diff --git a/src/LibHac/FsSrv/Impl/SaveDataExtender.cs b/src/LibHac/FsSrv/Impl/SaveDataExtender.cs
index 0a05bfbb..7c3507ec 100644
--- a/src/LibHac/FsSrv/Impl/SaveDataExtender.cs
+++ b/src/LibHac/FsSrv/Impl/SaveDataExtender.cs
@@ -1,16 +1,25 @@
-// ReSharper disable UnusedMember.Local UnusedType.Local
-#pragma warning disable CS0169 // Field is never used
-#pragma warning disable CS0649 // Field is never assigned to, and will always have its default value
-using System;
-using System.Runtime.CompilerServices;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using LibHac.Common;
+using LibHac.Diag;
 using LibHac.Fs;
 using LibHac.FsSystem;
 using LibHac.FsSystem.Save;
+using LibHac.Util;
 
 namespace LibHac.FsSrv.Impl;
 
+/// <summary>
+/// Extends a save data image to a larger size. Keeps track of the extension progress by writing information about
+/// the extension to an "extension context" storage.  
+/// </summary>
+/// <remarks>Based on nnSdk 17.5.0 (FS 17.0.0)</remarks>
 public class SaveDataExtender
 {
+    private const uint MagicCode = 0x43545845; // EXTC
+    private const uint Version1 = 0x10000;
+    private const uint Version2 = 0x20000;
+
     private enum State
     {
         Initial = 1,
@@ -18,6 +27,7 @@ public class SaveDataExtender
         Committed = 3
     }
 
+    [StructLayout(LayoutKind.Sequential)]
     private struct Context
     {
         public uint Magic;
@@ -36,62 +46,119 @@ public class SaveDataExtender
 
     public SaveDataExtender()
     {
-        throw new NotImplementedException();
+        _contextStorage = null;
     }
 
+    public long GetLogSize() => JournalIntegritySaveDataFileSystemDriver.QueryExpandLogSize(_context.BlockSize,
+        GetJournalBlockCount(), GetAvailableBlockCount());
+
+    public long GetAvailableSize() => _context.AvailableSize;
+    public long GetJournalSize() => _context.JournalSize;
+    public long GetExtendedSaveDataSize() => _context.ExtendedSaveDataSize;
+
+    private uint GetAvailableBlockCount() => (uint)BitUtil.DivideUp(_context.AvailableSize, _context.BlockSize);
+    private uint GetJournalBlockCount() => (uint)BitUtil.DivideUp(_context.JournalSize, _context.BlockSize);
+
     public Result InitializeContext(in JournalIntegritySaveDataParameters param, long sizeAvailable, long sizeReserved)
     {
-        throw new NotImplementedException();
+        _context.Magic = MagicCode;
+        _context.Version = Version2;
+        _context.State = State.Initial;
+        _context.AvailableSize = sizeAvailable;
+        _context.JournalSize = sizeReserved;
+        _context.BlockSize = param.BlockSize;
+
+        Result res = JournalIntegritySaveDataFileSystemDriver.QueryTotalSize(out _context.ExtendedSaveDataSize,
+            param.BlockSize, GetAvailableBlockCount(), GetJournalBlockCount(), param.CountExpandMax, param.Version);
+        if (res.IsFailure()) return res.Miss();
+
+        return Result.Success;
     }
 
     public Result WriteContext(IStorage contextStorage)
     {
-        throw new NotImplementedException();
+        Result res = contextStorage.Write(0, SpanHelpers.AsReadOnlyByteSpan(in _context));
+        if (res.IsFailure()) return res.Miss();
+
+        res = contextStorage.Flush();
+        if (res.IsFailure()) return res.Miss();
+
+        return Result.Success;
     }
 
     public Result ReadContext(IStorage contextStorage)
     {
-        throw new NotImplementedException();
-    }
+        Assert.SdkRequiresNull(_contextStorage);
+        Assert.SdkRequiresNotNull(contextStorage);
 
