dasd.c

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		}

		/* Process finished ERP request. */
		if (cqr->refers) {
			__dasd_process_erp(device, cqr);
			goto restart;
		}

		/* Rechain finished requests to final queue */
		cqr->endclk = get_clock();
		list_move_tail(&cqr->list, final_queue);
	}
}

static void
dasd_end_request_cb(struct dasd_ccw_req * cqr, void *data)
{
	struct request *req;
	struct dasd_device *device;
	int status;

	req = (struct request *) data;
	device = cqr->device;
	dasd_profile_end(device, cqr, req);
	status = cqr->device->discipline->free_cp(cqr,req);
	spin_lock_irq(&device->request_queue_lock);
	dasd_end_request(req, status);
	spin_unlock_irq(&device->request_queue_lock);
}


/*
 * Fetch requests from the block device queue.
 */
static void
__dasd_process_blk_queue(struct dasd_device * device)
{
	struct request_queue *queue;
	struct request *req;
	struct dasd_ccw_req *cqr;
	int nr_queued;

	queue = device->request_queue;
	/* No queue ? Then there is nothing to do. */
	if (queue == NULL)
		return;

	/*
	 * We requeue request from the block device queue to the ccw
	 * queue only in two states. In state DASD_STATE_READY the
	 * partition detection is done and we need to requeue requests
	 * for that. State DASD_STATE_ONLINE is normal block device
	 * operation.
	 */
	if (device->state != DASD_STATE_READY &&
	    device->state != DASD_STATE_ONLINE)
		return;
	nr_queued = 0;
	/* Now we try to fetch requests from the request queue */
	list_for_each_entry(cqr, &device->ccw_queue, list)
		if (cqr->status == DASD_CQR_QUEUED)
			nr_queued++;
	while (!blk_queue_plugged(queue) &&
	       elv_next_request(queue) &&
		nr_queued < DASD_CHANQ_MAX_SIZE) {
		req = elv_next_request(queue);

		if (device->features & DASD_FEATURE_READONLY &&
		    rq_data_dir(req) == WRITE) {
			DBF_DEV_EVENT(DBF_ERR, device,
				      "Rejecting write request %p",
				      req);
			blkdev_dequeue_request(req);
			dasd_end_request(req, 0);
			continue;
		}
		if (device->stopped & DASD_STOPPED_DC_EIO) {
			blkdev_dequeue_request(req);
			dasd_end_request(req, 0);
			continue;
		}
		cqr = device->discipline->build_cp(device, req);
		if (IS_ERR(cqr)) {
			if (PTR_ERR(cqr) == -ENOMEM)
				break;	/* terminate request queue loop */
			if (PTR_ERR(cqr) == -EAGAIN) {
				/*
				 * The current request cannot be build right
				 * now, we have to try later. If this request
				 * is the head-of-queue we stop the device
				 * for 1/2 second.
				 */
				if (!list_empty(&device->ccw_queue))
					break;
				device->stopped |= DASD_STOPPED_PENDING;
				dasd_set_timer(device, HZ/2);
				break;
			}
			DBF_DEV_EVENT(DBF_ERR, device,
				      "CCW creation failed (rc=%ld) "
				      "on request %p",
				      PTR_ERR(cqr), req);
			blkdev_dequeue_request(req);
			dasd_end_request(req, 0);
			continue;
		}
		cqr->callback = dasd_end_request_cb;
		cqr->callback_data = (void *) req;
		cqr->status = DASD_CQR_QUEUED;
		blkdev_dequeue_request(req);
		list_add_tail(&cqr->list, &device->ccw_queue);
		dasd_profile_start(device, cqr, req);
		nr_queued++;
	}
}

/*
 * Take a look at the first request on the ccw queue and check
 * if it reached its expire time. If so, terminate the IO.
 */
static void
__dasd_check_expire(struct dasd_device * device)
{
	struct dasd_ccw_req *cqr;

	if (list_empty(&device->ccw_queue))
		return;
	cqr = list_entry(device->ccw_queue.next, struct dasd_ccw_req, list);
	if ((cqr->status == DASD_CQR_IN_IO && cqr->expires != 0) &&
	    (time_after_eq(jiffies, cqr->expires + cqr->starttime))) {
		if (device->discipline->term_IO(cqr) != 0) {
			/* Hmpf, try again in 5 sec */
			dasd_set_timer(device, 5*HZ);
			DEV_MESSAGE(KERN_ERR, device,
				    "internal error - timeout (%is) expired "
				    "for cqr %p, termination failed, "
				    "retrying in 5s",
				    (cqr->expires/HZ), cqr);
		} else {
			DEV_MESSAGE(KERN_ERR, device,
				    "internal error - timeout (%is) expired "
				    "for cqr %p (%i retries left)",
				    (cqr->expires/HZ), cqr, cqr->retries);
		}
	}
}

