selftests/mm: fix cgroup task placement and drop memory.current checks in hugetlb_reparenting_test.sh

The test currently moves the calling shell ($$) into the target cgroup
before executing write_to_hugetlbfs.  This results in the shell and any
intermediate allocations being charged to the cgroup, introducing noise
and nondeterminism in accounting.  It also requires moving the shell back
to the root cgroup after execution.

Spawn a helper process that joins the target cgroup and exec()'s
write_to_hugetlbfs.  This ensures that only the workload is accounted to
the cgroup and avoids unintended charging from the shell.

The test currently validates both hugetlb usage and memory.current. 
However, memory.current includes internal memcg allocations and per-CPU
batched accounting (MEMCG_CHARGE_BATCH), which are not synchronized and
can vary across systems, leading to non-deterministic results.

Since hugetlb memory is accounted via hugetlb.<size>.current,
memory.current is not a reliable indicator here.  Drop memory.current
checks and rely only on hugetlb controller statistics for stable and
accurate validation.

Link: https://lore.kernel.org/fb57491ba83cb0a499c72922e1579b61bee514db.1779296493.git.sayalip@linux.ibm.com
Fixes: 29750f71a9b4 ("hugetlb_cgroup: add hugetlb_cgroup reservation tests")
Signed-off-by: Sayali Patil <sayalip@linux.ibm.com>
Cc: David Hildenbrand (Arm) <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>
Cc: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

0 files changed, 0 insertions, 0 deletions