Name only physical volumes in a restricted LVM scan and keep its own reads from counting as activity

- An explicit --devices list makes LVM open every device in it, while a plain scan opens only known volumes; the list now names only LVM physical volumes, read from udev by lsblk, so no other disk is touched
- RAID, multipath and encrypted volumes follow the disks they are built on, instead of turning the whole check off
- After each pvs, lvs or vgs run, the disks it read take their counters as the new baseline, so an unused disk can become idle

tests/test_lvm_disk_read_policy.py

@@ -1,5 +1,6 @@
 """Automatic LVM readers must not bypass disk exclusions/idle policy."""
 import ast
+import json
 from pathlib import Path
 import subprocess
 import sys
@@ -11,7 +12,14 @@ SCRIPTS = Path(__file__).resolve().parents[1] / "AppImage/scripts"
 sys.path.insert(0, str(SCRIPTS))
 import lvm_device_scope as scope
 
-INVENTORY = "nvme0n1 disk\nnvme0n1p1 part nvme0n1\nsda disk\nsda1 part sda\nsdb disk\nsdb1 part sdb\n"
+def lsblk(*devices):
+    """lsblk -J -l output from (kname, type, pkname, fstype) rows."""
+    return json.dumps({"blockdevices": [dict(zip(("kname", "type", "pkname", "fstype"), row)) for row in devices]})
+
+
+INVENTORY = lsblk(("nvme0n1", "disk", None, None), ("nvme0n1p1", "part", "nvme0n1", "LVM2_member"),
+                  ("sda", "disk", None, None), ("sda1", "part", "sda", "LVM2_member"),
+                  ("sdb", "disk", None, None), ("sdb1", "part", "sdb", "LVM2_member"))
 
 
 class LvmScopeTests(unittest.TestCase):
@@ -29,24 +37,24 @@ class LvmScopeTests(unittest.TestCase):
     def args(self, inventory=INVENTORY, code=0):
         with patch.object(scope.subprocess, "run", return_value=types.SimpleNamespace(returncode=code, stdout=inventory)) as run:
             args = scope.lvm_device_args(self.standby)
-        self.assertEqual(run.call_args.args[0], ["lsblk", "-rno", "NAME,TYPE,PKNAME"])
+        self.assertEqual(run.call_args.args[0], ["lsblk", "-J", "-l", "-o", "KNAME,TYPE,PKNAME,FSTYPE"])
         return args
 
     def test_excluded_disks_and_their_partitions_are_not_in_the_scan(self):
-        self.assertEqual(self.args(), ["--devices", "/dev/nvme0n1,/dev/nvme0n1p1,/dev/sdb,/dev/sdb1"])
+        self.assertEqual(self.args(), ["--devices", "/dev/nvme0n1p1,/dev/sdb1"])
         self.assertNotIn((("sda",), {}), self.standby.call_args_list)
         self.assertEqual({call.args[0] for call in self.standby.call_args_list}, {"nvme0n1", "sdb"})
 
     def test_idle_disks_receive_no_power_query(self):
         self.excluded = set()
         self.policy.side_effect = lambda disk, excluded: "idle" if disk == "sda" else "read"
-        self.assertNotIn("/dev/sda", self.args()[1])
+        self.assertNotIn("/dev/sda1", self.args()[1])
         self.assertEqual({call.args[0] for call in self.standby.call_args_list}, {"nvme0n1", "sdb"})
 
     def test_a_standby_disk_is_excluded_even_when_its_io_changed(self):
         self.excluded = set()
         self.standby.side_effect = lambda disk: disk == "sdb"
-        self.assertEqual(self.args(), ["--devices", "/dev/nvme0n1,/dev/nvme0n1p1,/dev/sda,/dev/sda1"])
+        self.assertEqual(self.args(), ["--devices", "/dev/nvme0n1p1,/dev/sda1"])
 
     def test_all_allowed_disks_keep_existing_scan_behaviour(self):
         self.excluded = set()
@@ -63,7 +71,8 @@ class LvmScopeTests(unittest.TestCase):
         self.assertIsNone(self.args())
 
     def test_bad_inventory_or_policy_never_authorizes_an_unrestricted_scan(self):
-        for inventory, code in (("", 0), (INVENTORY, 1), ("sda1 part sda", 0), ("../sda disk", 0)):
+        for inventory, code in (("", 0), (INVENTORY, 1), ("sda1 part sda", 0),
+                                (lsblk(("sda1", "part", "sda", None)), 0), (lsblk(("../sda", "disk", None, None)), 0)):
             self.assertIsNone(self.args(inventory, code))
         for error in (FileNotFoundError(), subprocess.TimeoutExpired("lsblk", 5)):
             with patch.object(scope.subprocess, "run", side_effect=error):
@@ -72,6 +81,32 @@ class LvmScopeTests(unittest.TestCase):
         self.assertIsNone(self.args())
 
 
+    def test_raid_multipath_and_encrypted_devices_follow_their_disks(self):
+        inventory = lsblk(
+            ("sda", "disk", None, None), ("sda1", "part", "sda", "linux_raid_member"),
+            ("sdb", "disk", None, None), ("sdb1", "part", "sdb", "linux_raid_member"),
+            ("md0", "raid1", "sda1", "LVM2_member"), ("md0", "raid1", "sdb1", "LVM2_member"),
+            ("sdc", "disk", None, None), ("sdc1", "part", "sdc", "crypto_LUKS"),
+            ("dm-0", "crypt", "sdc1", "LVM2_member"), ("dm-1", "lvm", "dm-0", "ext4"),
+            ("sdd", "disk", None, None), ("sde", "disk", None, None),
+            ("dm-2", "mpath", "sdd", None), ("dm-2", "mpath", "sde", None), ("dm-3", "part", "dm-2", "LVM2_member"))
+        self.excluded = {"sdb"}
+        # md0 reads sdb as well, so it stays out; the LUKS volume and the
+        # multipath partition are built only on readable disks. Disks that
+        # hold no physical volume are never named, so LVM does not open them.
+        self.assertEqual(self.args(inventory), ["--devices", "/dev/dm-0,/dev/dm-3"])
+        self.excluded = set()
+        self.assertEqual(self.args(inventory), [])
+
+    def test_the_scan_settles_its_own_reads_on_the_disks_it_read(self):
+        self.excluded = {"sda"}
+        settled = Mock()
+        self.disk_module.settle_own_reads = settled
+        self.args()
+        scope.settle_scan_reads()
+        settled.assert_called_once_with({"nvme0n1", "sdb"})
+
+
 class LvmReaderTests(unittest.TestCase):
     def extract(self, file, name, owner=None, namespace=None):
         tree = ast.parse((SCRIPTS / file).read_text())