diff --git a/inc/winfsp/winfsp.h b/inc/winfsp/winfsp.h
index 6caa3177..143e1eca 100644
--- a/inc/winfsp/winfsp.h
+++ b/inc/winfsp/winfsp.h
@@ -21,6 +21,139 @@
 
 #include <winfsp/fsctl.h>
 
+/*
+ * File System
+ */
+typedef struct _FSP_FILE_SYSTEM FSP_FILE_SYSTEM;
+typedef VOID FSP_FILE_SYSTEM_DISPATCHER(FSP_FILE_SYSTEM *, FSP_FSCTL_TRANSACT_REQ *);
+typedef NTSTATUS FSP_FILE_SYSTEM_OPERATION(FSP_FILE_SYSTEM *, FSP_FSCTL_TRANSACT_REQ *);
+typedef struct _FSP_FILE_SYSTEM_INTERFACE
+{
+    NTSTATUS (*GetSecurity)(FSP_FILE_SYSTEM *FileSystem,
+        PWSTR FileName, PDWORD PFileAttributes,
+        PSECURITY_DESCRIPTOR SecurityDescriptor, SIZE_T *PSecurityDescriptorSize);
+#if 0
+    NTSTATUS (*Create)(FSP_FILE_SYSTEM *FileSystem,
+        FSP_FSCTL_TRANSACT_REQ *Request, FSP_FILE_NODE **PFileNode);
+    NTSTATUS (*Open)(FSP_FILE_SYSTEM *FileSystem,
+        FSP_FSCTL_TRANSACT_REQ *Request, FSP_FILE_NODE **PFileNode);
+    NTSTATUS (*Overwrite)(FSP_FILE_SYSTEM *FileSystem,
+        FSP_FSCTL_TRANSACT_REQ *Request, BOOLEAN ReplaceFileAttributes, FSP_FILE_NODE *FileNode);
+    VOID (*Cleanup)(FSP_FILE_SYSTEM *FileSystem,
+        FSP_FSCTL_TRANSACT_REQ *Request, FSP_FILE_NODE *FileNode, BOOLEAN Delete);
+    VOID (*Close)(FSP_FILE_SYSTEM *FileSystem,
+        FSP_FSCTL_TRANSACT_REQ *Request, FSP_FILE_NODE *FileNode);
+#endif
+} FSP_FILE_SYSTEM_INTERFACE;
+typedef struct _FSP_FILE_SYSTEM
+{
+    UINT16 Version;
+    WCHAR VolumePath[FSP_FSCTL_VOLUME_NAME_SIZEMAX / sizeof(WCHAR)];
+    HANDLE VolumeHandle;
+    PVOID UserContext;
+    NTSTATUS DispatcherResult;
+    FSP_FILE_SYSTEM_DISPATCHER *Dispatcher;
+    FSP_FILE_SYSTEM_DISPATCHER *EnterOperation, *LeaveOperation;
+    FSP_FILE_SYSTEM_OPERATION *Operations[FspFsctlTransactKindCount];
+    const FSP_FILE_SYSTEM_INTERFACE *Interface;
+} FSP_FILE_SYSTEM;
+
+FSP_API NTSTATUS FspFileSystemCreate(PWSTR DevicePath,
+    const FSP_FSCTL_VOLUME_PARAMS *VolumeParams,
+    const FSP_FILE_SYSTEM_INTERFACE *Interface,
+    FSP_FILE_SYSTEM **PFileSystem);
+FSP_API VOID FspFileSystemDelete(FSP_FILE_SYSTEM *FileSystem);
+FSP_API NTSTATUS FspFileSystemLoop(FSP_FILE_SYSTEM *FileSystem);
+
+FSP_API VOID FspFileSystemDirectDispatcher(FSP_FILE_SYSTEM *FileSystem,
+    FSP_FSCTL_TRANSACT_REQ *Request);
+FSP_API VOID FspFileSystemPoolDispatcher(FSP_FILE_SYSTEM *FileSystem,
+    FSP_FSCTL_TRANSACT_REQ *Request);
+static inline
+VOID FspFileSystemSetDispatcher(FSP_FILE_SYSTEM *FileSystem,
+    FSP_FILE_SYSTEM_DISPATCHER *Dispatcher,
+    FSP_FILE_SYSTEM_DISPATCHER *EnterOperation,
+    FSP_FILE_SYSTEM_DISPATCHER *LeaveOperation)
+{
+    FileSystem->Dispatcher = Dispatcher;
+    FileSystem->EnterOperation = EnterOperation;
+    FileSystem->LeaveOperation = LeaveOperation;
+}
+static inline
+VOID FspFileSystemSetOperation(FSP_FILE_SYSTEM *FileSystem,
+    ULONG Index,
+    FSP_FILE_SYSTEM_OPERATION *Operation)
+{
+    FileSystem->Operations[Index] = Operation;
+}
+
+static inline
