DriveInfo.DriveFormat property reports ext3 format on ext4 formatted filesystems (Unix)

[alphons]

Description

using System;
namespace GetFileSystemEntries
{
    class Class1
    {
        static void Main(string[] args)
        {
            foreach (var drive in DriveInfo.GetDrives())
                Console.WriteLine(drive.Name + "\t\t" + drive.DriveFormat);
        }
    }
}

vmt@kvm:~/a$ dotnet run
/mnt/nvme1n1p1     ext3
/mnt/nvme0n1p1     ext3
/mnt/sda2          ext3
/mnt/sdb1          ext3
/mnt/sdc1          ext3
/mnt/loop/joe-4.6  squashfs

Using unix df tool for comparison (same system)

vmt@kvm:~/a$ df -T
/dev/nvme1n1p1     ext4
/dev/nvme0n1p1     ext4
/dev/sda2          ext4
/dev/sdb1          ext4
/dev/sdc1          ext4
/dev/loop0         squashfs

Configuration

vmt@kvm:~/a$ dotnet --info
.NET SDK:
Version: 8.0.100
Commit: 57efcf1350
Workload version: 8.0.100-manifests.6c33ef20

Runtime Environment:
OS Name: vmtux
OS Version: 2.0
OS Platform: Linux
RID: linux-x64
Base Path: /mnt/loop/dotnet-sdk-8.0.100/usr/local/share/dotnet/sdk/8.0.100/

.NET workloads installed:
Workload version: 8.0.100-manifests.6c33ef20
There are no installed workloads to display.

Host:
Version: 8.0.0
Architecture: x64
Commit: 5535e31

.NET SDKs installed:
8.0.100 [/mnt/loop/dotnet-sdk-8.0.100/usr/local/share/dotnet/sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 8.0.0 [/mnt/loop/dotnet-sdk-8.0.100/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 8.0.0 [/mnt/loop/dotnet-sdk-8.0.100/usr/local/share/dotnet/shared/Microsoft.NETCore.App]

[rzikm]

@dotnet/area-system-io Can you please take a look?

Tagging subscribers to this area: @dotnet/area-system-io
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

using System;
namespace GetFileSystemEntries
{
    class Class1
    {
        static void Main(string[] args)
        {
            foreach (var drive in DriveInfo.GetDrives())
                Console.WriteLine(drive.Name + "\t\t" + drive.DriveFormat);
        }
    }
}

vmt@kvm:~/a$ dotnet run
/mnt/nvme1n1p1     ext3
/mnt/nvme0n1p1     ext3
/mnt/sda2          ext3
/mnt/sdb1          ext3
/mnt/sdc1          ext3
/mnt/loop/joe-4.6  squashfs

Using unix df tool for comparison (same system)

vmt@kvm:~/a$ df -T
/dev/nvme1n1p1     ext4
/dev/nvme0n1p1     ext4
/dev/sda2          ext4
/dev/sdb1          ext4
/dev/sdc1          ext4
/dev/loop0         squashfs

Configuration

vmt@kvm:~/a$ dotnet --info
.NET SDK:
Version: 8.0.100
Commit: 57efcf1350
Workload version: 8.0.100-manifests.6c33ef20

Runtime Environment:
OS Name: vmtux
OS Version: 2.0
OS Platform: Linux
RID: linux-x64
Base Path: /mnt/loop/dotnet-sdk-8.0.100/usr/local/share/dotnet/sdk/8.0.100/

.NET workloads installed:
Workload version: 8.0.100-manifests.6c33ef20
There are no installed workloads to display.

Host:
Version: 8.0.0
Architecture: x64
Commit: 5535e31

.NET SDKs installed:
8.0.100 [/mnt/loop/dotnet-sdk-8.0.100/usr/local/share/dotnet/sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 8.0.0 [/mnt/loop/dotnet-sdk-8.0.100/usr/local/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 8.0.0 [/mnt/loop/dotnet-sdk-8.0.100/usr/local/share/dotnet/shared/Microsoft.NETCore.App]

Author:	alphons
Assignees:	-
Labels:	area-System.IO, untriaged, needs-area-label
Milestone:	-

[jozkee]

DriveFormat uses statfs and it returns the same value for ext2, ext3 and ext4.

runtime/src/libraries/Common/src/Interop/Unix/System.Native/Interop.UnixFileSystemTypes.cs

Lines 57 to 59 in 52b4c82

	ext2 = 0xEF53,
	ext3 = 0xEF53,
	ext4 = 0xEF53,

.

[adamsitnik]

The magic numbers come from the official Linux man page for statfs: https://man7.org/linux/man-pages/man2/statfs.2.html

But there are other ways of getting the file system name, we currently use them as a fallback:

runtime/src/libraries/Common/src/Interop/Unix/System.Native/Interop.MountPoints.FormatInfo.cs

Lines 60 to 63 in e440ebc

	// Check if we have a numeric answer or string
	format = numericFormat != -1 ?
	Enum.GetName(typeof(UnixFileSystemTypes), numericFormat) ?? string.Empty :
	Marshal.PtrToStringUTF8((IntPtr)formatBuffer)!;

We could experiment with what we have in

runtime/src/native/libs/System.Native/pal_mount.c

Line 162 in e440ebc

SafeStringCopy(formatNameBuffer, Int32ToSizeT(bufferLength), stats.f_fstypename);

and take some lessons from

runtime/src/native/libs/System.Native/pal_io.c

Line 1703 in e440ebc

uint32_t SystemNative_GetFileSystemType(intptr_t fd)

and try to use the stats.f_fstypename for enums with duplicate values.

BTW .NET is not the only tool with the same issue: https://unix.stackexchange.com/a/274030

I am going to re-open it and apply help-wanted label.