-    public long GetLogSize()
-    {
-        throw new NotImplementedException();
-    }
+        Result res = contextStorage.Read(0, SpanHelpers.AsByteSpan(ref _context));
+        if (res.IsFailure()) return res.Miss();
 
-    public long GetAvailableSize()
-    {
-        throw new NotImplementedException();
-    }
+        if (_context.Magic != MagicCode)
+            return ResultFs.IncorrectSaveDataExtensionContextMagicCode.Log();
 
-    public long GetJournalSize()
-    {
-        throw new NotImplementedException();
-    }
+        if (_context.Version == Version1)
+        {
+            UpdateContextV1ToV2(ref _context);
+        }
 
-    public long GetExtendedSaveDataSize()
-    {
-        throw new NotImplementedException();
-    }
+        if (_context.Version != Version2)
+            return ResultFs.UnsupportedSaveDataVersion.Log();
 
-    private uint GetAvailableBlockCount()
-    {
-        throw new NotImplementedException();
-    }
+        State state = _context.State;
+        if (state != State.Initial && state != State.Extended && state != State.Committed)
+            return ResultFs.InvalidSaveDataExtensionContextState.Log();
 
-    private uint GetJournalBlockCount()
-    {
-        throw new NotImplementedException();
+        if (_context.BlockSize <= 0)
+            return ResultFs.InvalidSaveDataExtensionContextParameter.Log();
+
+        if (_context.ExtendedSaveDataSize <= 0)
+            return ResultFs.InvalidSaveDataExtensionContextParameter.Log();
+
+        _contextStorage = contextStorage;
+        return Result.Success;
     }
 
     public Result Extend(in ValueSubStorage saveDataStorage, in ValueSubStorage logStorage, IBufferManager bufferManager,
         IMacGenerator macGenerator, IHash256GeneratorFactorySelector hashGeneratorFactorySelector, uint minimumVersion)
     {
-        throw new NotImplementedException();
+        Assert.SdkRequiresNotNull(_contextStorage);
+
+        if (_context.State == State.Initial)
+        {
+            Result res = JournalIntegritySaveDataFileSystemDriver.OperateExpand(in saveDataStorage, in logStorage,
+                _context.BlockSize, GetAvailableBlockCount(), GetJournalBlockCount(), bufferManager, macGenerator,
+                hashGeneratorFactorySelector, minimumVersion);
+            if (res.IsFailure()) return res.Miss();
+
+            _context.State = State.Extended;
+            res = WriteContext(_contextStorage);
+            if (res.IsFailure()) return res.Miss();
+        }
+
+        if (_context.State == State.Extended)
+        {
+            Result res = JournalIntegritySaveDataFileSystemDriver.CommitExpand(in saveDataStorage, in logStorage,
+                _context.BlockSize, bufferManager);
+            if (res.IsFailure()) return res.Miss();
+
+            _context.State = State.Committed;
+            res = WriteContext(_contextStorage);
+            if (res.IsFailure()) return res.Miss();
+        }
+
+        if (_context.State != State.Committed)
+            return ResultFs.BadState.Log();
+
+        return Result.Success;
     }
 
