s390/dasd: fix hanging device offline processing

BugLink: https://bugs.launchpad.net/bugs/1910822

commit 658a337 upstream.

For an LCU update a read unit address configuration IO is required.
This is started using sleep_on(), which has early exit paths in case the
device is not usable for IO. For example when it is in offline processing.

In those cases the LCU update should fail and not be retried.
Therefore lcu_update_work checks if EOPNOTSUPP is returned or not.

Commit 4199534 ("s390/dasd: fix endless loop after read unit address configuration")
accidentally removed the EOPNOTSUPP return code from
read_unit_address_configuration(), which in turn might lead to an endless
loop of the LCU update in offline processing.

Fix by returning EOPNOTSUPP again if the device is not able to perform the
request.

Fixes: 4199534 ("s390/dasd: fix endless loop after read unit address configuration")
Cc: [email protected] delphix#5.3
Signed-off-by: Stefan Haberland <[email protected]>
Reviewed-by: Jan Hoeppner <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Kamal Mostafa <[email protected]>
Signed-off-by: Kelsey Skunberg <[email protected]>

Author: Stefan Haberland

drivers/s390/block/dasd_alias.c

@@ -462,11 +462,19 @@ static int read_unit_address_configuration(struct dasd_device *device,
 	spin_unlock_irqrestore(&lcu->lock, flags);
 
 	rc = dasd_sleep_on(cqr);
-	if (rc && !suborder_not_supported(cqr)) {
+	if (!rc)
+		goto out;
+
+	if (suborder_not_supported(cqr)) {
+		/* suborder not supported or device unusable for IO */
+		rc = -EOPNOTSUPP;
+	} else {
+		/* IO failed but should be retried */
 		spin_lock_irqsave(&lcu->lock, flags);
 		lcu->flags |= NEED_UAC_UPDATE;
 		spin_unlock_irqrestore(&lcu->lock, flags);
 	}
+out:
 	dasd_sfree_request(cqr, cqr->memdev);
 	return rc;
 }