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

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@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 16 insertions, 3 deletions

diff --git a/drivers/s390/block/dasd_diag.c b/drivers/s390/block/dasd_diag.c
index 4e49b4a6c880..8174ec921769 100644
--- a/drivers/s390/block/dasd_diag.c
+++ b/drivers/s390/block/dasd_diag.c
@@ -145,6 +145,15 @@ 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_warn(&device->cdev->dev, "DIAG ERP failed with "
                             "rc=%d\n", rc);
@@ -433,16 +442,20 @@ dasd_diag_check_device(struct dasd_device *device)
         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_warn(&device->cdev->dev, "DIAG initialization "
                         "failed with rc=%d\n", rc);
                 rc = -EIO;
         } else {
+                if (rc == 4)
+                        device->features |= DASD_FEATURE_READONLY;
                 dev_info(&device->cdev->dev,
-                         "New DASD with %ld byte/block, total size %ld KB\n",
+                         "New DASD with %ld byte/block, total size %ld KB%s\n",
                          (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);