s390/dasd: fix handling of internal requests

Internal DASD device driver I/O such as query host access count or
path verification is started using the _sleep_on() function.
To mark a request as started or ended the callback_data is set to either
DASD_SLEEPON_START_TAG or DASD_SLEEPON_END_TAG.

In cases where the request has to be stopped unconditionally the status is
set to DASD_SLEEPON_END_TAG as well which leads to immediate clearing of
the request.
But the request might still be on a device request queue for normal
operation which might lead to a panic because of a BUG() statement in
__dasd_device_process_final_queue() or a list corruption of the device
request queue.

Fix by removing the setting of DASD_SLEEPON_END_TAG in the
dasd_cancel_req() and dasd_generic_requeue_all_requests() functions and
ensure that the request is not deleted in the requeue function.
Trigger the device tasklet in the requeue function and let the normal
processing cleanup the request.

Signed-off-by: Stefan Haberland <sth@linux.vnet.ibm.com>
Reviewed-by: Jan Hoeppner <hoeppner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

Author: stefan-haberland

drivers/s390/block/dasd.c

@@ -2581,8 +2581,6 @@ int dasd_cancel_req(struct dasd_ccw_req *cqr)
 	case DASD_CQR_QUEUED:
 		/* request was not started - just set to cleared */
 		cqr->status = DASD_CQR_CLEARED;
-		if (cqr->callback_data == DASD_SLEEPON_START_TAG)
-			cqr->callback_data = DASD_SLEEPON_END_TAG;
 		break;
 	case DASD_CQR_IN_IO:
 		/* request in IO - terminate IO and release again */
@@ -3902,9 +3900,12 @@ static int dasd_generic_requeue_all_requests(struct dasd_device *device)
 		wait_event(dasd_flush_wq,
 			   (cqr->status != DASD_CQR_CLEAR_PENDING));
 
-		/* mark sleepon requests as ended */
-		if (cqr->callback_data == DASD_SLEEPON_START_TAG)
-			cqr->callback_data = DASD_SLEEPON_END_TAG;
+		/*
+		 * requeue requests to blocklayer will only work
+		 * for block device requests
+		 */
+		if (_dasd_requeue_request(cqr))
+			continue;
 
 		/* remove requests from device and block queue */
 		list_del_init(&cqr->devlist);
@@ -3917,13 +3918,6 @@ static int dasd_generic_requeue_all_requests(struct dasd_device *device)
 			cqr = refers;
 		}
 
-		/*
-		 * requeue requests to blocklayer will only work
-		 * for block device requests
-		 */
-		if (_dasd_requeue_request(cqr))
-			continue;
-
 		if (cqr->block)
 			list_del_init(&cqr->blocklist);
 		cqr->block->base->discipline->free_cp(
@@ -3940,8 +3934,7 @@ static int dasd_generic_requeue_all_requests(struct dasd_device *device)
 		list_splice_tail(&requeue_queue, &device->ccw_queue);
 		spin_unlock_irq(get_ccwdev_lock(device->cdev));
 	}
-	/* wake up generic waitqueue for eventually ended sleepon requests */
-	wake_up(&generic_waitq);
+	dasd_schedule_device_bh(device);
 	return rc;
 }