meta/format: fix format decrypt error (#6542)

Signed-off-by: Changxin Miao <miaochangxin@step.ai>

Author: polyrabbit

pkg/meta/config.go

@@ -125,7 +125,15 @@ func (f *Format) update(old *Format, force bool) error {
 			args = []interface{}{"meta version", old.MetaVersion, f.MetaVersion}
 		}
 		if args == nil {
-			f.UUID = old.UUID
+			if f.UUID != old.UUID {
+				if err := f.Decrypt(); err != nil {
+					return fmt.Errorf("decrypt format: %s", err)
+				}
+				f.UUID = old.UUID // UUID cannot be changed alone
+				if err := f.Encrypt(); err != nil {
+					return fmt.Errorf("encrypt format: %s", err)
+				}
+			}
 		} else {
 			return fmt.Errorf("cannot update volume %s from %v to %v", args...)
 		}

pkg/meta/config_test.go

@@ -21,6 +21,7 @@ import (
 	"testing"
 
 	"github.com/juicedata/juicefs/pkg/object"
+	"github.com/stretchr/testify/assert"
 )
 
 func TestRemoveSecret(t *testing.T) {
@@ -66,3 +67,26 @@ func TestEncrypt(t *testing.T) {
 		})
 	}
 }
+
+func TestFormat_Update_KeyConflict(t *testing.T) {
+	oldFormat := Format{Name: "test", UUID: "UUID-A"}
+
+	newFormat := Format{Name: "test", UUID: "UUID-B", SecretKey: "secret"}
+	if err := newFormat.Encrypt(); err != nil {
+		t.Fatal(err)
+	}
+	assert.True(t, newFormat.KeyEncrypted)
+
+	if err := newFormat.update(&oldFormat, false); err != nil {
+		t.Fatal(err)
+	}
+
+	assert.Equal(t, "UUID-A", newFormat.UUID)
+	assert.True(t, newFormat.KeyEncrypted)
+
+	if err := newFormat.Decrypt(); err != nil {
+		t.Fatalf("failed to decrypt with new UUID (which is old UUID A): %s", err)
+	}
+
+	assert.Equal(t, "secret", newFormat.SecretKey)
+}