/*
 * Take a look at the first request on the ccw queue and check
 * if it needs to be started.
 */
static void
__dasd_start_head(struct dasd_device * device)
{
	struct dasd_ccw_req *cqr;
	int rc;

	if (list_empty(&device->ccw_queue))
		return;
	cqr = list_entry(device->ccw_queue.next, struct dasd_ccw_req, list);
	if (cqr->status != DASD_CQR_QUEUED)
		return;
	/* Non-temporary stop condition will trigger fail fast */
	if (device->stopped & ~DASD_STOPPED_PENDING &&
	    test_bit(DASD_CQR_FLAGS_FAILFAST, &cqr->flags) &&
	    (!dasd_eer_enabled(device))) {
		cqr->status = DASD_CQR_FAILED;
		dasd_schedule_bh(device);
		return;
	}
	/* Don't try to start requests if device is stopped */
	if (device->stopped)
		return;

	rc = device->discipline->start_IO(cqr);
	if (rc == 0)
		dasd_set_timer(device, cqr->expires);
	else if (rc == -EACCES) {
		dasd_schedule_bh(device);
	} else
		/* Hmpf, try again in 1/2 sec */
		dasd_set_timer(device, 50);
}

static inline int
_wait_for_clear(struct dasd_ccw_req *cqr)
{
	return (cqr->status == DASD_CQR_QUEUED);
}

/*
 * Remove all requests from the ccw queue (all = '1') or only block device
 * requests in case all = '0'.
 * Take care of the erp-chain (chained via cqr->refers) and remove either
 * the whole erp-chain or none of the erp-requests.
 * If a request is currently running, term_IO is called and the request
 * is re-queued. Prior to removing the terminated request we need to wait
 * for the clear-interrupt.
 * In case termination is not possible we stop processing and just finishing
 * the already moved requests.
 */
static int
dasd_flush_ccw_queue(struct dasd_device * device, int all)
{
	struct dasd_ccw_req *cqr, *orig, *n;
	int rc, i;

	struct list_head flush_queue;

	INIT_LIST_HEAD(&flush_queue);
	spin_lock_irq(get_ccwdev_lock(device->cdev));
	rc = 0;
restart:
	list_for_each_entry_safe(cqr, n, &device->ccw_queue, list) {
		/* get original request of erp request-chain */
		for (orig = cqr; orig->refers != NULL; orig = orig->refers);

		/* Flush all request or only block device requests? */
		if (all == 0 && cqr->callback != dasd_end_request_cb &&
		    orig->callback != dasd_end_request_cb) {
			continue;
		}
		/* Check status and move request to flush_queue */
		switch (cqr->status) {
		case DASD_CQR_IN_IO:
			rc = device->discipline->term_IO(cqr);
			if (rc) {
				/* unable to terminate requeust */
				DEV_MESSAGE(KERN_ERR, device,
					    "dasd flush ccw_queue is unable "
					    " to terminate request %p",
					    cqr);
				/* stop flush processing */
				goto finished;
			}
			break;
		case DASD_CQR_QUEUED:
		case DASD_CQR_ERROR:
			/* set request to FAILED */
			cqr->stopclk = get_clock();
			cqr->status = DASD_CQR_FAILED;
			break;
		default: /* do not touch the others */
			break;
		}
		/* Rechain request (including erp chain) */
		for (i = 0; cqr != NULL; cqr = cqr->refers, i++) {
			cqr->endclk = get_clock();
			list_move_tail(&cqr->list, &flush_queue);
		}
		if (i > 1)
			/* moved more than one request - need to restart */
			goto restart;
	}

finished:
	spin_unlock_irq(get_ccwdev_lock(device->cdev));
	/* Now call the callback function of flushed requests */
restart_cb:
	list_for_each_entry_safe(cqr, n, &flush_queue, list) {
		if (cqr->status == DASD_CQR_CLEAR) {
			/* wait for clear interrupt! */
			wait_event(dasd_flush_wq, _wait_for_clear(cqr));
			cqr->status = DASD_CQR_FAILED;
		}
		/* Process finished ERP request. */
		if (cqr->refers) {
			__dasd_process_erp(device, cqr);
			/* restart list_for_xx loop since dasd_process_erp
			 * might remove multiple elements */
			goto restart_cb;
		}
		/* call the callback function */
		cqr->endclk = get_clock();
		if (cqr->callback != NULL)
			(cqr->callback)(cqr, cqr->callback_data);
	}
	return rc;
}

