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Delivery-date: Thu, 23 Oct 2025 12:14:53 +0000
From: Vineeth Vijayan <vneethv@linux.ibm.com>
To: stable@vger.kernel.org
Cc: hca@linux.ibm.com, oberpar@linux.ibm.com
Subject: [PATCH 5.15.y] s390/cio: Update purge function to unregister the unused subchannels
Date: Thu, 23 Oct 2025 14:11:05 +0200
Message-ID: <20251023121105.2414775-1-vneethv@linux.ibm.com>
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Starting with 'commit 2297791c92d0 ("s390/cio: dont unregister
subchannel from child-drivers")', cio no longer unregisters
subchannels when the attached device is invalid or unavailable.

As an unintended side-effect, the cio_ignore purge function no longer
removes subchannels for devices on the cio_ignore list if no CCW device
is attached. This situation occurs when a CCW device is non-operational
or unavailable

To ensure the same outcome of the purge function as when the
current cio_ignore list had been active during boot, update the purge
function to remove I/O subchannels without working CCW devices if the
associated device number is found on the cio_ignore list.

Fixes: 2297791c92d0 ("s390/cio: dont unregister subchannel from child-drivers")
Suggested-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
(cherry picked from commit 9daa5a8795865f9a3c93d8d1066785b07ded6073)
---
 drivers/s390/cio/device.c | 37 ++++++++++++++++++++++++-------------
 1 file changed, 24 insertions(+), 13 deletions(-)

diff --git a/drivers/s390/cio/device.c b/drivers/s390/cio/device.c
index 70c5b85d2dfc..7f1d4b41391a 100644
--- a/drivers/s390/cio/device.c
+++ b/drivers/s390/cio/device.c
@@ -1323,23 +1323,34 @@ void ccw_device_schedule_recovery(void)
 	spin_unlock_irqrestore(&recovery_lock, flags);
 }
 
-static int purge_fn(struct device *dev, void *data)
+static int purge_fn(struct subchannel *sch, void *data)
 {
-	struct ccw_device *cdev = to_ccwdev(dev);
-	struct ccw_dev_id *id = &cdev->private->dev_id;
-	struct subchannel *sch = to_subchannel(cdev->dev.parent);
+	struct ccw_device *cdev;
 
-	spin_lock_irq(cdev->ccwlock);
-	if (is_blacklisted(id->ssid, id->devno) &&
-	    (cdev->private->state == DEV_STATE_OFFLINE) &&
-	    (atomic_cmpxchg(&cdev->private->onoff, 0, 1) == 0)) {
-		CIO_MSG_EVENT(3, "ccw: purging 0.%x.%04x\n", id->ssid,
-			      id->devno);
+	spin_lock_irq(sch->lock);
+	if (sch->st != SUBCHANNEL_TYPE_IO || !sch->schib.pmcw.dnv)
+		goto unlock;
+
+	if (!is_blacklisted(sch->schid.ssid, sch->schib.pmcw.dev))
+		goto unlock;
+
+	cdev = sch_get_cdev(sch);
+	if (cdev) {
+		if (cdev->private->state != DEV_STATE_OFFLINE)
+			goto unlock;
+
+		if (atomic_cmpxchg(&cdev->private->onoff, 0, 1) != 0)
+			goto unlock;
 		ccw_device_sched_todo(cdev, CDEV_TODO_UNREG);
-		css_sched_sch_todo(sch, SCH_TODO_UNREG);
 		atomic_set(&cdev->private->onoff, 0);
 	}
-	spin_unlock_irq(cdev->ccwlock);
+
+	css_sched_sch_todo(sch, SCH_TODO_UNREG);
+	CIO_MSG_EVENT(3, "ccw: purging 0.%x.%04x%s\n", sch->schid.ssid,
+		      sch->schib.pmcw.dev, cdev ? "" : " (no cdev)");
+
+unlock:
+	spin_unlock_irq(sch->lock);
 	/* Abort loop in case of pending signal. */
 	if (signal_pending(current))
 		return -EINTR;
@@ -1355,7 +1366,7 @@ static int purge_fn(struct device *dev, void *data)
 int ccw_purge_blacklisted(void)
 {
 	CIO_MSG_EVENT(2, "ccw: purging blacklisted devices\n");
-	bus_for_each_dev(&ccw_bus_type, NULL, NULL, purge_fn);
+	for_each_subchannel_staged(purge_fn, NULL, NULL);
 	return 0;
 }
 
-- 
2.48.1



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