[RFC PATCH 2/6] mm/mglru: refactor Bloom filter helpers for two filter levels

[Baoquan He <baoquan.he@linux.dev>]

Split test/update/reset_bloom_filter() into __ prefixed helpers that
operate on a generic filters array, and thin wrappers that pass the
PMD-level mm_state->filters. This lets a second, coarser (PUD-level)
filter pair reuse the exact same hash, double-buffering and reset
machinery without duplicating code. Purely mechanical; no behavior
change.

Signed-off-by: Baoquan He <baoquan.he@linux.dev>
---
 mm/vmscan.c | 33 ++++++++++++++++++++++++---------
 1 file changed, 24 insertions(+), 9 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 17d2b793cbfc..a397c62b2e5d 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2841,14 +2841,13 @@ static void get_item_key(void *item, int *key)
 	key[1] = hash >> BLOOM_FILTER_SHIFT;
 }
 
-static bool test_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long seq,
-			      void *item)
+static bool __test_bloom_filter(unsigned long **filters, unsigned long seq, void *item)
 {
 	int key[2];
 	unsigned long *filter;
 	int gen = filter_gen_from_seq(seq);
 
-	filter = READ_ONCE(mm_state->filters[gen]);
+	filter = READ_ONCE(filters[gen]);
 	if (!filter)
 		return true;
 
@@ -2857,14 +2856,13 @@ static bool test_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long s
 	return test_bit(key[0], filter) && test_bit(key[1], filter);
 }
 
-static void update_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long seq,
-				void *item)
+static void __update_bloom_filter(unsigned long **filters, unsigned long seq, void *item)
 {
 	int key[2];
 	unsigned long *filter;
 	int gen = filter_gen_from_seq(seq);
 
-	filter = READ_ONCE(mm_state->filters[gen]);
+	filter = READ_ONCE(filters[gen]);
 	if (!filter)
 		return;
 
@@ -2876,12 +2874,12 @@ static void update_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long
 		set_bit(key[1], filter);
 }
 
-static void reset_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long seq)
+static void __reset_bloom_filter(unsigned long **filters, unsigned long seq)
 {
 	unsigned long *filter;
 	int gen = filter_gen_from_seq(seq);
 
-	filter = mm_state->filters[gen];
+	filter = filters[gen];
 	if (filter) {
 		bitmap_clear(filter, 0, BIT(BLOOM_FILTER_SHIFT));
 		return;
@@ -2889,7 +2887,24 @@ static void reset_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long
 
 	filter = bitmap_zalloc(BIT(BLOOM_FILTER_SHIFT),
 			       __GFP_HIGH | __GFP_NOMEMALLOC | __GFP_NOWARN);
-	WRITE_ONCE(mm_state->filters[gen], filter);
+	WRITE_ONCE(filters[gen], filter);
+}
+
+static bool test_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long seq,
+			      void *item)
+{
+	return __test_bloom_filter(mm_state->filters, seq, item);
+}
+
+static void update_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long seq,
+				void *item)
+{
+	__update_bloom_filter(mm_state->filters, seq, item);
+}
+
+static void reset_bloom_filter(struct lru_gen_mm_state *mm_state, unsigned long seq)
+{
+	__reset_bloom_filter(mm_state->filters, seq);
 }
 
 /******************************************************************************
-- 
2.54.0