/*
 * Acquire the device lock and process queues for the device.
 */
static void
dasd_tasklet(struct dasd_device * device)
{
	struct list_head final_queue;
	struct list_head *l, *n;
	struct dasd_ccw_req *cqr;

	atomic_set (&device->tasklet_scheduled, 0);
	INIT_LIST_HEAD(&final_queue);
	spin_lock_irq(get_ccwdev_lock(device->cdev));
	/* Check expire time of first request on the ccw queue. */
	__dasd_check_expire(device);
	/* Finish off requests on ccw queue */
	__dasd_process_ccw_queue(device, &final_queue);
	spin_unlock_irq(get_ccwdev_lock(device->cdev));
	/* Now call the callback function of requests with final status */
	list_for_each_safe(l, n, &final_queue) {
		cqr = list_entry(l, struct dasd_ccw_req, list);
		list_del_init(&cqr->list);
		if (cqr->callback != NULL)
			(cqr->callback)(cqr, cqr->callback_data);
	}
	spin_lock_irq(&device->request_queue_lock);
	spin_lock(get_ccwdev_lock(device->cdev));
	/* Get new request from the block device request queue */
	__dasd_process_blk_queue(device);
	/* Now check if the head of the ccw queue needs to be started. */
	__dasd_start_head(device);
	spin_unlock(get_ccwdev_lock(device->cdev));
	spin_unlock_irq(&device->request_queue_lock);
	dasd_put_device(device);
}

/*
 * Schedules a call to dasd_tasklet over the device tasklet.
 */
void
dasd_schedule_bh(struct dasd_device * device)
{
	/* Protect against rescheduling. */
	if (atomic_cmpxchg (&device->tasklet_scheduled, 0, 1) != 0)
		return;
	dasd_get_device(device);
	tasklet_hi_schedule(&device->tasklet);
}

/*
 * Queue a request to the head of the ccw_queue. Start the I/O if
 * possible.
 */
void
dasd_add_request_head(struct dasd_ccw_req *req)
{
	struct dasd_device *device;
	unsigned long flags;

	device = req->device;
	spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
	req->status = DASD_CQR_QUEUED;
	req->device = device;
	list_add(&req->list, &device->ccw_queue);
	/* let the bh start the request to keep them in order */
	dasd_schedule_bh(device);
	spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
}

/*
 * Queue a request to the tail of the ccw_queue. Start the I/O if
 * possible.
 */
void
dasd_add_request_tail(struct dasd_ccw_req *req)
{
	struct dasd_device *device;
	unsigned long flags;

	device = req->device;
	spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
	req->status = DASD_CQR_QUEUED;
	req->device = device;
	list_add_tail(&req->list, &device->ccw_queue);
	/* let the bh start the request to keep them in order */
	dasd_schedule_bh(device);
	spin_unlock_irqrestore(get_ccwdev_lock(device->cdev), flags);
}

/*
 * Wakeup callback.
 */
static void
dasd_wakeup_cb(struct dasd_ccw_req *cqr, void *data)
{
	wake_up((wait_queue_head_t *) data);
}

static inline int
_wait_for_wakeup(struct dasd_ccw_req *cqr)
{
	struct dasd_device *device;
	int rc;

	device = cqr->device;
	spin_lock_irq(get_ccwdev_lock(device->cdev));
	rc = ((cqr->status == DASD_CQR_DONE ||
	       cqr->status == DASD_CQR_FAILED) &&
	      list_empty(&cqr->list));
	spin_unlock_irq(get_ccwdev_lock(device->cdev));
	return rc;
}

/*
 * Attempts to start a special ccw queue and waits for its completion.
 */
int
dasd_sleep_on(struct dasd_ccw_req * cqr)
{
	wait_queue_head_t wait_q;
	struct dasd_device *device;
	int rc;

	device = cqr->device;
	spin_lock_irq(get_ccwdev_lock(device->cdev));

	init_waitqueue_head (&wait_q);
	cqr->callback = dasd_wakeup_cb;
	cqr->callback_data = (void *) &wait_q;
	cqr->status = DASD_CQR_QUEUED;
	list_add_tail(&cqr->list, &device->ccw_queue);

	/* let the bh start the request to keep them in order */
	dasd_schedule_bh(device);

	spin_unlock_irq(get_ccwdev_lock(device->cdev));

	wait_event(wait_q, _wait_for_wakeup(cqr));

	/* Request status is either done or failed. */
	rc = (cqr->status == DASD_CQR_FAILED) ? -EIO : 0;
	return rc;
}

/*
 * Attempts to start a special ccw queue and wait interruptible
 * for its completion.
 */
int
dasd_sleep_on_interruptible(struct dasd_ccw_req * cqr)
{
	wait_queue_head_t wait_q;
	struct dasd_device *device;
	int rc, finished;

	device = cqr->device;
	spin_lock_irq(get_ccwdev_lock(device->cdev));

	init_waitqueue_head (&wait_q);
	cqr->callback = dasd_wakeup_cb;
	cqr->callback_data = (void *) &wait_q;
	cqr->status = DASD_CQR_QUEUED;
	list_add_tail(&cqr->list, &device->ccw_queue);

