From: Hans-Joachim Picht <hpicht@redhat.com>
Date: Tue, 30 Oct 2007 16:57:09 +0100
Subject: [s390] cio: Device status validity
Message-id: 20071030155709.GB6604@redhat.com
O-Subject: [RHEL5.2 PATCH 2/5] s390 cio: Device status validity
Bugzilla: 354821

Problem:
=========

The device driver assumes the final status for a request while it isn't
finished yet.
The device status in the irb contains the channel end/device end.
The problem was hit by performing I/O stress tesits while pulling/plugging storage
cables or performing  a variety of logical operations. At some point, data written to disk
diverged from expected data (dasd driver received incorrect channel end/device
end, however, data was not written to disk).

Bugzilla
=========

BZ 354821
https://bugzilla.redhat.com/show_bug.cgi?id=354821

Upstream status of the patch:
=============================
Fix included in git as commit 25c61a1fe8c97d1352a2dc0eda25128b3be0db27

Test status:
============
Kernel with patch was built and successfully tested

Please ACK.

With best regards,

Hans

diff --git a/drivers/s390/cio/device_status.c b/drivers/s390/cio/device_status.c
index 1d53ac1..418954f 100644
--- a/drivers/s390/cio/device_status.c
+++ b/drivers/s390/cio/device_status.c
@@ -264,7 +264,11 @@ ccw_device_accumulate_irb(struct ccw_device *cdev, struct irb *irb)
 		cdev_irb->scsw.cpa = irb->scsw.cpa;
 	/* Accumulate device status, but not the device busy flag. */
 	cdev_irb->scsw.dstat &= ~DEV_STAT_BUSY;
-	cdev_irb->scsw.dstat |= irb->scsw.dstat;
+	/* dstat is not always valid. */
+	if (irb->scsw.stctl &
+	    (SCSW_STCTL_PRIM_STATUS | SCSW_STCTL_SEC_STATUS
+	     | SCSW_STCTL_INTER_STATUS | SCSW_STCTL_ALERT_STATUS))
+		cdev_irb->scsw.dstat |= irb->scsw.dstat;
 	/* Accumulate subchannel status. */
 	cdev_irb->scsw.cstat |= irb->scsw.cstat;
 	/* Copy residual count if it is valid. */