at_dt_iscsi_disk: fix disk_discovery

The code found new disks by their target name, e.g.
'vdX'. Those names can change between reboots.

Instead, use function to identify new disks that don't mount the root
file system.

The function raises an error if there is no such disk, so handle that to
confirm that disks are detached correctly.

Signed-off-by: Sebastian Mitterle <[email protected]>

libvirt/tests/src/virtual_disks/at_dt_iscsi_disk.py

@@ -8,6 +8,7 @@
 
 from aexpect import ShellError
 
+from avocado.core.exceptions import TestError
 from avocado.utils import process
 
 from virttest import virsh
@@ -16,6 +17,7 @@
 from virttest.remote import LoginError
 from virttest.virt_vm import VMError
 from virttest.utils_test import libvirt
+from virttest.utils_libvirt import libvirt_disk
 from virttest.libvirt_xml import vm_xml
 from virttest.libvirt_xml import pool_xml
 from virttest.libvirt_xml.secret_xml import SecretXML
@@ -386,13 +388,10 @@ def find_attach_disk(expect=True):
                     # recognize the hotplugged disk on PPC
                     if on_ppc:
                         time.sleep(10)
-                    cmd = "grep %s /proc/partitions" % disk_target
-                    s, o = session.cmd_status_output(cmd)
-                    logging.info("%s output: %s", cmd, o)
-                    session.close()
-                    if s == 0:
-                        found_disk = True
-                except (LoginError, VMError, ShellError) as e:
+                    disk, _ = libvirt_disk.get_non_root_disk_name(session)
+                    logging.debug("Found new disk in VM as %s", disk)
+                    found_disk = True
+                except (LoginError, VMError, ShellError, TestError) as e:
                     logging.error(str(e))
             if found_disk == expect:
                 logging.debug("Check disk inside the VM PASS as expected")