[S390] dasd: automatic recognition of read-only devices

In z/VM it is possible to attach a device as read-only. To prevent
unintentional write requests and subsequent I/O errors, we can detect
this configuration using the z/VM DIAG 210 interface and set the
respective linux block device to read-only as well.

Signed-off-by: Stefan Weinhuber <[e-mail]>
Signed-off-by: Martin Schwidefsky <[e-mail]>

drivers/s390/block/dasd.c

···
 #include <asm/ebcdic.h>
 #include <asm/idals.h>
 #include <asm/itcw.h>
+#include <asm/diag.h>
 
 /* This is ugly... */
 #define PRINTK_HEADER "dasd:"
···
 		goto out;
 	}
 
+	if ((mode & FMODE_WRITE) &&
+	    (test_bit(DASD_FLAG_DEVICE_RO, &base->flags) ||
+	     (base->features & DASD_FEATURE_READONLY))) {
+		rc = -EROFS;
+		goto out;
+	}
+
 	return 0;
 
 out:
···
 /*
  * SECTION: common functions for ccw_driver use
  */
+
+/*
+ * Is the device read-only?
+ * Note that this function does not report the setting of the
+ * readonly device attribute, but how it is configured in z/VM.
+ */
+int dasd_device_is_ro(struct dasd_device *device)
+{
+	struct ccw_dev_id dev_id;
+	struct diag210 diag_data;
+	int rc;
+
+	if (!MACHINE_IS_VM)
+		return 0;
+	ccw_device_get_id(device->cdev, &dev_id);
+	memset(&diag_data, 0, sizeof(diag_data));
+	diag_data.vrdcdvno = dev_id.devno;
+	diag_data.vrdclen = sizeof(diag_data);
+	rc = diag210(&diag_data);
+	if (rc == 0 || rc == 2) {
+		return diag_data.vrdcvfla & 0x80;
+	} else {
+		DBF_EVENT(DBF_WARNING, "diag210 failed for dev=%04x with rc=%d",
+			  dev_id.devno, rc);
+		return 0;
+	}
+}
+EXPORT_SYMBOL_GPL(dasd_device_is_ro);
 
 static void dasd_generic_auto_online(void *data, async_cookie_t cookie)
 {

drivers/s390/block/dasd_3990_erp.c

···
 
 		erp->retries = 5;
 
+	} else if (sense[1] & SNS1_WRITE_INHIBITED) {
+		dev_err(&device->cdev->dev, "An I/O request was rejected"
+			" because writing is inhibited\n");
+		erp = dasd_3990_erp_cleanup(erp, DASD_CQR_FAILED);
 	} else {
 		/* fatal error -  set status to FAILED
 		   internal error 09 - Command Reject */

drivers/s390/block/dasd_devmap.c

···
 	      const char *buf, size_t count)
 {
 	struct dasd_devmap *devmap;
+	struct dasd_device *device;
 	int val;
 	char *endp;
 
···
 		devmap->features |= DASD_FEATURE_READONLY;
 	else
 		devmap->features &= ~DASD_FEATURE_READONLY;
-	if (devmap->device)
-		devmap->device->features = devmap->features;
-	if (devmap->device && devmap->device->block
-	    && devmap->device->block->gdp)
-		set_disk_ro(devmap->device->block->gdp, val);
+	device = devmap->device;
+	if (device) {
+		device->features = devmap->features;
+		val = val || test_bit(DASD_FLAG_DEVICE_RO, &device->flags);
+	}
 	spin_unlock(&dasd_devmap_lock);
+	if (device && device->block && device->block->gdp)
+		set_disk_ro(device->block->gdp, val);
 	return count;
 }
 

drivers/s390/block/dasd_diag.c

···
 	mdsk_term_io(device);
 	rc = mdsk_init_io(device, device->block->bp_block, 0, NULL);
 	if (rc == 4) {
-		if (!(device->features & DASD_FEATURE_READONLY)) {
+		if (!(test_and_set_bit(DASD_FLAG_DEVICE_RO, &device->flags)))
 			pr_warning("%s: The access mode of a DIAG device "
 				   "changed to read-only\n",
 				   dev_name(&device->cdev->dev));
-			device->features |= DASD_FEATURE_READONLY;
-		}
 		rc = 0;
 	}
 	if (rc)
···
 		rc = -EIO;
 	} else {
 		if (rc == 4)
-			device->features |= DASD_FEATURE_READONLY;
+			set_bit(DASD_FLAG_DEVICE_RO, &device->flags);
 		pr_info("%s: New DASD with %ld byte/block, total size %ld "
 			"KB%s\n", dev_name(&device->cdev->dev),
 			(unsigned long) block->bp_block,

drivers/s390/block/dasd_eckd.c

···
 	struct dasd_eckd_private *private;
 	struct dasd_block *block;
 	int is_known, rc;
+	int readonly;
 
 	if (!ccw_device_is_pathgroup(device->cdev)) {
 		dev_warn(&device->cdev->dev,
···
 	else
 		private->real_cyl = private->rdc_data.no_cyl;
 
