[PATCH 02/10] selftests/damon/_damon_sysfs: check errors from nr_schemes file reads

[SeongJae Park <sj@xxxxxxxxxx>]

DAMON context staging method in _damon_sysfs.py is not checking the
returned error from nr_schemes file read.  Check it.

Fixes: f5f0e5a2bef9 ("selftests/damon/_damon_sysfs: implement kdamonds start function")
Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
---
 tools/testing/selftests/damon/_damon_sysfs.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/testing/selftests/damon/_damon_sysfs.py b/tools/testing/selftests/damon/_damon_sysfs.py
index f80fdcef507c..fffa74a78bd7 100644
--- a/tools/testing/selftests/damon/_damon_sysfs.py
+++ b/tools/testing/selftests/damon/_damon_sysfs.py
@@ -341,6 +341,8 @@ class DamonCtx:
         nr_schemes_file = os.path.join(
                 self.sysfs_dir(), 'schemes', 'nr_schemes')
         content, err = read_file(nr_schemes_file)
+        if err is not None:
+            return err
         if int(content) != len(self.schemes):
             err = write_file(nr_schemes_file, '%d' % len(self.schemes))
             if err != None:
-- 
2.39.2