mm: memcontrol: constify the lruvec helpers

The lruvec lookup helpers only read from the memcg, folio, or lruvec they
are given.  Constify them, along with lruvec_pgdat() and the folio
argument of the folio_lruvec_relock_irq() helpers.  mem_cgroup_lruvec()
may update lruvec->pgdat for a newly onlined node, but that lives in the
per-node structure, not the memcg.  Similarly, lruvec_pgdat() still
returns a non-const pgdat and does not use container_of_const().

Use container_of_const() in lruvec_memcg() and
mem_cgroup_get_zone_lru_size(), so the const isn't silently cast away.

Link: https://lore.kernel.org/20260915-folio_memcg-const-v3-3-c239a6010b58@columbia.edu
Signed-off-by: Tal Zussman <tz2294@columbia.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-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>

2 files changed, 24 insertions, 24 deletions

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 65cb45f4be32..436934030d79 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -722,7 +722,7 @@ void mem_cgroup_migrate(struct folio *old, struct folio *new);
  * @pgdat combination. This can be the node lruvec, if the memory
  * controller is disabled.
  */
-static inline struct lruvec *mem_cgroup_lruvec(struct mem_cgroup *memcg,
+static inline struct lruvec *mem_cgroup_lruvec(const struct mem_cgroup *memcg,
 					       struct pglist_data *pgdat)
 {
 	struct mem_cgroup_per_node *mz;
@@ -763,7 +763,7 @@ out:
  * their binding is stable if the returned lruvec matches the one the caller has
  * locked. Useful for lock batching.
  */
-static inline struct lruvec *folio_lruvec(struct folio *folio)
+static inline struct lruvec *folio_lruvec(const struct folio *folio)
 {
 	struct mem_cgroup *memcg = folio_memcg(folio);
 
@@ -779,9 +779,9 @@ struct mem_cgroup *get_mem_cgroup_from_current(void);
 
 struct mem_cgroup *get_mem_cgroup_from_folio(const struct folio *folio);
 
-struct lruvec *folio_lruvec_lock(struct folio *folio);
-struct lruvec *folio_lruvec_lock_irq(struct folio *folio);
-struct lruvec *folio_lruvec_lock_irqsave(struct folio *folio,
+struct lruvec *folio_lruvec_lock(const struct folio *folio);
+struct lruvec *folio_lruvec_lock_irq(const struct folio *folio);
+struct lruvec *folio_lruvec_lock_irqsave(const struct folio *folio,
 						unsigned long *flags);
 
 static inline
@@ -861,14 +861,14 @@ static inline struct mem_cgroup *mem_cgroup_from_seq(struct seq_file *m)
 	return mem_cgroup_from_css(seq_css(m));
 }
 
-static inline struct mem_cgroup *lruvec_memcg(struct lruvec *lruvec)
+static inline struct mem_cgroup *lruvec_memcg(const struct lruvec *lruvec)
 {
-	struct mem_cgroup_per_node *mz;
+	const struct mem_cgroup_per_node *mz;
 
 	if (mem_cgroup_disabled())
 		return NULL;
 
-	mz = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
+	mz = container_of_const(lruvec, struct mem_cgroup_per_node, lruvec);
 	return mz->memcg;
 }
 
@@ -919,13 +919,13 @@ void mem_cgroup_update_lru_size(struct lruvec *lruvec, enum lru_list lru,
 		int zid, long nr_pages);
 
 static inline
-unsigned long mem_cgroup_get_zone_lru_size(struct lruvec *lruvec,
+unsigned long mem_cgroup_get_zone_lru_size(const struct lruvec *lruvec,
 		enum lru_list lru, int zone_idx)
 {
 	long val;
-	struct mem_cgroup_per_node *mz;
+	const struct mem_cgroup_per_node *mz;
 
-	mz = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
+	mz = container_of_const(lruvec, struct mem_cgroup_per_node, lruvec);
 	val = READ_ONCE(mz->lru_zone_size[zone_idx][lru]);
 	if (WARN_ON_ONCE(val < 0))
 		return 0;
@@ -1215,13 +1215,13 @@ static inline void mem_cgroup_migrate(struct folio *old, struct folio *new)
 {
 }
 
-static inline struct lruvec *mem_cgroup_lruvec(struct mem_cgroup *memcg,
+static inline struct lruvec *mem_cgroup_lruvec(const struct mem_cgroup *memcg,
 					       struct pglist_data *pgdat)
 {
 	return &pgdat->__lruvec;
 }
 
