virtiofs reparse point workaround using bindflt CreateBindLink

cowork-drives.c

/*
 * cowork-drives - bind windows drive roots into a folder via bindflt
 *
 * virtiofs cant follow NTFS reparse points (junctions/symlinks),
 * so we use CreateBindLink to create kernel-level bind mounts
 * that show up as real directories. must run as SYSTEM.
 *
 * usage: cowork-drives.exe <folder> <letter> [letter ...]
 * example: cowork-drives.exe C:\Users\me\AllDrives C D F
 */

#include <windows.h>
#include <stdio.h>

typedef HRESULT (WINAPI *CreateBindLinkFn)(
    LPCWSTR virtualPath,
    LPCWSTR backingPath,
    ULONG flags,
    ULONG extraInfoCount,
    void *extraInfo
);

typedef HRESULT (WINAPI *RemoveBindLinkFn)(LPCWSTR virtualPath);

int wmain(int argc, wchar_t *argv[]) {
    if (argc < 3) {
        wprintf(L"usage: %s <folder> <drive> [drive ...]\n", argv[0]);
        wprintf(L"example: %s C:\\Users\\me\\AllDrives C D F\n", argv[0]);
        return 1;
    }

    HMODULE lib = LoadLibraryW(L"bindfltapi.dll");
    if (!lib) {
        wprintf(L"err: cant load bindfltapi.dll (%lu)\n", GetLastError());
        return 1;
    }

    CreateBindLinkFn bind =
        (CreateBindLinkFn)GetProcAddress(lib, "CreateBindLink");
    RemoveBindLinkFn unbind =
        (RemoveBindLinkFn)GetProcAddress(lib, "RemoveBindLink");

    if (!bind) {
        wprintf(L"err: CreateBindLink not in bindfltapi.dll\n");
        FreeLibrary(lib);
        return 1;
    }

    LPCWSTR root = argv[1];
    CreateDirectoryW(root, NULL);

    int ok = 0, fail = 0, skip = 0;

    for (int i = 2; i < argc; i++) {
        wchar_t letter = argv[i][0];
        if (letter >= L'a' && letter <= L'z')
            letter -= 32;

        /* build paths */
        wchar_t virt[MAX_PATH], target[8];
        swprintf(virt, MAX_PATH, L"%s\\%c", root, letter);
        swprintf(target, 8, L"%c:\\", letter);

        /* check drive exists */
        if (GetDriveTypeW(target) == DRIVE_NO_ROOT_DIR) {
            wprintf(L"  skip %c  (drive not found)\n", letter);
            skip++;
            continue;
        }

        /* remove old junction/symlink if present */
        DWORD attr = GetFileAttributesW(virt);
        if (attr != INVALID_FILE_ATTRIBUTES &&
            (attr & FILE_ATTRIBUTE_REPARSE_POINT)) {
            RemoveDirectoryW(virt);
        }

        CreateDirectoryW(virt, NULL);
        if (unbind) unbind(virt);

        HRESULT hr = bind(virt, target, 0, 0, NULL);
        if (SUCCEEDED(hr)) {
            wprintf(L"  ok   %c  %s -> %s\n", letter, virt, target);
            ok++;
        } else {
            wprintf(L"  FAIL %c  0x%08lX\n", letter, hr);
            fail++;
        }
    }

    wprintf(L"\n%d ok, %d failed, %d skipped\n", ok, fail, skip);
    if (ok > 0)
        wprintf(L"bind links active until reboot\n");

    FreeLibrary(lib);
    return fail > 0 ? 1 : 0;
}

cowork-mount-drives.ps1

#requires -RunAsAdministrator
<#
.SYNOPSIS
    mounts windows drives into a folder so cowork's virtiofs can see them.
    
.DESCRIPTION
    virtiofs cant follow NTFS reparse points (junctions/symlinks), so this
    script uses CreateBindLink (via bindflt minifilter) to create kernel-level
    bind mounts that show up as real directories.
    
    CreateBindLink requires SYSTEM privileges, so the script creates a
    one-shot scheduled task to run the bind tool as SYSTEM.
    
    bind links persist until reboot. run this after each boot before
    opening cowork, or set it up as a startup task.

.PARAMETER Folder
    target folder. defaults to $env:USERPROFILE\AllDrives

.PARAMETER Drives
    drive letters to bind. defaults to all fixed drives on the system.
#>

param(
    [string]$Folder = "$env:USERPROFILE\AllDrives",
    [string[]]$Drives
)

# self-elevate if needed
if (-NOT ([Security.Principal.WindowsPrincipal][Security.Principal.WindowsIdentity]::GetCurrent()).IsInRole([Security.Principal.WindowsBuiltInRole]::Administrator)) {
    $args_str = "-Folder `"$Folder`""
    if ($Drives) { $args_str += " -Drives $($Drives -join ',')" }
    Start-Process powershell.exe "-NoProfile -ExecutionPolicy Bypass -File `"$PSCommandPath`" $args_str" -Verb RunAs
    exit
}

$scriptDir = Split-Path -Parent $PSCommandPath
$exe = Join-Path $scriptDir "cowork-drives.exe"

if (-not (Test-Path $exe)) {
    Write-Host "error: cowork-drives.exe not found at $exe" -ForegroundColor Red
    Write-Host "put it next to this script"
    exit 1
}

# auto-detect fixed drives if none specified
if (-not $Drives) {
    $Drives = (Get-WmiObject Win32_LogicalDisk | Where-Object { $_.DriveType -eq 3 }).DeviceID -replace ':', ''
    Write-Host "detected drives: $($Drives -join ', ')"
}

# clean up old junctions in the folder
if (Test-Path $Folder) {
    Get-ChildItem $Folder -Directory | ForEach-Object {
        if ($_.Attributes -band [IO.FileAttributes]::ReparsePoint) {
            Write-Host "removing old junction: $($_.Name)"
            [IO.Directory]::Delete($_.FullName)
        }
    }
}

# build args
$driveArgs = ($Drives | ForEach-Object { $_.Substring(0,1).ToUpper() }) -join ' '
$argString = "`"$Folder`" $driveArgs"

# write a bat to capture output
$logFile = Join-Path $scriptDir "cowork-drives.log"
$batFile = Join-Path $env:TEMP "cowork-drives-run.bat"
"@echo off`r`n`"$exe`" $argString > `"$logFile`" 2>&1" | Out-File $batFile -Encoding ascii

# run as SYSTEM via scheduled task
$taskName = "CoworkDrivesBind"
try {
    Unregister-ScheduledTask -TaskName $taskName -Confirm:$false -ErrorAction SilentlyContinue
} catch {}

$action = New-ScheduledTaskAction -Execute $batFile
$principal = New-ScheduledTaskPrincipal -UserId "SYSTEM" -LogonType ServiceAccount -RunLevel Highest
$task = New-ScheduledTask -Action $action -Principal $principal

Register-ScheduledTask -TaskName $taskName -InputObject $task -Force | Out-Null
Start-ScheduledTask -TaskName $taskName

# wait for it
$timeout = 10
for ($i = 0; $i -lt $timeout; $i++) {
    Start-Sleep 1
    $info = Get-ScheduledTaskInfo -TaskName $taskName -ErrorAction SilentlyContinue
    if ($info -and $info.LastTaskResult -ne 267009) { break }  # 267009 = still running
}

Unregister-ScheduledTask -TaskName $taskName -Confirm:$false -ErrorAction SilentlyContinue

# show results
if (Test-Path $logFile) {
    Write-Host ""
    Get-Content $logFile | Write-Host
}

Write-Host ""
Write-Host "drives mounted at: $Folder" -ForegroundColor Green
Write-Host "these persist until reboot. run this script again after rebooting."

mount-drives.bat

@echo off
powershell -NoProfile -ExecutionPolicy Bypass -File "%~dp0cowork-mount-drives.ps1"
pause