Revert "Virtual Filesystem (#597)"

This reverts commit 77c684c1140f6bf3fb7d4560d06d2efb1a2ee5e2.

5 files changed, 71 insertions, 405 deletions

diff --git a/src/core/hle/service/am/am.cpp b/src/core/hle/service/am/am.cpp
index 7bb13c735..a871b3eaa 100644
--- a/src/core/hle/service/am/am.cpp
+++ b/src/core/hle/service/am/am.cpp
@@ -621,7 +621,7 @@ void IApplicationFunctions::EnsureSaveData(Kernel::HLERequestContext& ctx) {
     IPC::ResponseBuilder rb{ctx, 4};
 
     FileSys::Path unused;
-    auto savedata = FileSystem::OpenFileSystem(FileSystem::Type::SaveData);
+    auto savedata = FileSystem::OpenFileSystem(FileSystem::Type::SaveData, unused);
     if (savedata.Failed()) {
         // Create the save data and return an error indicating that the operation was performed.
         FileSystem::FormatFileSystem(FileSystem::Type::SaveData);
diff --git a/src/core/hle/service/filesystem/filesystem.cpp b/src/core/hle/service/filesystem/filesystem.cpp
index 25810c165..f58b518b6 100644
--- a/src/core/hle/service/filesystem/filesystem.cpp
+++ b/src/core/hle/service/filesystem/filesystem.cpp
@@ -2,221 +2,36 @@
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
-#include "boost/container/flat_map.hpp"
-#include "common/assert.h"
-#include "common/common_paths.h"
+#include <boost/container/flat_map.hpp>
 #include "common/file_util.h"
-#include "core/core.h"
-#include "core/file_sys/errors.h"
 #include "core/file_sys/filesystem.h"
-#include "core/file_sys/vfs.h"
-#include "core/file_sys/vfs_offset.h"
-#include "core/file_sys/vfs_real.h"
-#include "core/hle/kernel/process.h"
+#include "core/file_sys/savedata_factory.h"
+#include "core/file_sys/sdmc_factory.h"
 #include "core/hle/service/filesystem/filesystem.h"
 #include "core/hle/service/filesystem/fsp_srv.h"
 
