* + mm-memcontrol-constify-the-mem_cgroup-accessors.patch added to mm-new branch
@ 2026-09-16 21:54 Andrew Morton
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From: Andrew Morton @ 2026-09-16 21:54 UTC (permalink / raw)
To: mm-commits, tz2294, akpm
The patch titled
Subject: mm: memcontrol: constify the mem_cgroup accessors
has been added to the -mm mm-new branch. Its filename is
mm-memcontrol-constify-the-mem_cgroup-accessors.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memcontrol-constify-the-mem_cgroup-accessors.patch
This patch will later appear in the mm-new branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews. Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.
The mm-new branch of mm.git is not included in linux-next
If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next
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------------------------------------------------------
From: Tal Zussman <tz2294@columbia.edu>
Subject: mm: memcontrol: constify the mem_cgroup accessors
Date: Tue, 15 Sep 2026 19:20:09 -0400
mem_cgroup_id(), parent_mem_cgroup(), mem_cgroup_is_root(),
mem_cgroup_is_descendant(), memcg_kmem_id(), and the other memcg accessors
only read from the memcg. Constify them, along with
mem_cgroup_shrink_is_root()'s shrink_control.
mem_cgroup_print_oom_context()'s task stays non-const, as task_cgroup()
takes a non-const task.
Link: https://lore.kernel.org/20260915-folio_memcg-const-v3-5-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 | 41 +++++++++++++++++------------------
mm/memcontrol.c | 3 +-
2 files changed, 23 insertions(+), 21 deletions(-)
--- a/include/linux/memcontrol.h~mm-memcontrol-constify-the-mem_cgroup-accessors
+++ a/include/linux/memcontrol.h
@@ -539,7 +539,7 @@ static inline bool PageMemcgKmem(const s
return folio_memcg_kmem(page_folio(page));
}
-static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg)
+static inline bool mem_cgroup_is_root(const struct mem_cgroup *memcg)
{
return (memcg == root_mem_cgroup);
}
@@ -555,7 +555,7 @@ static inline bool mem_cgroup_is_root(st
* and do not honour sc->memcg can use this to early-return 0 in per-memcg
* contexts.
*/
-static inline bool mem_cgroup_shrink_is_root(struct shrink_control *sc)
+static inline bool mem_cgroup_shrink_is_root(const struct shrink_control *sc)
{
return !sc->memcg || mem_cgroup_is_root(sc->memcg);
}
@@ -840,7 +840,7 @@ void mem_cgroup_iter_break(struct mem_cg
void mem_cgroup_scan_tasks(struct mem_cgroup *memcg,
int (*)(struct task_struct *, void *), void *arg);
-static inline unsigned short mem_cgroup_private_id(struct mem_cgroup *memcg)
+static inline unsigned short mem_cgroup_private_id(const struct mem_cgroup *memcg)
{
if (mem_cgroup_disabled())
return 0;
@@ -849,7 +849,7 @@ static inline unsigned short mem_cgroup_
}
struct mem_cgroup *mem_cgroup_from_private_id(unsigned short id);
-static inline u64 mem_cgroup_id(struct mem_cgroup *memcg)
+static inline u64 mem_cgroup_id(const struct mem_cgroup *memcg)
{
return memcg ? cgroup_id(memcg->css.cgroup) : 0;
}
@@ -878,13 +878,13 @@ static inline struct mem_cgroup *lruvec_
*
* Returns the parent memcg, or NULL if this is the root.
*/
-static inline struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg)
+static inline struct mem_cgroup *parent_mem_cgroup(const struct mem_cgroup *memcg)
{
return mem_cgroup_from_css(memcg->css.parent);
}
-static inline bool mem_cgroup_is_descendant(struct mem_cgroup *memcg,
- struct mem_cgroup *root)
+static inline bool mem_cgroup_is_descendant(const struct mem_cgroup *memcg,
+ const struct mem_cgroup *root)
{
if (root == memcg)
return true;
@@ -892,7 +892,7 @@ static inline bool mem_cgroup_is_descend
}
static inline bool mm_match_cgroup(struct mm_struct *mm,
- struct mem_cgroup *memcg)
+ const struct mem_cgroup *memcg)
{
struct mem_cgroup *task_memcg;
bool match = false;
@@ -943,7 +943,7 @@ static inline void mem_cgroup_handle_ove
unsigned long mem_cgroup_get_max(struct mem_cgroup *memcg);
-void mem_cgroup_print_oom_context(struct mem_cgroup *memcg,
+void mem_cgroup_print_oom_context(const struct mem_cgroup *memcg,
struct task_struct *p);
void mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg);
@@ -1119,12 +1119,12 @@ static inline bool PageMemcgKmem(const s
return false;
}
-static inline bool mem_cgroup_is_root(struct mem_cgroup *memcg)
+static inline bool mem_cgroup_is_root(const struct mem_cgroup *memcg)
{
return true;
}
-static inline bool mem_cgroup_shrink_is_root(struct shrink_control *sc)
+static inline bool mem_cgroup_shrink_is_root(const struct shrink_control *sc)
{
return true;
}
@@ -1227,13 +1227,13 @@ static inline struct lruvec *folio_lruve
return &pgdat->__lruvec;
}
-static inline struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg)
+static inline struct mem_cgroup *parent_mem_cgroup(const struct mem_cgroup *memcg)
{
return NULL;
}
static inline bool mm_match_cgroup(struct mm_struct *mm,
- struct mem_cgroup *memcg)
+ const struct mem_cgroup *memcg)
{
return true;
}
@@ -1327,7 +1327,7 @@ static inline void mem_cgroup_scan_tasks
{
}
-static inline unsigned short mem_cgroup_private_id(struct mem_cgroup *memcg)
+static inline unsigned short mem_cgroup_private_id(const struct mem_cgroup *memcg)
{
return 0;
}
@@ -1339,7 +1339,7 @@ static inline struct mem_cgroup *mem_cgr
return NULL;
}
-static inline u64 mem_cgroup_id(struct mem_cgroup *memcg)
+static inline u64 mem_cgroup_id(const struct mem_cgroup *memcg)
{
return 0;
}
@@ -1377,7 +1377,8 @@ static inline unsigned long mem_cgroup_g
}
static inline void
-mem_cgroup_print_oom_context(struct mem_cgroup *memcg, struct task_struct *p)
+mem_cgroup_print_oom_context(const struct mem_cgroup *memcg,
+ struct task_struct *p)
{
}
@@ -1813,7 +1814,7 @@ static inline void memcg_kmem_uncharge_p
* A helper for accessing memcg's kmem_id, used for getting
* corresponding LRU lists.