	/* let the bh start the request to keep them in order */
	dasd_schedule_bh(device);
	spin_unlock_irq(get_ccwdev_lock(device->cdev));

	finished = 0;
	while (!finished) {
		rc = wait_event_interruptible(wait_q, _wait_for_wakeup(cqr));
		if (rc != -ERESTARTSYS) {
			/* Request is final (done or failed) */
			rc = (cqr->status == DASD_CQR_DONE) ? 0 : -EIO;
			break;
		}
		spin_lock_irq(get_ccwdev_lock(device->cdev));
		switch (cqr->status) {
		case DASD_CQR_IN_IO:
                        /* terminate runnig cqr */
			if (device->discipline->term_IO) {
				cqr->retries = -1;
				device->discipline->term_IO(cqr);
				/* wait (non-interruptible) for final status
				 * because signal ist still pending */
				spin_unlock_irq(get_ccwdev_lock(device->cdev));
				wait_event(wait_q, _wait_for_wakeup(cqr));
				spin_lock_irq(get_ccwdev_lock(device->cdev));
				rc = (cqr->status == DASD_CQR_DONE) ? 0 : -EIO;
				finished = 1;
			}
			break;
		case DASD_CQR_QUEUED:
			/* request  */
			list_del_init(&cqr->list);
			rc = -EIO;
			finished = 1;
			break;
		default:
			/* cqr with 'non-interruptable' status - just wait */
			break;
		}
		spin_unlock_irq(get_ccwdev_lock(device->cdev));
	}
	return rc;
}

/*
 * Whoa nelly now it gets really hairy. For some functions (e.g. steal lock
 * for eckd devices) the currently running request has to be terminated
 * and be put back to status queued, before the special request is added
 * to the head of the queue. Then the special request is waited on normally.
 */
static inline int
_dasd_term_running_cqr(struct dasd_device *device)
{
	struct dasd_ccw_req *cqr;

	if (list_empty(&device->ccw_queue))
		return 0;
	cqr = list_entry(device->ccw_queue.next, struct dasd_ccw_req, list);
	return device->discipline->term_IO(cqr);
}

int
dasd_sleep_on_immediatly(struct dasd_ccw_req * cqr)
{
	wait_queue_head_t wait_q;
	struct dasd_device *device;
	int rc;

	device = cqr->device;
	spin_lock_irq(get_ccwdev_lock(device->cdev));
	rc = _dasd_term_running_cqr(device);
	if (rc) {
		spin_unlock_irq(get_ccwdev_lock(device->cdev));
		return rc;
	}

	init_waitqueue_head (&wait_q);
	cqr->callback = dasd_wakeup_cb;
	cqr->callback_data = (void *) &wait_q;
	cqr->status = DASD_CQR_QUEUED;
	list_add(&cqr->list, &device->ccw_queue);

	/* let the bh start the request to keep them in order */
	dasd_schedule_bh(device);

	spin_unlock_irq(get_ccwdev_lock(device->cdev));

	wait_event(wait_q, _wait_for_wakeup(cqr));

	/* Request status is either done or failed. */
	rc = (cqr->status == DASD_CQR_FAILED) ? -EIO : 0;
	return rc;
}

/*
 * Cancels a request that was started with dasd_sleep_on_req.
 * This is useful to timeout requests. The request will be
 * terminated if it is currently in i/o.
 * Returns 1 if the request has been terminated.
 */
int
dasd_cancel_req(struct dasd_ccw_req *cqr)
{
	struct dasd_device *device = cqr->device;
	unsigned long flags;
	int rc;

	rc = 0;
	spin_lock_irqsave(get_ccwdev_lock(device->cdev), flags);
	switch (cqr->status) {
	case DASD_CQR_QUEUED:
		/* request was not started - just set to failed */
		cqr->status = DASD_CQR_FAILED;
		break;
	case DASD_CQR_IN_IO:
		/* request in IO - terminate IO and release again */
		if (device->discipline->term_IO(cqr) != 0)
			/* what to do if unable to terminate ??????
			   e.g. not _IN_IO */
			cqr->status = DASD_CQR_FAILED;
		cqr->stopclk = get_clock();
		rc = 1;
		break;
	case DASD_CQR_DONE:
	case DASD_CQR_FAILED:
		/* already finished - do nothing */
		break;
	default:
		DEV_MESSAGE(KERN_ALERT, device,
			    "invalid status %02x in request",
			    cqr->status);
		BUG();