 namespace Service::FileSystem {
 
-// Size of emulated sd card free space, reported in bytes.
-// Just using 32GB because thats reasonable
-// TODO(DarkLordZach): Eventually make this configurable in settings.
-constexpr u64 EMULATED_SD_REPORTED_SIZE = 32000000000;
-
-static FileSys::VirtualDir GetDirectoryRelativeWrapped(FileSys::VirtualDir base,
-                                                       const std::string& dir_name) {
-    if (dir_name == "." || dir_name == "" || dir_name == "/" || dir_name == "\\")
-        return base;
-
-    return base->GetDirectoryRelative(dir_name);
-}
-
-VfsDirectoryServiceWrapper::VfsDirectoryServiceWrapper(FileSys::VirtualDir backing_)
-    : backing(backing_) {}
-
-std::string VfsDirectoryServiceWrapper::GetName() const {
-    return backing->GetName();
-}
-
-ResultCode VfsDirectoryServiceWrapper::CreateFile(const std::string& path, u64 size) const {
-    auto dir = GetDirectoryRelativeWrapped(backing, FileUtil::GetParentPath(path));
-    auto file = dir->CreateFile(FileUtil::GetFilename(path));
-    if (file == nullptr)
-        return ResultCode(-1);
-    if (!file->Resize(size))
-        return ResultCode(-1);
-    return RESULT_SUCCESS;
-}
-
-ResultCode VfsDirectoryServiceWrapper::DeleteFile(const std::string& path) const {
-    auto dir = GetDirectoryRelativeWrapped(backing, FileUtil::GetParentPath(path));
-    if (!backing->DeleteFile(FileUtil::GetFilename(path)))
-        return ResultCode(-1);
-    return RESULT_SUCCESS;
-}
-
-ResultCode VfsDirectoryServiceWrapper::CreateDirectory(const std::string& path) const {
-    auto dir = GetDirectoryRelativeWrapped(backing, FileUtil::GetParentPath(path));
-    if (dir == nullptr && FileUtil::GetFilename(FileUtil::GetParentPath(path)).empty())
-        dir = backing;
-    auto new_dir = dir->CreateSubdirectory(FileUtil::GetFilename(path));
-    if (new_dir == nullptr)
-        return ResultCode(-1);
-    return RESULT_SUCCESS;
-}
-
-ResultCode VfsDirectoryServiceWrapper::DeleteDirectory(const std::string& path) const {
-    auto dir = GetDirectoryRelativeWrapped(backing, FileUtil::GetParentPath(path));
-    if (!dir->DeleteSubdirectory(FileUtil::GetFilename(path)))
-        return ResultCode(-1);
-    return RESULT_SUCCESS;
-}
-
-ResultCode VfsDirectoryServiceWrapper::DeleteDirectoryRecursively(const std::string& path) const {
-    auto dir = GetDirectoryRelativeWrapped(backing, FileUtil::GetParentPath(path));
-    if (!dir->DeleteSubdirectoryRecursive(FileUtil::GetFilename(path)))
-        return ResultCode(-1);
-    return RESULT_SUCCESS;
-}
-
-ResultCode VfsDirectoryServiceWrapper::RenameFile(const std::string& src_path,
-                                                  const std::string& dest_path) const {
-    auto src = backing->GetFileRelative(src_path);
-    if (FileUtil::GetParentPath(src_path) == FileUtil::GetParentPath(dest_path)) {
-        // Use more-optimized vfs implementation rename.
-        if (src == nullptr)
-            return FileSys::ERROR_PATH_NOT_FOUND;
-        if (!src->Rename(FileUtil::GetFilename(dest_path)))
-            return ResultCode(-1);
-        return RESULT_SUCCESS;
-    }
-
-    // Move by hand -- TODO(DarkLordZach): Optimize
-    auto c_res = CreateFile(dest_path, src->GetSize());
-    if (c_res != RESULT_SUCCESS)
-        return c_res;
-
-    auto dest = backing->GetFileRelative(dest_path);
-    ASSERT_MSG(dest != nullptr, "Newly created file with success cannot be found.");
-
-    ASSERT_MSG(dest->WriteBytes(src->ReadAllBytes()) == src->GetSize(),
-               "Could not write all of the bytes but everything else has succeded.");
-
-    if (!src->GetContainingDirectory()->DeleteFile(FileUtil::GetFilename(src_path)))
-        return ResultCode(-1);
-
-    return RESULT_SUCCESS;
-}
-
-ResultCode VfsDirectoryServiceWrapper::RenameDirectory(const std::string& src_path,
-                                                       const std::string& dest_path) const {
-    auto src = GetDirectoryRelativeWrapped(backing, src_path);
-    if (FileUtil::GetParentPath(src_path) == FileUtil::GetParentPath(dest_path)) {
-        // Use more-optimized vfs implementation rename.
-        if (src == nullptr)
-            return FileSys::ERROR_PATH_NOT_FOUND;
-        if (!src->Rename(FileUtil::GetFilename(dest_path)))
-            return ResultCode(-1);
-        return RESULT_SUCCESS;
-    }
-
-    // TODO(DarkLordZach): Implement renaming across the tree (move).
-    ASSERT_MSG(false,
-               "Could not rename directory with path \"{}\" to new path \"{}\" because parent dirs "
-               "don't match -- UNIMPLEMENTED",
-               src_path, dest_path);
-
-    return ResultCode(-1);
-}
-
-ResultVal<FileSys::VirtualFile> VfsDirectoryServiceWrapper::OpenFile(const std::string& path,
-                                                                     FileSys::Mode mode) const {
-    auto file = backing->GetFileRelative(path);
-    if (file == nullptr)
-        return FileSys::ERROR_PATH_NOT_FOUND;
-
-    if ((static_cast<u32>(mode) & static_cast<u32>(FileSys::Mode::Append)) != 0) {
-        return MakeResult<FileSys::VirtualFile>(
-            std::make_shared<FileSys::OffsetVfsFile>(file, 0, file->GetSize()));
-    }
-
-    return MakeResult<FileSys::VirtualFile>(file);
-}
-
-ResultVal<FileSys::VirtualDir> VfsDirectoryServiceWrapper::OpenDirectory(const std::string& path) {
-    auto dir = GetDirectoryRelativeWrapped(backing, path);
-    if (dir == nullptr)
-        return ResultCode(-1);
-    return MakeResult(dir);
-}
-
-u64 VfsDirectoryServiceWrapper::GetFreeSpaceSize() const {
-    if (backing->IsWritable())
-        return EMULATED_SD_REPORTED_SIZE;
-
-    return 0;
-}
-
-ResultVal<FileSys::EntryType> VfsDirectoryServiceWrapper::GetEntryType(
-    const std::string& path) const {
-    auto dir = GetDirectoryRelativeWrapped(backing, FileUtil::GetParentPath(path));
-    if (dir == nullptr)
-        return ResultCode(-1);
-    auto filename = FileUtil::GetFilename(path);
-    if (dir->GetFile(filename) != nullptr)
-        return MakeResult(FileSys::EntryType::File);
-    if (dir->GetSubdirectory(filename) != nullptr)
-        return MakeResult(FileSys::EntryType::Directory);
-    return ResultCode(-1);
-}
-
-// A deferred filesystem for nand save data.
-// This must be deferred because the directory is dependent on title id, which is not set at
-// registration time.
-struct SaveDataDeferredFilesystem : DeferredFilesystem {
-protected:
-    FileSys::VirtualDir CreateFilesystem() override {
-        u64 title_id = Core::CurrentProcess()->program_id;
-        // TODO(DarkLordZach): Users
-        u32 user_id = 0;
-        std::string nand_directory = fmt::format(
-            "{}save/{:016X}/{:08X}/", FileUtil::GetUserPath(D_NAND_IDX), title_id, user_id);
-
-        auto savedata =
-            std::make_shared<FileSys::RealVfsDirectory>(nand_directory, FileSys::Mode::Write);
-        return savedata;
-    }
-};
-
 /**
  * Map of registered file systems, identified by type. Once an file system is registered here, it
  * is never removed until UnregisterFileSystems is called.
  */
-static boost::container::flat_map<Type, std::unique_ptr<DeferredFilesystem>> filesystem_map;
-static FileSys::VirtualFile filesystem_romfs = nullptr;
+static boost::container::flat_map<Type, std::unique_ptr<FileSys::FileSystemFactory>> filesystem_map;
 
-ResultCode RegisterFileSystem(std::unique_ptr<DeferredFilesystem>&& factory, Type type) {
+ResultCode RegisterFileSystem(std::unique_ptr<FileSys::FileSystemFactory>&& factory, Type type) {
     auto result = filesystem_map.emplace(type, std::move(factory));
 
     bool inserted = result.second;
     ASSERT_MSG(inserted, "Tried to register more than one system with same id code");
 
     auto& filesystem = result.first->second;
-    LOG_DEBUG(Service_FS, "Registered file system with id code 0x{:08X}", static_cast<u32>(type));
-    return RESULT_SUCCESS;
-}
-
-ResultCode RegisterRomFS(FileSys::VirtualFile filesystem) {
-    ASSERT_MSG(filesystem_romfs == nullptr,
-               "Tried to register more than one system with same id code");
-
-    filesystem_romfs = filesystem;
     LOG_DEBUG(Service_FS, "Registered file system {} with id code 0x{:08X}", filesystem->GetName(),
-              static_cast<u32>(Type::RomFS));
+              static_cast<u32>(type));
     return RESULT_SUCCESS;
 }
 
-ResultVal<FileSys::VirtualDir> OpenFileSystem(Type type) {
+ResultVal<std::unique_ptr<FileSys::FileSystemBackend>> OpenFileSystem(Type type,
+                                                                      FileSys::Path& path) {
     LOG_TRACE(Service_FS, "Opening FileSystem with type={}", static_cast<u32>(type));
 
     auto itr = filesystem_map.find(type);
@@ -225,13 +40,7 @@ ResultVal<FileSys::VirtualDir> OpenFileSystem(Type type) {
         return ResultCode(-1);
     }
 
-    return MakeResult(itr->second->Get());
-}
-
-ResultVal<FileSys::VirtualFile> OpenRomFS() {
-    if (filesystem_romfs == nullptr)
-        return ResultCode(-1);
-    return MakeResult(filesystem_romfs);
+    return itr->second->Open(path);
 }
 
 ResultCode FormatFileSystem(Type type) {
@@ -243,21 +52,21 @@ ResultCode FormatFileSystem(Type type) {
         return ResultCode(-1);
     }
 
-    return itr->second->Get()->GetParentDirectory()->DeleteSubdirectory(
-               itr->second->Get()->GetName())
-               ? RESULT_SUCCESS
-               : ResultCode(-1);
+    FileSys::Path unused;
+    return itr->second->Format(unused);
 }
 
 void RegisterFileSystems() {
     filesystem_map.clear();
-    filesystem_romfs = nullptr;
 
