mm: memcontrol: constify the swap accounting helpers

mem_cgroup_get_nr_swap_pages(), mem_cgroup_get_folio_swap_margin(), and
mem_cgroup_swap_full() only read swap counters and limits.  Constify them.

Remove externs from function declarations while at it.

Link: https://lore.kernel.org/20260915-folio_memcg-const-v3-9-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>

1 files changed, 6 insertions, 6 deletions

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 61005501888c..82f0bfec611f 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -527,9 +527,9 @@ static inline void mem_cgroup_uncharge_swap(unsigned short id, unsigned int nr_p
 	__mem_cgroup_uncharge_swap(id, nr_pages);
 }
 
-long mem_cgroup_get_folio_swap_margin(struct folio *folio);
-extern long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg);
-extern bool mem_cgroup_swap_full(struct folio *folio);
+long mem_cgroup_get_folio_swap_margin(const struct folio *folio);
+long mem_cgroup_get_nr_swap_pages(const struct mem_cgroup *memcg);
+bool mem_cgroup_swap_full(const struct folio *folio);
 #else
 static inline int mem_cgroup_try_charge_swap(struct folio *folio)
 {
@@ -541,17 +541,17 @@ static inline void mem_cgroup_uncharge_swap(unsigned short id,
 {
 }
 
-static inline long mem_cgroup_get_folio_swap_margin(struct folio *folio)
+static inline long mem_cgroup_get_folio_swap_margin(const struct folio *folio)
 {
 	return PAGE_COUNTER_MAX;
 }
 
-static inline long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
+static inline long mem_cgroup_get_nr_swap_pages(const struct mem_cgroup *memcg)
 {
 	return get_nr_swap_pages();
 }
 
-static inline bool mem_cgroup_swap_full(struct folio *folio)
+static inline bool mem_cgroup_swap_full(const struct folio *folio)
 {
 	return vm_swap_full();
 }