mm: constify oom_control, scan_control, and alloc_context nodemask

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.

Link: https://lore.kernel.org/20260609002919.3967782-1-gourry@gourry.net
Signed-off-by: Gregory Price <gourry@gourry.net>
Reviewed-by: Lorenzo Stoakes <ljs@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Barry Song <baohua@kernel.org>
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Tested-by: SeongJae Park <sj@kernel.org>
Acked-by: SeongJae Park <sj@kernel.org>
Acked-by: Waiman Long <longman@redhat.com>
Acked-by: Zi Yan <ziy@nvidia.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Baoquan He <baoquan.he@linux.dev>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Rientjes <rientjes@google.com>
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: Michal Hocko <mhocko@suse.com>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

5 files changed, 9 insertions, 9 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 35d1a7643dc4..242ec3cb8b52 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 46c25523d7b8..3f31b6a56788 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -345,7 +345,7 @@ 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)