+    std::string nand_directory = FileUtil::GetUserPath(D_NAND_IDX);
     std::string sd_directory = FileUtil::GetUserPath(D_SDMC_IDX);
-    auto sdcard = std::make_shared<FileSys::RealVfsDirectory>(sd_directory, FileSys::Mode::Write);
-    RegisterFileSystem(std::make_unique<DeferredFilesystem>(sdcard), Type::SDMC);
 
-    RegisterFileSystem(std::make_unique<SaveDataDeferredFilesystem>(), Type::SaveData);
+    auto savedata = std::make_unique<FileSys::SaveData_Factory>(std::move(nand_directory));
+    RegisterFileSystem(std::move(savedata), Type::SaveData);
+
+    auto sdcard = std::make_unique<FileSys::SDMC_Factory>(std::move(sd_directory));
+    RegisterFileSystem(std::move(sdcard), Type::SDMC);
 }
 
 void InstallInterfaces(SM::ServiceManager& service_manager) {
diff --git a/src/core/hle/service/filesystem/filesystem.h b/src/core/hle/service/filesystem/filesystem.h
index d3de797f1..56d26146e 100644
--- a/src/core/hle/service/filesystem/filesystem.h
+++ b/src/core/hle/service/filesystem/filesystem.h
@@ -6,8 +6,6 @@
 
 #include <memory>
 #include "common/common_types.h"
-#include "core/file_sys/filesystem.h"
-#include "core/file_sys/vfs.h"
 #include "core/hle/result.h"
 
 namespace FileSys {
@@ -31,136 +29,12 @@ enum class Type {
     SDMC = 3,
 };
 
-// A class that wraps a VfsDirectory with methods that return ResultVal and ResultCode instead of
-// pointers and booleans. This makes using a VfsDirectory with switch services much easier and
-// avoids repetitive code.
-class VfsDirectoryServiceWrapper {
-public:
-    explicit VfsDirectoryServiceWrapper(FileSys::VirtualDir backing);
-
-    /**
-     * Get a descriptive name for the archive (e.g. "RomFS", "SaveData", etc.)
-     */
-    std::string GetName() const;
-
-    /**
-     * Create a file specified by its path
-     * @param path Path relative to the Archive
-     * @param size The size of the new file, filled with zeroes
-     * @return Result of the operation
-     */
-    ResultCode CreateFile(const std::string& path, u64 size) const;
-
-    /**
-     * Delete a file specified by its path
-     * @param path Path relative to the archive
-     * @return Result of the operation
-     */
-    ResultCode DeleteFile(const std::string& path) const;
-
-    /**
-     * Create a directory specified by its path
-     * @param path Path relative to the archive
-     * @return Result of the operation
-     */
-    ResultCode CreateDirectory(const std::string& path) const;
-
-    /**
-     * Delete a directory specified by its path
-     * @param path Path relative to the archive
-     * @return Result of the operation
-     */
-    ResultCode DeleteDirectory(const std::string& path) const;
-
-    /**
-     * Delete a directory specified by its path and anything under it
-     * @param path Path relative to the archive
-     * @return Result of the operation
-     */
-    ResultCode DeleteDirectoryRecursively(const std::string& path) const;
-
-    /**
-     * Rename a File specified by its path
-     * @param src_path Source path relative to the archive
-     * @param dest_path Destination path relative to the archive
-     * @return Result of the operation
-     */
-    ResultCode RenameFile(const std::string& src_path, const std::string& dest_path) const;
-
-    /**
-     * Rename a Directory specified by its path
-     * @param src_path Source path relative to the archive
-     * @param dest_path Destination path relative to the archive
-     * @return Result of the operation
-     */
-    ResultCode RenameDirectory(const std::string& src_path, const std::string& dest_path) const;
-
-    /**
-     * Open a file specified by its path, using the specified mode
-     * @param path Path relative to the archive
-     * @param mode Mode to open the file with
-     * @return Opened file, or error code
-     */
-    ResultVal<FileSys::VirtualFile> OpenFile(const std::string& path, FileSys::Mode mode) const;
-
-    /**
-     * Open a directory specified by its path
-     * @param path Path relative to the archive
-     * @return Opened directory, or error code
-     */
-    ResultVal<FileSys::VirtualDir> OpenDirectory(const std::string& path);
-
-    /**
-     * Get the free space
-     * @return The number of free bytes in the archive
-     */
-    u64 GetFreeSpaceSize() const;
-
-    /**
-     * Get the type of the specified path
-     * @return The type of the specified path or error code
-     */
-    ResultVal<FileSys::EntryType> GetEntryType(const std::string& path) const;
-
-private:
-    FileSys::VirtualDir backing;
-};
-
-// A class that deferres the creation of a filesystem until a later time.
-// This is useful if construction depends on a variable not known when the filesystem is registered.
-// Construct this with a filesystem (VirtualDir) to avoid the deferrence feature or override the
-//     CreateFilesystem method which will be called on first use.
-struct DeferredFilesystem {
-    DeferredFilesystem() = default;
-
-    explicit DeferredFilesystem(FileSys::VirtualDir vfs_directory) : fs(std::move(vfs_directory)) {}
-
-    FileSys::VirtualDir Get() {
-        if (fs == nullptr)
-            fs = CreateFilesystem();
-
-        return fs;
-    }
-
-    virtual ~DeferredFilesystem() = default;
-
-protected:
-    virtual FileSys::VirtualDir CreateFilesystem() {
-        return fs;
-    }
-
-private:
-    FileSys::VirtualDir fs;
-};
-
 /**
  * Registers a FileSystem, instances of which can later be opened using its IdCode.
  * @param factory FileSystem backend interface to use
  * @param type Type used to access this type of FileSystem
  */
-ResultCode RegisterFileSystem(std::unique_ptr<DeferredFilesystem>&& fs, Type type);
-
-ResultCode RegisterRomFS(FileSys::VirtualFile fs);
+ResultCode RegisterFileSystem(std::unique_ptr<FileSys::FileSystemFactory>&& factory, Type type);
 
