From 82af0be1aaac3dd7916329ca04c89743e022249d Mon Sep 17 00:00:00 2001
From: Krishna Srinivas <634494+krishnasrinivas@users.noreply.github.com>
Date: Wed, 23 Jan 2019 15:29:29 -0800
Subject: [PATCH] Healing process should not heal root disk (#7089)

---
 cmd/posix.go                  | 22 ++++++++++++++--------
 cmd/xl-sets.go                | 12 ++++++++++++
 pkg/disk/root-disk-unix.go    | 31 +++++++++++++++++++++++++++++++
 pkg/disk/root-disk-windows.go |  9 +++++++++
 4 files changed, 66 insertions(+), 8 deletions(-)
 create mode 100644 pkg/disk/root-disk-unix.go
 create mode 100644 pkg/disk/root-disk-windows.go

diff --git a/cmd/posix.go b/cmd/posix.go
index 7ca778d90..01b49b933 100644
--- a/cmd/posix.go
+++ b/cmd/posix.go
@@ -303,9 +303,10 @@ func (s *posix) IsOnline() bool {
 // DiskInfo is an extended type which returns current
 // disk usage per path.
 type DiskInfo struct {
-	Total uint64
-	Free  uint64
-	Used  uint64
+	Total    uint64
+	Free     uint64
+	Used     uint64
+	RootDisk bool
 }
 
 // DiskInfo provides current information about disk space usage,
@@ -319,12 +320,17 @@ func (s *posix) DiskInfo() (info DiskInfo, err error) {
 	if !s.diskMount {
 		used = atomic.LoadUint64(&s.totalUsed)
 	}
-	return DiskInfo{
-		Total: di.Total,
-		Free:  di.Free,
-		Used:  used,
-	}, nil
 
+	rootDisk, err := disk.IsRootDisk(s.diskPath)
+	if err != nil {
+		return info, err
+	}
+	return DiskInfo{
+		Total:    di.Total,
+		Free:     di.Free,
+		Used:     used,
+		RootDisk: rootDisk,
+	}, nil
 }
 
 // getVolDir - will convert incoming volume names to
diff --git a/cmd/xl-sets.go b/cmd/xl-sets.go
index dbeb6b254..2c9216236 100644
--- a/cmd/xl-sets.go
+++ b/cmd/xl-sets.go
@@ -1029,6 +1029,18 @@ func (s *xlSets) HealFormat(ctx context.Context, dryRun bool) (res madmin.HealRe
 		}
 	}(storageDisks)
 
+	for i, disk := range storageDisks {
+		info, err := disk.DiskInfo()
+		if err != nil {
+			storageDisks[i] = nil
+		}
+		if info.RootDisk {
+			// We should not heal on root disk. i.e in a situation where the minio-administrator has unmounted a
+			// defective drive we should not heal a path on the root disk.
+			storageDisks[i] = nil
+		}
+	}
+
 	formats, sErrs := loadFormatXLAll(storageDisks)
 	if err = checkFormatXLValues(formats); err != nil {
 		return madmin.HealResultItem{}, err
diff --git a/pkg/disk/root-disk-unix.go b/pkg/disk/root-disk-unix.go
new file mode 100644
index 000000000..be51f0df7
--- /dev/null
+++ b/pkg/disk/root-disk-unix.go
@@ -0,0 +1,31 @@
+// +build !windows
+
+package disk
+
+import (
+	"os"
+	"syscall"
+)
+
+// IsRootDisk returns if diskPath belongs to root-disk, i.e the disk mounted at "/"
+func IsRootDisk(diskPath string) (bool, error) {
+	rootDisk := false
+	diskInfo, err := os.Stat(diskPath)
+	if err != nil {
+		return false, err
+	}
+	rootInfo, err := os.Stat("/")
+	if err != nil {
+		return false, err
+	}
+	diskStat, diskStatOK := diskInfo.Sys().(*syscall.Stat_t)
+	rootStat, rootStatOK := rootInfo.Sys().(*syscall.Stat_t)
+	if diskStatOK && rootStatOK {
+		if diskStat.Dev == rootStat.Dev {
+			// Indicate if the disk path is on root disk. This is used to indicate the healing
+			// process not to format the drive and end up healing it.
+			rootDisk = true
+		}
+	}
+	return rootDisk, nil
+}
diff --git a/pkg/disk/root-disk-windows.go b/pkg/disk/root-disk-windows.go
new file mode 100644
index 000000000..b19034f3b
--- /dev/null
+++ b/pkg/disk/root-disk-windows.go
@@ -0,0 +1,9 @@
+// +build windows
+
+package disk
+
+// IsRootDisk returns if diskPath belongs to root-disk, i.e the disk mounted at "/"
+func IsRootDisk(diskPath string) (bool, error) {
+	// On windows a disk can never be mounted on a subpath.
+	return false, nil
+}