From 41995342b40c418a47603e1321256d2c4a2ed0fb Mon Sep 17 00:00:00 2001
From: Stefan Haberland <sth@linux.ibm.com>
Date: Thu, 1 Aug 2019 13:06:30 +0200
Subject: [PATCH] s390/dasd: fix endless loop after read unit address
 configuration

References: bsc#1144912 LTC#179907
Patch-mainline: v5.3-rc3
Git-commit: 41995342b40c418a47603e1321256d2c4a2ed0fb

Description:   dasd: fix endless loop after read unit address configuration
Symptom:       After getting a storage server event that causes the
               DASD device driver to update its unit address
               configuration during a device shutdown there is the
               possibility of an endless loop in the device driver.
               In the system log there will be ongoing DASD error
               messages with RC: -19.
Problem:       The loop starting the ruac request only terminates when
               the retry counter is decreased to 0. But in the
               sleep_on function there are early exit paths that do
               not decrease the retry counter.
Solution:      Prevent an endless loop by handling those cases separately.
               Remove the unnecessary do..while loop since the
               sleep_on function takes care of retries by itself.
Reproduction:  Disable a device when a storage server event causes
               unit address configuration updates.

After getting a storage server event that causes the DASD device driver
to update its unit address configuration during a device shutdown there is
the possibility of an endless loop in the device driver.

In the system log there will be ongoing DASD error messages with RC: -19.

The reason is that the loop starting the ruac request only terminates when
the retry counter is decreased to 0. But in the sleep_on function there are
early exit paths that do not decrease the retry counter.

Prevent an endless loop by handling those cases separately.

Remove the unnecessary do..while loop since the sleep_on function takes
care of retries by itself.

Fixes: 8e09f21574ea ("[S390] dasd: add hyper PAV support to DASD device driver, part 1")
Cc: stable@vger.kernel.org # 2.6.25+
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Reviewed-by: Jan Hoeppner <hoeppner@linux.ibm.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
 drivers/s390/block/dasd_alias.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/drivers/s390/block/dasd_alias.c b/drivers/s390/block/dasd_alias.c
index b9ce93e9df89..99f86612f775 100644
--- a/drivers/s390/block/dasd_alias.c
+++ b/drivers/s390/block/dasd_alias.c
@@ -383,6 +383,20 @@ suborder_not_supported(struct dasd_ccw_req *cqr)
 	char msg_format;
 	char msg_no;
 
+	/*
+	 * intrc values ENODEV, ENOLINK and EPERM
+	 * will be optained from sleep_on to indicate that no
+	 * IO operation can be started
+	 */
+	if (cqr->intrc == -ENODEV)
+		return 1;
+
+	if (cqr->intrc == -ENOLINK)
+		return 1;
+
+	if (cqr->intrc == -EPERM)
+		return 1;
+
 	sense = dasd_get_sense(&cqr->irb);
 	if (!sense)
 		return 0;
@@ -447,12 +461,8 @@ static int read_unit_address_configuration(struct dasd_device *device,
 	lcu->flags &= ~NEED_UAC_UPDATE;
 	spin_unlock_irqrestore(&lcu->lock, flags);
 
-	do {
-		rc = dasd_sleep_on(cqr);
-		if (rc && suborder_not_supported(cqr))
-			return -EOPNOTSUPP;
-	} while (rc && (cqr->retries > 0));
-	if (rc) {
+	rc = dasd_sleep_on(cqr);
+	if (rc && !suborder_not_supported(cqr)) {
 		spin_lock_irqsave(&lcu->lock, flags);
 		lcu->flags |= NEED_UAC_UPDATE;
 		spin_unlock_irqrestore(&lcu->lock, flags);
-- 
2.22.0