+ selftests-mm-ensure-destination-is-hugetlb-backed-in-hugepage-mremap.patch added to mm-new branch

+ selftests-mm-ensure-destination-is-hugetlb-backed-in-hugepage-mremap.patch added to mm-new branch

[Andrew Morton]

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The patch titled
     Subject: selftests/mm: ensure destination is hugetlb-backed in hugepage-mremap
has been added to the -mm mm-new branch.  Its filename is
     selftests-mm-ensure-destination-is-hugetlb-backed-in-hugepage-mremap.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-mm-ensure-destination-is-hugetlb-backed-in-hugepage-mremap.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: Sayali Patil <sayalip@linux.ibm.com>
Subject: selftests/mm: ensure destination is hugetlb-backed in hugepage-mremap
Date: Tue, 10 Mar 2026 15:19:26 +0530

The hugepage-mremap selftest reserves the destination address using a
anonymous base-page mapping before calling mremap() with MREMAP_FIXED,
while the source region is hugetlb-backed.

When remapping a hugetlb mapping into a base-page VMA may fail with:

    mremap: Device or resource busy

This is observed on powerpc hash MMU systems where slice constraints and
page size incompatibilities prevent the remap.

Ensure the destination region is created using MAP_HUGETLB so that both
source and destination VMAs are hugetlb-backed and compatible.  Also add
MAP_POPULATE to the destination mapping to prefault hugepages, matching
the behaviour used for other hugetlb mappiing in the test and ensuring
deterministic behaviour.

This ensures the test reliably exercises hugetlb mremap instead of failing
due to VMA type mismatch.

Link: https://lkml.kernel.org/r/2c8858154273159f964236810c7304dec665b28b.1773134177.git.sayalip@linux.ibm.com
Fixes: 12b613206474 ("mm, hugepages: add hugetlb vma mremap() test")
Signed-off-by: Sayali Patil <sayalip@linux.ibm.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: "Michal Koutný" <mkoutny@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/mm/hugepage-mremap.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/tools/testing/selftests/mm/hugepage-mremap.c~selftests-mm-ensure-destination-is-hugetlb-backed-in-hugepage-mremap
+++ a/tools/testing/selftests/mm/hugepage-mremap.c
@@ -136,8 +136,8 @@ int main(int argc, char *argv[])
 		ksft_exit_fail_msg("mmap3: %s\n", strerror(errno));
 
 	suggested_addr = 0x7faa40000000;
-	void *vaddr =
-		mmap((void *)suggested_addr, length, PROTECTION, FLAGS, -1, 0);
+	void *vaddr = mmap((void *)suggested_addr, length, PROTECTION,
+			MAP_HUGETLB | MAP_SHARED | MAP_POPULATE, fd, 0);
 	ksft_print_msg("Map vaddr: Returned address is %p\n", vaddr);
 	if (vaddr == MAP_FAILED)
 		ksft_exit_fail_msg("mmap2: %s\n", strerror(errno));
_

Patches currently in -mm which might be from sayalip@linux.ibm.com are

selftests-mm-restore-default-nr_hugepages-value-during-cleanup-in-charge_reserved_hugetlbsh.patch
selftests-mm-fix-hugetlb-pathname-construction-in-charge_reserved_hugetlbsh.patch
selftests-mm-fix-hugetlb-pathname-construction-in-hugetlb_reparenting_testsh.patch
selftest-mm-fix-cgroup-task-placement-and-tolerance-in-hugetlb_reparenting_testsh.patch
selftests-mm-size-tmpfs-according-to-pmd-page-size-in-split_huge_page_test.patch
selftest-mm-adjust-hugepage-mremap-test-size-for-large-huge-pages.patch
selftest-mm-register-existing-mapping-with-userfaultfd-in-hugepage-mremap.patch
selftests-mm-ensure-destination-is-hugetlb-backed-in-hugepage-mremap.patch
selftests-mm-skip-uffd-wp-mremap-if-uffd-write-protect-is-unsupported.patch
selftests-mm-skip-uffd-stress-test-when-nr_pages_per_cpu-is-zero.patch
selftests-mm-fix-double-increment-in-linked-list-cleanup-in-compaction_test.patch
selftests-mm-move-hwpoison-setup-into-run_test-and-silence-modprobe-output-for-memory-failure-category.patch
selftests-cgroup-extend-test_hugetlb_memcgc-to-support-all-huge-page-sizes.patch