From dd259ad45cfe9590cd41219f0caa85c78322c1fb Mon Sep 17 00:00:00 2001
From: Bill Zissimopoulos <billziss@navimatics.com>
Date: Thu, 31 Dec 2015 16:00:31 -0800
Subject: [PATCH] dll: FSP_FILE_SYSTEM::DispatcherResult

---
 inc/winfsp/winfsp.h | 24 +++++++++++++++---
 src/dll/loop.c      | 61 +++++++++++++++++++++++++++------------------
 2 files changed, 57 insertions(+), 28 deletions(-)

diff --git a/inc/winfsp/winfsp.h b/inc/winfsp/winfsp.h
index e31e90fb..6d65f5f8 100644
--- a/inc/winfsp/winfsp.h
+++ b/inc/winfsp/winfsp.h
@@ -22,8 +22,8 @@
 #include <winfsp/fsctl.h>
 
 typedef struct _FSP_FILE_SYSTEM FSP_FILE_SYSTEM;
-typedef NTSTATUS FSP_FILE_SYSTEM_DISPATCHER(FSP_FILE_SYSTEM *, FSP_FSCTL_TRANSACT_REQ *);
-typedef VOID FSP_FILE_SYSTEM_OPERATION(FSP_FILE_SYSTEM *, FSP_FSCTL_TRANSACT_REQ *);
+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
 {
     UINT16 Version;
@@ -31,6 +31,7 @@ typedef struct _FSP_FILE_SYSTEM
     HANDLE VolumeHandle;
     PVOID UserContext;
     FSP_FILE_SYSTEM_DISPATCHER *Dispatcher;
+    NTSTATUS DispatcherResult;
     FSP_FILE_SYSTEM_OPERATION *Operations[FspFsctlTransactKindCount];
 } FSP_FILE_SYSTEM;
 
@@ -40,11 +41,26 @@ FSP_API NTSTATUS FspFileSystemCreate(PWSTR DevicePath,
     FSP_FILE_SYSTEM **PFileSystem);
 FSP_API VOID FspFileSystemDelete(FSP_FILE_SYSTEM *FileSystem);
 FSP_API NTSTATUS FspFileSystemLoop(FSP_FILE_SYSTEM *FileSystem);
-FSP_API NTSTATUS FspFileSystemDirectDispatcher(FSP_FILE_SYSTEM *FileSystem,
+FSP_API VOID FspFileSystemDirectDispatcher(FSP_FILE_SYSTEM *FileSystem,
     FSP_FSCTL_TRANSACT_REQ *Request);
-FSP_API NTSTATUS FspFileSystemPoolDispatcher(FSP_FILE_SYSTEM *FileSystem,
+FSP_API VOID FspFileSystemPoolDispatcher(FSP_FILE_SYSTEM *FileSystem,
     FSP_FSCTL_TRANSACT_REQ *Request);
 
+static VOID FspFileSystemGetDispatcherResult(FSP_FILE_SYSTEM *FileSystem,
+    NTSTATUS *PDispatcherResult)
+{
+    /* 32-bit reads are atomic */
+    *PDispatcherResult = FileSystem->DispatcherResult;
+    MemoryBarrier();
+}
+static VOID FspFileSystemSetDispatcherResult(FSP_FILE_SYSTEM *FileSystem,
+    NTSTATUS DispatcherResult)
+{
+    if (NT_SUCCESS(DispatcherResult))
+        return;
+    InterlockedCompareExchange(&FileSystem->DispatcherResult, DispatcherResult, 0);
+}
+
 FSP_API NTSTATUS FspSendResponse(FSP_FILE_SYSTEM *FileSystem,
     FSP_FSCTL_TRANSACT_RSP *Response);
 FSP_API NTSTATUS FspSendResponseWithStatus(FSP_FILE_SYSTEM *FileSystem,
diff --git a/src/dll/loop.c b/src/dll/loop.c
index 50a690e4..b5f81b44 100644
--- a/src/dll/loop.c
+++ b/src/dll/loop.c
@@ -75,7 +75,9 @@ FSP_API NTSTATUS FspFileSystemLoop(FSP_FILE_SYSTEM *FileSystem)
             if (0 == NextRequest)
                 break;
 
