From d5c32fb2c2435040ea9549fbfaad2625d98fb951 Mon Sep 17 00:00:00 2001
From: Tal Zussman <tz2294@columbia.edu>
Date: Tue, 15 Sep 2026 19:20:12 -0400
Subject: mm: memcontrol: constify the memcg and lruvec stat readers

The memcg_page_state(), memcg_events(), and lruvec_page_state() families
only read counters.  Constify them.

Use container_of_const() in the lruvec_page_state() family while at it, so
the const isn't silently cast away.

Link: https://lore.kernel.org/20260915-folio_memcg-const-v3-8-c239a6010b58@columbia.edu
Signed-off-by: Tal Zussman <tz2294@columbia.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Muchun Song <muchun.song@linux.dev>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <baoquan.he@linux.dev>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
---
 include/linux/memcontrol.h | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

(limited to 'include/linux')

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 22067899eb6c..9beb065c0879 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -971,15 +971,16 @@ static inline void mod_memcg_page_state(const struct page *page,
 	rcu_read_unlock();
 }
 
-unsigned long memcg_events(struct mem_cgroup *memcg, int event);
-unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx);
-unsigned long memcg_page_state_output(struct mem_cgroup *memcg, int item);
+unsigned long memcg_events(const struct mem_cgroup *memcg, int event);
+unsigned long memcg_page_state(const struct mem_cgroup *memcg, int idx);
+unsigned long memcg_page_state_output(const struct mem_cgroup *memcg, int item);
 bool memcg_stat_item_valid(int idx);
 bool memcg_vm_event_item_valid(enum vm_event_item idx);
-unsigned long lruvec_page_state(struct lruvec *lruvec, enum node_stat_item idx);
-unsigned long lruvec_page_state_monotonic(struct lruvec *lruvec,
+unsigned long lruvec_page_state(const struct lruvec *lruvec,
+				enum node_stat_item idx);
+unsigned long lruvec_page_state_monotonic(const struct lruvec *lruvec,
 					  enum node_stat_item idx);
-unsigned long lruvec_page_state_local(struct lruvec *lruvec,
+unsigned long lruvec_page_state_local(const struct lruvec *lruvec,
 				      enum node_stat_item idx);
 
 void mem_cgroup_flush_stats(struct mem_cgroup *memcg);
@@ -1412,12 +1413,12 @@ static inline void mod_memcg_page_state(const struct page *page,
 {
 }
 
-static inline unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx)
+static inline unsigned long memcg_page_state(const struct mem_cgroup *memcg, int idx)
 {
 	return 0;
 }
 
-static inline unsigned long memcg_page_state_output(struct mem_cgroup *memcg, int item)
+static inline unsigned long memcg_page_state_output(const struct mem_cgroup *memcg, int item)
 {
 	return 0;
 }
@@ -1432,19 +1433,19 @@ static inline bool memcg_vm_event_item_valid(enum vm_event_item idx)
 	return false;
 }
 
-static inline unsigned long lruvec_page_state(struct lruvec *lruvec,
+static inline unsigned long lruvec_page_state(const struct lruvec *lruvec,
 					      enum node_stat_item idx)
 {
 	return node_page_state(lruvec_pgdat(lruvec), idx);
 }
 
-static inline unsigned long lruvec_page_state_monotonic(struct lruvec *lruvec,
+static inline unsigned long lruvec_page_state_monotonic(const struct lruvec *lruvec,
 							enum node_stat_item idx)
 {
 	return node_page_state_monotonic(lruvec_pgdat(lruvec), idx);
 }
 
-static inline unsigned long lruvec_page_state_local(struct lruvec *lruvec,
+static inline unsigned long lruvec_page_state_local(const struct lruvec *lruvec,
 						    enum node_stat_item idx)
 {
 	return node_page_state(lruvec_pgdat(lruvec), idx);
-- 
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