[PATCH v2] selftests: mm: skip charge_reserved_hugetlb without killall

[Cao Ruichuang <create0818@163.com>]

charge_reserved_hugetlb.sh tears down background writers with
killall from psmisc. Minimal Ubuntu images do not always provide
that tool, so the selftest fails in cleanup for an environment reason
rather than for the hugetlb behavior it is trying to cover.

Skip the test when killall is unavailable, similar to the existing
root check, so these environments report the dependency clearly
instead of failing the test.

Signed-off-by: Cao Ruichuang <create0818@163.com>
---
v2:
- replace the PID tracking approach with a simple skip when killall is
  unavailable
- follow Mike Rapoport's review suggestion

 tools/testing/selftests/mm/charge_reserved_hugetlb.sh | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/testing/selftests/mm/charge_reserved_hugetlb.sh b/tools/testing/selftests/mm/charge_reserved_hugetlb.sh
index 44776965763..44f4e703deb 100755
--- a/tools/testing/selftests/mm/charge_reserved_hugetlb.sh
+++ b/tools/testing/selftests/mm/charge_reserved_hugetlb.sh
@@ -11,6 +11,11 @@ if [[ $(id -u) -ne 0 ]]; then
   exit $ksft_skip
 fi
 
+if ! command -v killall >/dev/null 2>&1; then
+  echo "killall not available. Skipping..."
+  exit $ksft_skip
+fi
+
 nr_hugepgs=$(cat /proc/sys/vm/nr_hugepages)
 
 fault_limit_file=limit_in_bytes
-- 
2.39.5 (Apple Git-154)