[PATCH v2 01/11] mm: memcontrol: take a const folio in folio_memcg() and friends
From: Tal Zussman
Date: Tue Sep 08 2026 - 14:29:05 EST
The folio_memcg() family only reads from the folio, and everything it
calls already takes a const folio. Constify it, along with the page
wrappers built on top of it.
Signed-off-by: Tal Zussman <tz2294@xxxxxxxxxxxx>
---
include/linux/memcontrol.h | 46 +++++++++++++++++++++++-----------------------
mm/memcontrol.c | 6 +++---
2 files changed, 26 insertions(+), 26 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 4f720791a31c..8a614a36c05d 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -410,7 +410,7 @@ static inline struct mem_cgroup *obj_cgroup_memcg(struct obj_cgroup *objcg)
* or NULL. This function assumes that the folio is known to have a
* proper object cgroup pointer.
*/
-static inline struct obj_cgroup *folio_objcg(struct folio *folio)
+static inline struct obj_cgroup *folio_objcg(const struct folio *folio)
{
unsigned long memcg_data = folio->memcg_data;
@@ -448,7 +448,7 @@ static inline struct obj_cgroup *folio_objcg(struct folio *folio)
* Note: The caller should hold an rcu read lock or cgroup_mutex to protect
* memcg associated with a folio from being released.
*/
-static inline struct mem_cgroup *folio_memcg(struct folio *folio)
+static inline struct mem_cgroup *folio_memcg(const struct folio *folio)
{
struct obj_cgroup *objcg = folio_objcg(folio);
@@ -461,7 +461,7 @@ static inline struct mem_cgroup *folio_memcg(struct folio *folio)
*
* Returns true if folio is charged to a memory cgroup, otherwise returns false.
*/
-static inline bool folio_memcg_charged(struct folio *folio)
+static inline bool folio_memcg_charged(const struct folio *folio)
{
return folio->memcg_data != 0;
}
@@ -481,7 +481,7 @@ static inline bool folio_memcg_charged(struct folio *folio)
* A caller should hold an rcu read lock to protect memcg associated with a
* page from being released.
*/
-static inline struct mem_cgroup *folio_memcg_check(struct folio *folio)
+static inline struct mem_cgroup *folio_memcg_check(const struct folio *folio)
{
/*
* Because folio->memcg_data might be changed asynchronously
@@ -498,11 +498,11 @@ static inline struct mem_cgroup *folio_memcg_check(struct folio *folio)
return obj_cgroup_memcg(objcg);
}
-static inline struct mem_cgroup *page_memcg_check(struct page *page)
+static inline struct mem_cgroup *page_memcg_check(const struct page *page)
{
if (PageTail(page))
return NULL;
- return folio_memcg_check((struct folio *)page);
+ return folio_memcg_check((const struct folio *)page);
}
static inline struct mem_cgroup *get_mem_cgroup_from_objcg(struct obj_cgroup *objcg)
@@ -527,14 +527,14 @@ static inline struct mem_cgroup *get_mem_cgroup_from_objcg(struct obj_cgroup *ob
* that the folio has an associated memory cgroup. It's not safe to call
* this function against some types of folios, e.g. slab folios.
*/
-static inline bool folio_memcg_kmem(struct folio *folio)
+static inline bool folio_memcg_kmem(const struct folio *folio)
{
VM_BUG_ON_PGFLAGS(PageTail(&folio->page), &folio->page);
VM_BUG_ON_FOLIO(folio->memcg_data & MEMCG_DATA_OBJEXTS, folio);
return folio->memcg_data & MEMCG_DATA_KMEM;
}
-static inline bool PageMemcgKmem(struct page *page)
+static inline bool PageMemcgKmem(const struct page *page)
{
return folio_memcg_kmem(page_folio(page));
}
@@ -777,7 +777,7 @@ struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm);
struct mem_cgroup *get_mem_cgroup_from_current(void);
-struct mem_cgroup *get_mem_cgroup_from_folio(struct folio *folio);
+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);
@@ -905,8 +905,8 @@ static inline bool mm_match_cgroup(struct mm_struct *mm,
return match;
}
-struct cgroup_subsys_state *get_mem_cgroup_css_from_folio(struct folio *folio);
-ino_t page_cgroup_ino(struct page *page);
+struct cgroup_subsys_state *get_mem_cgroup_css_from_folio(const struct folio *folio);
+ino_t page_cgroup_ino(const struct page *page);
static inline bool mem_cgroup_online(struct mem_cgroup *memcg)
{
