Re: [PATCH v3 5/6] mm: swap: make should_try_to_free_swap() support large-folio

From: David Hildenbrand
Date: Mon May 06 2024 - 04:15:14 EST


On 03.05.24 02:50, Barry Song wrote:
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>
Reviewed-by: "Huang, Ying" <ying.huang@xxxxxxxxx>
---
mm/memory.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memory.c b/mm/memory.c
index 74cdefd58f5f..22e7c33cc747 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3877,7 +3877,7 @@ 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)


Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>

--
Cheers,

David / dhildenb