 /**
  * Opens a file system
@@ -168,9 +42,8 @@ ResultCode RegisterRomFS(FileSys::VirtualFile fs);
  * @param path Path to the file system, used with Binary paths
  * @return FileSys::FileSystemBackend interface to the file system
  */
-ResultVal<FileSys::VirtualDir> OpenFileSystem(Type type);
-
-ResultVal<FileSys::VirtualFile> OpenRomFS();
+ResultVal<std::unique_ptr<FileSys::FileSystemBackend>> OpenFileSystem(Type type,
+                                                                      FileSys::Path& path);
 
 /**
  * Formats a file system
diff --git a/src/core/hle/service/filesystem/fsp_srv.cpp b/src/core/hle/service/filesystem/fsp_srv.cpp
index 26e8a8c88..216bfea0a 100644
--- a/src/core/hle/service/filesystem/fsp_srv.cpp
+++ b/src/core/hle/service/filesystem/fsp_srv.cpp
@@ -19,8 +19,8 @@ namespace Service::FileSystem {
 
 class IStorage final : public ServiceFramework<IStorage> {
 public:
-    IStorage(FileSys::VirtualFile backend_)
-        : ServiceFramework("IStorage"), backend(std::move(backend_)) {
+    IStorage(std::unique_ptr<FileSys::StorageBackend>&& backend)
+        : ServiceFramework("IStorage"), backend(std::move(backend)) {
         static const FunctionInfo functions[] = {
             {0, &IStorage::Read, "Read"}, {1, nullptr, "Write"},   {2, nullptr, "Flush"},
             {3, nullptr, "SetSize"},      {4, nullptr, "GetSize"}, {5, nullptr, "OperateRange"},
@@ -29,7 +29,7 @@ public:
     }
 
 private:
-    FileSys::VirtualFile backend;
+    std::unique_ptr<FileSys::StorageBackend> backend;
 
     void Read(Kernel::HLERequestContext& ctx) {
         IPC::RequestParser rp{ctx};
@@ -51,8 +51,8 @@ private:
         }
 
