selftests/damon/_damon_sysfs: support pause file staging

DAMON test-purpose sysfs interface control Python module, _damon_sysfs, is
not supporting the newly added pause file.  Add the support of the file,
for future test and use of the feature.

Link: https://lore.kernel.org/20260427151231.113429-8-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Brendan Higgins <brendan.higgins@linux.dev>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/damon/_damon_sysfs.py

@@ -621,10 +621,11 @@ class DamonCtx:
     targets = None
     schemes = None
     kdamond = None
+    pause = None
     idx = None
 
     def __init__(self, ops='paddr', monitoring_attrs=DamonAttrs(), targets=[],
-            schemes=[]):
+            schemes=[], pause=False):
         self.ops = ops
         self.monitoring_attrs = monitoring_attrs
         self.monitoring_attrs.context = self
@@ -639,6 +640,8 @@ class DamonCtx:
             scheme.idx = idx
             scheme.context = self
 
+        self.pause=pause
+
     def sysfs_dir(self):
         return os.path.join(self.kdamond.sysfs_dir(), 'contexts',
                 '%d' % self.idx)
@@ -679,6 +682,11 @@ class DamonCtx:
             err = scheme.stage()
             if err is not None:
                 return err
+
+        err = write_file(os.path.join(self.sysfs_dir(), 'pause'), self.pause)
+        if err is not None:
+            return err
+
         return None
 
 class Kdamond: