Pull request overview

Addresses deterministic failures in Windows MountVolume-related filesystem tests on ARM64 Helix by improving second-drive selection and adding Helix diagnostics to make drive/volume issues easier to diagnose from logs.

Changes:

• Filter candidate “other NTFS drives” to only those that support volume mount point operations (via GetVolumeNameForVolumeMountPoint).
• Add a Helix-only diagnostic test that logs drive details and volume GUID availability.
• Improve Mount/Unmount error messages by using P/Invoke error messages instead of raw codes, and add a Helix guard for missing second-drive scenarios.

Copilot's findings

        bool r = DeleteVolumeMountPoint(mountPoint);
        if (!r)
        {
            int error = Marshal.GetLastPInvokeError();
            // Ignore expected cleanup errors: 4390 (ERROR_NOT_A_REPARSE_POINT),
            // 3 (ERROR_PATH_NOT_FOUND), 2 (ERROR_FILE_NOT_FOUND)
            if (error != 4390 && error != 3 && error != 2)
                throw new Exception(string.Format("DeleteVolumeMountPoint({0}) failed: {1}", mountPoint, Marshal.GetLastPInvokeErrorMessage()));
            Console.WriteLine(string.Format("Ignoring expected error while unmounting {0}: {1}", mountPoint, Marshal.GetLastPInvokeErrorMessage()));

• Files reviewed: 7/7 changed files
• Comments generated: 4

Pull request overview

This PR addresses deterministic failures in the System.IO mount-volume tests on Windows 11 ARM64 Helix machines by avoiding “fixed/NTFS/ready” drives that don’t actually support volume mount-point operations (no volume GUID), and by adding Helix-focused diagnostics/guards to keep cross-drive scenarios from silently becoming dead code.

Changes:

• Update IOServices.GetNtfsDriveOtherThan(...) to also require a successful GetVolumeNameForVolumeMountPoint (volume GUID present) before selecting a “usable” NTFS drive.
• Add Helix-only hard-fail guards in both mount-volume tests when no suitable second NTFS drive is available.
• Add a Helix-only diagnostic test to dump drive and volume GUID information into Helix logs.

Copilot's findings

• Files reviewed: 6/6 changed files
• Comments generated: 3

Pull request overview

This PR addresses deterministic failures in the MountVolume-related filesystem tests on Windows 11 ARM64 Helix machines by ensuring the “other NTFS drive” selection skips fixed/NTFS/ready drives that don’t actually support volume mount point operations (e.g., drives without a volume GUID).

Changes:

• Update IOServices.GetNtfsDriveOtherThan(...) to additionally require that candidate drives have a volume GUID via GetVolumeNameForVolumeMountPoint.
• Add a GetVolumeNameForVolumeMountPointW LibraryImport to the test DllImports helpers.
• Add a Helix-only diagnostic test (DumpDriveInformation) and wire it into the test project to print drive/volume details to the Helix console log.

Copilot's findings

• Files reviewed: 4/4 changed files
• Comments generated: 2

Pull request overview

This PR aims to address deterministic MountVolume-related test failures on Windows ARM64 Helix agents by ensuring the “other NTFS drive” selection excludes drives that don’t support volume mount point operations, and by adding Helix-only diagnostics to quickly identify problematic drives.

Changes:

• Update IOServices.GetNtfsDriveOtherThan() to require a successful GetVolumeNameForVolumeMountPoint call (filters out drives without a usable volume GUID).
• Add a new kernel32 P/Invoke (GetVolumeNameForVolumeMountPointW) to the test DllImports.
• Add a Helix-only diagnostic “test” that prints drive properties and volume GUID availability to the console, and include it in the test project.

Copilot's findings

• Files reviewed: 4/4 changed files
• Comments generated: 1

@copilot please address my feedback

LGTM, thank you @danmoseley !