mm/mglru: improve reset_mm_stats()

struct lruvec* is already a field of struct lru_gen_mm_walk.  Remove the
parameter struct lruvec* into functions that already have access to struct
lru_gen_mm_walk*.

Also, we do not need to handle reset histogram stats when
!should_walk_mmu().  Remove the call to reset_mm_stats() in
iterate_mm_list_nowalk().

Link: https://lkml.kernel.org/r/20240214060538.3524462-4-kinseyho@google.comSigned-off-by: Kinsey Ho <kinseyho@google.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Donet Tom <donettom@linux.vnet.ibm.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/vmscan.c

@@ -2879,38 +2879,37 @@ static struct mm_struct *get_next_mm(struct lru_gen_mm_walk *walk)
 
 #endif
 
-static void reset_mm_stats(struct lruvec *lruvec, struct lru_gen_mm_walk *walk, bool last)
+static void reset_mm_stats(struct lru_gen_mm_walk *walk, bool last)
 {
 	int i;
 	int hist;
+	struct lruvec *lruvec = walk->lruvec;
 	struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
 
 	lockdep_assert_held(&get_mm_list(lruvec_memcg(lruvec))->lock);
 
-	if (walk) {
-		hist = lru_hist_from_seq(walk->max_seq);
+	hist = lru_hist_from_seq(walk->max_seq);
 
-		for (i = 0; i < NR_MM_STATS; i++) {
-			WRITE_ONCE(mm_state->stats[hist][i],
-				   mm_state->stats[hist][i] + walk->mm_stats[i]);
-			walk->mm_stats[i] = 0;
-		}
+	for (i = 0; i < NR_MM_STATS; i++) {
+		WRITE_ONCE(mm_state->stats[hist][i],
+			   mm_state->stats[hist][i] + walk->mm_stats[i]);
+		walk->mm_stats[i] = 0;
 	}
 
 	if (NR_HIST_GENS > 1 && last) {
-		hist = lru_hist_from_seq(mm_state->seq + 1);
+		hist = lru_hist_from_seq(walk->max_seq + 1);
 
 		for (i = 0; i < NR_MM_STATS; i++)
 			WRITE_ONCE(mm_state->stats[hist][i], 0);
 	}
 }
 
-static bool iterate_mm_list(struct lruvec *lruvec, struct lru_gen_mm_walk *walk,
-			    struct mm_struct **iter)
+static bool iterate_mm_list(struct lru_gen_mm_walk *walk, struct mm_struct **iter)
 {
 	bool first = false;
 	bool last = false;
 	struct mm_struct *mm = NULL;
+	struct lruvec *lruvec = walk->lruvec;
 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
 	struct lru_gen_mm_list *mm_list = get_mm_list(memcg);
 	struct lru_gen_mm_state *mm_state = get_mm_state(lruvec);
@@ -2954,7 +2953,7 @@ static bool iterate_mm_list(struct lruvec *lruvec, struct lru_gen_mm_walk *walk,
 	} while (!(mm = get_next_mm(walk)));
 done:
 	if (*iter || last)
-		reset_mm_stats(lruvec, walk, last);
+		reset_mm_stats(walk, last);
 
 	spin_unlock(&mm_list->lock);
 
@@ -2984,7 +2983,6 @@ static bool iterate_mm_list_nowalk(struct lruvec *lruvec, unsigned long max_seq)
 		mm_state->head = NULL;
 		mm_state->tail = NULL;
 		WRITE_ONCE(mm_state->seq, mm_state->seq + 1);
-		reset_mm_stats(lruvec, NULL, true);
 		success = true;
 	}
 
@@ -3159,9 +3157,10 @@ static void update_batch_size(struct lru_gen_mm_walk *walk, struct folio *folio,
 	walk->nr_pages[new_gen][type][zone] += delta;
 }
 
-static void reset_batch_size(struct lruvec *lruvec, struct lru_gen_mm_walk *walk)
+static void reset_batch_size(struct lru_gen_mm_walk *walk)
 {
 	int gen, type, zone;
+	struct lruvec *lruvec = walk->lruvec;
 	struct lru_gen_folio *lrugen = &lruvec->lrugen;
 
 	walk->batched = 0;
@@ -3591,7 +3590,7 @@ static int walk_pud_range(p4d_t *p4d, unsigned long start, unsigned long end,
 	return -EAGAIN;
 }
 
-static void walk_mm(struct lruvec *lruvec, struct mm_struct *mm, struct lru_gen_mm_walk *walk)
+static void walk_mm(struct mm_struct *mm, struct lru_gen_mm_walk *walk)
 {
 	static const struct mm_walk_ops mm_walk_ops = {
 		.test_walk = should_skip_vma,
@@ -3600,6 +3599,7 @@ static void walk_mm(struct lruvec *lruvec, struct mm_struct *mm, struct lru_gen_
 	};
 
 	int err;
+	struct lruvec *lruvec = walk->lruvec;
 	struct mem_cgroup *memcg = lruvec_memcg(lruvec);
 
 	walk->next_addr = FIRST_USER_ADDRESS;
@@ -3628,7 +3628,7 @@ static void walk_mm(struct lruvec *lruvec, struct mm_struct *mm, struct lru_gen_
 
 		if (walk->batched) {
 			spin_lock_irq(&lruvec->lru_lock);
-			reset_batch_size(lruvec, walk);
+			reset_batch_size(walk);
 			spin_unlock_irq(&lruvec->lru_lock);
 		}
 
@@ -3856,9 +3856,9 @@ static bool try_to_inc_max_seq(struct lruvec *lruvec, unsigned long max_seq,
 	walk->force_scan = force_scan;
 
 	do {
-		success = iterate_mm_list(lruvec, walk, &mm);
+		success = iterate_mm_list(walk, &mm);
 		if (mm)
-			walk_mm(lruvec, mm, walk);
+			walk_mm(mm, walk);
 	} while (mm);
 done:
 	if (success) {
@@ -4558,8 +4558,10 @@ static int evict_folios(struct lruvec *lruvec, struct scan_control *sc, int swap
 	move_folios_to_lru(lruvec, &list);
 
 	walk = current->reclaim_state->mm_walk;
-	if (walk && walk->batched)
-		reset_batch_size(lruvec, walk);
+	if (walk && walk->batched) {
+		walk->lruvec = lruvec;
+		reset_batch_size(walk);
+	}
 
 	item = PGSTEAL_KSWAPD + reclaimer_offset();
 	if (!cgroup_reclaim(sc))