cpqarray deadlocks the entire
system when it tries to do partition detection. The bits from the 2.5.19 patch
which seem to relate are:

> @@ -916,6 +915,7 @@
>       goto queue_next;
>
>  startio:
> +     blk_stop_queue(q);
>       start_io(h);
>  }
>
> @@ -1066,8 +1066,8 @@
>       /*
>        * See if we can queue up some more IO
>        */
> -     do_ida_request(BLK_DEFAULT_QUEUE(MAJOR_NR + h->ctlr));
>       spin_unlock_irqrestore(IDA_LOCK(h->ctlr), flags);
> +     blk_start_queue(BLK_DEFAULT_QUEUE(MAJOR_NR + h->ctlr));
>  }
>
>  /*

Simply reverting these changes allows the driver to successfully do partition
detect, but it quickly hangs if any significant amount of I/O is attempted. The
hang in this case seems to just affect processes trying to do I/O on the array;
it is not a whole-system-deadlock.

Test machine is SMP ppro.

--Adam