3 files changed, 28 insertions, 9 deletions
diff --git a/weed/topology/volume_growth_test.go b/weed/topology/volume_growth_test.go
index a3473c677..04c5e8aeb 100644
--- a/weed/topology/volume_growth_test.go
+++ b/weed/topology/volume_growth_test.go
@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"github.com/seaweedfs/seaweedfs/weed/storage/types"
+	"github.com/seaweedfs/seaweedfs/weed/util"
 	"testing"
 
 	"github.com/seaweedfs/seaweedfs/weed/sequence"
@@ -419,11 +420,13 @@ func TestPickForWrite(t *testing.T) {
 		Rack:       "",
 		DataNode:   "",
 	}
+	v := util.GetViper()
+	v.Set("master.volume_growth.threshold", 0.9)
 	for _, rpStr := range []string{"001", "010", "100"} {
 		rp, _ := super_block.NewReplicaPlacementFromString(rpStr)
 		vl := topo.GetVolumeLayout("test", rp, needle.EMPTY_TTL, types.HardDriveType)
 		volumeGrowOption.ReplicaPlacement = rp
-		for _, dc := range []string{"", "dc1", "dc2", "dc3"} {
+		for _, dc := range []string{"", "dc1", "dc2", "dc3", "dc0"} {
 			volumeGrowOption.DataCenter = dc
 			for _, r := range []string{""} {
 				volumeGrowOption.Rack = r
@@ -432,8 +435,13 @@ func TestPickForWrite(t *testing.T) {
 						continue
 					}
 					volumeGrowOption.DataNode = dn
-					fileId, count, _, _, err := topo.PickForWrite(1, volumeGrowOption, vl)
-					if err != nil {
+					fileId, count, _, shouldGrow, err := topo.PickForWrite(1, volumeGrowOption, vl)
+					if dc == "dc0" {
+						if err == nil || count != 0 || !shouldGrow {
+							fmt.Println(dc, r, dn, "pick for write should be with error")
+							t.Fail()
+						}
+					} else if err != nil {
 						fmt.Println(dc, r, dn, "pick for write error :", err)
 						t.Fail()
 					} else if count == 0 {
@@ -442,6 +450,9 @@ func TestPickForWrite(t *testing.T) {
 					} else if len(fileId) == 0 {
 						fmt.Println(dc, r, dn, "pick for write file id is empty")
 						t.Fail()
+					} else if shouldGrow {
+						fmt.Println(dc, r, dn, "pick for write error : not should grow")
+						t.Fail()
 					}
 				}
 			}
diff --git a/weed/topology/volume_layout.go b/weed/topology/volume_layout.go
index 278978292..d04552d35 100644
--- a/weed/topology/volume_layout.go
+++ b/weed/topology/volume_layout.go
@@ -234,13 +234,18 @@ func (vl *VolumeLayout) ensureCorrectWritables(vid needle.VolumeId) {
 }
 
 func (vl *VolumeLayout) isAllWritable(vid needle.VolumeId) bool {
-	for _, dn := range vl.vid2location[vid].list {
-		if v, getError := dn.GetVolumesById(vid); getError == nil {
-			if v.ReadOnly {
-				return false
+	if location, ok := vl.vid2location[vid]; ok {
+		for _, dn := range location.list {
+			if v, getError := dn.GetVolumesById(vid); getError == nil {
+				if v.ReadOnly {
+					return false
+				}
 			}
 		}
+	} else {
+		return false
 	}
+
 	return true
 }
 
@@ -301,7 +306,7 @@ func (vl *VolumeLayout) PickForWrite(count uint64, option *VolumeGrowOption) (vi
 			if float64(info.Size) > float64(vl.volumeSizeLimit)*option.Threshold() {
 				shouldGrow = true
 			}
-			return vid, count, locationList, shouldGrow, nil
+			return vid, count, locationList.Copy(), shouldGrow, nil
 		}
 		return 0, 0, nil, shouldGrow, errors.New("Strangely vid " + vid.String() + " is on no machine!")
 	}
@@ -336,7 +341,7 @@ func (vl *VolumeLayout) PickForWrite(count uint64, option *VolumeGrowOption) (vi
 			return
 		}
 	}
-	return vid, count, locationList, shouldGrow, fmt.Errorf("No writable volumes in DataCenter:%v Rack:%v DataNode:%v", option.DataCenter, option.Rack, option.DataNode)
+	return vid, count, locationList, true, fmt.Errorf("No writable volumes in DataCenter:%v Rack:%v DataNode:%v", option.DataCenter, option.Rack, option.DataNode)
 }
 
 func (vl *VolumeLayout) HasGrowRequest() bool {
diff --git a/weed/topology/volume_location_list.go b/weed/topology/volume_location_list.go
index c26f77104..127ad67eb 100644
--- a/weed/topology/volume_location_list.go
+++ b/weed/topology/volume_location_list.go
@@ -28,6 +28,9 @@ func (dnll *VolumeLocationList) Copy() *VolumeLocationList {
 
 func (dnll *VolumeLocationList) Head() *DataNode {
 	//mark first node as master volume
+	if dnll.Length() == 0 {
+		return nil
+	}
 	return dnll.list[0]
 }