[PATCH 1/6] mm/damon: move damon_hugetlb_mkold() from vaddr to ops-common

[Krishna Iyer <kiyer@crusoe.ai>]

damon_hugetlb_mkold() clears the accessed bit of a hugetlb-mapping huge
PTE and propagates the aging to secondary MMUs via
mmu_notifier_clear_young(), spanning the whole huge page size.  It
currently lives in vaddr.c, and is thus usable only by the virtual
address space monitoring operations set.

The physical address space monitoring operations set will need the same
logic, to support access monitoring of hugetlb-backed memory.  Move the
function to ops-common as-is, with no behavioral change.  A follow-up
change will use it from the folio-granular rmap walkers.

Assisted-by: Claude:claude-fable-5
Signed-off-by: Krishna Iyer <kiyer@crusoe.ai>
---
 mm/damon/ops-common.c | 30 ++++++++++++++++++++++++++++++
 mm/damon/ops-common.h |  9 +++++++++
 mm/damon/vaddr.c      | 27 ---------------------------
 3 files changed, 39 insertions(+), 27 deletions(-)

diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c
index fbda70d8ea4d..f5fe92b825bb 100644
--- a/mm/damon/ops-common.c
+++ b/mm/damon/ops-common.c
@@ -3,6 +3,7 @@
  * Common Code for Data Access Monitoring
  */
 
+#include <linux/hugetlb.h>
 #include <linux/migrate.h>
 #include <linux/mmu_notifier.h>
 #include <linux/page_idle.h>
@@ -98,6 +99,35 @@ void damon_pmdp_mkold(pmd_t *pmd, struct vm_area_struct *vma, unsigned long addr
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 }
 
+#ifdef CONFIG_HUGETLB_PAGE
+void damon_hugetlb_mkold(pte_t *pte, struct mm_struct *mm,
+		struct vm_area_struct *vma, unsigned long addr)
+{
+	bool referenced = false;
+	pte_t entry = huge_ptep_get(mm, addr, pte);
+	struct folio *folio = pfn_folio(pte_pfn(entry));
+	unsigned long psize = huge_page_size(hstate_vma(vma));
+
+	folio_get(folio);
+
+	if (pte_young(entry)) {
+		referenced = true;
+		entry = pte_mkold(entry);
+		set_huge_pte_at(mm, addr, pte, entry, psize);
+	}
+
+	if (mmu_notifier_clear_young(mm, addr,
+				     addr + huge_page_size(hstate_vma(vma))))
+		referenced = true;
+
+	if (referenced)
+		folio_set_young(folio);
+
+	folio_set_idle(folio);
+	folio_put(folio);
+}
+#endif	/* CONFIG_HUGETLB_PAGE */
+
 #define DAMON_MAX_SUBSCORE	(100)
 #define DAMON_MAX_AGE_IN_LOG	(32)
 
diff --git a/mm/damon/ops-common.h b/mm/damon/ops-common.h
index 38d295488fa1..f7811c9c7a02 100644
--- a/mm/damon/ops-common.h
+++ b/mm/damon/ops-common.h
@@ -9,6 +9,15 @@ struct folio *damon_get_folio(unsigned long pfn);
 
 void damon_ptep_mkold(pte_t *pte, struct vm_area_struct *vma, unsigned long addr);
 void damon_pmdp_mkold(pmd_t *pmd, struct vm_area_struct *vma, unsigned long addr);
+#ifdef CONFIG_HUGETLB_PAGE
+void damon_hugetlb_mkold(pte_t *pte, struct mm_struct *mm,
+		struct vm_area_struct *vma, unsigned long addr);
+#else
+static inline void damon_hugetlb_mkold(pte_t *pte, struct mm_struct *mm,
+		struct vm_area_struct *vma, unsigned long addr)
+{
+}
+#endif	/* CONFIG_HUGETLB_PAGE */
 void damon_folio_mkold(struct folio *folio);
 bool damon_folio_young(struct folio *folio);
 
diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index 0648400b2d65..15379d984689 100644
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -293,33 +293,6 @@ static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned long addr,
 }
 
 #ifdef CONFIG_HUGETLB_PAGE
-static void damon_hugetlb_mkold(pte_t *pte, struct mm_struct *mm,
-				struct vm_area_struct *vma, unsigned long addr)
-{
-	bool referenced = false;
-	pte_t entry = huge_ptep_get(mm, addr, pte);
-	struct folio *folio = pfn_folio(pte_pfn(entry));
-	unsigned long psize = huge_page_size(hstate_vma(vma));
-
-	folio_get(folio);
-
-	if (pte_young(entry)) {
-		referenced = true;
-		entry = pte_mkold(entry);
-		set_huge_pte_at(mm, addr, pte, entry, psize);
-	}
-
-	if (mmu_notifier_clear_young(mm, addr,
-				     addr + huge_page_size(hstate_vma(vma))))
-		referenced = true;
-
-	if (referenced)
-		folio_set_young(folio);
-
-	folio_set_idle(folio);
-	folio_put(folio);
-}
-
 static int damon_mkold_hugetlb_entry(pte_t *pte, unsigned long hmask,
 				     unsigned long addr, unsigned long end,
 				     struct mm_walk *walk)
-- 
2.54.0