correct count for free ec slots, avoid removing generated shards

weed/shell/command_ec_balance.go

@@ -256,6 +256,7 @@ func pickOneEcNodeAndMoveOneShard(ctx context.Context, commandEnv *commandEnv, a
 		}
 
 		destEcNode.freeEcSlot--
+		existingLocation.freeEcSlot++
 		return nil
 	}
 

weed/shell/command_ec_rebuild.go

@@ -144,23 +144,18 @@ func rebuildOneEcVolume(ctx context.Context, commandEnv *commandEnv, rebuilder *
 			fmt.Fprintf(writer, "%s delete copied ec shards %s %d.%v\n", rebuilder.info.Id, collection, volumeId, copiedShardIds)
 		}
 
-		// ask the rebuilder to delete the copied shards
-		err = sourceServerDeleteEcShards(ctx, commandEnv.option.GrpcDialOption, collection, volumeId, rebuilder.info.Id, generatedShardIds)
-		if err != nil {
-			fmt.Fprintf(writer, "%s delete generated ec shards %s %d.%v\n", rebuilder.info.Id, collection, volumeId, generatedShardIds)
-		}
-
 	}()
 
 	if !applyChanges {
 		return nil
 	}
 
-	// generate ec shards, and maybe ecx file, and mount them
+	// generate ec shards, and maybe ecx file
 	generatedShardIds, err = generateMissingShards(ctx, commandEnv.option.GrpcDialOption, collection, volumeId, rebuilder.info.Id)
 	if err != nil {
 		return err
 	}
+	rebuilder.freeEcSlot -= len(generatedShardIds)
 
 	// mount the generated shards
 	err = mountEcShards(ctx, commandEnv.option.GrpcDialOption, collection, volumeId, rebuilder.info.Id, generatedShardIds)
@@ -205,14 +200,14 @@ func prepareDataToRecover(ctx context.Context, commandEnv *commandEnv, rebuilder
 			continue
 		}
 
-		if localShardBits.HasShardId(erasure_coding.ShardId(shardId)){
+		if localShardBits.HasShardId(erasure_coding.ShardId(shardId)) {
 			localShardIds = append(localShardIds, uint32(shardId))
 			fmt.Fprintf(writer, "use existing shard %d.%d\n", volumeId, shardId)
 			continue
 		}
 
 		var copyErr error
-		if applyBalancing{
+		if applyBalancing {
 			copyErr = operation.WithVolumeServerClient(rebuilder.info.Id, commandEnv.option.GrpcDialOption, func(volumeServerClient volume_server_pb.VolumeServerClient) error {
 				_, copyErr := volumeServerClient.VolumeEcShardsCopy(ctx, &volume_server_pb.VolumeEcShardsCopyRequest{
 					VolumeId:       uint32(volumeId),