[PATCH RFC 11/32] mm/smap: report workingset folios as referenced

[Kairui Song via B4 Relay]

From: Kairui Song <kasong@xxxxxxxxxxx>

For MGLRU, switch smap to use the folio refs count API so smap will
report all folio with referenced count >= 1 as "Referenced". Current
smap checking PG_referenced is causing folios to flick between
referenced and not-reference status, because for both MGLRU and
active/inactive LRU, PG_referenced may got cleared on second access.
(Increase of LRU referenced times count for MGLRU, and movig to active
list active/inactive all clears that bit).

After this, we will have a more reliable and useful reading for MGLRU.

Signed-off-by: Kairui Song <kasong@xxxxxxxxxxx>
---
 fs/proc/task_mmu.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 751b9ba160fb..617f457c75bb 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -913,6 +913,22 @@ static void smaps_page_accumulate(struct mem_size_stats *mss,
 	}
 }
 
+static bool smap_check_folio_referenced(struct folio *folio)
+{
+	if (lru_gen_enabled())
+		return folio_is_referenced(folio);
+	else
+		return folio_is_referenced_by_bit(folio);
+}
+
+static void smap_clear_folio_referenced(struct folio *folio)
+{
+	if (lru_gen_enabled())
+		folio_set_lru_refs(folio, 0);
+	else
+		folio_clear_referenced_by_bit(folio);
+}
+
 static void smaps_account(struct mem_size_stats *mss, struct page *page,
 		bool compound, bool young, bool dirty, bool locked,
 		bool present)
@@ -939,7 +955,7 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
 
 	mss->resident += size;
 	/* Accumulate the size in pages that have been accessed. */
-	if (young || folio_test_young(folio) || folio_test_referenced(folio))
+	if (young || folio_test_young(folio) || smap_check_folio_referenced(folio))
 		mss->referenced += size;
 
 	/*
@@ -1701,7 +1717,7 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr,
 		/* Clear accessed and referenced bits. */
 		pmdp_test_and_clear_young(vma, addr, pmd);
 		folio_test_clear_young(folio);
-		folio_clear_referenced(folio);
+		smap_clear_folio_referenced(folio);
 out:
 		spin_unlock(ptl);
 		return 0;
@@ -1730,7 +1746,7 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr,
 		/* Clear accessed and referenced bits. */
 		ptep_test_and_clear_young(vma, addr, pte);
 		folio_test_clear_young(folio);
-		folio_clear_referenced(folio);
+		smap_clear_folio_referenced(folio);
 	}
 	pte_unmap_unlock(pte - 1, ptl);
 	cond_resched();

-- 
2.54.0