     private void UpdateContextV1ToV2(ref Context context)
     {
-        throw new NotImplementedException();
+        Assert.SdkAssert(context.Version == Version1);
+
+        context.AvailableSize *= context.BlockSize;
+        context.JournalSize *= context.BlockSize;
+        context.Version = Version2;
     }
 }
\ No newline at end of file
diff --git a/src/LibHac/FsSrv/Impl/SaveDataExtraDataAccessorCacheManager.cs b/src/LibHac/FsSrv/Impl/SaveDataExtraDataAccessorCacheManager.cs
index 5e16e00c..c0fa512c 100644
--- a/src/LibHac/FsSrv/Impl/SaveDataExtraDataAccessorCacheManager.cs
+++ b/src/LibHac/FsSrv/Impl/SaveDataExtraDataAccessorCacheManager.cs
@@ -10,13 +10,13 @@ namespace LibHac.FsSrv.Impl;
 /// <summary>
 /// Holds the <see cref="ISaveDataExtraDataAccessor"/>s for opened save data file systems.
 /// </summary>
-/// <remarks>Based on nnSdk 14.3.0 (FS 14.1.0)</remarks>
+/// <remarks>Based on nnSdk 17.5.0 (FS 17.0.0)</remarks>
 public class SaveDataExtraDataAccessorCacheManager : ISaveDataExtraDataAccessorObserver
 {
     /// <summary>
     /// Holds a single cached extra data accessor identified by its save data ID and save data space ID.
     /// </summary>
-    /// <remarks>Based on nnSdk 14.3.0 (FS 14.1.0)</remarks>
+    /// <remarks>Based on nnSdk 17.5.0 (FS 17.0.0)</remarks>
     [NonCopyable]
     private struct Cache : IDisposable
     {
diff --git a/src/LibHac/FsSrv/Impl/SaveDataFileSystemCacheManager.cs b/src/LibHac/FsSrv/Impl/SaveDataFileSystemCacheManager.cs
index 1259e327..7e15c7df 100644
--- a/src/LibHac/FsSrv/Impl/SaveDataFileSystemCacheManager.cs
+++ b/src/LibHac/FsSrv/Impl/SaveDataFileSystemCacheManager.cs
@@ -11,7 +11,7 @@ namespace LibHac.FsSrv.Impl;
 /// Manages a list of cached save data file systems. Each file system is registered and retrieved
 /// based on its save data ID and save data space ID.
 /// </summary>
-/// <remarks>Based on nnSdk 14.3.0 (FS 14.1.0)</remarks>
+/// <remarks>Based on nnSdk 17.5.0 (FS 17.0.0)</remarks>
 public class SaveDataFileSystemCacheManager : IDisposable
 {
     [NonCopyable]
diff --git a/src/LibHac/FsSrv/Impl/SaveDataFileSystemCacheRegister.cs b/src/LibHac/FsSrv/Impl/SaveDataFileSystemCacheRegister.cs
index c6b2993b..4f9d6122 100644
--- a/src/LibHac/FsSrv/Impl/SaveDataFileSystemCacheRegister.cs
+++ b/src/LibHac/FsSrv/Impl/SaveDataFileSystemCacheRegister.cs
@@ -9,7 +9,7 @@ namespace LibHac.FsSrv.Impl;
 /// Wraps an <see cref="ISaveDataFileSystem"/>.
 /// Upon disposal the base file system is returned to the provided <see cref="SaveDataFileSystemCacheManager"/>.
 /// </summary>
-/// <remarks>Based on nnSdk 14.3.0 (FS 14.1.0)</remarks>
+/// <remarks>Based on nnSdk 17.5.0 (FS 17.0.0)</remarks>
 public class SaveDataFileSystemCacheRegister : IFileSystem
 {
     private SharedRef<ISaveDataFileSystem> _baseFileSystem;
@@ -36,87 +36,87 @@ public class SaveDataFileSystemCacheRegister : IFileSystem
 
     protected override Result DoOpenFile(ref UniqueRef<IFile> outFile, ref readonly Path path, OpenMode mode)
     {
-        return _baseFileSystem.Get.OpenFile(ref outFile, in path, mode);
+        return _baseFileSystem.Get.OpenFile(ref outFile, in path, mode).Ret();
     }
 
     protected override Result DoOpenDirectory(ref UniqueRef<IDirectory> outDirectory, ref readonly Path path,
         OpenDirectoryMode mode)
     {
-        return _baseFileSystem.Get.OpenDirectory(ref outDirectory, in path, mode);
+        return _baseFileSystem.Get.OpenDirectory(ref outDirectory, in path, mode).Ret();
     }
 