@@ -956,7 +956,7 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg);
void mod_memcg_state(struct mem_cgroup *memcg,
enum memcg_stat_item idx, int val);
-static inline void mod_memcg_page_state(struct page *page,
+static inline void mod_memcg_page_state(const struct page *page,
enum memcg_stat_item idx, int val)
{
struct mem_cgroup *memcg;
@@ -990,7 +990,7 @@ void mod_lruvec_kmem_state(void *p, enum node_stat_item idx, int val);
void count_memcg_events(struct mem_cgroup *memcg, enum vm_event_item idx,
unsigned long count);
-static inline void count_memcg_folio_events(struct folio *folio,
+static inline void count_memcg_folio_events(const struct folio *folio,
enum vm_event_item idx, unsigned long nr)
{
struct mem_cgroup *memcg;
@@ -1084,22 +1084,22 @@ static inline struct mem_cgroup *obj_cgroup_memcg(struct obj_cgroup *objcg)
#define root_mem_cgroup (NULL)
-static inline struct mem_cgroup *folio_memcg(struct folio *folio)
+static inline struct mem_cgroup *folio_memcg(const struct folio *folio)
{
return NULL;
}
-static inline bool folio_memcg_charged(struct folio *folio)
+static inline bool folio_memcg_charged(const struct folio *folio)
{
return false;
}
-static inline struct mem_cgroup *folio_memcg_check(struct folio *folio)
+static inline struct mem_cgroup *folio_memcg_check(const struct folio *folio)
{
return NULL;
}
-static inline struct mem_cgroup *page_memcg_check(struct page *page)
+static inline struct mem_cgroup *page_memcg_check(const struct page *page)
{
return NULL;
}
@@ -1109,12 +1109,12 @@ static inline struct mem_cgroup *get_mem_cgroup_from_objcg(struct obj_cgroup *ob
return NULL;
}
-static inline bool folio_memcg_kmem(struct folio *folio)
+static inline bool folio_memcg_kmem(const struct folio *folio)
{
return false;
}
-static inline bool PageMemcgKmem(struct page *page)
+static inline bool PageMemcgKmem(const struct page *page)
{
return false;
}
@@ -1248,7 +1248,7 @@ static inline struct mem_cgroup *get_mem_cgroup_from_current(void)
return NULL;
}
-static inline struct mem_cgroup *get_mem_cgroup_from_folio(struct folio *folio)
+static inline struct mem_cgroup *get_mem_cgroup_from_folio(const struct folio *folio)
{
return NULL;
}
@@ -1406,7 +1406,7 @@ static inline void mod_memcg_state(struct mem_cgroup *memcg,
{
}
-static inline void mod_memcg_page_state(struct page *page,
+static inline void mod_memcg_page_state(const struct page *page,
enum memcg_stat_item idx, int val)
{
}
@@ -1471,7 +1471,7 @@ static inline void count_memcg_events(struct mem_cgroup *memcg,
{
}
-static inline void count_memcg_folio_events(struct folio *folio,
+static inline void count_memcg_folio_events(const struct folio *folio,
enum vm_event_item idx, unsigned long nr)
{
}
@@ -1901,7 +1901,7 @@ static inline void count_objcg_events(struct obj_cgroup *objcg,
{
}
-static inline ino_t page_cgroup_ino(struct page *page)
+static inline ino_t page_cgroup_ino(const struct page *page)
{
return 0;
}
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 307203301a2a..1ad7de092611 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -332,7 +332,7 @@ EXPORT_SYMBOL(memcg_bpf_enabled_key);
* If memcg is bound to a traditional hierarchy, the css of root_mem_cgroup
* is returned.
*/
-struct cgroup_subsys_state *get_mem_cgroup_css_from_folio(struct folio *folio)
+struct cgroup_subsys_state *get_mem_cgroup_css_from_folio(const struct folio *folio)
{
struct mem_cgroup *memcg;
@@ -357,7 +357,7 @@ struct cgroup_subsys_state *get_mem_cgroup_css_from_folio(struct folio *folio)
* after page_cgroup_ino() returns, so it only should be used by callers that
* do not care (such as procfs interfaces).
*/
-ino_t page_cgroup_ino(struct page *page)
+ino_t page_cgroup_ino(const struct page *page)
{
struct mem_cgroup *memcg;
unsigned long ino = 0;
@@ -1242,7 +1242,7 @@ struct mem_cgroup *get_mem_cgroup_from_current(void)
*
* See folio_memcg() for folio->objcg/memcg binding rules.
*/
-struct mem_cgroup *get_mem_cgroup_from_folio(struct folio *folio)
+struct mem_cgroup *get_mem_cgroup_from_folio(const struct folio *folio)
{
struct mem_cgroup *memcg;
--
2.39.5