Prevent shared FC/iSCSI LUNs from being used simultaneously across hosts

Use WWNs in the disk fixture to:
- Mark a LUN unavailable on all hosts if it is already in use on any host
  (cross-host deduplication for shared FC/iSCSI LUNs).
- Deprioritize LUNs listed in LVMOHBA_DEVICE_CONFIG or LVMOISCSI_DEVICE_CONFIG
  so they are only selected when no other disk is available.

Signed-off-by: Gaëtan Lehmann <gaetan.lehmann@vates.tech>

Author: glehmann

conftest.py

@@ -3,6 +3,7 @@
 import pytest
 
 import argparse
+import dataclasses
 import itertools
 import logging
 import os
@@ -435,6 +436,42 @@ def _host_disks(host: Host, hosts_cli_disks: list[DiskDevName] | None) -> Iterab
     ret = {host: list(_host_disks(host, cli_disks.get(host.hostname_or_ip)))
            for host in pools_hosts_by_name_or_ip.values()
            }
+    # Cross-host deduplication: a LUN in use on any host (same WWN) is unavailable on all hosts.
+    # This matters for shared FC/iSCSI LUNs visible on multiple hosts simultaneously.
+    used_wwns = {
+        disk.wwn
+        for host_disks in ret.values()
+        for disk in host_disks
+        if disk.wwn and not disk.available
+    }
+    if used_wwns:
+        logging.debug("cross-host used WWNs: %s", used_wwns)
+        ret = {
+            host: [
+                dataclasses.replace(disk, available=False) if (disk.wwn and disk.wwn in used_wwns) else disk
+                for disk in host_disks
+            ]
+            for host, host_disks in ret.items()
+        }
+    # LUNs reserved for lvmohba/lvmoiscsi: sort them to the end so they are
+    # only picked if no other disk is available.
+    reserved_wwns: set[str] = set()
+    try:
+        import data
+        for key in ('LVMOHBA_DEVICE_CONFIG', 'LVMOISCSI_DEVICE_CONFIG'):
+            cfg = getattr(data, key, None)
+            if isinstance(cfg, dict):
+                scsiid = cfg.get('SCSIid', '').lower().removeprefix('0x')
+                if len(scsiid) >= 16:
+                    reserved_wwns.add(scsiid[:16])
+    except ImportError:
+        pass
+    if reserved_wwns:
+        logging.debug("reserved WWNs (lvmohba/lvmoiscsi): %s", reserved_wwns)
+        ret = {
+            host: sorted(host_disks, key=lambda d: d.wwn in reserved_wwns)
+            for host, host_disks in ret.items()
+        }
     logging.debug("disks collected: %s", {host.hostname_or_ip: value for host, value in ret.items()})
     return ret