fix: ignore lost+found properly while reading disks (#9278)

Fixes #9277

cmd/format-xl.go

@@ -378,22 +378,23 @@ func saveFormatXL(disk StorageAPI, format interface{}, diskID string) error {
 	return nil
 }
 
-var ignoredHiddenDirectories = []string{
-	minioMetaBucket,
-	".snapshot",
-	"lost+found",
-	"$RECYCLE.BIN",
-	"System Volume Information",
+var ignoredHiddenDirectories = map[string]struct{}{
+	minioMetaBucket:             {},
+	".snapshot":                 {},
+	"lost+found":                {},
+	"$RECYCLE.BIN":              {},
+	"System Volume Information": {},
 }
 
-func isIgnoreHiddenDirectories(dir string) bool {
-	for _, ignDir := range ignoredHiddenDirectories {
-		if dir == ignDir {
-			return true
-		}
+func isHiddenDirectories(vols ...VolInfo) bool {
+	for _, vol := range vols {
+		if _, ok := ignoredHiddenDirectories[vol.Name]; ok {
+			continue
 		}
 		return false
 	}
+	return true
+}
 
 // loadFormatXL - loads format.json from disk.
 func loadFormatXL(disk StorageAPI) (format *formatXLV3, err error) {
@@ -407,9 +408,8 @@ func loadFormatXL(disk StorageAPI) (format *formatXLV3, err error) {
 			if err != nil {
 				return nil, err
 			}
-			if len(vols) > 1 || (len(vols) == 1 && !isIgnoreHiddenDirectories(vols[0].Name)) {
-				// 'format.json' not found, but we
-				// found user data.
+			if !isHiddenDirectories(vols...) {
+				// 'format.json' not found, but we found user data, reject such disks.
 				return nil, errCorruptedFormat
 			}
 			// No other data found, its a fresh disk.