s390/dasd: add copy pair setup

A copy relation that is configured on the storage server side needs to be
enabled separately in the device driver. A sysfs interface is created
that allows userspace tooling to control such setup.

The following sysfs entries are added to store and read copy relation
information:

copy_pair
    - Add/Delete a copy pair relation to the DASD device driver
    - Query all previously added copy pair relations
copy_role
    - Query the copy pair role of the device

To add a copy pair to the DASD device driver it has to be specified
through the sysfs attribute copy_pair. Only one secondary device can be
specified at a time together with the primary device. Both, secondary
and primary can be used equally to define the copy pair.
The secondary devices have to be offline when adding the copy relation.
The primary device needs to be specified first followed by the comma
separated secondary device.
Read from the copy_pair attribute to get the current setup and write
"clear" to the attribute to delete any existing setup.

Example:
$ echo 0.0.9700,0.0.9740 > /sys/bus/ccw/devices/0.0.9700/copy_pair
$ cat /sys/bus/ccw/devices/0.0.9700/copy_pair
0.0.9700,0.0.9740

During device online processing the required data will be read from the
storage server and the information will be compared to the setup
requested through the copy_pair attribute. The registration of the
primary and secondary device will be handled accordingly.
A blockdevice is only allocated for copy relation primary devices.

To query the copy role of a device read from the copy_role sysfs
attribute. Possible values are primary, secondary, and none.

Example:
$ cat /sys/bus/ccw/devices/0.0.9700/copy_role
primary

Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Reviewed-by: Jan Hoeppner <hoeppner@linux.ibm.com>
Link: https://lore.kernel.org/r/20220920192616.808070-4-sth@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 20 insertions, 0 deletions

diff --git a/drivers/s390/block/dasd_int.h b/drivers/s390/block/dasd_int.h
index 39316020529d..d9794ec03722 100644
--- a/drivers/s390/block/dasd_int.h
+++ b/drivers/s390/block/dasd_int.h
@@ -290,6 +290,24 @@ struct dasd_pprc_data_sc4 {
 	struct dasd_pprc_dev_info dev_info[5];
 } __packed;
 
+#define DASD_BUS_ID_SIZE 20
+#define DASD_CP_ENTRIES 5
+
+struct dasd_copy_entry {
+	char busid[DASD_BUS_ID_SIZE];
+	struct dasd_device *device;
+	bool primary;
+	bool configured;
+};
+
+struct dasd_copy_relation {
+	struct dasd_copy_entry entry[DASD_CP_ENTRIES];
+	struct dasd_copy_entry *active;
+};
+
+int dasd_devmap_set_device_copy_relation(struct ccw_device *,
+					 bool pprc_enabled);
+
 /*
  * the struct dasd_discipline is
  * sth like a table of virtual functions, if you think of dasd_eckd
@@ -419,6 +437,7 @@ struct dasd_discipline {
 					   struct dasd_ccw_req *, struct irb *);
 	int (*ese_read)(struct dasd_ccw_req *, struct irb *);
 	int (*pprc_status)(struct dasd_device *, struct	dasd_pprc_data_sc4 *);
+	bool (*pprc_enabled)(struct dasd_device *);
 };
 
 extern struct dasd_discipline *dasd_diag_discipline_pointer;
@@ -615,6 +634,7 @@ struct dasd_device {
 	struct dasd_profile profile;
 	struct dasd_format_entry format_entry;
 	struct kset *paths_info;
+	struct dasd_copy_relation *copy;
 };
 
 struct dasd_block {