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b=RIRQR/GAbofpH1QBueIh1OaTOA2SiQZBYiBJ4sw/z2ARoJtRrjfMSJo+seg140UtD B1MBnFooj/G5RLf7AAh7P4li+Cv9uP7IzMoR3RYeIKN/vCkTxCnWddH+8JTvt7nFNN TlNqyfe8AmJd5l55fZTKFNCAuiU8xv3zX4n0qZA+h4Dl+W3DVtnmhPFGYuqY66fNNO 3gKc9WVnjWrMvsSNoPXFXMEFBaLfrirLBZ/sEMu7fZ4E81lk8REgJAPZteGbmR15wy X+WJG1fhLdbUgfH3NuBeN3seVnans3dTGyb41I0io7ytOYUeTFO6DjkWmgHko5L8Vu 7jDAW2J06CODg== Date: Tue, 9 Jun 2026 08:41:59 +0100 From: Lorenzo Stoakes To: Gregory Price 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 Message-ID: References: <20260609002919.3967782-1-gourry@gourry.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260609002919.3967782-1-gourry@gourry.net> X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: F3EA41C000A X-Stat-Signature: o1pnrc18tw77c8jzopeg8m6wc35pjhut X-Rspam-User: X-HE-Tag: 1780990929-30787 X-HE-Meta: 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 +wlHC5iV 1aoT4OSu2en+5uEfnSDKX5J/h84UHLmKr3hWnnrzVer2HZMHvYuK8axqzVpcyTDcFfVPtAK9rbuN7vYLbqD94SZKdARz+hqZ4txitny15PSTpDNayAtp5UKy7CyRz3BtYJ6+rU6OxN855aUiAaWtbqGCYWUiS6Jy52yZKfWZTkueGNUe3TlcGd8Cf080jtSCScEkVsqrJ6Gr8WJWV9/boJBxdlwM/sHwSQRJvgUiOaWlOLQy+fVebYNhLpi2zBZPyo4/SZANEHy01BDS/ejHQwr1t84qC7iTyKbAL69kLnYb/1dTxG/6J3b0wT/gDmM2Qs0uGHPQmg2J2E2nXe/uqg81952Xhf1G/JLYVxGLt9j9abzRACOo9xg7tF6Yc2lK9jZWZBAHJgW3uzD0exdhVA4cZ7E8xkQs7qnul Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 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 > --- > 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 >