mm/memcontrol.c: make cgroup_memory_noswap static

cgroup_memory_noswap is only used in mm/memcontrol.c, therefore just make
it static, and remove export in include/linux/memcontrol.h

Link: https://lkml.kernel.org/r/20220421124736.62180-1-lujialin4@huawei.comSigned-off-by: NLu Jialin <lujialin4@huawei.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Acked-by: NShakeel Butt <shakeelb@google.com>
Acked-by: NRoman Gushchin <roman.gushchin@linux.dev>
Reviewed-by: NMuchun Song <songmuchun@bytedance.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

include/linux/memcontrol.h

@@ -937,10 +937,6 @@ struct mem_cgroup *mem_cgroup_get_oom_group(struct task_struct *victim,
 					    struct mem_cgroup *oom_domain);
 void mem_cgroup_print_oom_group(struct mem_cgroup *memcg);
 
-#ifdef CONFIG_MEMCG_SWAP
-extern bool cgroup_memory_noswap;
-#endif
-
 void folio_memcg_lock(struct folio *folio);
 void folio_memcg_unlock(struct folio *folio);
 void lock_page_memcg(struct page *page);

mm/memcontrol.c

@@ -89,7 +89,7 @@ static bool cgroup_memory_nokmem __ro_after_init;
 
 /* Whether the swap controller is active */
 #ifdef CONFIG_MEMCG_SWAP
-bool cgroup_memory_noswap __ro_after_init;
+static bool cgroup_memory_noswap __ro_after_init;
 #else
 #define cgroup_memory_noswap		1
 #endif