[PATCH v3 2/7] mm/khugepaged: extract young page check into pte_is_referenced() helper

["Nico Pache (Red Hat)" <nico.pache@linux.dev>]

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.

Acked-by: Usama Arif <usama.arif@linux.dev>
Signed-off-by: Nico Pache (Red Hat) <nico.pache@linux.dev>
---
 mm/khugepaged.c | 35 +++++++++++++++++++----------------
 1 file changed, 19 insertions(+), 16 deletions(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 1e26ea97381a..9b15c1740943 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -672,6 +672,23 @@ static void release_pte_pages(pte_t *pte, 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_page_isolate(struct vm_area_struct *vma,
 		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_pmd(struct mm_struct *mm,
 			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 &&

-- 
2.55.0