+ selftests-mm-stop-khugepaged-during-the-madv_collapse-cases.patch added to mm-new branch

+ selftests-mm-stop-khugepaged-during-the-madv_collapse-cases.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: selftests/mm: stop khugepaged during the MADV_COLLAPSE cases
has been added to the -mm mm-new branch.  Its filename is
     selftests-mm-stop-khugepaged-during-the-madv_collapse-cases.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-mm-stop-khugepaged-during-the-madv_collapse-cases.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: "Kiryl Shutsemau (Meta)" <kas@kernel.org>
Subject: selftests/mm: stop khugepaged during the MADV_COLLAPSE cases
Date: Tue, 8 Sep 2026 13:50:52 +0100

__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, setting them to "inherit" rather than
"never": khugepaged honours the global never and stays out, while
MADV_COLLAPSE on shmem still finds an order to build.

Link: https://lore.kernel.org/20260908125105.1510704-7-kirill@shutemov.name
Fixes: 9f0704eae8a4 ("selftests/mm/khugepaged: enlighten for multi-size THP")
Signed-off-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
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 <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Liam R. 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: Muhammad Usama Anjum <usama.anjum@arm.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Usama Arif <usama.arif@linux.dev>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/mm/khugepaged.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

--- a/tools/testing/selftests/mm/khugepaged.c~selftests-mm-stop-khugepaged-during-the-madv_collapse-cases
+++ a/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);
 
@@ -552,9 +552,16 @@ static void __madvise_collapse(const cha
 	/*
 	 * Prevent khugepaged interference and tests that MADV_COLLAPSE
 	 * ignores /sys/kernel/mm/transparent_hugepage/enabled
+	 *
+	 * "inherit" rather than "never" so that MADV_COLLAPSE on shmem still
+	 * finds an order to build.
 	 */
 	settings.thp_enabled = THP_NEVER;
 	settings.shmem_enabled = SHMEM_NEVER;
+	for (i = 0; i < NR_ORDERS; i++) {
+		settings.hugepages[i].enabled = THP_INHERIT;
+		settings.shmem_hugepages[i].enabled = SHMEM_INHERIT;
+	}
 	thp_push_settings(&settings);
 
 	/* Clear VM_NOHUGEPAGE */
_

Patches currently in -mm which might be from kas@kernel.org are

mm-huge_memory-do-not-touch-frozen-folios-in-deferred_split_isolate.patch
mm-huge_memory-dequeue-the-deferred-split-after-the-split-freeze.patch
selftests-mm-raise-the-khugepaged-test-case-cap.patch
selftests-mm-skip-collapse_compound_extreme-where-the-pmd-is-too-large.patch
selftests-mm-scale-khugepageds-collapse-wait-with-the-pmd-size.patch
selftests-mm-skip-khugepaged-page-cache-cases-without-a-pmd-folio.patch
selftests-mm-make-the-swap-cases-swapout-reliable.patch
selftests-mm-stop-khugepaged-during-the-madv_collapse-cases.patch
selftests-mm-move-is_backed_by_folio-into-vm_util.patch
selftests-mm-add-folio-order-check-for-address-ranges.patch
selftests-mm-add-folio-order-detection-self-check.patch
selftests-mm-add-khugepaged-completion-barrier-helper.patch
selftests-mm-add-order-parameterized-khugepaged-collapse-cases.patch
selftests-mm-parameterize-the-mixed-source-collapse-case-by-source-order.patch
selftests-mm-cover-a-shared-source-collapse-write-race.patch
selftests-mm-run-every-supported-collapse-order-by-default.patch
selftests-mm-check-that-one-khugepaged-pass-collapses-one-window.patch
selftests-mm-add-khugepaged-race-harness.patch
selftests-mm-race-the-collapse-of-windows-with-holes.patch
selftests-mm-add-memory-pressure-threads-to-the-khugepaged-race-harness.patch
selftests-mm-zap-whole-pte-tables-in-the-khugepaged-race-harness.patch