selftests/mm: add folio-order detection self-check

The khugepaged mTHP tests detect collapse results with the vm_util
folio-order helpers rather than smaps AnonHugePages, which only sees PMD
mappings.  If those helpers are wrong, every case built on them is wrong
the same way, and nothing says so.

Check them directly.  For every anon THP order the kernel supports, fault
memory in with only that order enabled.  Require the helpers to classify
the backing as exactly that order: not the order below it, and base-page
memory as order 0.

Run it in the thp category, ahead of ./khugepaged, so a broken helper is
reported as itself rather than as a collapse failure.  Verified on x86-64
4K (orders 0, 2-9) and arm64 64K (orders 0, 2-13).

The test needs ALIGN(), which hmm-tests.c and migration.c each defined
privately.  Move it to vm_util.h and drop both copies.

Link: https://lore.kernel.org/20260919002451.496763-10-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Muhammad Usama Anjum <usama.anjum@arm.com>
Assisted-by: LLM
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: "David Hildenbrand (arm)" <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Hugh Dickens <hughd@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: kernel-team@meta.com
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Nico Pache (Red Hat) <nico.pache@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan (Samsung OSG) <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Usama Arif <usama.arif@linux.dev>
Cc: "Vlastimil Babka (SUSE)" <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>

0 files changed, 0 insertions, 0 deletions