mm: memcontrol: make cgroup_memory_nokmem static

Commit 494c1dfe85 ("mm: memcg/slab: create a new set of kmalloc-cg-<n>
caches") makes cgroup_memory_nokmem global, however, it is unnecessary
because there is already a function mem_cgroup_kmem_disabled() which
exports it.

Just make it static and replace it with mem_cgroup_kmem_disabled() in
mm/slab_common.c.

Link: https://lkml.kernel.org/r/20211109065418.21693-1-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Chris Down <chris@chrisdown.name>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/internal.h

@@ -157,11 +157,6 @@ extern void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason
  */
 extern pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address);
 
-/*
- * in mm/memcontrol.c:
- */
-extern bool cgroup_memory_nokmem;
-
 /*
  * in mm/page_alloc.c
  */

mm/memcontrol.c

@@ -84,7 +84,7 @@ EXPORT_PER_CPU_SYMBOL_GPL(int_active_memcg);
 static bool cgroup_memory_nosocket __ro_after_init;
 
 /* Kernel memory accounting disabled? */
-bool cgroup_memory_nokmem __ro_after_init;
+static bool cgroup_memory_nokmem __ro_after_init;
 
 /* Whether the swap controller is active */
 #ifdef CONFIG_MEMCG_SWAP

mm/slab_common.c

@@ -844,7 +844,7 @@ new_kmalloc_cache(int idx, enum kmalloc_cache_type type, slab_flags_t flags)
 	if (type == KMALLOC_RECLAIM) {
 		flags |= SLAB_RECLAIM_ACCOUNT;
 	} else if (IS_ENABLED(CONFIG_MEMCG_KMEM) && (type == KMALLOC_CGROUP)) {
-		if (cgroup_memory_nokmem) {
+		if (mem_cgroup_kmem_disabled()) {
 			kmalloc_caches[type][idx] = kmalloc_caches[KMALLOC_NORMAL][idx];
 			return;
 		}