osd/osd_types: mark unused variable [[maybe_unused]]

silences warning like:

rc/osd/osd_types.h:5482:18: warning: unused variable '_' [-Wunused-variable]
     auto [iter, _] = ref_delta.try_emplace(hoid, 0);
                  ^

Signed-off-by: Kefu Chai <kchai@redhat.com>

diff --git a/src/osd/osd_types.h b/src/osd/osd_types.h
index 636c3e710c5a8541dc59ebc03620561da9e30717..0d61765ba143179376420c726814190e104cbecf 100644 (file)
--- a/src/osd/osd_types.h
+++ b/src/osd/osd_types.h
@@ -5479,7 +5479,7 @@ public:
     mut_ref(hoid, num);
   }
   void mut_ref(const hobject_t &hoid, int num) {
-    auto [iter, _] = ref_delta.try_emplace(hoid, 0);
+    [[maybe_unused]] auto [iter, _] = ref_delta.try_emplace(hoid, 0);
     iter->second += num;
     if (iter->second == 0)
       ref_delta.erase(iter);