+VOID FspFileSystemGetDispatcherResult(FSP_FILE_SYSTEM *FileSystem,
+    NTSTATUS *PDispatcherResult)
+{
+    /* 32-bit reads are atomic */
+    *PDispatcherResult = FileSystem->DispatcherResult;
+    MemoryBarrier();
+}
+static inline
+VOID FspFileSystemSetDispatcherResult(FSP_FILE_SYSTEM *FileSystem,
+    NTSTATUS DispatcherResult)
+{
+    if (NT_SUCCESS(DispatcherResult))
+        return;
+    InterlockedCompareExchange(&FileSystem->DispatcherResult, DispatcherResult, 0);
+}
+
+static inline
+VOID FspFileSystemEnterOperation(FSP_FILE_SYSTEM *FileSystem,
+    FSP_FSCTL_TRANSACT_REQ *Request)
+{
+    if (0 != FileSystem->EnterOperation)
+        FileSystem->EnterOperation(FileSystem, Request);
+}
+static inline
+VOID FspFileSystemLeaveOperation(FSP_FILE_SYSTEM *FileSystem,
+    FSP_FSCTL_TRANSACT_REQ *Request)
+{
+    if (0 != FileSystem->LeaveOperation)
+        FileSystem->LeaveOperation(FileSystem, Request);
+}
+
+FSP_API NTSTATUS FspFileSystemSendResponse(FSP_FILE_SYSTEM *FileSystem,
+    FSP_FSCTL_TRANSACT_RSP *Response);
+FSP_API NTSTATUS FspFileSystemSendResponseWithStatus(FSP_FILE_SYSTEM *FileSystem,
+    FSP_FSCTL_TRANSACT_REQ *Request, NTSTATUS Result);
+
+/*
+ * File System Operations
+ */
+FSP_API PGENERIC_MAPPING FspGetFileGenericMapping(VOID);
+FSP_API NTSTATUS FspAccessCheck(FSP_FILE_SYSTEM *FileSystem,
+    FSP_FSCTL_TRANSACT_REQ *Request, BOOLEAN CheckParentDirectory, BOOLEAN AllowTraverseCheck,
+    DWORD DesiredAccess, PDWORD PGrantedAccess);
+FSP_API NTSTATUS FspFileSystemOpCreate(FSP_FILE_SYSTEM *FileSystem,
+    FSP_FSCTL_TRANSACT_REQ *Request);
+FSP_API NTSTATUS FspFileSystemOpOverwrite(FSP_FILE_SYSTEM *FileSystem,
+    FSP_FSCTL_TRANSACT_REQ *Request);
+FSP_API NTSTATUS FspFileSystemOpCleanup(FSP_FILE_SYSTEM *FileSystem,
+    FSP_FSCTL_TRANSACT_REQ *Request);
+FSP_API NTSTATUS FspFileSystemOpClose(FSP_FILE_SYSTEM *FileSystem,
+    FSP_FSCTL_TRANSACT_REQ *Request);
+
+/*
+ * Path Handling
+ */
+FSP_API VOID FspPathPrefix(PWSTR Path, PWSTR *PPrefix, PWSTR *PRemain);
+FSP_API VOID FspPathSuffix(PWSTR Path, PWSTR *PRemain, PWSTR *PSuffix);
+FSP_API VOID FspPathCombine(PWSTR Prefix, PWSTR Suffix);
+
+/*
+ * Utility
+ */
+FSP_API NTSTATUS FspNtStatusFromWin32(DWORD Error);
+FSP_API VOID FspDebugLog(const char *format, ...);
+
+#if 0
 /*
  * File Nodes
  */
@@ -218,18 +351,6 @@ FSP_API NTSTATUS FspFileSystemSendCloseResponse(FSP_FILE_SYSTEM *FileSystem,
     FSP_FSCTL_TRANSACT_REQ *Request);
 FSP_API NTSTATUS FspFileSystemSendCleanupResponse(FSP_FILE_SYSTEM *FileSystem,
     FSP_FSCTL_TRANSACT_REQ *Request);
-
-/*
- * Path Handling
- */
-FSP_API VOID FspPathPrefix(PWSTR Path, PWSTR *PPrefix, PWSTR *PRemain);
-FSP_API VOID FspPathSuffix(PWSTR Path, PWSTR *PRemain, PWSTR *PSuffix);
-FSP_API VOID FspPathCombine(PWSTR Prefix, PWSTR Suffix);
-
-/*
- * Utility
- */
-FSP_API NTSTATUS FspNtStatusFromWin32(DWORD Error);
-FSP_API VOID FspDebugLog(const char *format, ...);
+#endif
 
