+ mm-khugepaged-extract-young-page-check-into-pte_is_referenced-helper.patch added to mm-new branch

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

The patch titled
     Subject: mm/khugepaged: extract young page check into pte_is_referenced() helper
has been added to the -mm mm-new branch.  Its filename is
     mm-khugepaged-extract-young-page-check-into-pte_is_referenced-helper.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-khugepaged-extract-young-page-check-into-pte_is_referenced-helper.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: "Nico Pache (Red Hat)" <nico.pache@linux.dev>
Subject: mm/khugepaged: extract young page check into pte_is_referenced() helper
Date: Tue, 04 Aug 2026 13:25:00 -0600

This change deduplicates the "is this PTE/folio referenced enough to be
considered for a collapse" condition that was repeated in both
__collapse_huge_page_isolate() and collapse_scan_pmd(), extracting it into
a single inline helper function.

Also move the comment and use it as the function header.  While we are at
it, updated the comment to clarify that a young pte is a recently accessed
one.

Link: https://lore.kernel.org/20260804-khugepaged_pte_refactor-v3-2-0364cad642a0@linux.dev
Signed-off-by: Nico Pache (Red Hat) <nico.pache@linux.dev>
Acked-by: Usama Arif <usama.arif@linux.dev>
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: Jonathan Corbet <corbet@lwn.net>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/khugepaged.c |   35 +++++++++++++++++++----------------
 1 file changed, 19 insertions(+), 16 deletions(-)

--- a/mm/khugepaged.c~mm-khugepaged-extract-young-page-check-into-pte_is_referenced-helper
+++ a/mm/khugepaged.c
@@ -672,6 +672,23 @@ static void release_pte_pages(pte_t *pte
 	}
 }
 
+/*
+ * pte_is_referenced() - Check for enough referenced PTEs to justify collapsing
+ *
+ * If collapse was initiated by khugepaged, check that the page has been
+ * recently accessed (young pte) to justify collapsing the page.
+ *
+ * Return: true if the page has been recently accessed.
+ */
+static inline bool pte_is_referenced(struct collapse_control *cc, pte_t pteval,
+	struct folio *folio, struct vm_area_struct *vma, unsigned long addr)
+{
+	return cc->is_khugepaged &&
+	       (pte_young(pteval) || folio_test_young(folio) ||
+		folio_test_referenced(folio) ||
+		mmu_notifier_test_young(vma->vm_mm, addr));
+}
+
 static enum scan_result __collapse_huge_page_isolate(struct vm_area_struct *vma,
 		unsigned long start_addr, pte_t *pte, struct collapse_control *cc,
 		unsigned int order, struct list_head *compound_pagelist)
@@ -810,14 +827,7 @@ static enum scan_result __collapse_huge_
 		if (folio_test_large(folio))
 			list_add_tail(&folio->lru, compound_pagelist);
 next:
-		/*
-		 * If collapse was initiated by khugepaged, check that there is
-		 * enough young pte to justify collapsing the page
-		 */
-		if (cc->is_khugepaged &&
-		    (pte_young(pteval) || folio_test_young(folio) ||
-		     folio_test_referenced(folio) ||
-		     mmu_notifier_test_young(vma->vm_mm, addr)))
+		if (pte_is_referenced(cc, pteval, folio, vma, addr))
 			referenced++;
 	}
 
@@ -1766,14 +1776,7 @@ static enum scan_result collapse_scan_pm
 			goto out_unmap;
 		}
 
-		/*
-		 * If collapse was initiated by khugepaged, check that there is
-		 * enough young pte to justify collapsing the page
-		 */
-		if (cc->is_khugepaged &&
-		    (pte_young(pteval) || folio_test_young(folio) ||
-		     folio_test_referenced(folio) ||
-		     mmu_notifier_test_young(vma->vm_mm, addr)))
+		if (pte_is_referenced(cc, pteval, folio, vma, addr))
 			referenced++;
 	}
 	if (cc->is_khugepaged &&
_

Patches currently in -mm which might be from nico.pache@linux.dev are

mm-khugepaged-refactor-per-scan-state-clearing-into-collapse_control_init_scan.patch
mm-khugepaged-extract-young-page-check-into-pte_is_referenced-helper.patch
mm-khugepaged-introduce-a-count_collapse_event-helper.patch
mm-khugepaged-fix-outdated-comments.patch
mm-khugepaged-refactor-the-pte-state-checks-into-a-helper.patch
mm-khugepaged-unmap-pte-before-releasing-vma-write-lock.patch
mm-documentation-clarify-where-the-mthp-stats-live.patch