xl: Always set root disk to true in test environment (#11094)

Tests environments (go test or manual testing) should always consider
the passed disks are root disks and should not rely on disk.IsRootDisk()
function. The reason is that this latter can return a false negative
when called in a busy system. However, returning a false negative will
only occur in a testing environment and not in a production, so we can
accept this trade-off for now.

cmd/test-utils_test.go

@@ -115,6 +115,8 @@ func TestMain(m *testing.M) {
 
 	resetTestGlobals()
 
+	os.Setenv("MINIO_CI_CD", "ci")
+
 	os.Exit(m.Run())
 }
 

cmd/xl-storage.go

@@ -240,9 +240,14 @@ func newXLStorage(ep Endpoint) (*xlStorage, error) {
 		return nil, err
 	}
 
-	rootDisk, err := disk.IsRootDisk(path, "/")
-	if err != nil {
-		return nil, err
+	var rootDisk bool
+	if env.Get("MINIO_CI_CD", "") != "" {
+		rootDisk = true
+	} else {
+		rootDisk, err = disk.IsRootDisk(path, "/")
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	p := &xlStorage{