 #endif
diff --git a/src/dll/cleanup.c b/src/dll/cleanup.c
index 93411bd8..b18893a4 100644
--- a/src/dll/cleanup.c
+++ b/src/dll/cleanup.c
@@ -6,24 +6,13 @@
 
 #include <dll/library.h>
 
-#if 0
-FSP_API VOID FspShareAccessRemove(FSP_FILE_SYSTEM *FileSystem,
-    FSP_FSCTL_TRANSACT_REQ *Request, FSP_FILE_NODE *FileNode)
+FSP_API NTSTATUS FspFileSystemOpCleanup(FSP_FILE_SYSTEM *FileSystem,
+    FSP_FSCTL_TRANSACT_REQ *Request)
 {
-    if (Request->Req.Cleanup.ReadAccess ||
-        Request->Req.Cleanup.WriteAccess ||
-        Request->Req.Cleanup.DeleteAccess)
-    {
-        FileNode->ShareAccess.OpenCount--;
-        FileNode->ShareAccess.Readers -= Request->Req.Cleanup.ReadAccess;
-        FileNode->ShareAccess.Writers -= Request->Req.Cleanup.WriteAccess;
-        FileNode->ShareAccess.Deleters -= Request->Req.Cleanup.DeleteAccess;
-        FileNode->ShareAccess.SharedRead -= Request->Req.Cleanup.SharedRead;
-        FileNode->ShareAccess.SharedWrite -= Request->Req.Cleanup.SharedWrite;
-        FileNode->ShareAccess.SharedDelete -= Request->Req.Cleanup.SharedDelete;
-    }
+    return STATUS_INVALID_DEVICE_REQUEST;
 }
 
+#if 0
 FSP_API NTSTATUS FspFileSystemOpCleanup(FSP_FILE_SYSTEM *FileSystem,
     FSP_FSCTL_TRANSACT_REQ *Request)
 {
diff --git a/src/dll/close.c b/src/dll/close.c
index 14250550..d85c9b18 100644
--- a/src/dll/close.c
+++ b/src/dll/close.c
@@ -6,6 +6,13 @@
 
 #include <dll/library.h>
 
+FSP_API NTSTATUS FspFileSystemOpClose(FSP_FILE_SYSTEM *FileSystem,
+    FSP_FSCTL_TRANSACT_REQ *Request)
+{
+    return STATUS_INVALID_DEVICE_REQUEST;
+}
+
+#if 0
 FSP_API NTSTATUS FspFileSystemOpClose(FSP_FILE_SYSTEM *FileSystem,
     FSP_FSCTL_TRANSACT_REQ *Request)
 {
@@ -32,3 +39,4 @@ FSP_API NTSTATUS FspFileSystemSendCloseResponse(FSP_FILE_SYSTEM *FileSystem,
     Response.IoStatus.Information = 0;
     return FspFileSystemSendResponse(FileSystem, &Response);
 }
+#endif
diff --git a/src/dll/create.c b/src/dll/create.c
index 2af7fd3a..13d2a9ea 100644
--- a/src/dll/create.c
+++ b/src/dll/create.c
@@ -166,60 +166,8 @@ exit:
     return Result;
 }
 
