[PATCH 2/3] mm/damon: use damon_get_monitor_folio() for hugetlb entries

[SJ Park <sj@kernel.org>]

From: Gregory Price <gourry@gourry.net>

Hugetlb folio acquisition is open-coded in three places:
  - damon_hugetlb_mkold()
  - damon_young_hugetlb_entry()
  - damon_va_probe_hugetlb_entry()

DAMON already has damon_get_monitor_folio(), which paddr uses to
get monitored LRU and hugetlb folios and to filter them through
damon_folio_acceptable().  These paths bypass that check.

Use that helper in these paths too, so that DAMON acquires hugetlb
folios and applies its acceptance policy in one place.

No functional change intended. All callers reach these paths with a
present hugetlb PTE under the page table lock, so the folio is always
a mapped hugetlb folio and the helper always returns it.

Cc: Gregory Price <gourry@gourry.net>
Signed-off-by: Gregory Price (Meta) <gourry@gourry.net>
Reviewed-by: SJ Park <sj@kernel.org>
Signed-off-by: SJ Park <sj@kernel.org>
---
Changes from v1
- v1: https://lore.kernel.org/20261002140727.701709-1-gourry@gourry.net
- Collect R-b: from SJ.
- Rebase to the latest mm-new.

 mm/damon/ops-common.c |  6 ++++--
 mm/damon/vaddr.c      | 10 ++++++----
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c
index 7a7429359dc8..2f3bf86a221b 100644
--- a/mm/damon/ops-common.c
+++ b/mm/damon/ops-common.c
@@ -140,9 +140,11 @@ void damon_hugetlb_mkold(pte_t *pte, struct mm_struct *mm,
 {
 	bool referenced = false;
 	pte_t entry = huge_ptep_get(mm, addr, pte);
-	struct folio *folio = pfn_folio(pte_pfn(entry));
+	struct folio *folio;
 
-	folio_get(folio);
+	folio = damon_get_monitor_folio(pte_pfn(entry));
+	if (!folio)
+		return;
 
 	referenced = damon_hugetlb_ptep_mkold(pte, mm, vma, addr, &entry);
 	if (mmu_notifier_clear_young(mm, addr,
diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index d5dde97b3cd0..b549496ea8e2 100644
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -411,8 +411,9 @@ static int damon_young_hugetlb_entry(pte_t *pte, unsigned long hmask,
 	if (!pte_present(entry))
 		goto out;
 
-	folio = pfn_folio(pte_pfn(entry));
-	folio_get(folio);
+	folio = damon_get_monitor_folio(pte_pfn(entry));
+	if (!folio)
+		goto out;
 
 	if (pte_young(entry) || !folio_test_idle(folio) ||
 	    mmu_notifier_test_young(walk->mm, addr))
@@ -660,8 +661,9 @@ static int damon_va_probe_hugetlb_entry(pte_t *pte, unsigned long hmask,
 	if (!pte_present(entry))
 		goto out;
 
-	folio = pfn_folio(pte_pfn(entry));
-	folio_get(folio);
+	folio = damon_get_monitor_folio(pte_pfn(entry));
+	if (!folio)
+		goto out;
 	damon_va_probe_folio(priv->ctx, priv->r, folio, &entry, NULL,
 			walk->vma->vm_mm);
 	folio_put(folio);
-- 
2.47.3