[06/10] S390: dasd: support DIAG access for read-only devices

[Greg KH]

2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Stefan Weinhuber <wein@xxxxxxxxxx>

commit 22825ab7693fd29769518a0d25ba43c01a50092a upstream.

When a DASD device is used with the DIAG discipline, the DIAG
initialization will indicate success or error with a respective
return code. So far we have interpreted a return code of 4 as error,
but it actually means that the initialization was successful, but
the device is read-only. To allow read-only devices to be used with
DIAG we need to accept a return code of 4 as success.

Re-initialization of the DIAG access is also part of the DIAG error
recovery. If we find that the access mode of a device has been
changed from writable to read-only while the device was in use,
we print an error message.

Signed-off-by: Stefan Weinhuber <wein@xxxxxxxxxx>
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: Stephen Powell <zlinuxman@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 drivers/s390/block/dasd_diag.c |   19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

--- a/drivers/s390/block/dasd_diag.c
+++ b/drivers/s390/block/dasd_diag.c
@@ -143,6 +143,15 @@ dasd_diag_erp(struct dasd_device *device
 
 	mdsk_term_io(device);
 	rc = mdsk_init_io(device, device->block->bp_block, 0, NULL);
+	if (rc == 4) {
+		if (!(device->features & DASD_FEATURE_READONLY)) {
+			dev_warn(&device->cdev->dev,
+				 "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);
@@ -432,16 +441,20 @@ dasd_diag_check_device(struct dasd_devic
 	for (sb = 512; sb < bsize; sb = sb << 1)
 		block->s2b_shift++;
 	rc = mdsk_init_io(device, block->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) block->bp_block,
 			    (unsigned long) (block->blocks <<
-				block->s2b_shift) >> 1);
+				block->s2b_shift) >> 1,
+				(rc == 4) ? ", read-only device" : "");
+		rc = 0;
 	}
 out_label:
 	free_page((long) label);


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