remember oversized volumes

fix https://github.com/chrislusf/seaweedfs/issues/331

weed/topology/volume_layout.go

@@ -16,6 +16,7 @@ type VolumeLayout struct {
 	ttl              *storage.TTL
 	vid2location     map[storage.VolumeId]*VolumeLocationList
 	writables        []storage.VolumeId        // transient array of writable volume id
+	oversizedVolumes map[storage.VolumeId]bool // set of oversized volumes
 	volumeSizeLimit  uint64
 	accessLock       sync.RWMutex
 }
@@ -26,6 +27,7 @@ func NewVolumeLayout(rp *storage.ReplicaPlacement, ttl *storage.TTL, volumeSizeL
 		ttl:              ttl,
 		vid2location:     make(map[storage.VolumeId]*VolumeLocationList),
 		writables:        *new([]storage.VolumeId),
+		oversizedVolumes: make(map[storage.VolumeId]bool),
 		volumeSizeLimit:  volumeSizeLimit,
 	}
 }
@@ -44,12 +46,21 @@ func (vl *VolumeLayout) RegisterVolume(v *storage.VolumeInfo, dn *DataNode) {
 	vl.vid2location[v.Id].Set(dn)
 	glog.V(4).Infoln("volume", v.Id, "added to dn", dn.Id(), "len", vl.vid2location[v.Id].Length(), "copy", v.ReplicaPlacement.GetCopyCount())
 	if vl.vid2location[v.Id].Length() == vl.rp.GetCopyCount() && vl.isWritable(v) {
+		if _, ok := vl.oversizedVolumes[v.Id]; !ok {
 			vl.addToWritable(v.Id)
+		}
 	} else {
+		vl.rememberOversizedVolumne(v)
 		vl.removeFromWritable(v.Id)
 	}
 }
 
+func (vl *VolumeLayout) rememberOversizedVolumne(v *storage.VolumeInfo) {
+	if vl.isOversized(v) {
+		vl.oversizedVolumes[v.Id] = true
+	}
+}
+
 func (vl *VolumeLayout) UnRegisterVolume(v *storage.VolumeInfo, dn *DataNode) {
 	vl.accessLock.Lock()
 	defer vl.accessLock.Unlock()
@@ -67,8 +78,12 @@ func (vl *VolumeLayout) addToWritable(vid storage.VolumeId) {
 	vl.writables = append(vl.writables, vid)
 }
 
+func (vl *VolumeLayout) isOversized(v *storage.VolumeInfo) bool {
+	return uint64(v.Size) < vl.volumeSizeLimit
+}
+
 func (vl *VolumeLayout) isWritable(v *storage.VolumeInfo) bool {
-	return uint64(v.Size) < vl.volumeSizeLimit &&
+	return vl.isOversized(v) &&
 		v.Version == storage.CurrentVersion &&
 		!v.ReadOnly
 }