multer stop file upload immediate on validation fail

I am working on mean stack application and I face one issue with file uploading.

I want to stop all uploading immediately as soon as the global.isProcessKilled variable is true.

My code is as bellow

photo.js

var express = require("express");
var app = express()
var router = express.Router();
var multer = require("multer");
var mongoose = require("mongoose");
var fs = require("fs");
var jwt = require("jsonwebtoken");
var lib = require("../../../config/lib");

var storage = multer.diskStorage({
    destination: function(req, file, cb) {
        cb(null, dirPath);
    },
    filename: function(req, file, cb) {
        var datetimestamp = Date.now() + Math.floor(Math.random());
        cb(null, datetimestamp + '.' + file.originalname.split('.')[file.originalname.split('.').length - 1].toLowerCase());
    }
});

var photoUpload = multer({ 
    storage: storage,
    fileFilter : function (req, file, cb) {
        if(global.isProcessKilled){ //my custom validation flag
                // To reject this file pass `false`, like so:
                cb(null, false);
        }else{
            // To accept the file pass `true`, like so:
            cb(null, true);    
        }
    }
});

router
    .route("/api/photo/photoUpload")
    .post(
        photoUpload.array("file"),        
        function(req, res) {
            .....
            .....
            ....
        });

By this code file uploading is working fine but my next original API call occurs only after processing the current(previous) file.

More information: All selected files are more than 1mb and less than 10mb

• Step 1 : upload 30 file simultaneously
• Step 2 : the process will start
• Step 3 : suppose global.isProcessKilled variable will be true at 10 files
• Step 4 : next all files will not process for upload because of filter
• Step 5 : but the previous file means 9th file is running and I don't know how to stop it
• Step 6 : the process will not call next callback until file no 9th will not be uploaded and it takes about 2min
• Step 7 : for this reason api response I too delay

Please help me to resolve this issue.