fix: for containers use root-disk detection cleverly (#11593)

root-disk implemented currently had issues where root
disk partitions getting modified might race and provide
incorrect results, to avoid this lets rely again back on
DeviceID and match it instead.

In-case of containers `/data` is one such extra entity that
needs to be verified for root disk, due to how 'overlay'
filesystem works and the 'overlay' presents a completely
different 'device' id - using `/data` as another entity
for fallback helps because our containers describe 'VOLUME'
parameter that allows containers to automatically have a
virtual `/data` that points to the container root path this
can either be at `/` or `/var/lib/` (on different partition)

pkg/disk/disk.go

@@ -30,21 +30,3 @@ type Info struct {
 	Ffree  uint64
 	FSType string
 }
-
-// SameDisk reports whether di1 and di2 describe the same disk.
-func SameDisk(di1, di2 Info) bool {
-	if di1.Total != di2.Total {
-		// disk total size different
-		return false
-	}
-
-	if di1.Files != di2.Files {
-		// disk total inodes different
-		return false
-	}
-
-	// returns true only if Used, Free are same, then its the same disk.
-	// we are deliberately not using free inodes as that is unreliable
-	// due the fact that Ffree can vary even for temporary files
-	return di1.Used == di2.Used && di1.Free == di2.Free
-}

pkg/disk/disk_unix.go

@@ -0,0 +1,39 @@
+// +build !windows
+
+/*
+ * MinIO Cloud Storage, (C) 2021 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 disk
+
+import (
+	"syscall"
+)
+
+// SameDisk reports whether di1 and di2 describe the same disk.
+func SameDisk(disk1, disk2 string) (bool, error) {
+	st1 := syscall.Stat_t{}
+	st2 := syscall.Stat_t{}
+
+	if err := syscall.Stat(disk1, &st1); err != nil {
+		return false, err
+	}
+
+	if err := syscall.Stat(disk2, &st2); err != nil {
+		return false, err
+	}
+
+	return st1.Dev == st2.Dev, nil
+}

pkg/disk/disk_windows.go

@@ -0,0 +1,24 @@
+// +build windows
+
+/*
+ * MinIO Cloud Storage, (C) 2021 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 disk
+
+// SameDisk reports whether di1 and di2 describe the same disk.
+func SameDisk(disk1, disk2 string) (bool, error) {
+	return false, nil
+}

pkg/disk/root_disk.go

@@ -25,13 +25,5 @@ func IsRootDisk(diskPath string, rootDisk string) (bool, error) {
 		// On windows this function is not implemented.
 		return false, nil
 	}
-	info, err := GetInfo(diskPath)
-	if err != nil {
-		return false, err
-	}
-	rootInfo, err := GetInfo(rootDisk)
-	if err != nil {
-		return false, err
-	}
-	return SameDisk(info, rootInfo), nil
+	return SameDisk(diskPath, rootDisk)
 }