From: Lorenzo Stoakes <ljs@kernel.org>
To: Gregory Price <gourry@gourry.net>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
cgroups@vger.kernel.org, kernel-team@meta.com,
longman@redhat.com, chenridong@huaweicloud.com,
akpm@linux-foundation.org, david@kernel.org, liam@infradead.org,
vbabka@kernel.org, rppt@kernel.org, surenb@google.com,
mhocko@suse.com, kasong@tencent.com, qi.zheng@linux.dev,
shakeel.butt@linux.dev, baohua@kernel.org,
axelrasmussen@google.com, yuanchu@google.com,
weixugc@google.com, rientjes@google.com, chrisl@kernel.org,
shikemeng@huaweicloud.com, nphamcs@gmail.com,
baoquan.he@linux.dev, youngjun.park@lge.com, tj@kernel.org,
hannes@cmpxchg.org, mkoutny@suse.com, jackmanb@google.com,
ziy@nvidia.com
Subject: Re: [PATCH] mm: constify oom_control, scan_control, and alloc_context nodemask
Date: Tue, 9 Jun 2026 08:41:59 +0100 [thread overview]
Message-ID: <aifDlU96HSRy72Rb@lucifer> (raw)
In-Reply-To: <20260609002919.3967782-1-gourry@gourry.net>
On Mon, Jun 08, 2026 at 08:29:19PM -0400, Gregory Price wrote:
> The nodemasks in these structures may come from a variety of sources,
> including tasks and cpusets - and should never be modified by any code
> when being passed around inside another context.
>
> Signed-off-by: Gregory Price <gourry@gourry.net>
Thanks for doing this, it's nice to gradually up our const correctness game
(as much as C can ever be const correct :)
LGTM, builds locally too, so:
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
> ---
> include/linux/cpuset.h | 4 ++--
> include/linux/mm.h | 4 ++--
> include/linux/mmzone.h | 6 +++---
> include/linux/oom.h | 2 +-
> include/linux/swap.h | 2 +-
> kernel/cgroup/cpuset.c | 2 +-
> mm/internal.h | 2 +-
> mm/mmzone.c | 5 +++--
> mm/page_alloc.c | 6 +++---
> mm/show_mem.c | 9 ++++++---
> mm/vmscan.c | 6 +++---
> 11 files changed, 26 insertions(+), 22 deletions(-)
>
> diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
> index 65d76a38974b..a80d38e752d2 100644
> --- a/include/linux/cpuset.h
> +++ b/include/linux/cpuset.h
> @@ -83,7 +83,7 @@ extern bool cpuset_cpus_allowed_fallback(struct task_struct *p);
> extern nodemask_t cpuset_mems_allowed(struct task_struct *p);
> #define cpuset_current_mems_allowed (current->mems_allowed)
> void cpuset_init_current_mems_allowed(void);
> -int cpuset_nodemask_valid_mems_allowed(nodemask_t *nodemask);
> +int cpuset_nodemask_valid_mems_allowed(const nodemask_t *nodemask);
>
> extern bool cpuset_current_node_allowed(int node, gfp_t gfp_mask);
>
> @@ -224,7 +224,7 @@ static inline nodemask_t cpuset_mems_allowed(struct task_struct *p)
> #define cpuset_current_mems_allowed (node_states[N_MEMORY])
> static inline void cpuset_init_current_mems_allowed(void) {}
>
> -static inline int cpuset_nodemask_valid_mems_allowed(nodemask_t *nodemask)
> +static inline int cpuset_nodemask_valid_mems_allowed(const nodemask_t *nodemask)
> {
> return 1;
> }
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 485df9c2dbdd..2101e5205fc0 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -4042,7 +4042,7 @@ extern int __meminit early_pfn_to_nid(unsigned long pfn);
> extern void mem_init(void);
> extern void __init mmap_init(void);
>
> -extern void __show_mem(unsigned int flags, nodemask_t *nodemask, int max_zone_idx);
> +extern void __show_mem(unsigned int flags, const nodemask_t *nodemask, int max_zone_idx);
> static inline void show_mem(void)
> {
> __show_mem(0, NULL, MAX_NR_ZONES - 1);
> @@ -4052,7 +4052,7 @@ extern void si_meminfo(struct sysinfo * val);
> extern void si_meminfo_node(struct sysinfo *val, int nid);
>
> extern __printf(3, 4)
> -void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...);
> +void warn_alloc(gfp_t gfp_mask, const nodemask_t *nodemask, const char *fmt, ...);
>
> extern void setup_per_cpu_pageset(void);
>
