[master] fix master panic (#5893)

weed/topology/disk.go

@@ -2,11 +2,12 @@ package topology
 
 import (
 	"fmt"
-	"github.com/seaweedfs/seaweedfs/weed/storage/types"
-	"github.com/seaweedfs/seaweedfs/weed/util"
 	"sync"
 	"sync/atomic"
 
+	"github.com/seaweedfs/seaweedfs/weed/storage/types"
+	"github.com/seaweedfs/seaweedfs/weed/util"
+
 	"github.com/seaweedfs/seaweedfs/weed/pb/master_pb"
 	"github.com/seaweedfs/seaweedfs/weed/storage/erasure_coding"
 	"github.com/seaweedfs/seaweedfs/weed/storage/needle"
@@ -201,6 +202,12 @@ func (d *Disk) GetVolumesById(id needle.VolumeId) (storage.VolumeInfo, error) {
 	}
 }
 
+func (d *Disk) DeleteVolumeById(id needle.VolumeId) {
+	d.Lock()
+	defer d.Unlock()
+	delete(d.volumes, id)
+}
+
 func (d *Disk) GetDataCenter() *DataCenter {
 	dn := d.Parent()
 	rack := dn.Parent()