linux-kernel - [PATCH v2 2/5] mm: swap: make should_try_to_free

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Date: Tue,  9 Apr 2024 20:26:28 +1200
From: Barry Song <21cnbao@...il.com>
To: akpm@...ux-foundation.org,
	linux-mm@...ck.org
Cc: baolin.wang@...ux.alibaba.com,
	chrisl@...nel.org,
	david@...hat.com,
	hanchuanhua@...o.com,
	hannes@...xchg.org,
	hughd@...gle.com,
	kasong@...cent.com,
	ryan.roberts@....com,
	surenb@...gle.com,
	v-songbaohua@...o.com,
	willy@...radead.org,
	xiang@...nel.org,
	ying.huang@...el.com,
	yosryahmed@...gle.com,
	yuzhao@...gle.com,
	ziy@...dia.com,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/5] mm: swap: make should_try_to_free_swap() support large-folio

From: Chuanhua Han <hanchuanhua@...o.com>

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@...o.com>
Co-developed-by: Barry Song <v-songbaohua@...o.com>
Signed-off-by: Barry Song <v-songbaohua@...o.com>
Acked-by: Chris Li <chrisl@...nel.org>
Reviewed-by: Ryan Roberts <ryan.roberts@....com>
---
 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