[PATCH linux-next] mm: workingset: simplify the calculation of workingset size

[<yang.yang29@zte.com.cn>]

From: Yang Yang <yang.yang29@zte.com.cn>

After we implemented workingset detection for anonymous LRU[1],
the calculation of workingset size is a little complex. Actually there is
no need to call mem_cgroup_get_nr_swap_pages() if refault page is
anonymous page, since we are doing swapping then should always
give pressure to NR_ACTIVE_ANON.
So avoid using mem_cgroup_get_nr_swap_pages() when handling
swapin in workingset_refault(). This also give us a chance to refactor
the code to make it simpler and more understandable.

[1] commit aae466b0052e ("mm/swap: implement workingset detection for anonymous LRU")

Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
Reviewed-by: Wang Yong <wang.yong12@zte.com.cn>
Reviewed-by: Xiaokai Ran <ran.xiaokai@zte.com.cn>
---
 mm/workingset.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/mm/workingset.c b/mm/workingset.c
index 00c6f4d9d9be..a304e8571d54 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -466,22 +466,23 @@ void workingset_refault(struct folio *folio, void *shadow)
 	/*
 	 * Compare the distance to the existing workingset size. We
 	 * don't activate pages that couldn't stay resident even if
-	 * all the memory was available to the workingset. Whether
-	 * workingset competition needs to consider anon or not depends
-	 * on having swap.
+	 * all the memory was available to the workingset. For page
+	 * cache whether workingset competition needs to consider
+	 * anon or not depends on having swap.
 	 */
 	workingset_size = lruvec_page_state(eviction_lruvec, NR_ACTIVE_FILE);
+	/* For anonymous page */
 	if (!file) {
+		workingset_size += lruvec_page_state(eviction_lruvec,
+						     NR_ACTIVE_ANON);
 		workingset_size += lruvec_page_state(eviction_lruvec,
 						     NR_INACTIVE_FILE);
-	}
-	if (mem_cgroup_get_nr_swap_pages(eviction_memcg) > 0) {
+	/* For page cache */
+	} else if (mem_cgroup_get_nr_swap_pages(eviction_memcg) > 0) {
 		workingset_size += lruvec_page_state(eviction_lruvec,
 						     NR_ACTIVE_ANON);
-		if (file) {
-			workingset_size += lruvec_page_state(eviction_lruvec,
+		workingset_size += lruvec_page_state(eviction_lruvec,
 						     NR_INACTIVE_ANON);
-		}
 	}
 	if (refault_distance > workingset_size)
 		goto out;
-- 
2.25.1