         // Read the data from the Storage backend
-        std::vector<u8> output = backend->ReadBytes(length, offset);
-        auto res = MakeResult<size_t>(output.size());
+        std::vector<u8> output(length);
+        ResultVal<size_t> res = backend->Read(offset, length, output.data());
         if (res.Failed()) {
             IPC::ResponseBuilder rb{ctx, 2};
             rb.Push(res.Code());
@@ -69,8 +69,8 @@ private:
 
 class IFile final : public ServiceFramework<IFile> {
 public:
-    explicit IFile(FileSys::VirtualFile backend_)
-        : ServiceFramework("IFile"), backend(std::move(backend_)) {
+    explicit IFile(std::unique_ptr<FileSys::StorageBackend>&& backend)
+        : ServiceFramework("IFile"), backend(std::move(backend)) {
         static const FunctionInfo functions[] = {
             {0, &IFile::Read, "Read"},       {1, &IFile::Write, "Write"},
             {2, &IFile::Flush, "Flush"},     {3, &IFile::SetSize, "SetSize"},
@@ -80,7 +80,7 @@ public:
     }
 
 private:
-    FileSys::VirtualFile backend;
+    std::unique_ptr<FileSys::StorageBackend> backend;
 
     void Read(Kernel::HLERequestContext& ctx) {
         IPC::RequestParser rp{ctx};
@@ -103,8 +103,8 @@ private:
         }
 
         // Read the data from the Storage backend
-        std::vector<u8> output = backend->ReadBytes(length, offset);
-        auto res = MakeResult<size_t>(output.size());
+        std::vector<u8> output(length);
+        ResultVal<size_t> res = backend->Read(offset, length, output.data());
         if (res.Failed()) {
             IPC::ResponseBuilder rb{ctx, 2};
             rb.Push(res.Code());
@@ -139,10 +139,9 @@ private:
             return;
         }
 
-        std::vector<u8> data = ctx.ReadBuffer();
-        data.resize(length);
         // Write the data to the Storage backend
-        auto res = MakeResult<size_t>(backend->WriteBytes(data, offset));
+        std::vector<u8> data = ctx.ReadBuffer();
+        ResultVal<size_t> res = backend->Write(offset, length, true, data.data());
         if (res.Failed()) {
             IPC::ResponseBuilder rb{ctx, 2};
             rb.Push(res.Code());
@@ -155,8 +154,7 @@ private:
 
     void Flush(Kernel::HLERequestContext& ctx) {
         LOG_DEBUG(Service_FS, "called");
-
-        // Exists for SDK compatibiltity -- No need to flush file.
+        backend->Flush();
 
         IPC::ResponseBuilder rb{ctx, 2};
         rb.Push(RESULT_SUCCESS);
@@ -165,7 +163,7 @@ private:
     void SetSize(Kernel::HLERequestContext& ctx) {
         IPC::RequestParser rp{ctx};
         const u64 size = rp.Pop<u64>();
-        backend->Resize(size);
+        backend->SetSize(size);
         LOG_DEBUG(Service_FS, "called, size={}", size);
 
         IPC::ResponseBuilder rb{ctx, 2};
@@ -182,38 +180,19 @@ private:
     }
 };
 
-template <typename T>
-static void BuildEntryIndex(std::vector<FileSys::Entry>& entries, const std::vector<T>& new_data,
-                            FileSys::EntryType type) {
-    for (const auto& new_entry : new_data) {
-        FileSys::Entry entry;
-        entry.filename[0] = '\0';
-        std::strncat(entry.filename, new_entry->GetName().c_str(), FileSys::FILENAME_LENGTH - 1);
-        entry.type = type;
-        entry.file_size = new_entry->GetSize();
-        entries.emplace_back(std::move(entry));
-    }
-}
-
 class IDirectory final : public ServiceFramework<IDirectory> {
 public:
-    explicit IDirectory(FileSys::VirtualDir backend_)
-        : ServiceFramework("IDirectory"), backend(std::move(backend_)) {
+    explicit IDirectory(std::unique_ptr<FileSys::DirectoryBackend>&& backend)
+        : ServiceFramework("IDirectory"), backend(std::move(backend)) {
         static const FunctionInfo functions[] = {
             {0, &IDirectory::Read, "Read"},
             {1, &IDirectory::GetEntryCount, "GetEntryCount"},
         };
         RegisterHandlers(functions);
-
-        // Build entry index now to save time later.
-        BuildEntryIndex(entries, backend->GetFiles(), FileSys::File);
-        BuildEntryIndex(entries, backend->GetSubdirectories(), FileSys::Directory);
     }
 
 private:
-    FileSys::VirtualDir backend;
-    std::vector<FileSys::Entry> entries;
-    u64 next_entry_index = 0;
+    std::unique_ptr<FileSys::DirectoryBackend> backend;
 
     void Read(Kernel::HLERequestContext& ctx) {
         IPC::RequestParser rp{ctx};
@@ -224,31 +203,26 @@ private:
         // Calculate how many entries we can fit in the output buffer
         u64 count_entries = ctx.GetWriteBufferSize() / sizeof(FileSys::Entry);
 
