selftests/mm: restore default nr_hugepages value via exit trap in charge_reserved_hug...

Patch series "selftests/mm: fix failures and robustness improvements", v7.

Powerpc systems with a 64K base page size exposed several issues while
running mm selftests. Some tests assume specific hugetlb configurations,
use incorrect interfaces, or fail instead of skipping when the required
kernel features are not available.

This series fixes these issues and improves test robustness.

This patch (of 13):

cleanup() resets nr_hugepages to 0 on every invocation, while the test
reconfigures it again in the next iteration.  This leads to repeated
allocation and freeing of large numbers of hugepages, especially when the
original value is high.

Additionally, with set -e, failures in earlier cleanup steps (e.g., rmdir
or umount returning EBUSY while background activity is still ongoing) can
cause the script to exit before restoring the original value, leaving the
system in a modified state.

Introduce a trap on EXIT, INT, and TERM to restore the original
nr_hugepages value once at script termination.  This avoids unnecessary
allocation churn and ensures the original value is reliably restored on
all exit paths.

Link: https://lore.kernel.org/cover.1779296493.git.sayalip@linux.ibm.com
Link: https://lore.kernel.org/5b8fbb29cd6ceffe6752e0af104f60cec072aa10.1779296493.git.sayalip@linux.ibm.com
Fixes: 7d695b1c3695 ("selftests/mm: save and restore nr_hugepages value")
Signed-off-by: Sayali Patil <sayalip@linux.ibm.com>
Acked-by: Zi Yan <ziy@nvidia.com>
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/tools/testing/selftests/mm/charge_reserved_hugetlb.sh b/tools/testing/selftests/mm/charge_reserved_hugetlb.sh
index 44f4e703deb9b53edce64438af88a3b82f61c200..e1945901fd207c6df97529410442480b49dc8450 100755 (executable)
--- a/tools/testing/selftests/mm/charge_reserved_hugetlb.sh
+++ b/tools/testing/selftests/mm/charge_reserved_hugetlb.sh
@@ -17,6 +17,7 @@ if ! command -v killall >/dev/null 2>&1; then
 fi
 
 nr_hugepgs=$(cat /proc/sys/vm/nr_hugepages)
+trap 'echo "$nr_hugepgs" > /proc/sys/vm/nr_hugepages' EXIT INT TERM
 
 fault_limit_file=limit_in_bytes
 reservation_limit_file=rsvd.limit_in_bytes
@@ -70,7 +71,6 @@ function cleanup() {
   if [[ -e $cgroup_path/hugetlb_cgroup_test2 ]]; then
     rmdir $cgroup_path/hugetlb_cgroup_test2
   fi
-  echo 0 >/proc/sys/vm/nr_hugepages
   echo CLEANUP DONE
 }
 
@@ -599,4 +599,3 @@ if [[ $do_umount ]]; then
   rmdir $cgroup_path
 fi
 
-echo "$nr_hugepgs" > /proc/sys/vm/nr_hugepages