Fail to start server if detected cross-device mounts. (#4807)

Fixes #4764

pkg/mountinfo/mountinfo.go

@@ -0,0 +1,34 @@
+/*
+ * Minio Cloud Storage, (C) 2017 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 mountinfo
+
+// mountInfo - This represents a single line in /proc/mounts.
+type mountInfo struct {
+	Device  string
+	Path    string
+	FSType  string
+	Options []string
+	Freq    string
+	Pass    string
+}
+
+func (m mountInfo) String() string {
+	return m.Path
+}
+
+// mountInfos - This represents the entire /proc/mounts.
+type mountInfos []mountInfo