-        // Cap at total number of entries.
-        u64 actual_entries = std::min(count_entries, entries.size() - next_entry_index);
-
         // Read the data from the Directory backend
-        std::vector<FileSys::Entry> entry_data(entries.begin() + next_entry_index,
-                                               entries.begin() + next_entry_index + actual_entries);
-
-        next_entry_index += actual_entries;
+        std::vector<FileSys::Entry> entries(count_entries);
+        u64 read_entries = backend->Read(count_entries, entries.data());
 
         // Convert the data into a byte array
-        std::vector<u8> output(entry_data.size() * sizeof(FileSys::Entry));
-        std::memcpy(output.data(), entry_data.data(), output.size());
+        std::vector<u8> output(entries.size() * sizeof(FileSys::Entry));
+        std::memcpy(output.data(), entries.data(), output.size());
 
         // Write the data to memory
         ctx.WriteBuffer(output);
 
         IPC::ResponseBuilder rb{ctx, 4};
         rb.Push(RESULT_SUCCESS);
-        rb.Push(actual_entries);
+        rb.Push(read_entries);
     }
 
     void GetEntryCount(Kernel::HLERequestContext& ctx) {
         LOG_DEBUG(Service_FS, "called");
 
-        u64 count = entries.size() - next_entry_index;
+        u64 count = backend->GetEntryCount();
 
         IPC::ResponseBuilder rb{ctx, 4};
         rb.Push(RESULT_SUCCESS);
@@ -258,7 +232,7 @@ private:
 
 class IFileSystem final : public ServiceFramework<IFileSystem> {
 public:
-    explicit IFileSystem(FileSys::VirtualDir backend)
+    explicit IFileSystem(std::unique_ptr<FileSys::FileSystemBackend>&& backend)
         : ServiceFramework("IFileSystem"), backend(std::move(backend)) {
         static const FunctionInfo functions[] = {
             {0, &IFileSystem::CreateFile, "CreateFile"},
@@ -293,7 +267,7 @@ public:
         LOG_DEBUG(Service_FS, "called file {} mode 0x{:X} size 0x{:08X}", name, mode, size);
 
         IPC::ResponseBuilder rb{ctx, 2};
-        rb.Push(backend.CreateFile(name, size));
+        rb.Push(backend->CreateFile(name, size));
     }
 
     void DeleteFile(Kernel::HLERequestContext& ctx) {
@@ -305,7 +279,7 @@ public:
         LOG_DEBUG(Service_FS, "called file {}", name);
 
         IPC::ResponseBuilder rb{ctx, 2};
-        rb.Push(backend.DeleteFile(name));
+        rb.Push(backend->DeleteFile(name));
     }
 
     void CreateDirectory(Kernel::HLERequestContext& ctx) {
@@ -317,7 +291,7 @@ public:
         LOG_DEBUG(Service_FS, "called directory {}", name);
 
         IPC::ResponseBuilder rb{ctx, 2};
-        rb.Push(backend.CreateDirectory(name));
+        rb.Push(backend->CreateDirectory(name));
     }
 
     void RenameFile(Kernel::HLERequestContext& ctx) {
@@ -335,7 +309,7 @@ public:
         LOG_DEBUG(Service_FS, "called file '{}' to file '{}'", src_name, dst_name);
 
         IPC::ResponseBuilder rb{ctx, 2};
-        rb.Push(backend.RenameFile(src_name, dst_name));
+        rb.Push(backend->RenameFile(src_name, dst_name));
     }
 
     void OpenFile(Kernel::HLERequestContext& ctx) {
@@ -348,14 +322,14 @@ public:
 
         LOG_DEBUG(Service_FS, "called file {} mode {}", name, static_cast<u32>(mode));
 
-        auto result = backend.OpenFile(name, mode);
+        auto result = backend->OpenFile(name, mode);
         if (result.Failed()) {
             IPC::ResponseBuilder rb{ctx, 2};
             rb.Push(result.Code());
             return;
         }
 
-        IFile file(result.Unwrap());
+        auto file = std::move(result.Unwrap());
 
         IPC::ResponseBuilder rb{ctx, 2, 0, 1};
         rb.Push(RESULT_SUCCESS);
@@ -373,14 +347,14 @@ public:
 
         LOG_DEBUG(Service_FS, "called directory {} filter {}", name, filter_flags);
 