     protected override Result DoGetEntryType(out DirectoryEntryType entryType, ref readonly Path path)
     {
-        return _baseFileSystem.Get.GetEntryType(out entryType, in path);
+        return _baseFileSystem.Get.GetEntryType(out entryType, in path).Ret();
     }
 
     protected override Result DoCreateFile(ref readonly Path path, long size, CreateFileOptions option)
     {
-        return _baseFileSystem.Get.CreateFile(in path, size, option);
+        return _baseFileSystem.Get.CreateFile(in path, size, option).Ret();
     }
 
     protected override Result DoDeleteFile(ref readonly Path path)
     {
-        return _baseFileSystem.Get.DeleteFile(in path);
+        return _baseFileSystem.Get.DeleteFile(in path).Ret();
     }
 
     protected override Result DoCreateDirectory(ref readonly Path path)
     {
-        return _baseFileSystem.Get.CreateDirectory(in path);
+        return _baseFileSystem.Get.CreateDirectory(in path).Ret();
     }
 
     protected override Result DoDeleteDirectory(ref readonly Path path)
     {
-        return _baseFileSystem.Get.DeleteDirectory(in path);
+        return _baseFileSystem.Get.DeleteDirectory(in path).Ret();
     }
 
     protected override Result DoDeleteDirectoryRecursively(ref readonly Path path)
     {
-        return _baseFileSystem.Get.DeleteDirectoryRecursively(in path);
+        return _baseFileSystem.Get.DeleteDirectoryRecursively(in path).Ret();
     }
 
     protected override Result DoCleanDirectoryRecursively(ref readonly Path path)
     {
-        return _baseFileSystem.Get.CleanDirectoryRecursively(in path);
+        return _baseFileSystem.Get.CleanDirectoryRecursively(in path).Ret();
     }
 
     protected override Result DoRenameFile(ref readonly Path currentPath, ref readonly Path newPath)
     {
-        return _baseFileSystem.Get.RenameFile(in currentPath, in newPath);
+        return _baseFileSystem.Get.RenameFile(in currentPath, in newPath).Ret();
     }
 
     protected override Result DoRenameDirectory(ref readonly Path currentPath, ref readonly Path newPath)
     {
-        return _baseFileSystem.Get.RenameDirectory(in currentPath, in newPath);
+        return _baseFileSystem.Get.RenameDirectory(in currentPath, in newPath).Ret();
     }
 
     protected override Result DoCommit()
     {
-        return _baseFileSystem.Get.Commit();
+        return _baseFileSystem.Get.Commit().Ret();
     }
 
     protected override Result DoCommitProvisionally(long counter)
     {
-        return _baseFileSystem.Get.CommitProvisionally(counter);
+        return _baseFileSystem.Get.CommitProvisionally(counter).Ret();
     }
 
     protected override Result DoRollback()
     {
-        return _baseFileSystem.Get.Rollback();
+        return _baseFileSystem.Get.Rollback().Ret();
     }
 
     protected override Result DoGetFreeSpaceSize(out long freeSpace, ref readonly Path path)
     {
-        return _baseFileSystem.Get.GetFreeSpaceSize(out freeSpace, in path);
+        return _baseFileSystem.Get.GetFreeSpaceSize(out freeSpace, in path).Ret();
     }
 
     protected override Result DoGetTotalSpaceSize(out long totalSpace, ref readonly Path path)
     {
-        return _baseFileSystem.Get.GetTotalSpaceSize(out totalSpace, in path);
+        return _baseFileSystem.Get.GetTotalSpaceSize(out totalSpace, in path).Ret();
     }
 
     protected override Result DoGetFileSystemAttribute(out FileSystemAttribute outAttribute)
     {
-        return _baseFileSystem.Get.GetFileSystemAttribute(out outAttribute);
+        return _baseFileSystem.Get.GetFileSystemAttribute(out outAttribute).Ret();
     }
 }
\ No newline at end of file