fix(quota): a disk whose size is unknown is not counted as 0 GiB

A disk of the user's VMs whose size could not be read (its volume not in a
pool, the pool stopped) counted as 0 GiB, so a disk-limited user's increase
could pass over the limit. A disk no pool holds now has the size libvirt
reads from the file or device (blockInfo, also for a shut-off VM); one whose
size is still unknown makes the usage unverified and the increase is
refused, as when a host cannot be reached. Users without a disk limit are
not affected.

vrtManager/instance.py

@@ -926,6 +926,11 @@ class wvmInstance(wvmConnect):
                             volume, disk_size, used_size, storage = details
                         else:
                             volume = src_file
+                            # a disk no pool holds: libvirt reads its size from the file or device,
+                            # named by its path: a target names the running VM's disk, which may
+                            # be another file than the one saved for its next start (that one: unknown)
+                            with contextlib.suppress(libvirtError):
+                                disk_size, used_size = self.instance.blockInfo(src_file)[:2]
                     except Exception as e:
                         logger.warning("Disk %s of %s not fully read: %s", dev, self.instance.name(), e)
                     finally:

vrtManager/tests/test_instance_getters.py

@@ -48,6 +48,15 @@ class DeviceGettersTestCase(unittest.TestCase):
         self.assertEqual([(n["inbound"], n["outbound"]) for n in nics[1:]], [([], [])] * 2)
         self.assertEqual([(n["nic"], n["model"]) for n in nics], [("default", "virtio"), ("br0", ""), ("", "")])
 
+    def test_a_disk_no_pool_holds_has_the_size_libvirt_reads(self):
+        p = proxy()
+        p.instance = MagicMock()
+        # vda: libvirt reads it, by its path; vdb: it cannot
+        p.instance.blockInfo.side_effect = lambda path: [20 << 30, 5 << 30, 20 << 30] if path == "/pool/a.qcow2" else \
+            (_ for _ in ()).throw(libvirtError("cannot read"))
+        self.assertEqual([(d["dev"], d["size"], d["used"]) for d in p.get_disk_devices()],
+                         [("vda", 20 << 30, 5 << 30), ("vdb", None, None)])
+
     def test_an_empty_cdrom_shows_no_pool(self):
         media = proxy().get_media_devices()
         self.assertEqual(

vrtManager/tests/test_read_cache.py

@@ -25,6 +25,9 @@ class FakeDomain:
         self.reads.append(flags)
         return f"<domain flags='{flags}' read='{len(self.reads)}'/>"
 
+    def blockInfo(self, dev):  # a disk no pool holds that libvirt cannot read either
+        raise libvirtError("cannot read")
+
 
 class FakeConn:
     def __init__(self):