-        auto result = backend.OpenDirectory(name);
+        auto result = backend->OpenDirectory(name);
         if (result.Failed()) {
             IPC::ResponseBuilder rb{ctx, 2};
             rb.Push(result.Code());
             return;
         }
 
-        IDirectory directory(result.Unwrap());
+        auto directory = std::move(result.Unwrap());
 
         IPC::ResponseBuilder rb{ctx, 2, 0, 1};
         rb.Push(RESULT_SUCCESS);
@@ -395,7 +369,7 @@ public:
 
         LOG_DEBUG(Service_FS, "called file {}", name);
 
-        auto result = backend.GetEntryType(name);
+        auto result = backend->GetEntryType(name);
         if (result.Failed()) {
             IPC::ResponseBuilder rb{ctx, 2};
             rb.Push(result.Code());
@@ -415,7 +389,7 @@ public:
     }
 
 private:
-    VfsDirectoryServiceWrapper backend;
+    std::unique_ptr<FileSys::FileSystemBackend> backend;
 };
 
 FSP_SRV::FSP_SRV() : ServiceFramework("fsp-srv") {
@@ -516,7 +490,8 @@ void FSP_SRV::TryLoadRomFS() {
     if (romfs) {
         return;
     }
-    auto res = OpenRomFS();
+    FileSys::Path unused;
+    auto res = OpenFileSystem(Type::RomFS, unused);
     if (res.Succeeded()) {
         romfs = std::move(res.Unwrap());
     }
@@ -532,7 +507,8 @@ void FSP_SRV::Initialize(Kernel::HLERequestContext& ctx) {
 void FSP_SRV::MountSdCard(Kernel::HLERequestContext& ctx) {
     LOG_DEBUG(Service_FS, "called");
 
-    IFileSystem filesystem(OpenFileSystem(Type::SDMC).Unwrap());
+    FileSys::Path unused;
+    auto filesystem = OpenFileSystem(Type::SDMC, unused).Unwrap();
 
     IPC::ResponseBuilder rb{ctx, 2, 0, 1};
     rb.Push(RESULT_SUCCESS);
@@ -555,7 +531,8 @@ void FSP_SRV::CreateSaveData(Kernel::HLERequestContext& ctx) {
 void FSP_SRV::MountSaveData(Kernel::HLERequestContext& ctx) {
     LOG_WARNING(Service_FS, "(STUBBED) called");
 
-    IFileSystem filesystem(OpenFileSystem(Type::SaveData).Unwrap());
+    FileSys::Path unused;
+    auto filesystem = OpenFileSystem(Type::SaveData, unused).Unwrap();
 
     IPC::ResponseBuilder rb{ctx, 2, 0, 1};
     rb.Push(RESULT_SUCCESS);
@@ -582,11 +559,18 @@ void FSP_SRV::OpenDataStorageByCurrentProcess(Kernel::HLERequestContext& ctx) {
         return;
     }
 
-    IStorage storage(romfs);
+    // Attempt to open a StorageBackend interface to the RomFS
+    auto storage = romfs->OpenFile({}, {});
+    if (storage.Failed()) {
+        LOG_CRITICAL(Service_FS, "no storage interface available!");
+        IPC::ResponseBuilder rb{ctx, 2};
+        rb.Push(storage.Code());
+        return;
+    }
 
     IPC::ResponseBuilder rb{ctx, 2, 0, 1};
     rb.Push(RESULT_SUCCESS);
-    rb.PushIpcInterface<IStorage>(std::move(storage));
+    rb.PushIpcInterface<IStorage>(std::move(storage.Unwrap()));
 }
 
 void FSP_SRV::OpenRomStorage(Kernel::HLERequestContext& ctx) {
diff --git a/src/core/hle/service/filesystem/fsp_srv.h b/src/core/hle/service/filesystem/fsp_srv.h
index b1ef6397f..acb78fac1 100644
--- a/src/core/hle/service/filesystem/fsp_srv.h
+++ b/src/core/hle/service/filesystem/fsp_srv.h
@@ -29,7 +29,7 @@ private:
     void OpenDataStorageByCurrentProcess(Kernel::HLERequestContext& ctx);
     void OpenRomStorage(Kernel::HLERequestContext& ctx);
 
-    FileSys::VirtualFile romfs;
+    std::unique_ptr<FileSys::FileSystemBackend> romfs;
 };
 
 } // namespace Service::FileSystem