Clean up lock-instrumentation and improve comments (#3499)

- Add a lockStat type to group counters
- Remove unnecessary helper functions
- Fix stats computation on force unlock
- Removed unnecessary checks and cleaned up comments

cmd/lock-stat.go

@@ -0,0 +1,49 @@
+/*
+ * Minio Cloud Storage, (C) 2016 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cmd
+
+// lockStat - encapsulates total, blocked and granted lock counts.
+type lockStat struct {
+	total   int64
+	blocked int64
+	granted int64
+}
+
+// lockWaiting - updates lock stat when a lock becomes blocked.
+func (ls *lockStat) lockWaiting() {
+	ls.blocked++
+	ls.total++
+}
+
+// lockGranted - updates lock stat when a lock is granted.
+func (ls *lockStat) lockGranted() {
+	ls.blocked--
+	ls.granted++
+}
+
+// lockRemoved - updates lock stat when a lock is removed, by Unlock
+// or ForceUnlock.
+func (ls *lockStat) lockRemoved(granted bool) {
+	if granted {
+		ls.granted--
+		ls.total--
+
+	} else {
+		ls.blocked--
+		ls.total--
+	}
+}