[PATCH v2 2/5] mm: swap: make should_try_to_free_swap() support large-folio

[Barry Song]

From: Chuanhua Han <hanchuanhua@xxxxxxxx>

The function should_try_to_free_swap() operates under the assumption that
swap-in always occurs at the normal page granularity, i.e., folio_nr_pages
= 1. However, in reality, for large folios, add_to_swap_cache() will
invoke folio_ref_add(folio, nr). To accommodate large folio swap-in,
this patch eliminates this assumption.

Signed-off-by: Chuanhua Han <hanchuanhua@xxxxxxxx>
Co-developed-by: Barry Song <v-songbaohua@xxxxxxxx>
Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
Acked-by: Chris Li <chrisl@xxxxxxxxxx>
Reviewed-by: Ryan Roberts <ryan.roberts@xxxxxxx>
---
 mm/memory.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memory.c b/mm/memory.c
index 78422d1c7381..2702d449880e 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3856,7 +3856,7 @@ static inline bool should_try_to_free_swap(struct folio *folio,
 	 * reference only in case it's likely that we'll be the exlusive user.
 	 */
 	return (fault_flags & FAULT_FLAG_WRITE) && !folio_test_ksm(folio) &&
-		folio_ref_count(folio) == 2;
+		folio_ref_count(folio) == (1 + folio_nr_pages(folio));
 }
 
 static vm_fault_t pte_marker_clear(struct vm_fault *vmf)
-- 
2.34.1