-static inline struct lruvec *folio_lruvec(struct folio *folio)
+static inline struct lruvec *folio_lruvec(const struct folio *folio)
 {
 	struct pglist_data *pgdat = folio_pgdat(folio);
 	return &pgdat->__lruvec;
@@ -1281,7 +1281,7 @@ static inline void mem_cgroup_put(struct mem_cgroup *memcg)
 {
 }
 
-static inline struct lruvec *folio_lruvec_lock(struct folio *folio)
+static inline struct lruvec *folio_lruvec_lock(const struct folio *folio)
 {
 	struct pglist_data *pgdat = folio_pgdat(folio);
 
@@ -1290,7 +1290,7 @@ static inline struct lruvec *folio_lruvec_lock(struct folio *folio)
 	return &pgdat->__lruvec;
 }
 
-static inline struct lruvec *folio_lruvec_lock_irq(struct folio *folio)
+static inline struct lruvec *folio_lruvec_lock_irq(const struct folio *folio)
 {
 	struct pglist_data *pgdat = folio_pgdat(folio);
 
@@ -1299,7 +1299,7 @@ static inline struct lruvec *folio_lruvec_lock_irq(struct folio *folio)
 	return &pgdat->__lruvec;
 }
 
-static inline struct lruvec *folio_lruvec_lock_irqsave(struct folio *folio,
+static inline struct lruvec *folio_lruvec_lock_irqsave(const struct folio *folio,
 		unsigned long *flagsp)
 {
 	struct pglist_data *pgdat = folio_pgdat(folio);
@@ -1354,7 +1354,7 @@ static inline struct mem_cgroup *mem_cgroup_from_seq(struct seq_file *m)
 	return NULL;
 }
 
-static inline struct mem_cgroup *lruvec_memcg(struct lruvec *lruvec)
+static inline struct mem_cgroup *lruvec_memcg(const struct lruvec *lruvec)
 {
 	return NULL;
 }
@@ -1365,7 +1365,7 @@ static inline bool mem_cgroup_online(struct mem_cgroup *memcg)
 }
 
 static inline
-unsigned long mem_cgroup_get_zone_lru_size(struct lruvec *lruvec,
+unsigned long mem_cgroup_get_zone_lru_size(const struct lruvec *lruvec,
 		enum lru_list lru, int zone_idx)
 {
 	return 0;
@@ -1505,7 +1505,7 @@ static inline void mem_cgroup_flush_workqueue(void) { }
 static inline int mem_cgroup_init(void) { return 0; }
 #endif /* CONFIG_MEMCG */
 
-static inline struct lruvec *parent_lruvec(struct lruvec *lruvec)
+static inline struct lruvec *parent_lruvec(const struct lruvec *lruvec)
 {
 	struct mem_cgroup *memcg;
 
@@ -1568,15 +1568,15 @@ static inline void lruvec_unlock_irqrestore(struct lruvec *lruvec, unsigned long
 }
 
 /* Test requires a stable folio->memcg binding, see folio_memcg() */
-static inline bool folio_matches_lruvec(struct folio *folio,
-		struct lruvec *lruvec)
+static inline bool folio_matches_lruvec(const struct folio *folio,
+		const struct lruvec *lruvec)
 {
 	return lruvec_pgdat(lruvec) == folio_pgdat(folio) &&
 	       lruvec_memcg(lruvec) == folio_memcg(folio);
 }
 
 /* Don't lock again iff page's lruvec locked */
-static inline struct lruvec *folio_lruvec_relock_irq(struct folio *folio,
+static inline struct lruvec *folio_lruvec_relock_irq(const struct folio *folio,
 		struct lruvec *locked_lruvec)
 {
 	if (locked_lruvec) {
@@ -1590,7 +1590,7 @@ static inline struct lruvec *folio_lruvec_relock_irq(struct folio *folio,
 }
 
 /* Don't lock again iff folio's lruvec locked */
-static inline void folio_lruvec_relock_irqsave(struct folio *folio,
+static inline void folio_lruvec_relock_irqsave(const struct folio *folio,
 		struct lruvec **lruvecp, unsigned long *flags)
 {
 	if (*lruvecp) {
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 65de3bb13eb3..8e4e0bda3b58 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1638,7 +1638,7 @@ extern void init_currently_empty_zone(struct zone *zone, unsigned long start_pfn
 
 extern void lruvec_init(struct lruvec *lruvec);
 
-static inline struct pglist_data *lruvec_pgdat(struct lruvec *lruvec)
+static inline struct pglist_data *lruvec_pgdat(const struct lruvec *lruvec)
 {
 #ifdef CONFIG_MEMCG
 	return lruvec->pgdat;