selftests/damon/_damon_sysfs: set Kdamond.pid in start()

_damon_sysfs.py is a Python module for reading and writing DAMON sysfs for
testing.  It is not reading resulting kdamond pids.  Read and update those
when starting kdamonds.

Link: https://lkml.kernel.org/r/20250628160428.53115-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/damon/_damon_sysfs.py b/tools/testing/selftests/damon/_damon_sysfs.py
index 5b1cb6b3ce4e2fe8b4f3ec9ec4f26387130827f3..f587e117472ed0ee4fbd626fd481dde4a4ac95c6 100644 (file)
--- a/tools/testing/selftests/damon/_damon_sysfs.py
+++ b/tools/testing/selftests/damon/_damon_sysfs.py
@@ -408,6 +408,9 @@ class Kdamond:
             if err is not None:
                 return err
         err = write_file(os.path.join(self.sysfs_dir(), 'state'), 'on')
+        if err is not None:
+            return err
+        self.pid, err = read_file(os.path.join(self.sysfs_dir(), 'pid'))
         return err
 
     def stop(self):