-FSP_API NTSTATUS FspShareAccessCheck(FSP_FILE_SYSTEM *FileSystem,
-    FSP_FSCTL_TRANSACT_REQ *Request, DWORD GrantedAccess, FSP_FILE_NODE *FileNode)
-{
-    DWORD ShareAccess = Request->Req.Create.ShareAccess;
-    BOOLEAN ReadAccess, WriteAccess, DeleteAccess;
-    BOOLEAN SharedRead, SharedWrite, SharedDelete;
-    ULONG OpenCount;
-
-    ReadAccess = 0 != (GrantedAccess & (FILE_READ_DATA | FILE_EXECUTE));
-    WriteAccess = 0 != (GrantedAccess & (FILE_WRITE_DATA | FILE_APPEND_DATA));
-    DeleteAccess = 0 != (GrantedAccess & DELETE);
-
-    if (ReadAccess || WriteAccess || DeleteAccess)
-    {
-        SharedRead = 0 != (ShareAccess & FILE_SHARE_READ);
-        SharedWrite = 0 != (ShareAccess & FILE_SHARE_WRITE);
-        SharedDelete = 0 != (ShareAccess & FILE_SHARE_DELETE);
-
-        OpenCount = FileNode->ShareAccess.OpenCount;
-
-        /*
-         * IF ReadAccess AND there are already some exclusive readers
-         * OR WriteAccess AND there are already some exclusive writers
-         * OR DeleteAccess AND there are already some exclusive deleters
-         * OR exclusive read requested AND there are already some readers
-         * OR exclusive write requested AND there are already some writers
-         * OR exclusive delete requested AND there are already some deleters
-         */
-        if (ReadAccess && (FileNode->ShareAccess.SharedRead < OpenCount))
-            return STATUS_SHARING_VIOLATION;
-        if (WriteAccess && (FileNode->ShareAccess.SharedWrite < OpenCount))
-            return STATUS_SHARING_VIOLATION;
-        if (DeleteAccess && (FileNode->ShareAccess.SharedDelete < OpenCount))
-            return STATUS_SHARING_VIOLATION;
-        if (!SharedRead && 0 != FileNode->ShareAccess.Readers)
-            return STATUS_SHARING_VIOLATION;
-        if (!SharedWrite && 0 != FileNode->ShareAccess.Writers)
-            return STATUS_SHARING_VIOLATION;
-        if (!SharedDelete && 0 != FileNode->ShareAccess.Deleters)
-            return STATUS_SHARING_VIOLATION;
-
-        FileNode->ShareAccess.OpenCount++;
-        FileNode->ShareAccess.Readers += ReadAccess;
-        FileNode->ShareAccess.Writers += WriteAccess;
-        FileNode->ShareAccess.Deleters += DeleteAccess;
-        FileNode->ShareAccess.SharedRead += SharedRead;
-        FileNode->ShareAccess.SharedWrite += SharedWrite;
-        FileNode->ShareAccess.SharedDelete += SharedDelete;
-    }
-
-    return STATUS_SUCCESS;
-}
-
-FSP_API NTSTATUS FspFileSystemPreCreateCheck(FSP_FILE_SYSTEM *FileSystem,
+static inline
+NTSTATUS FspFileSystemCreateCheck(FSP_FILE_SYSTEM *FileSystem,
     FSP_FSCTL_TRANSACT_REQ *Request, BOOLEAN AllowTraverseCheck, PDWORD PGrantedAccess)
 {
     NTSTATUS Result;
@@ -235,57 +183,16 @@ FSP_API NTSTATUS FspFileSystemPreCreateCheck(FSP_FILE_SYSTEM *FileSystem,
     return Result;
 }
 
-FSP_API VOID FspFileSystemPostCreateCheck(FSP_FILE_SYSTEM *FileSystem,
-    FSP_FSCTL_TRANSACT_REQ *Request, DWORD GrantedAccess, FSP_FILE_NODE *FileNode)
-{
-    FspFileNodeLock(FileNode);
-
-    FspShareAccessCheck(FileSystem, Request, GrantedAccess, FileNode);
-
-    if (Request->Req.Create.CreateOptions & FILE_DELETE_ON_CLOSE)
-        FileNode->Flags.DeleteOnClose = TRUE;
-
-    FspFileNodeOpen(FileNode);
-
-    FspFileNodeUnlock(FileNode);
-}
-
-FSP_API NTSTATUS FspFileSystemPreOpenCheck(FSP_FILE_SYSTEM *FileSystem,
+static inline
+NTSTATUS FspFileSystemPreOpenCheck(FSP_FILE_SYSTEM *FileSystem,
     FSP_FSCTL_TRANSACT_REQ *Request, BOOLEAN AllowTraverseCheck, PDWORD PGrantedAccess)
 {
     return FspAccessCheck(FileSystem, Request, FALSE, AllowTraverseCheck,
         Request->Req.Create.DesiredAccess, PGrantedAccess);
 }
 
