[PATCH v2] mm: Make mem_cgroup_id_get_many() __maybe_unused

mem_cgroup_id_get_many() is currently used only when MMU or MEMCG_SWAP
configuration options are enabled. Having them disabled triggers the
following warning at compile time:

linux/mm/memcontrol.c:4797:13: warning: ‘mem_cgroup_id_get_many’ defined
but not used [-Wunused-function]
 static void mem_cgroup_id_get_many(struct mem_cgroup *memcg, unsigned
 int n)

Make mem_cgroup_id_get_many() __maybe_unused to address the issue.

Cc: Johannes Weiner <redacted>
Cc: Michal Hocko <redacted>
Cc: Vladimir Davydov <redacted>
Cc: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Signed-off-by: Vincenzo Frascino <redacted>
---
 mm/memcontrol.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d09776cd6e10..2b9533ed52f5 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c

@@ -4794,7 +4794,8 @@ static void mem_cgroup_id_remove(struct mem_cgroup *memcg)
 	}
 }
 
-static void mem_cgroup_id_get_many(struct mem_cgroup *memcg, unsigned int n)
+static void __maybe_unused mem_cgroup_id_get_many(struct mem_cgroup *memcg,
+						  unsigned int n)
 {
 	refcount_add(n, &memcg->id.ref);
 }

-- 
2.25.1