[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, 8 insertions, 5 deletions

diff --git a/drivers/s390/block/dasd_devmap.c b/drivers/s390/block/dasd_devmap.c
index d49766f3b94..8e23919c870 100644
--- a/drivers/s390/block/dasd_devmap.c
+++ b/drivers/s390/block/dasd_devmap.c
@@ -742,6 +742,7 @@ dasd_ro_store(struct device *dev, struct device_attribute *attr,
               const char *buf, size_t count)
 {
         struct dasd_devmap *devmap;
+        struct dasd_device *device;
         int val;
         char *endp;
 
@@ -758,12 +759,14 @@ dasd_ro_store(struct device *dev, struct device_attribute *attr,
                 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;
 }