[PATCH -next] mm/mmap_lock: fix warning when CONFIG_TRACING is not defined

[Bixuan Cui]

Fix the warning: [-Wunused-function]
mm/mmap_lock.c:157:20: warning: ‘get_mm_memcg_path’ defined but not used
 static const char *get_mm_memcg_path(struct mm_struct *mm)
                    ^~~~~~~~~~~~~~~~~

Signed-off-by: Bixuan Cui <cuibixuan@xxxxxxxxxx>
---
 mm/mmap_lock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/mmap_lock.c b/mm/mmap_lock.c
index 03ee85c696ef..ec7899b08690 100644
--- a/mm/mmap_lock.c
+++ b/mm/mmap_lock.c
@@ -154,7 +154,7 @@ static inline void put_memcg_path_buf(void)
  * The caller must call put_memcg_path_buf() once the buffer is no longer
  * needed. This must be done while preemption is still disabled.
  */
-static const char *get_mm_memcg_path(struct mm_struct *mm)
+static const char __maybe_unused *get_mm_memcg_path(struct mm_struct *mm)
 {
 	char *buf = NULL;
 	struct mem_cgroup *memcg = get_mem_cgroup_from_mm(mm);
-- 
2.17.1