dht: fix potential of-by-one largest computation, cleanup

src/dht.cpp

@@ -1403,26 +1403,26 @@ Dht::expireStore()
             break;
         }
         auto largest = store_quota.begin();
-        for (auto it = ++largest; it != store_quota.end(); ++it) {
+        for (auto it = std::next(largest); it != store_quota.end(); ++it) {
             if (it->second.size() > largest->second.size())
                 largest = it;
         }
-        if (logger_)
-            logger_->w("No space left: discarding value of largest consumer %s", largest->first.toString().c_str());
+        if (largest != store_quota.end()) {
             while (true) {
                 auto exp_value = largest->second.getOldest();
                 auto storage = store.find(exp_value.first);
                 if (storage != store.end()) {
+                    if (logger_)
+                        logger_->w("Storage quota full: discarding value from %s at %s %016" PRIx64, largest->first.toString().c_str(), exp_value.first.to_c_str(), exp_value.second);
                     auto ret = storage->second.remove(exp_value.first, exp_value.second);
                     total_store_size += ret.size_diff;
                     total_values += ret.values_diff;
-                if (logger_)
-                    logger_->w("Discarded %ld bytes, still %ld used", largest->first.toString().c_str(), total_store_size);
                     if (ret.values_diff)
                         break;
                 }
             }
         }
+    }
 
     // remove unused quota entires
     for (auto i = store_quota.begin(); i != store_quota.end();) {