struct blk_dev_struct {
	/*
	 * queue_proc has to be atomic
	 */
	request_queue_t		request_queue;
	queue_proc		*queue;
	void			*data;
};

struct request_queue
{
	/*
	 * the queue request freelist, one for reads and one for writes
	 */
	struct list_head	request_freelist[2];
	struct list_head	pending_freelist[2];
	int			pending_free[2];

	/*
	 * Together with queue_head for cacheline sharing
	 */
	struct list_head	queue_head;
	elevator_t		elevator;

	request_fn_proc		* request_fn;
	merge_request_fn	* back_merge_fn;
	merge_request_fn	* front_merge_fn;
	merge_requests_fn	* merge_requests_fn;
	make_request_fn		* make_request_fn;
	plug_device_fn		* plug_device_fn;
	/*
	 * The queue owner gets to use this for whatever they like.
	 * ll_rw_blk doesn't touch it.
	 */
	void			* queuedata;

	/*
	 * This is used to remove the plug when tq_disk runs.
	 */
	struct tq_struct	plug_tq;

	/*
	 * Boolean that indicates whether this queue is plugged or not.
	 */
	char			plugged;

	/*
	 * Boolean that indicates whether current_request is active or
	 * not.
	 */
	char			head_active;

        /*
	 * Boolean, if true then make_request injects one artifical
         * IO error into the next bh that is submitted. Useful for
         * testing the effects of IO errors.
         */
        char                    oneshot_error;
                                                    
                                                    
	/*	
	 * Is meant to protect the queue in the future instead of
	 * io_request_lock
	 */
	spinlock_t		queue_lock;

	/*
	 * Tasks wait here for free request
	 */
	wait_queue_head_t	wait_for_request;
};

struct request {
	struct list_head queue;
	int elevator_sequence;
	struct list_head table;

	volatile int rq_status;	/* should split this into a few status bits */
#define RQ_INACTIVE		(-1)
#define RQ_ACTIVE		1
#define RQ_SCSI_BUSY		0xffff
#define RQ_SCSI_DONE		0xfffe
#define RQ_SCSI_DISCONNECTING	0xffe0

	kdev_t rq_dev;
	int cmd;		/* READ or WRITE */
	int errors;
	unsigned long start_time;
	unsigned long sector;
	unsigned long nr_sectors;
	unsigned long hard_sector, hard_nr_sectors;
	unsigned int nr_segments;
	unsigned int nr_hw_segments;
	unsigned long current_nr_sectors;
	void * special;
	char * buffer;
	struct completion * waiting;
	struct buffer_head * bh;
	struct buffer_head * bhtail;
	request_queue_t *q;
};