From: Hendrik Brueckner <brueckner@redhat.com>
Date: Tue, 17 Nov 2009 11:10:43 -0500
Subject: [s390] dasd: fix DIAG access for read-only devices
Message-id: <20091117111042.GA21180@redhat.com>
Patchwork-id: 21392
O-Subject: [RHEL5 U5 PATCH 1/1] s390 - dasd: Fix DIAG access for read-only
	devices
Bugzilla: 537859
RH-Acked-by: Pete Zaitcev <zaitcev@redhat.com>

Description
===========
If a DASD is attached as read-only under z/VM and it is configured
to be used with the DIAG discipline, then setting the device online
will fail.
The message log will show a message 'DIAG initialization failed (rc=4)'.

The DIAG return code 4 indicates that the initialization was successful
and the device is read-only, but the DASD device driver interprets this
as an error.

The solution is to fix the DIAG device initialization to accept a return
value of 4 as indication of success.

Bugzilla
========
BZ 537859
https://bugzilla.redhat.com/show_bug.cgi?id=537859

Upstream status of the patch
============================
The patch will be upstream in kernel version 2.6.33.

The patch has been posted to LKML: http://lkml.org/lkml/2009/11/13/232

Test status
===========
The patch has been tested and fixes the problem.
The fix has been verified by the IBM test department.

Signed-off-by: Don Zickus <dzickus@redhat.com>

diff --git a/drivers/s390/block/dasd_diag.c b/drivers/s390/block/dasd_diag.c
index a919fed..4b15fa4 100644
--- a/drivers/s390/block/dasd_diag.c
+++ b/drivers/s390/block/dasd_diag.c
@@ -160,6 +160,15 @@ dasd_diag_erp(struct dasd_device *device)
 
 	mdsk_term_io(device);
 	rc = mdsk_init_io(device, device->bp_block, 0, NULL);
+	if (rc == 4) {
+		if (!(device->features & DASD_FEATURE_READONLY)) {
+			DEV_MESSAGE(KERN_WARNING, device, "%s",
+				 "The access mode of a DIAG device changed"
+				 " to read-only");
+			device->features |= DASD_FEATURE_READONLY;
+		}
+		rc = 0;
+	}
 	if (rc)
 		DEV_MESSAGE(KERN_WARNING, device, "DIAG ERP unsuccessful, "
 			    "rc=%d", rc);
@@ -433,16 +442,20 @@ dasd_diag_check_device(struct dasd_device *device)
 	for (sb = 512; sb < bsize; sb = sb << 1)
 		device->s2b_shift++;
 	rc = mdsk_init_io(device, device->bp_block, 0, NULL);
-	if (rc) {
+	if (rc && (rc != 4)) {
 		DEV_MESSAGE(KERN_WARNING, device, "DIAG initialization "
 			"failed (rc=%d)", rc);
 		rc = -EIO;
 	} else {
+		if (rc == 4)
+			device->features |= DASD_FEATURE_READONLY;
 		DEV_MESSAGE(KERN_INFO, device,
-			    "(%ld B/blk): %ldkB",
+			    "(%ld B/blk): %ldkB%s",
 			    (unsigned long) device->bp_block,
 			    (unsigned long) (device->blocks <<
-				device->s2b_shift) >> 1);
+					     device->s2b_shift) >> 1,
+			    (rc == 4) ? ", read-only device" : "");
+		rc = 0;
 	}
 out:
 	free_page((long) label);