[PATCH v2 03/11] mm: memcontrol: constify the lruvec helpers
From: Tal Zussman
Date: Tue Sep 08 2026 - 12:15:06 EST
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.
Use container_of_const() in lruvec_memcg() while at it, so the const
isn't silently cast away.
Signed-off-by: Tal Zussman <tz2294@xxxxxxxxxxxx>
---
include/linux/memcontrol.h | 42 +++++++++++++++++++++---------------------
include/linux/mmzone.h | 2 +-
mm/memcontrol.c | 6 +++---
3 files changed, 25 insertions(+), 25 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index d2577a064894..dde828a1206f 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 @@ static inline struct lruvec *mem_cgroup_lruvec(struct mem_cgroup *memcg,
* 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;
}
@@ -919,7 +919,7 @@ 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;
@@ -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 c9ae7991a8b2..da6f84530022 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1660,7 +1660,7 @@ 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;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1ad7de092611..49d2e7e3c023 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1463,7 +1463,7 @@ void mem_cgroup_scan_tasks(struct mem_cgroup *memcg,
*
* Return: The lruvec this folio is on with its lock held and rcu read lock held.
*/
-struct lruvec *folio_lruvec_lock(struct folio *folio)
+struct lruvec *folio_lruvec_lock(const struct folio *folio)
{
struct lruvec *lruvec;
@@ -1491,7 +1491,7 @@ struct lruvec *folio_lruvec_lock(struct folio *folio)
* Return: The lruvec this folio is on with its lock held and interrupts
* disabled and rcu read lock held.
*/
-struct lruvec *folio_lruvec_lock_irq(struct folio *folio)
+struct lruvec *folio_lruvec_lock_irq(const struct folio *folio)
{
struct lruvec *lruvec;
@@ -1520,7 +1520,7 @@ struct lruvec *folio_lruvec_lock_irq(struct folio *folio)
* Return: The lruvec this folio is on with its lock held and interrupts
* disabled and rcu read lock held.
*/
-struct lruvec *folio_lruvec_lock_irqsave(struct folio *folio,
+struct lruvec *folio_lruvec_lock_irqsave(const struct folio *folio,
unsigned long *flags)
{
struct lruvec *lruvec;
--
2.39.5