CA-405215: attach tapdisk pid to correct cgroup path

  it works on both cgroup v1 and v2

Signed-off-by: Chunjie Zhu <chunjie.zhu@cloud.com>

Author: chunjiez

libs/sm/blktap2.py

@@ -758,14 +758,23 @@ def launch_from_arg(cls, arg):
 
     @staticmethod
     def cgclassify(pid):
-
-        # We dont provide any <controllers>:<path>
-        # so cgclassify uses /etc/cgrules.conf which
-        # we have configured in the spec file.
-        cmd = ["cgclassify", str(pid)]
         try:
-            util.pread2(cmd)
-        except util.CommandException as e:
+            # We dont provide any <controllers>:<path>
+            # so cgclassify uses /etc/cgrules.conf which
+            # we have configured in the spec file.
+            cmd = ["cgclassify", str(pid)]
+            try:
+                util.pread2(cmd)
+            except util.CommandException as e:
+                util.logException(e)
+                # cgroup-v2 path
+                cmd = ["cgcreate", "-g", "cpu:vm.slice/tapdisk"]
+                util.pread2(cmd)
+                cgroup_slice_dir = os.path.join("/sys/fs/cgroup", "vm.slice", "tapdisk")
+                procs_file = os.path.join(cgroup_slice_dir, "cgroup.procs")
+                with open(procs_file, 'w') as f:
+                    f.write(str(pid))
+        except Exception as e:
             util.logException(e)
 
     @classmethod

tests/test_blktap2.py

@@ -47,7 +47,7 @@ def test_cgclassify_normal_call(self, mock_pread2):
     def test_cgclassify_exception_swallow(self, mock_log, mock_pread2):
         mock_pread2.side_effect = util.CommandException(999)
         blktap2.Tapdisk.cgclassify(123)
-        mock_pread2.assert_called_with(['cgclassify', '123'])
+        mock_pread2.assert_called_with(['cgcreate', '-g', 'cpu:vm.slice/tapdisk'])
         self.assertEqual(mock_log.call_count, 1)
 
     @mock.patch('sm.blktap2.Tapdisk.cgclassify')