Patch "s390/cio: Do not unregister the subchannel based on DNV" has been added to the 6.1-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    s390/cio: Do not unregister the subchannel based on DNV

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     s390-cio-do-not-unregister-the-subchannel-based-on-d.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 75630e3fc7a1902e65d5967d0c43f665c1e0d390
Author: Vineeth Vijayan <vneethv@xxxxxxxxxxxxx>
Date:   Mon Sep 23 22:16:43 2024 +0200

    s390/cio: Do not unregister the subchannel based on DNV
    
    [ Upstream commit 8c58a229688ce3a097b3b1a2efe1b4f5508c2123 ]
    
    Starting with commit 2297791c92d0 ("s390/cio: dont unregister
    subchannel from child-drivers"), CIO does not unregister subchannels
    when the attached device is invalid or unavailable. Instead, it
    allows subchannels to exist without a connected device. However, if
    the DNV value is 0, such as, when all the CHPIDs of a subchannel are
    configured in standby state, the subchannel is unregistered, which
    contradicts the current subchannel specification.
    
    Update the logic so that subchannels are not unregistered based
    on the DNV value. Also update the SCHIB information even if the
    DNV bit is zero.
    
    Suggested-by: Peter Oberparleiter <oberpar@xxxxxxxxxxxxx>
    Signed-off-by: Vineeth Vijayan <vneethv@xxxxxxxxxxxxx>
    Fixes: 2297791c92d0 ("s390/cio: dont unregister subchannel from child-drivers")
    Reviewed-by: Peter Oberparleiter <oberpar@xxxxxxxxxxxxx>
    Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/s390/cio/cio.c b/drivers/s390/cio/cio.c
index 923f5ca4f5e6b..54bfa9fe3031b 100644
--- a/drivers/s390/cio/cio.c
+++ b/drivers/s390/cio/cio.c
@@ -459,10 +459,14 @@ int cio_update_schib(struct subchannel *sch)
 {
 	struct schib schib;
 
-	if (stsch(sch->schid, &schib) || !css_sch_is_valid(&schib))
+	if (stsch(sch->schid, &schib))
 		return -ENODEV;
 
 	memcpy(&sch->schib, &schib, sizeof(schib));
+
+	if (!css_sch_is_valid(&schib))
+		return -EACCES;
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(cio_update_schib);
diff --git a/drivers/s390/cio/device.c b/drivers/s390/cio/device.c
index 5666b9cc5d296..bdf5a50bd931d 100644
--- a/drivers/s390/cio/device.c
+++ b/drivers/s390/cio/device.c
@@ -1378,14 +1378,18 @@ enum io_sch_action {
 	IO_SCH_VERIFY,
 	IO_SCH_DISC,
 	IO_SCH_NOP,
+	IO_SCH_ORPH_CDEV,
 };
 
 static enum io_sch_action sch_get_action(struct subchannel *sch)
 {
 	struct ccw_device *cdev;
+	int rc;
 
 	cdev = sch_get_cdev(sch);
-	if (cio_update_schib(sch)) {
+	rc = cio_update_schib(sch);
+
+	if (rc == -ENODEV) {
 		/* Not operational. */
 		if (!cdev)
 			return IO_SCH_UNREG;
@@ -1393,6 +1397,16 @@ static enum io_sch_action sch_get_action(struct subchannel *sch)
 			return IO_SCH_UNREG;
 		return IO_SCH_ORPH_UNREG;
 	}
+
+	/* Avoid unregistering subchannels without working device. */
+	if (rc == -EACCES) {
+		if (!cdev)
+			return IO_SCH_NOP;
+		if (ccw_device_notify(cdev, CIO_GONE) != NOTIFY_OK)
+			return IO_SCH_UNREG_CDEV;
+		return IO_SCH_ORPH_CDEV;
+	}
+
 	/* Operational. */
 	if (!cdev)
 		return IO_SCH_ATTACH;
@@ -1462,6 +1476,7 @@ static int io_subchannel_sch_event(struct subchannel *sch, int process)
 		rc = 0;
 		goto out_unlock;
 	case IO_SCH_ORPH_UNREG:
+	case IO_SCH_ORPH_CDEV:
 	case IO_SCH_ORPH_ATTACH:
 		ccw_device_set_disconnected(cdev);
 		break;
@@ -1493,6 +1508,7 @@ static int io_subchannel_sch_event(struct subchannel *sch, int process)
 	/* Handle attached ccw device. */
 	switch (action) {
 	case IO_SCH_ORPH_UNREG:
+	case IO_SCH_ORPH_CDEV:
 	case IO_SCH_ORPH_ATTACH:
 		/* Move ccw device to orphanage. */
 		rc = ccw_device_move_to_orph(cdev);