Merge pull request #21886 from BlauFx/add_linux_hardlink

Add hardlink support for Linux & macOS

osu.Game/Database/RealmFileStore.cs

@@ -4,7 +4,6 @@
 using System;
 using System.IO;
 using System.Linq;
-using osu.Framework;
 using osu.Framework.Extensions;
 using osu.Framework.IO.Stores;
 using osu.Framework.Logging;
@@ -63,10 +62,10 @@ namespace osu.Game.Database
 
         private void copyToStore(RealmFile file, Stream data, bool preferHardLinks)
         {
-            if (RuntimeInfo.OS == RuntimeInfo.Platform.Windows && data is FileStream fs && preferHardLinks)
+            if (data is FileStream fs && preferHardLinks)
             {
                 // attempt to do a fast hard link rather than copy.
-                if (HardLinkHelper.CreateHardLink(Storage.GetFullPath(file.GetStoragePath(), true), fs.Name, IntPtr.Zero))
+                if (HardLinkHelper.TryCreateHardLink(Storage.GetFullPath(file.GetStoragePath(), true), fs.Name))
                     return;
             }
 

osu.Game/IO/HardLinkHelper.cs

@@ -14,9 +14,8 @@ namespace osu.Game.IO
     {
         public static bool CheckAvailability(string testDestinationPath, string testSourcePath)
         {
-            // We can support other operating systems quite easily in the future.
-            // Let's handle the most common one for now, though.
-            if (RuntimeInfo.OS != RuntimeInfo.Platform.Windows)
+            // For simplicity, only support desktop operating systems for now.
+            if (!RuntimeInfo.IsDesktop)
                 return false;
 
             const string test_filename = "_hard_link_test";
@@ -31,7 +30,7 @@ namespace osu.Game.IO
                 File.WriteAllText(testSourcePath, string.Empty);
 
                 // Test availability by creating an arbitrary hard link between the source and destination paths.
-                return CreateHardLink(testDestinationPath, testSourcePath, IntPtr.Zero);
+                return TryCreateHardLink(testDestinationPath, testSourcePath);
             }
             catch
             {
@@ -55,21 +54,60 @@ namespace osu.Game.IO
             }
         }
 
+        /// <summary>
+        /// Attempts to create a hard link from <paramref name="sourcePath"/> to <paramref name="destinationPath"/>,
+        /// using platform-specific native methods.
+        /// </summary>
+        /// <remarks>
+        /// Hard links are only available on desktop platforms.
+        /// </remarks>
+        /// <returns>Whether the hard link was successfully created.</returns>
+        public static bool TryCreateHardLink(string destinationPath, string sourcePath)
+        {
+            switch (RuntimeInfo.OS)
+            {
+                case RuntimeInfo.Platform.Windows:
+                    return CreateHardLink(destinationPath, sourcePath, IntPtr.Zero);
+
+                case RuntimeInfo.Platform.Linux:
+                case RuntimeInfo.Platform.macOS:
+                    return link(sourcePath, destinationPath) == 0;
+
+                default:
+                    return false;
+            }
+        }
+
         // For future use (to detect if a file is a hard link with other references existing on disk).
         public static int GetFileLinkCount(string filePath)
         {
             int result = 0;
-            SafeFileHandle handle = CreateFile(filePath, FileAccess.Read, FileShare.Read, IntPtr.Zero, FileMode.Open, FileAttributes.Archive, IntPtr.Zero);
 
-            ByHandleFileInformation fileInfo;
+            switch (RuntimeInfo.OS)
+            {
+                case RuntimeInfo.Platform.Windows:
+                    SafeFileHandle handle = CreateFile(filePath, FileAccess.Read, FileShare.Read, IntPtr.Zero, FileMode.Open, FileAttributes.Archive, IntPtr.Zero);
 
-            if (GetFileInformationByHandle(handle, out fileInfo))
-                result = (int)fileInfo.NumberOfLinks;
-            CloseHandle(handle);
+                    ByHandleFileInformation fileInfo;
+
+                    if (GetFileInformationByHandle(handle, out fileInfo))
+                        result = (int)fileInfo.NumberOfLinks;
+                    CloseHandle(handle);
+                    break;
+
+                case RuntimeInfo.Platform.Linux:
+                case RuntimeInfo.Platform.macOS:
+                    if (stat(filePath, out var statbuf) == 0)
+                        result = (int)statbuf.st_nlink;
+
+                    break;
+            }
 
             return result;
         }
 
+        #region Windows native methods
+
         [DllImport("Kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
         public static extern bool CreateHardLink(string lpFileName, string lpExistingFileName, IntPtr lpSecurityAttributes);
 
@@ -104,5 +142,49 @@ namespace osu.Game.IO
             public readonly uint FileIndexHigh;
             public readonly uint FileIndexLow;
         }
+
+        #endregion
+
+        #region Linux native methods
+
+#pragma warning disable IDE1006 // Naming rule violation
+
+        [DllImport("libc", SetLastError = true)]
+        public static extern int link(string oldpath, string newpath);
+
+        [DllImport("libc", SetLastError = true)]
+        private static extern int stat(string pathname, out struct_stat statbuf);
+
+        // ReSharper disable once InconsistentNaming
+        // Struct layout is likely non-portable across unices. Tread with caution.
+        [StructLayout(LayoutKind.Sequential)]
+        private struct struct_stat
+        {
+            public readonly long st_dev;
+            public readonly long st_ino;
+            public readonly long st_nlink;
+            public readonly int st_mode;
+            public readonly int st_uid;
+            public readonly int st_gid;
+            public readonly long st_rdev;
+            public readonly long st_size;
+            public readonly long st_blksize;
+            public readonly long st_blocks;
+            public readonly timespec st_atim;
+            public readonly timespec st_mtim;
+            public readonly timespec st_ctim;
+        }
+
+        // ReSharper disable once InconsistentNaming
+        [StructLayout(LayoutKind.Sequential)]
+        private struct timespec
+        {
+            public readonly long tv_sec;
+            public readonly long tv_nsec;
+        }
+
+#pragma warning restore IDE1006
+
+        #endregion
     }
 }

osu.Game/Overlays/FirstRunSetup/ScreenImportFromStable.cs

@@ -132,12 +132,13 @@ namespace osu.Game.Overlays.FirstRunSetup
 
                 copyInformation.AddLink("Learn more about how \"hard links\" work", LinkAction.OpenWiki, @"Client/Release_stream/Lazer/File_storage#via-hard-links");
             }
-            else if (RuntimeInfo.OS != RuntimeInfo.Platform.Windows)
+            else if (!RuntimeInfo.IsDesktop)
                 copyInformation.Text = "Lightweight linking of files is not supported on your operating system yet, so a copy of all files will be made during import.";
             else
             {
-                copyInformation.Text =
-                    "A second copy of all files will be made during import. To avoid this, please make sure the lazer data folder is on the same drive as your previous osu! install (and the file system is NTFS). ";
+                copyInformation.Text = RuntimeInfo.OS == RuntimeInfo.Platform.Windows
+                    ? "A second copy of all files will be made during import. To avoid this, please make sure the lazer data folder is on the same drive as your previous osu! install (and the file system is NTFS). "
+                    : "A second copy of all files will be made during import. To avoid this, please make sure the lazer data folder is on the same drive as your previous osu! install (and the file system supports hard links). ";
                 copyInformation.AddLink(GeneralSettingsStrings.ChangeFolderLocation, () =>
                 {
                     game?.PerformFromScreen(menu => menu.Push(new MigrationSelectScreen()));