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

1 files changed, 36 insertions, 0 deletions

diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c
index 4951aa82e9f..bbea90baf98 100644
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -26,6 +26,7 @@
 #include <asm/ebcdic.h>
 #include <asm/idals.h>
 #include <asm/itcw.h>
+#include <asm/diag.h>
 
 /* This is ugly... */
 #define PRINTK_HEADER "dasd:"
@@ -2212,6 +2213,13 @@ static int dasd_open(struct block_device *bdev, fmode_t mode)
 		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:
@@ -2289,6 +2297,34 @@ dasd_exit(void)
  * 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)
 {
 	struct ccw_device *cdev = data;