lock: Make some cleanup and moving the code around. (#2718)

This patch just avoids lot of ifs and inverts some logic.

cmd/lock-rpc-server-common.go

@@ -0,0 +1,85 @@
+/*
+ * 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
+
+import (
+	"errors"
+	"time"
+)
+
+// Similar to removeEntry but only removes an entry only if the lock entry exists in map.
+func (l *lockServer) removeEntryIfExists(nlrip nameLockRequesterInfoPair) {
+	// Check if entry is still in map (could have been removed altogether by 'concurrent' (R)Unlock of last entry)
+	if lri, ok := l.lockMap[nlrip.name]; ok {
+		if !l.removeEntry(nlrip.name, nlrip.lri.uid, &lri) {
+			// Remove failed, in case it is a:
+			if nlrip.lri.writer {
+				// Writer: this should never happen as the whole (mapped) entry should have been deleted
+				errorIf(errors.New(""), "Lock maintenance failed to remove entry for write lock (should never happen)", nlrip.name, nlrip.lri.uid, lri)
+			} // Reader: this can happen if multiple read locks were active and
+			// the one we are looking for has been released concurrently (so it is fine).
+		} // Removal went okay, all is fine.
+	}
+}
+
+// removeEntry either, based on the uid of the lock message, removes a single entry from the
+// lockRequesterInfo array or the whole array from the map (in case of a write lock or last read lock)
+func (l *lockServer) removeEntry(name, uid string, lri *[]lockRequesterInfo) bool {
+	// Find correct entry to remove based on uid.
+	for index, entry := range *lri {
+		if entry.uid == uid {
+			if len(*lri) == 1 {
+				// Remove the (last) lock.
+				delete(l.lockMap, name)
+			} else {
+				// Remove the appropriate read lock.
+				*lri = append((*lri)[:index], (*lri)[index+1:]...)
+				l.lockMap[name] = *lri
+			}
+			return true
+		}
+	}
+	// None found return false, perhaps entry removed in previous run.
+	return false
+}
+
+// Validate lock args.
+func (l *lockServer) validateLockArgs(args *LockArgs) error {
+	if !l.timestamp.Equal(args.Timestamp) {
+		return errInvalidTimestamp
+	}
+	if !isRPCTokenValid(args.Token) {
+		return errInvalidToken
+	}
+	return nil
+}
+
+// getLongLivedLocks returns locks that are older than a certain time and
+// have not been 'checked' for validity too soon enough
+func getLongLivedLocks(m map[string][]lockRequesterInfo, interval time.Duration) []nameLockRequesterInfoPair {
+	rslt := []nameLockRequesterInfoPair{}
+	for name, lriArray := range m {
+		for idx := range lriArray {
+			// Check whether enough time has gone by since last check
+			if time.Since(lriArray[idx].timeLastCheck) >= interval {
+				rslt = append(rslt, nameLockRequesterInfoPair{name: name, lri: lriArray[idx]})
+				lriArray[idx].timeLastCheck = time.Now().UTC()
+			}
+		}
+	}
+	return rslt
+}