Added test_linstor_sr_pool_update for pool update with VM availability check.

- Uses `@pytest.mark.upgrade_test` to mark need of upgrade during the test
- Updates of all hosts in a LINSTOR SR pool (starting with the master)
- Reboots updated hosts
- Verifies VM can start and shutdown successfully on each host after update
- Ensures SR remains usable throughout the process

Signed-off-by: Rushikesh Jadhav <rushikesh7@gmail.com>

Author: rushikeshjadhav

tests/storage/linstor/test_linstor_sr.py

@@ -234,6 +234,56 @@ def test_linstor_missing(self, linstor_sr: SR, host: Host) -> None:
             if not linstor_installed:
                 host.yum_install([LINSTOR_PACKAGE])
 
+    @pytest.mark.reboot
+    @pytest.mark.small_vm
+    @pytest.mark.upgrade_test
+    def test_linstor_sr_pool_update(self, linstor_sr, vm_on_linstor_sr):
+        """
+        Perform update on the Linstor SR pool hosts while ensuring VM availability.
+        1. Identify all hosts in the SR pool and order them with the master first.
+        2. Update all hosts if updates are available.
+        3. Reboot all hosts.
+        4. Sequentially ensure that the VM can start on all hosts.
+        """
+        import concurrent.futures, threading
+
+        sr = linstor_sr
+        vm = vm_on_linstor_sr
+        updates_applied = []
+        updates_lock = threading.Lock()
+
+        # Sort hosts so that pool master is first (optional)
+        hosts = sorted(sr.pool.hosts, key=lambda h: h != sr.pool.master)
+
+        # RPU is disabled for pools with XOSTOR SRs.
+        # LINSTOR expects that we always use satellites and controllers with the same version on all hosts.
+        def install_updates_on(host):
+            logging.info("Checking on host %s", host.hostname_or_ip)
+            if host.has_updates(enablerepo="xcp-ng-linstor-testing"):
+                host.install_updates(enablerepo="xcp-ng-linstor-testing")
+                with updates_lock:
+                    updates_applied.append(host)
+            else:
+                logging.info("No updates available for host %s", host.hostname_or_ip)
+
+        with concurrent.futures.ThreadPoolExecutor() as executor:
+            executor.map(install_updates_on, hosts)
+
+        # Reboot updated hosts
+        def reboot_updated(host):
+            host.reboot(verify=True)
+
+        with concurrent.futures.ThreadPoolExecutor() as executor:
+            executor.map(reboot_updated, updates_applied)
+
+        # Ensure VM is able to boot on all the hosts
+        for h in hosts:
+            vm.start(on=h.uuid)
+            vm.wait_for_os_booted()
+            vm.shutdown(verify=True)
+
+        sr.scan()
+
     # *** End of tests with reboots
 
 # --- Test diskless resources --------------------------------------------------