Add test to verify that DAMON status is not changed after a no-op
commit. Currently, it is failing. but after fix the bug it should be
success.

Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
---
 tools/testing/selftests/damon/Makefile        |  1 +
 .../damon/sysfs_no_op_commit_break.py         | 78 +++++++++++++++++++
 2 files changed, 79 insertions(+)
 create mode 100755 tools/testing/selftests/damon/sysfs_no_op_commit_break.py

diff --git a/tools/testing/selftests/damon/Makefile b/tools/testing/selftests/damon/Makefile
index 5b230deb19e8..44a4a819df55 100644
--- a/tools/testing/selftests/damon/Makefile
+++ b/tools/testing/selftests/damon/Makefile
@@ -17,6 +17,7 @@ TEST_PROGS += reclaim.sh lru_sort.sh
 TEST_PROGS += sysfs_update_removed_scheme_dir.sh
 TEST_PROGS += sysfs_update_schemes_tried_regions_hang.py
 TEST_PROGS += sysfs_memcg_path_leak.sh
+TEST_PROGS += sysfs_no_op_commit_break.py
 
 EXTRA_CLEAN = __pycache__
 
diff --git a/tools/testing/selftests/damon/sysfs_no_op_commit_break.py b/tools/testing/selftests/damon/sysfs_no_op_commit_break.py
new file mode 100755
index 000000000000..300cdbaa7eda
--- /dev/null
+++ b/tools/testing/selftests/damon/sysfs_no_op_commit_break.py
@@ -0,0 +1,78 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import json
+import os
+import subprocess
+import sys
+
+import _damon_sysfs
+
+def dump_damon_status_dict(pid):
+    try:
+        subprocess.check_output(['which', 'drgn'], stderr=subprocess.DEVNULL)
+    except:
+        return None, 'drgn not found'
+    file_dir = os.path.dirname(os.path.abspath(__file__))
+    dump_script = os.path.join(file_dir, 'drgn_dump_damon_status.py')
+    rc = subprocess.call(['drgn', dump_script, pid, 'damon_dump_output'],
+        stderr=subprocess.DEVNULL)
+
+    if rc != 0:
+        return None, f'drgn fail : return code({rc})'
+    try:
+        with open('damon_dump_output', 'r') as f:
+            return json.load(f), None
+    except Exception as e:
+        return None, 'json.load fail (%s)' % e
+
+def main():
+    # We can extend this test to change only the Given and reuse the When/Then.
+
+    # Given : setup filter with allow = True
+    proc = subprocess.Popen(['sleep', '10'])
+    kdamonds = _damon_sysfs.Kdamonds(
+        [_damon_sysfs.Kdamond(
+            contexts=[_damon_sysfs.DamonCtx(
+                targets=[_damon_sysfs.DamonTarget(pid=proc.pid)],
+                schemes=[_damon_sysfs.Damos(
+                    ops_filters=[
+                        _damon_sysfs.DamosFilter(type_='anon', matching=True, allow=True)
+                    ]
+                )],
+            )])]
+    )
+
+    err = kdamonds.start()
+    if err is not None:
+        print('kdamond start failed: %s' % err)
+        exit(1)
+
+    before_commit_status, err = dump_damon_status_dict(kdamonds.kdamonds[0].pid)
+    if err is not None:
+        print(err)
+        exit(1)
+
+    # When : No-op commit, it should not break anything
+    kdamonds.kdamonds[0].commit()
+
+    # Then : Check value with drgn
+    after_commit_status, err = dump_damon_status_dict(kdamonds.kdamonds[0].pid)
+    if err is not None:
+        print(err)
+        exit(1)
+
+    before_commit_dump = json.dumps(before_commit_status, sort_keys=True, indent=2)
+    after_commit_dump = json.dumps(after_commit_status, sort_keys=True, indent=2)
+    if before_commit_dump != after_commit_dump:
+        print("[TEST FAILED] : no-op commit break damon status")
+        print("===== before_commit =====")
+        print(before_commit_dump)
+        print("===== after_commit =====")
+        print(after_commit_dump)
+        exit(1)
+
+    kdamonds.stop()
+
+if __name__ == '__main__':
+    main()
-- 
2.43.0