[merged mm-stable] selftests-mm-move-is_backed_by_folio-into-vm_util.patch removed from -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

The quilt patch titled
     Subject: selftests/mm: move is_backed_by_folio() into vm_util
has been removed from the -mm tree.  Its filename was
     selftests-mm-move-is_backed_by_folio-into-vm_util.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: "Kiryl Shutsemau (Meta)" <kas@kernel.org>
Subject: selftests/mm: move is_backed_by_folio() into vm_util
Date: Sat, 19 Sep 2026 01:24:37 +0100

Checking that an address range is backed by a folio of a given order is
useful to any test that builds or collapses large folios.  mTHP collapse
coverage in the khugepaged selftest needs exactly that.

split_huge_page_test.c already has the building block:
is_backed_by_folio() reads the compound head and tail flags from
/proc/kpageflags to classify the folio behind a page.

Move it into vm_util so other tests can use it.  No functional change.

Link: https://lore.kernel.org/20260919002451.496763-8-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Tested-by: Muhammad Usama Anjum <usama.anjum@arm.com>
Assisted-by: LLM
Cc: Alexander Gordeev <agordeev@linux.ibm.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: Michal Hocko <mhocko@suse.com>
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>
---

 tools/testing/selftests/mm/split_huge_page_test.c |   61 ------------
 tools/testing/selftests/mm/vm_util.c              |   61 ++++++++++++
 tools/testing/selftests/mm/vm_util.h              |    2 
 3 files changed, 63 insertions(+), 61 deletions(-)

--- a/tools/testing/selftests/mm/split_huge_page_test.c~selftests-mm-move-is_backed_by_folio-into-vm_util
+++ a/tools/testing/selftests/mm/split_huge_page_test.c
@@ -41,67 +41,6 @@ const char *kpageflags_proc = "/proc/kpa
 int pagemap_fd;
 int kpageflags_fd;
 
-static bool is_backed_by_folio(char *vaddr, int order, int pagemap_fd,
-		int kpageflags_fd)
-{
-	const uint64_t folio_head_flags = KPF_THP | KPF_COMPOUND_HEAD;
-	const uint64_t folio_tail_flags = KPF_THP | KPF_COMPOUND_TAIL;
-	const unsigned long nr_pages = 1UL << order;
-	unsigned long pfn_head;
-	uint64_t pfn_flags;
-	unsigned long pfn;
-	unsigned long i;
-
-	pfn = pagemap_get_pfn(pagemap_fd, vaddr);
-
-	/* non present page */
-	if (pfn == -1UL)
-		return false;
-
-	if (pageflags_get(pfn, kpageflags_fd, &pfn_flags))
-		goto fail;
-
-	/* check for order-0 pages */
-	if (!order) {
-		if (pfn_flags & (folio_head_flags | folio_tail_flags))
-			return false;
-		return true;
-	}
-
-	/* non THP folio */
-	if (!(pfn_flags & KPF_THP))
-		return false;
-
-	pfn_head = pfn & ~(nr_pages - 1);
-
-	if (pageflags_get(pfn_head, kpageflags_fd, &pfn_flags))
-		goto fail;
-
-	/* head PFN has no compound_head flag set */
-	if ((pfn_flags & folio_head_flags) != folio_head_flags)
-		return false;
-
-	/* check all tail PFN flags */
-	for (i = 1; i < nr_pages; i++) {
-		if (pageflags_get(pfn_head + i, kpageflags_fd, &pfn_flags))
-			goto fail;
-		if ((pfn_flags & folio_tail_flags) != folio_tail_flags)
-			return false;
-	}
-
-	/*
-	 * check the PFN after this folio, but if its flags cannot be obtained,
-	 * assume this folio has the expected order
-	 */
-	if (pageflags_get(pfn_head + nr_pages, kpageflags_fd, &pfn_flags))
-		return true;
-
-	/* If we find another tail page, then the folio is larger. */
-	return (pfn_flags & folio_tail_flags) != folio_tail_flags;
-fail:
-	ksft_exit_fail_msg("Failed to get folio info\n");
-}
-
 static int check_after_split_folio_orders(char *vaddr_start, size_t len,
 		int pagemap_fd, int kpageflags_fd, int orders[], int nr_orders)
 {
--- a/tools/testing/selftests/mm/vm_util.c~selftests-mm-move-is_backed_by_folio-into-vm_util
+++ a/tools/testing/selftests/mm/vm_util.c
@@ -490,6 +490,67 @@ int pageflags_get(unsigned long pfn, int
 	return 0;
 }
 