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index ca2712187147..919be0d9b4fa 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -1815,7 +1815,7 @@ static inline int zonelist_node_idx(const struct zoneref *zoneref)
>
> struct zoneref *__next_zones_zonelist(struct zoneref *z,
> enum zone_type highest_zoneidx,
> - nodemask_t *nodes);
> + const nodemask_t *nodes);
>
> /**
> * next_zones_zonelist - Returns the next zone at or below highest_zoneidx within the allowed nodemask using a cursor within a zonelist as a starting point
> @@ -1834,7 +1834,7 @@ struct zoneref *__next_zones_zonelist(struct zoneref *z,
> */
> static __always_inline struct zoneref *next_zones_zonelist(struct zoneref *z,
> enum zone_type highest_zoneidx,
> - nodemask_t *nodes)
> + const nodemask_t *nodes)
> {
> if (likely(!nodes && zonelist_zone_idx(z) <= highest_zoneidx))
> return z;
> @@ -1860,7 +1860,7 @@ static __always_inline struct zoneref *next_zones_zonelist(struct zoneref *z,
> */
> static inline struct zoneref *first_zones_zonelist(struct zonelist *zonelist,
> enum zone_type highest_zoneidx,
> - nodemask_t *nodes)
> + const nodemask_t *nodes)
> {
> return next_zones_zonelist(zonelist->_zonerefs,
> highest_zoneidx, nodes);
> diff --git a/include/linux/oom.h b/include/linux/oom.h
> index 7b02bc1d0a7e..00da05d227e6 100644
> --- a/include/linux/oom.h
> +++ b/include/linux/oom.h
> @@ -30,7 +30,7 @@ struct oom_control {
> struct zonelist *zonelist;
>
> /* Used to determine mempolicy */
> - nodemask_t *nodemask;
> + const nodemask_t *nodemask;
>
> /* Memory cgroup in which oom is invoked, or NULL for global oom */
> struct mem_cgroup *memcg;
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index 8f0f68e245ba..bf76356d94fe 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -351,7 +351,7 @@ extern void swap_setup(void);
> /* linux/mm/vmscan.c */
> extern unsigned long zone_reclaimable_pages(struct zone *zone);
> extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
> - gfp_t gfp_mask, nodemask_t *mask);
> + gfp_t gfp_mask, const nodemask_t *mask);
> unsigned long lruvec_lru_size(struct lruvec *lruvec, enum lru_list lru, int zone_idx);
>
> #define MEMCG_RECLAIM_MAY_SWAP (1 << 1)
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 5c33ab20cc20..536ce591c7ba 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -4153,7 +4153,7 @@ nodemask_t cpuset_mems_allowed(struct task_struct *tsk)
> *
> * Are any of the nodes in the nodemask allowed in current->mems_allowed?
> */
> -int cpuset_nodemask_valid_mems_allowed(nodemask_t *nodemask)
> +int cpuset_nodemask_valid_mems_allowed(const nodemask_t *nodemask)
> {
> return nodes_intersects(*nodemask, current->mems_allowed);
> }
> diff --git a/mm/internal.h b/mm/internal.h
> index 181e79f1d6a2..a2ef9512b5bc 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -668,7 +668,7 @@ void page_alloc_sysctl_init(void);
> */
> struct alloc_context {
> struct zonelist *zonelist;
> - nodemask_t *nodemask;
> + const nodemask_t *nodemask;
> struct zoneref *preferred_zoneref;
> int migratetype;
>
> diff --git a/mm/mmzone.c b/mm/mmzone.c
> index 0c8f181d9d50..59dc3f2076a6 100644
> --- a/mm/mmzone.c
> +++ b/mm/mmzone.c
> @@ -43,7 +43,8 @@ struct zone *next_zone(struct zone *zone)
> return zone;
> }
>
> -static inline int zref_in_nodemask(struct zoneref *zref, nodemask_t *nodes)
> +static inline int zref_in_nodemask(struct zoneref *zref,
> + const nodemask_t *nodes)
> {
> #ifdef CONFIG_NUMA
> return node_isset(zonelist_node_idx(zref), *nodes);
> @@ -55,7 +56,7 @@ static inline int zref_in_nodemask(struct zoneref *zref, nodemask_t *nodes)
> /* Returns the next zone at or below highest_zoneidx in a zonelist */
> struct zoneref *__next_zones_zonelist(struct zoneref *z,
> enum zone_type highest_zoneidx,
> - nodemask_t *nodes)
> + const nodemask_t *nodes)
> {
> /*
> * Find the next suitable zone to use for the allocation.