+	readonly = dasd_device_is_ro(device);
+	if (readonly)
+		set_bit(DASD_FLAG_DEVICE_RO, &device->flags);
+
 	dev_info(&device->cdev->dev, "New DASD %04X/%02X (CU %04X/%02X) "
-		 "with %d cylinders, %d heads, %d sectors\n",
+		 "with %d cylinders, %d heads, %d sectors%s\n",
 		 private->rdc_data.dev_type,
 		 private->rdc_data.dev_model,
 		 private->rdc_data.cu_type,
 		 private->rdc_data.cu_model.model,
 		 private->real_cyl,
 		 private->rdc_data.trk_per_cyl,
-		 private->rdc_data.sec_per_trk);
+		 private->rdc_data.sec_per_trk,
+		 readonly ? ", read-only device" : "");
 	return 0;
 
 out_err3:

drivers/s390/block/dasd_fba.c

···
 	struct dasd_fba_private *private;
 	struct ccw_device *cdev = device->cdev;
 	int rc;
+	int readonly;
 
 	private = (struct dasd_fba_private *) device->private;
 	if (!private) {
···
 		return rc;
 	}
 
+	readonly = dasd_device_is_ro(device);
+	if (readonly)
+		set_bit(DASD_FLAG_DEVICE_RO, &device->flags);
+
 	dev_info(&device->cdev->dev,
 		 "New FBA DASD %04X/%02X (CU %04X/%02X) with %d MB "
-		 "and %d B/blk\n",
+		 "and %d B/blk%s\n",
 		 cdev->id.dev_type,
 		 cdev->id.dev_model,
 		 cdev->id.cu_type,
 		 cdev->id.cu_model,
 		 ((private->rdc_data.blk_bdsa *
 		   (private->rdc_data.blk_size >> 9)) >> 11),
-		 private->rdc_data.blk_size);
+		 private->rdc_data.blk_size,
+		 readonly ? ", read-only device" : "");
 	return 0;
 }
 

drivers/s390/block/dasd_genhd.c

···
 	}
 	len += sprintf(gdp->disk_name + len, "%c", 'a'+(base->devindex%26));
 
-	if (block->base->features & DASD_FEATURE_READONLY)
+	if (base->features & DASD_FEATURE_READONLY ||
+	    test_bit(DASD_FLAG_DEVICE_RO, &base->flags))
 		set_disk_ro(gdp, 1);
 	gdp->private_data = block;
 	gdp->queue = block->request_queue;

drivers/s390/block/dasd_int.h

···
 #define DASD_FLAG_OFFLINE	3	/* device is in offline processing */
 #define DASD_FLAG_EER_SNSS	4	/* A SNSS is required */
 #define DASD_FLAG_EER_IN_USE	5	/* A SNSS request is running */
+#define DASD_FLAG_DEVICE_RO	6	/* The device itself is read-only. Don't
+					 * confuse this with the user specified
+					 * read-only feature.
+					 */
 
 void dasd_put_device_wake(struct dasd_device *);
 
···
 
 void dasd_device_set_stop_bits(struct dasd_device *, int);
 void dasd_device_remove_stop_bits(struct dasd_device *, int);
+
+int dasd_device_is_ro(struct dasd_device *);
+
 
 /* externals in dasd_devmap.c */
 extern int dasd_max_devindex;

drivers/s390/block/dasd_ioctl.c

···
 	if (!argp)
 		return -EINVAL;
 
-	if (block->base->features & DASD_FEATURE_READONLY)
+	if (block->base->features & DASD_FEATURE_READONLY ||
+	    test_bit(DASD_FLAG_DEVICE_RO, &block->base->flags))
 		return -EROFS;
 	if (copy_from_user(&fdata, argp, sizeof(struct format_data_t)))
 		return -EFAULT;
···
 		return -EINVAL;
 	if (get_user(intval, (int __user *)argp))
 		return -EFAULT;
-
+	if (!intval && test_bit(DASD_FLAG_DEVICE_RO, &block->base->flags))
+		return -EROFS;
 	set_disk_ro(bdev->bd_disk, intval);
 	return dasd_set_feature(block->base->cdev, DASD_FEATURE_READONLY, intval);
 }