+bool is_backed_by_folio(char *vaddr, int order, int pagemap_fd,
+			int kpageflags_fd)
+{
+	const uint64_t folio_head_flags = KPF_THP | KPF_COMPOUND_HEAD;
+	const uint64_t folio_tail_flags = KPF_THP | KPF_COMPOUND_TAIL;
+	const unsigned long nr_pages = 1UL << order;
+	unsigned long pfn_head;
+	uint64_t pfn_flags;
+	unsigned long pfn;
+	unsigned long i;
+
+	pfn = pagemap_get_pfn(pagemap_fd, vaddr);
+
+	/* non present page */
+	if (pfn == -1UL)
+		return false;
+
+	if (pageflags_get(pfn, kpageflags_fd, &pfn_flags))
+		goto fail;
+
+	/* check for order-0 pages */
+	if (!order) {
+		if (pfn_flags & (folio_head_flags | folio_tail_flags))
+			return false;
+		return true;
+	}
+
+	/* non THP folio */
+	if (!(pfn_flags & KPF_THP))
+		return false;
+
+	pfn_head = pfn & ~(nr_pages - 1);
+
+	if (pageflags_get(pfn_head, kpageflags_fd, &pfn_flags))
+		goto fail;
+
+	/* head PFN has no compound_head flag set */
+	if ((pfn_flags & folio_head_flags) != folio_head_flags)
+		return false;
+
+	/* check all tail PFN flags */
+	for (i = 1; i < nr_pages; i++) {
+		if (pageflags_get(pfn_head + i, kpageflags_fd, &pfn_flags))
+			goto fail;
+		if ((pfn_flags & folio_tail_flags) != folio_tail_flags)
+			return false;
+	}
+
+	/*
+	 * check the PFN after this folio, but if its flags cannot be obtained,
+	 * assume this folio has the expected order
+	 */
+	if (pageflags_get(pfn_head + nr_pages, kpageflags_fd, &pfn_flags))
+		return true;
+
+	/* If we find another tail page, then the folio is larger. */
+	return (pfn_flags & folio_tail_flags) != folio_tail_flags;
+fail:
+	ksft_exit_fail_msg("Failed to get folio info\n");
+}
+
 /* If `ioctls' non-NULL, the allowed ioctls will be returned into the var */
 int uffd_register_with_ioctls(int uffd, void *addr, uint64_t len,
 			      bool miss, bool wp, bool minor, uint64_t *ioctls)
--- a/tools/testing/selftests/mm/vm_util.h~selftests-mm-move-is_backed_by_folio-into-vm_util
+++ a/tools/testing/selftests/mm/vm_util.h
@@ -99,6 +99,8 @@ int64_t allocate_transhuge(void *ptr, in
 int pageflags_get(unsigned long pfn, int kpageflags_fd, uint64_t *flags);
 int gather_folio_orders(char *vaddr_start, size_t len,
 		int pagemap_fd, int kpageflags_fd, int orders[], int nr_orders);
+bool is_backed_by_folio(char *vaddr, int order, int pagemap_fd,
+			int kpageflags_fd);
 
 int uffd_register(int uffd, void *addr, uint64_t len,
 		  bool miss, bool wp, bool minor);
_

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

mm-page_alloc-make-defrag_mode-retries-follow-the-promoted-order.patch
mm-khugepaged-drop-redundant-mm_struct-pin-in-madvise_collapse.patch
mm-khugepaged-count-collapses-where-khugepaged-makes-them.patch
mm-khugepaged-rename-mthp_present_ptes-bitmap-to-eligible_ptes.patch
mm-collapse-add-collapseh-for-the-collapse-interface.patch
mm-collapse-state-what-a-collapse-may-do-in-the-policy.patch
mm-collapse-drop-the-collapse_possible-wrapper.patch
mm-collapse-name-the-per-table-scan-reset-for-what-it-resets.patch
mm-collapse-call-collapse_file-from-collapse_single_pmd.patch
mm-collapse-separate-scanning-a-pte-table-from-collapsing-it.patch
mm-collapse-open-code-collapse_single_pmd-in-its-two-callers.patch
mm-collapse-work-out-the-orders-a-vma-allows-once-per-vma.patch
mm-collapse-declare-the-collapse-interface-in-collapseh.patch
mm-collapse-implement-madv_collapse-in-madvisec.patch