*/
-static inline int memcg_kmem_id(struct mem_cgroup *memcg)
+static inline int memcg_kmem_id(const struct mem_cgroup *memcg)
{
return memcg ? memcg->kmemcg_id : -1;
}
@@ -1885,7 +1886,7 @@ static inline bool memcg_kmem_online(voi
return false;
}
-static inline int memcg_kmem_id(struct mem_cgroup *memcg)
+static inline int memcg_kmem_id(const struct mem_cgroup *memcg)
{
return -1;
}
@@ -1962,7 +1963,7 @@ static inline bool mem_cgroup_zswap_writ
#ifdef CONFIG_MEMCG_V1
bool mem_cgroup_oom_synchronize(bool wait);
-static inline bool task_in_memcg_oom(struct task_struct *p)
+static inline bool task_in_memcg_oom(const struct task_struct *p)
{
return p->memcg_in_oom;
}
@@ -1980,7 +1981,7 @@ static inline void mem_cgroup_exit_user_
}
#else /* CONFIG_MEMCG_V1 */
-static inline bool task_in_memcg_oom(struct task_struct *p)
+static inline bool task_in_memcg_oom(const struct task_struct *p)
{
return false;
}
--- a/mm/memcontrol.c~mm-memcontrol-constify-the-mem_cgroup-accessors
+++ a/mm/memcontrol.c
@@ -1818,7 +1818,8 @@ static void memory_stat_format(struct me
* NOTE: @memcg and @p's mem_cgroup can be different when hierarchy is
* enabled
*/
-void mem_cgroup_print_oom_context(struct mem_cgroup *memcg, struct task_struct *p)
+void mem_cgroup_print_oom_context(const struct mem_cgroup *memcg,
+ struct task_struct *p)
{
rcu_read_lock();
_
Patches currently in -mm which might be from tz2294@columbia.edu are
mm-page_io-convert-write-completion-handlers-to-folios.patch
mm-remove-pagereclaim.patch
mm-page_io-use-swap-entries-directly-in-zeromap-helpers.patch
mm-page_io-rename-bio_associate_blkg_from_page.patch
mm-page_io-refer-to-folios-in-swap_writeout-comments.patch
mm-swap-rename-__swap_writepage-to-__swap_writeout.patch
mm-remove-unused-mark_page_reserved.patch
mm-remove-unused-totalram_pages_inc-and-totalram_pages_dec.patch
mm-remove-pagewriteback.patch
mm-swap-add-folio_swap_entry-and-folio_page_swap_entry.patch
mm-swap-add-folio_swap_entry-and-folio_page_swap_entry-fix.patch
mm-huge_memory-add-a-comment-to-the-open-coded-swap-entry.patch
mm-rmap-use-folio_page_swap_entry-in-ttu_anon_swapbacked_folio.patch
mm-zswap-use-folio_swap_entry-in-zswap_store_page.patch
mm-swapfile-use-folio_page_swap_entry.patch
arm64-mte-make-mte_save_tags-and-mte_restore_tags-static.patch
arm64-mte-pass-the-swap-entry-to-mte_save_tags.patch
mm-swap-remove-page_swap_entry.patch
mm-memcontrol-take-a-const-folio-in-folio_memcg-and-friends.patch
mm-memcontrol-constify-obj_cgroup_memcg-and-friends.patch
mm-memcontrol-constify-the-lruvec-helpers.patch
mm-page_io-take-a-const-folio-in-bio_associate_blkg_from_folio.patch
mm-memcontrol-constify-the-mem_cgroup-accessors.patch
mm-page_counter-constify-page_counter_read-and-page_counter_margin.patch
mm-memcontrol-constify-the-reclaim-protection-helpers.patch
mm-memcontrol-constify-the-memcg-and-lruvec-stat-readers.patch
mm-memcontrol-constify-the-swap-accounting-helpers.patch
mm-memcontrol-constify-mem_cgroup_swappiness-and-mem_cgroup_get_max.patch
mm-memcontrol-constify-the-zswap-and-socket-pressure-helpers.patch
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