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 81a9d4d1e6c0..586524bbde9c 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3979,7 +3979,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
> return NULL;
> }
>
> -static void warn_alloc_show_mem(gfp_t gfp_mask, nodemask_t *nodemask)
> +static void warn_alloc_show_mem(gfp_t gfp_mask, const nodemask_t *nodemask)
> {
> unsigned int filter = SHOW_MEM_FILTER_NODES;
>
> @@ -3999,7 +3999,7 @@ static void warn_alloc_show_mem(gfp_t gfp_mask, nodemask_t *nodemask)
> mem_cgroup_show_protected_memory(NULL);
> }
>
> -void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...)
> +void warn_alloc(gfp_t gfp_mask, const nodemask_t *nodemask, const char *fmt, ...)
> {
> struct va_format vaf;
> va_list args;
> @@ -4687,7 +4687,7 @@ check_retry_cpuset(int cpuset_mems_cookie, struct alloc_context *ac)
> return false;
> }
>
> -static void check_alloc_stall_warn(gfp_t gfp_mask, nodemask_t *nodemask,
> +static void check_alloc_stall_warn(gfp_t gfp_mask, const nodemask_t *nodemask,
> unsigned int order, unsigned long alloc_start_time)
> {
> static DEFINE_SPINLOCK(alloc_stall_lock);
> diff --git a/mm/show_mem.c b/mm/show_mem.c
> index 43aca5a2ac99..1b721a8ade67 100644
> --- a/mm/show_mem.c
> +++ b/mm/show_mem.c
> @@ -116,7 +116,8 @@ void si_meminfo_node(struct sysinfo *val, int nid)
> * Determine whether the node should be displayed or not, depending on whether
> * SHOW_MEM_FILTER_NODES was passed to show_free_areas().
> */
> -static bool show_mem_node_skip(unsigned int flags, int nid, nodemask_t *nodemask)
> +static bool show_mem_node_skip(unsigned int flags, int nid,
> + const nodemask_t *nodemask)
> {
> if (!(flags & SHOW_MEM_FILTER_NODES))
> return false;
> @@ -177,7 +178,8 @@ static bool node_has_managed_zones(pg_data_t *pgdat, int max_zone_idx)
> * SHOW_MEM_FILTER_NODES: suppress nodes that are not allowed by current's
> * cpuset.
> */
> -static void show_free_areas(unsigned int filter, nodemask_t *nodemask, int max_zone_idx)
> +static void show_free_areas(unsigned int filter, const nodemask_t *nodemask,
> + int max_zone_idx)
> {
> unsigned long free_pcp = 0;
> int cpu, nid;
> @@ -402,7 +404,8 @@ static void show_free_areas(unsigned int filter, nodemask_t *nodemask, int max_z
> show_swap_cache_info();
> }
>
> -void __show_mem(unsigned int filter, nodemask_t *nodemask, int max_zone_idx)
> +void __show_mem(unsigned int filter, const nodemask_t *nodemask,
> + int max_zone_idx)
> {
> unsigned long total = 0, reserved = 0, highmem = 0;
> struct zone *zone;
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index e8a90911bf88..47d3f3361fb9 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -79,7 +79,7 @@ struct scan_control {
> * Nodemask of nodes allowed by the caller. If NULL, all nodes
> * are scanned.
> */
> - nodemask_t *nodemask;
> + const nodemask_t *nodemask;
>
> /*
> * The memory cgroup that hit its limit and as a result is the
> @@ -6599,7 +6599,7 @@ static bool allow_direct_reclaim(pg_data_t *pgdat)
> * happens, the page allocator should not consider triggering the OOM killer.
> */
> static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
> - nodemask_t *nodemask)
> + const nodemask_t *nodemask)
> {
> struct zoneref *z;
> struct zone *zone;
> @@ -6679,7 +6679,7 @@ static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist,
> }
>
> unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
> - gfp_t gfp_mask, nodemask_t *nodemask)
> + gfp_t gfp_mask, const nodemask_t *nodemask)
> {
> unsigned long nr_reclaimed;
> struct scan_control sc = {
> --
> 2.54.0
>
next prev parent reply other threads:[~2026-06-09 7:42 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-09 0:29 [PATCH] mm: constify oom_control, scan_control, and alloc_context nodemask Gregory Price
2026-06-09 1:44 ` Zi Yan
2026-06-09 7:39 ` Lorenzo Stoakes
2026-06-09 14:43 ` Zi Yan
2026-06-09 15:41 ` Gregory Price
2026-06-09 7:41 ` Lorenzo Stoakes [this message]
2026-06-09 9:37 ` David Hildenbrand (Arm)
2026-06-09 15:42 ` Gregory Price
2026-06-09 7:48 ` Barry Song
2026-06-09 9:59 ` Vlastimil Babka (SUSE)
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