Merge pull request #40650 from tao12345666333/fix-backingFs

fix backingFs assignment

daemon/graphdriver/overlay/overlay.go

@@ -136,6 +136,14 @@ func Init(home string, options []string, uidMaps, gidMaps []idtools.IDMap) (grap
 		return nil, graphdriver.ErrNotSupported
 	}
 
+	fsMagic, err := graphdriver.GetFSMagic(testdir)
+	if err != nil {
+		return nil, err
+	}
+	if fsName, ok := graphdriver.FsNames[fsMagic]; ok {
+		backingFs = fsName
+	}
+
 	supportsDType, err := fsutils.SupportsDType(testdir)
 	if err != nil {
 		return nil, err

daemon/graphdriver/overlay2/overlay.go

@@ -145,6 +145,14 @@ func Init(home string, options []string, uidMaps, gidMaps []idtools.IDMap) (grap
 		return nil, graphdriver.ErrNotSupported
 	}
 
+	fsMagic, err := graphdriver.GetFSMagic(testdir)
+	if err != nil {
+		return nil, err
+	}
+	if fsName, ok := graphdriver.FsNames[fsMagic]; ok {
+		backingFs = fsName
+	}
+
 	supportsDType, err := fsutils.SupportsDType(testdir)
 	if err != nil {
 		return nil, err