s390/dasd: fix hanging device after clear subchannel

commit 9ba333dc upstream.

When a device is in a status where CIO has killed all I/O by itself the
interrupt for a clear request may not contain an irb to determine the
clear function. Instead it contains an error pointer -EIO.
This was ignored by the DASD int_handler leading to a hanging device
waiting for a clear interrupt.

Handle -EIO error pointer correctly for requests that are clear pending and
treat the clear as successful.
Signed-off-by: Stefan Haberland <sth@linux.vnet.ibm.com>
Reviewed-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/s390/block/dasd.c

@@ -1593,9 +1593,18 @@ void dasd_int_handler(struct ccw_device *cdev, unsigned long intparm,
 	unsigned long long now;
 	int expires;
 
+	cqr = (struct dasd_ccw_req *) intparm;
 	if (IS_ERR(irb)) {
 		switch (PTR_ERR(irb)) {
 		case -EIO:
+			if (cqr && cqr->status == DASD_CQR_CLEAR_PENDING) {
+				device = (struct dasd_device *) cqr->startdev;
+				cqr->status = DASD_CQR_CLEARED;
+				dasd_device_clear_timer(device);
+				wake_up(&dasd_flush_wq);
+				dasd_schedule_device_bh(device);
+				return;
+			}
 			break;
 		case -ETIMEDOUT:
 			DBF_EVENT_DEVID(DBF_WARNING, cdev, "%s: "
@@ -1611,7 +1620,6 @@ void dasd_int_handler(struct ccw_device *cdev, unsigned long intparm,
 	}
 
 	now = get_clock();
-	cqr = (struct dasd_ccw_req *) intparm;
 	/* check for conditions that should be handled immediately */
 	if (!cqr ||
 	    !(scsw_dstat(&irb->scsw) == (DEV_STAT_CHN_END | DEV_STAT_DEV_END) &&