[S390] dasd: add hyper PAV support to DASD device driver, part 1

Parallel access volumes (PAV) is a storage server feature, that allows
to start multiple channel programs on the same DASD in parallel. It
defines alias devices which can be used as alternative paths to the
same disk. With the old base PAV support we only needed rudimentary
functionality in the DASD device driver. As the mapping between base
and alias devices was static, we just had to export an identifier
(uid) and could leave the combining of devices to external layers
like a device mapper multipath.
Now hyper PAV removes the requirement to dedicate alias devices to
specific base devices. Instead each alias devices can be combined with
multiple base device on a per request basis. This requires full
support by the DASD device driver as now each channel program itself
has to identify the target base device.
The changes to the dasd device driver and the ECKD discipline are:
- Separate subchannel device representation (dasd_device) from block
  device representation (dasd_block). Only base devices are block
  devices.
- Gather information about base and alias devices and possible
  combinations.
- For each request decide which dasd_device should be used (base or
  alias) and build specific channel program.
- Support summary unit checks, which allow the storage server to
  upgrade / downgrade between base and hyper PAV at runtime (support
  is mandatory).

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

1 files changed, 13 insertions, 8 deletions

diff --git a/drivers/s390/block/dasd_proc.c b/drivers/s390/block/dasd_proc.c
index ac7e8ef504cb..0584a7dc5ede 100644
--- a/drivers/s390/block/dasd_proc.c
+++ b/drivers/s390/block/dasd_proc.c
@@ -54,11 +54,16 @@ static int
 dasd_devices_show(struct seq_file *m, void *v)
 {
         struct dasd_device *device;
+        struct dasd_block *block;
         char *substr;
 
         device = dasd_device_from_devindex((unsigned long) v - 1);
         if (IS_ERR(device))
                 return 0;
+        if (device->block)
+                block = device->block;
+        else
+                return 0;
         /* Print device number. */
         seq_printf(m, "%s", device->cdev->dev.bus_id);
         /* Print discipline string. */
@@ -67,14 +72,14 @@ dasd_devices_show(struct seq_file *m, void *v)
         else
                 seq_printf(m, "(none)");
         /* Print kdev. */
-        if (device->gdp)
+        if (block->gdp)
                 seq_printf(m, " at (%3d:%6d)",
-                           device->gdp->major, device->gdp->first_minor);
+                           block->gdp->major, block->gdp->first_minor);
         else
                 seq_printf(m, "  at (???:??????)");
         /* Print device name. */
-        if (device->gdp)
-                seq_printf(m, " is %-8s", device->gdp->disk_name);
+        if (block->gdp)
+                seq_printf(m, " is %-8s", block->gdp->disk_name);
         else
                 seq_printf(m, " is ????????");
         /* Print devices features. */
@@ -100,14 +105,14 @@ dasd_devices_show(struct seq_file *m, void *v)
         case DASD_STATE_READY:
         case DASD_STATE_ONLINE:
                 seq_printf(m, "active ");
-                if (dasd_check_blocksize(device->bp_block))
+                if (dasd_check_blocksize(block->bp_block))
                         seq_printf(m, "n/f       ");
                 else
                         seq_printf(m,
                                    "at blocksize: %d, %ld blocks, %ld MB",
-                                   device->bp_block, device->blocks,
-                                   ((device->bp_block >> 9) *
-                                    device->blocks) >> 11);
+                                   block->bp_block, block->blocks,
+                                   ((block->bp_block >> 9) *
+                                    block->blocks) >> 11);
                 break;
         default:
                 seq_printf(m, "no stat");