[PATCH v6 06/19] selftests/mm: stop khugepaged during the MADV_COLLAPSE cases

[Kiryl Shutsemau]

From: "Kiryl Shutsemau (Meta)" <k...@kernel.org>

__madvise_collapse() turns THP off before each MADV_COLLAPSE, both to keep
khugepaged out of the range and to prove MADV_COLLAPSE ignores the setting.
It clears the global controls only, which is no longer enough.  A per-order
control overrides them, and -s, which makes the cases fault in folios of
one order, leaves that order's control at "always".  khugepaged then
collapses the very range the case is working on, and the case fails on a
collapse that was interfered with rather than refused.

Clear the per-order controls too.  MADV_COLLAPSE does not consult them:
anon never did, and shmem stopped with "mm: shmem: ignore sysfs configs
for shmem forced collapse".

Fixes: b7f16963efe7 ("mm/khugepaged: run khugepaged for all orders")
Assisted-by: LLM
Signed-off-by: Kiryl Shutsemau (Meta) <k...@kernel.org>
---
 tools/testing/selftests/mm/khugepaged.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/khugepaged.c 
b/tools/testing/selftests/mm/khugepaged.c
index 13a2a47ab110..e013eebc7136 100644
--- a/tools/testing/selftests/mm/khugepaged.c
+++ b/tools/testing/selftests/mm/khugepaged.c
@@ -538,8 +538,8 @@ static bool is_anon(struct mem_ops *ops)
 static void __madvise_collapse(const char *msg, char *p, int nr_hpages,
                               struct mem_ops *ops, bool expect)
 {
-       int ret;
        struct thp_settings settings = *thp_current_settings();
+       int ret, i;
 
        ksft_print_msg("%s...", msg);
 
@@ -555,6 +555,10 @@ static void __madvise_collapse(const char *msg, char *p, 
int nr_hpages,
         */
        settings.thp_enabled = THP_NEVER;
        settings.shmem_enabled = SHMEM_NEVER;
+       for (i = 0; i < NR_ORDERS; i++) {
+               settings.hugepages[i].enabled = THP_NEVER;
+               settings.shmem_hugepages[i].enabled = SHMEM_NEVER;
+       }
        thp_push_settings(&settings);
 
        /* Clear VM_NOHUGEPAGE */
-- 
2.54.0