Linux Dir Sync - copy files to external HDD on Linux with sync command after every file

Program.cs

using System.Diagnostics;
using System.Runtime.InteropServices;

var cts = new CancellationTokenSource();
var cancelEvt = new ManualResetEventSlim();
Console.CancelKeyPress += delegate {
    cts.Cancel();
    cancelEvt.Wait();
};

const string src = "/media/pavel/DATA_4G/BACKUP/NAXAH-PC";
const string dst = "/media/pavel/New Volume/BACKUP/NAXAH-PC";

var count = 0;
long totalSize = 0;
var sw = Stopwatch.StartNew();
var existingDirs = new HashSet<string>();

foreach (var srcFile in Directory.EnumerateFiles(src, "*", new EnumerationOptions { RecurseSubdirectories = true }))
{
    var relPath = Path.GetRelativePath(src, srcFile);
    var dstFile = Path.Combine(dst, relPath);

    if (File.Exists(dstFile))
    {
        continue;
    }

    var dstDir = Path.GetDirectoryName(dstFile)!;

    if (!existingDirs.Contains(dstDir))
    {
        if (!Directory.Exists(dstDir))
        {
            Directory.CreateDirectory(dstDir);
        }

        existingDirs.Add(dstDir);
    }

    Console.Write(DateTime.Now + " " + relPath);

    File.Copy(srcFile, dstFile);

    Console.Write(" ... ");

    // Avoid USB stall on Linux due to huge dirty page queue.
    // https://lwn.net/Articles/572911/
    NativeMethodsLinux.sync();

    var info = new FileInfo(srcFile);

    count++;
    totalSize += info.Length;

    var totalSizeMib = totalSize / 1024 / 1024;
    var mibps = (double)totalSizeMib / sw.ElapsedMilliseconds * 1000;

    Console.WriteLine($"OK ({count} files, {totalSizeMib} MiB, {sw.Elapsed} elapsed, {mibps} MiB/s)");

    if (cts.IsCancellationRequested)
    {
        Console.WriteLine("Cancelled, exiting...");
        cancelEvt.Set();
        break;
    }
}


static class NativeMethodsLinux
{
    [DllImport("libdl.so", SetLastError = true, CharSet = CharSet.Ansi, BestFitMapping = false, ThrowOnUnmappableChar = true)]
    internal static extern void sync();
}