From 8730e622bfff3b9357ce537eb73f8649207c1ddb Mon Sep 17 00:00:00 2001
From: Qiliang Yuan <odys.yuan@gmail.com>
Date: Fri, 16 Oct 2026 20:54:48 +0800
Subject: [PATCH] selftests/mm: skip hugetlb cgroup v2 tests without the needed
 controllers

With -cgroup-v2, charge_reserved_hugetlb.sh and
hugetlb_reparenting_test.sh mount a cgroup2 hierarchy on a temporary
directory when none is mounted and enable the hugetlb controller
(hugetlb_reparenting_test.sh also enables memory) in its
cgroup.subtree_control.

On a system that still binds these controllers to cgroup v1, they are not
available in the new hierarchy.  Writing to cgroup.subtree_control fails
with ENOENT, "set -e" aborts the script, the test is reported as failed,
and the temporary cgroup2 mount is left behind.

Check cgroup.controllers first, and skip the test when a controller is
missing, after unmounting the hierarchy and removing the directory the
script created.

With hugetlb and memory bound to cgroup v1, per script:

                                before      after
  result                        fail        skip
  cgroup2 mounts left behind       1           0

Link: https://lore.kernel.org/20261016-bug-selftests-mm-hugetlb-cgroup2-skip-v1-1-7c78883a67b4@gmail.com
Fixes: 29750f71a9b4 ("hugetlb_cgroup: add hugetlb_cgroup reservation tests")
Signed-off-by: Qiliang Yuan <odys.yuan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
---
 tools/testing/selftests/mm/charge_reserved_hugetlb.sh  |  8 ++++++++
 tools/testing/selftests/mm/hugetlb_reparenting_test.sh | 10 ++++++++++
 2 files changed, 18 insertions(+)

diff --git a/tools/testing/selftests/mm/charge_reserved_hugetlb.sh b/tools/testing/selftests/mm/charge_reserved_hugetlb.sh
index a1cfd3a349db..65065b1377b2 100755
--- a/tools/testing/selftests/mm/charge_reserved_hugetlb.sh
+++ b/tools/testing/selftests/mm/charge_reserved_hugetlb.sh
@@ -39,6 +39,14 @@ if [[ $cgroup2 ]]; then
     mount -t cgroup2 none $cgroup_path
     do_umount=1
   fi
+  if ! grep -qw hugetlb $cgroup_path/cgroup.controllers; then
+    echo "hugetlb controller not available in cgroup v2. Skipping..."
+    if [[ $do_umount ]]; then
+      umount $cgroup_path
+      rmdir $cgroup_path
+    fi
+    exit $ksft_skip
+  fi
   echo "+hugetlb" >$cgroup_path/cgroup.subtree_control
 else
   cgroup_path=$(mount -t cgroup | grep ",hugetlb" | awk '{print $3}')
diff --git a/tools/testing/selftests/mm/hugetlb_reparenting_test.sh b/tools/testing/selftests/mm/hugetlb_reparenting_test.sh
index 95f517c3bd16..811912ae7d97 100755
--- a/tools/testing/selftests/mm/hugetlb_reparenting_test.sh
+++ b/tools/testing/selftests/mm/hugetlb_reparenting_test.sh
@@ -29,6 +29,16 @@ if [[ $cgroup2 ]]; then
     mount -t cgroup2 none $CGROUP_ROOT
     do_umount=1
   fi
+  for ctrl in hugetlb memory; do
+    if ! grep -qw $ctrl $CGROUP_ROOT/cgroup.controllers; then
+      echo "$ctrl controller not available in cgroup v2. Skipping..."
+      if [[ $do_umount ]]; then
+        umount $CGROUP_ROOT
+        rmdir $CGROUP_ROOT
+      fi
+      exit $ksft_skip
+    fi
+  done
   echo "+hugetlb +memory" >$CGROUP_ROOT/cgroup.subtree_control
 else
   CGROUP_ROOT=$(mount -t cgroup | grep ",hugetlb" | awk '{print $3}')