-FSP_API NTSTATUS FspFileSystemPostOpenCheck(FSP_FILE_SYSTEM *FileSystem,
-    FSP_FSCTL_TRANSACT_REQ *Request, DWORD GrantedAccess, FSP_FILE_NODE *FileNode)
-{
-    NTSTATUS Result;
-
-    FspFileNodeLock(FileNode);
-
-    if (FileNode->Flags.DeletePending)
-    {
-        Result = STATUS_DELETE_PENDING;
-        goto exit;
-    }
-
-    Result = FspShareAccessCheck(FileSystem, Request, GrantedAccess, FileNode);
-    if (!NT_SUCCESS(Result))
-        goto exit;
-
-    if (Request->Req.Create.CreateOptions & FILE_DELETE_ON_CLOSE)
-        FileNode->Flags.DeleteOnClose = TRUE;
-
-    FspFileNodeOpen(FileNode);
-
-exit:
-    FspFileNodeUnlock(FileNode);
-
-    return Result;
-}
-
-FSP_API NTSTATUS FspFileSystemPreOverwriteCheck(FSP_FILE_SYSTEM *FileSystem,
+static inline
+NTSTATUS FspFileSystemOverwriteCheck(FSP_FILE_SYSTEM *FileSystem,
     FSP_FSCTL_TRANSACT_REQ *Request, BOOLEAN AllowTraverseCheck, PDWORD PGrantedAccess)
 {
     NTSTATUS Result;
@@ -305,12 +212,19 @@ FSP_API NTSTATUS FspFileSystemPreOverwriteCheck(FSP_FILE_SYSTEM *FileSystem,
     return Result;
 }
 
-FSP_API NTSTATUS FspFileSystemPostOverwriteCheck(FSP_FILE_SYSTEM *FileSystem,
-    FSP_FSCTL_TRANSACT_REQ *Request, DWORD GrantedAccess, FSP_FILE_NODE *FileNode)
+FSP_API NTSTATUS FspFileSystemOpCreate(FSP_FILE_SYSTEM *FileSystem,
+    FSP_FSCTL_TRANSACT_REQ *Request)
 {
-    return FspFileSystemPostOpenCheck(FileSystem, Request, GrantedAccess, FileNode);
+    return STATUS_INVALID_DEVICE_REQUEST;
 }
 
+FSP_API NTSTATUS FspFileSystemOpOverwrite(FSP_FILE_SYSTEM *FileSystem,
+    FSP_FSCTL_TRANSACT_REQ *Request)
+{
+    return STATUS_INVALID_DEVICE_REQUEST;
+}
+
+#if 0
 static BOOLEAN FspIsRootDirectory(PWSTR FileName)
 {
     for (PWSTR Pointer = FileName; *Pointer; Pointer++)
@@ -621,3 +535,4 @@ FSP_API NTSTATUS FspFileSystemSendCreateResponse(FSP_FILE_SYSTEM *FileSystem,
     Response.Rsp.Create.Opened.GrantedAccess = GrantedAccess;
     return FspFileSystemSendResponse(FileSystem, &Response);
 }
+#endif
diff --git a/src/dll/loop.c b/src/dll/loop.c
index 719d29a2..131dd80c 100644
--- a/src/dll/loop.c
+++ b/src/dll/loop.c
@@ -43,6 +43,7 @@ FSP_API NTSTATUS FspFileSystemCreate(PWSTR DevicePath,
 
     FileSystem->Dispatcher = FspFileSystemDirectDispatcher;
     FileSystem->Operations[FspFsctlTransactCreateKind] = FspFileSystemOpCreate;
+    FileSystem->Operations[FspFsctlTransactOverwriteKind] = FspFileSystemOpOverwrite;
     FileSystem->Operations[FspFsctlTransactCleanupKind] = FspFileSystemOpCleanup;
     FileSystem->Operations[FspFsctlTransactCloseKind] = FspFileSystemOpClose;
     // !!!: ...