Fix wrong drive format on Unix

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

@@ -39,7 +39,7 @@ internal static unsafe partial int GetFormatInfoForMountPoint(
             byte* formatNameBuffer,
             int bufferLength,
             long* formatType);
-
+			
         internal static int GetFormatInfoForMountPoint(string name, out string format)
         {
             return GetFormatInfoForMountPoint(name, out format, out _);
@@ -49,9 +49,69 @@ internal static int GetFormatInfoForMountPoint(string name, out DriveType type)
         {
             return GetFormatInfoForMountPoint(name, out _, out type);
         }
+
+		/// <summary>
+		/// Retrieves format information for the specified mount point.
+		/// </summary>
+		/// <remarks>
+		/// This method uses a two-step approach to retrieve filesystem information:
+		/// 1. On Linux systems, it first attempts to read from `/proc/self/mountinfo`.
+		/// 2. If step 1 fails or on non-Linux systems, it falls back to a P/Invoke call.
+		///
+		/// The `/proc/self/mountinfo` approach is preferred on Linux because 
+		/// it's more reliable when procfs is available and functioning correctly.
+		///
+		/// For other systems:
+		/// - SunOS and similar: procfs provides a binary interface, not suitable for this method.
+		/// - macOS: procfs is not available.
+		/// - FreeBSD: procfs is optional and not enabled by default.
+		///
+		/// The method uses try/catch blocks to ensure robustness, even though `/proc/self/mountinfo`
+		/// should be specific to each process according to kernel documentation.
+		/// </remarks>
+		/// <param name="name">The mount point name to query.</param>
+		/// <param name="format">Output parameter for the filesystem format.</param>
+		/// <param name="type">Output parameter for the drive type.</param>
+		/// <returns>0 if successful, otherwise an error code.</returns>
+		private static unsafe int GetFormatInfoForMountPoint(string name, out string format, out DriveType type)
+		{
+			#if TARGET_LINUX
+				try
+				{
+					const string mountInfoFilePath = "/proc/self/mountinfo";
+					var mountInfoFileContent = File.ReadAllLines(mountInfoFilePath);
+					foreach (var line in mountInfoFileContent)
+					{
+						var parser = new StringParser(line, ' ');
+
+						// Skip fields we don't care about (Fields 1-4)
+						parser.MoveNext(); // Skip Mount ID
+						parser.MoveNext(); // Skip Parent ID
+						parser.MoveNext(); // Skip Major:Minor
+						parser.MoveNext(); // Skip Root
+
+						// Get the mount point (Field 5)
+						string mountPoint = parser.MoveAndExtractNext();
+
+						// Skip to the separator which is end of optional fields (Field 8)
+						while (parser.MoveAndExtractNext() != "-")
+						{
+						}
+
+						// Get filesystem type (Field 9)
+						string filesystemType = parser.MoveAndExtractNext();
+
+						if (mountPoint.Equals(name, StringComparison.Ordinal))
+						{
+							format = filesystemType;
+							type = GetDriveType(filesystemType);
+							return 0;
+						}
+					}
+				}
+				catch { /* ignored */ }
+			#endif
 
-        private static unsafe int GetFormatInfoForMountPoint(string name, out string format, out DriveType type)
-        {
             byte* formatBuffer = stackalloc byte[MountPointFormatBufferSizeInBytes];    // format names should be small
             long numericFormat;
             int result = GetFormatInfoForMountPoint(name, formatBuffer, MountPointFormatBufferSizeInBytes, &numericFormat);
@@ -70,7 +130,8 @@ private static unsafe int GetFormatInfoForMountPoint(string name, out string for
             }
 
             return result;
-        }
+		}
+
 
         /// <summary>Categorizes a file system name into a drive type.</summary>
         /// <param name="fileSystemName">The name to categorize.</param>

src/native/libs/System.Native/entrypoints.c

@@ -131,7 +131,7 @@ static const Entry s_sysNative[] =
     DllImportEntry(SystemNative_Malloc)
     DllImportEntry(SystemNative_Realloc)
     DllImportEntry(SystemNative_GetSpaceInfoForMountPoint)
-    DllImportEntry(SystemNative_GetFormatInfoForMountPoint)
+	DllImportEntry(SystemNative_GetFormatInfoForMountPoint)
     DllImportEntry(SystemNative_GetAllMountPoints)
     DllImportEntry(SystemNative_ReadEvents)
     DllImportEntry(SystemNative_CreateNetworkChangeListenerSocket)

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

@@ -176,4 +176,4 @@ SystemNative_GetFormatInfoForMountPoint(const char* name, char* formatNameBuffer
     }
 
     return result;
-}
+}

src/native/libs/System.Native/pal_mount_wasi.c

@@ -27,4 +27,4 @@ SystemNative_GetFormatInfoForMountPoint(const char* name, char* formatNameBuffer
     assert((formatNameBuffer != NULL) && (formatType != NULL));
     assert(bufferLength > 0);
     return -1;
-}
+}