-            Result = FileSystem->Dispatcher(FileSystem, Request);
+            FileSystem->Dispatcher(FileSystem, Request);
+
+            FspFileSystemGetDispatcherResult(FileSystem, &Result);
             if (!NT_SUCCESS(Result))
                 goto exit;
 
@@ -89,50 +91,61 @@ exit:
     return Result;
 }
 
-FSP_API NTSTATUS FspFileSystemDirectDispatcher(FSP_FILE_SYSTEM *FileSystem,
+FSP_API VOID FspFileSystemDirectDispatcher(FSP_FILE_SYSTEM *FileSystem,
     FSP_FSCTL_TRANSACT_REQ *Request)
 {
-    if (FspFsctlTransactKindCount <= Request->Kind || 0 == FileSystem->Operations[Request->Kind])
-        return FspSendResponseWithStatus(FileSystem, Request, STATUS_INVALID_DEVICE_REQUEST);
+    NTSTATUS DispatcherResult;
 
-    FileSystem->Operations[Request->Kind](FileSystem, Request);
-    return STATUS_SUCCESS;
+    if (FspFsctlTransactKindCount <= Request->Kind || 0 == FileSystem->Operations[Request->Kind])
+        DispatcherResult = FspSendResponseWithStatus(FileSystem, Request, STATUS_INVALID_DEVICE_REQUEST);
+    else
+        DispatcherResult = FileSystem->Operations[Request->Kind](FileSystem, Request);
+
+    FspFileSystemSetDispatcherResult(FileSystem, DispatcherResult);
 }
 
 static DWORD WINAPI FspFileSystemPoolDispatcherWorker(PVOID Param)
 {
+    NTSTATUS DispatcherResult;
     FSP_DISPATCHER_WORK_ITEM *WorkItem = Param;
     FSP_FSCTL_TRANSACT_REQ *Request = (PVOID)WorkItem->RequestBuf;
 
-    WorkItem->FileSystem->Operations[Request->Kind](WorkItem->FileSystem, Request);
+    DispatcherResult = WorkItem->FileSystem->Operations[Request->Kind](WorkItem->FileSystem, Request);
     MemFree(WorkItem);
 
+    FspFileSystemSetDispatcherResult(WorkItem->FileSystem, DispatcherResult);
+
     return 0;
 }
 
-FSP_API NTSTATUS FspFileSystemPoolDispatcher(FSP_FILE_SYSTEM *FileSystem,
+FSP_API VOID FspFileSystemPoolDispatcher(FSP_FILE_SYSTEM *FileSystem,
     FSP_FSCTL_TRANSACT_REQ *Request)
 {
+    NTSTATUS DispatcherResult;
+
     if (FspFsctlTransactKindCount <= Request->Kind || 0 == FileSystem->Operations[Request->Kind])
-        return FspSendResponseWithStatus(FileSystem, Request, STATUS_INVALID_DEVICE_REQUEST);
-
-    FSP_DISPATCHER_WORK_ITEM *WorkItem = MemAlloc(sizeof *WorkItem + Request->Size);
-    if (0 == WorkItem)
-        return STATUS_INSUFFICIENT_RESOURCES;
-
-    WorkItem->FileSystem = FileSystem;
-    memcpy(WorkItem->RequestBuf, Request, Request->Size);
-
-    BOOLEAN Success = QueueUserWorkItem(
-        FspFileSystemPoolDispatcherWorker, WorkItem, WT_EXECUTEDEFAULT);
-    if (!Success)
+        DispatcherResult = FspSendResponseWithStatus(FileSystem, Request, STATUS_INVALID_DEVICE_REQUEST);
+    else
     {
-        NTSTATUS Result0 = FspNtStatusFromWin32(GetLastError());
-        MemFree(WorkItem);
-        return Result0;
+        FSP_DISPATCHER_WORK_ITEM *WorkItem = MemAlloc(sizeof *WorkItem + Request->Size);
+        if (0 == WorkItem)
+            DispatcherResult = STATUS_INSUFFICIENT_RESOURCES;
+        else
+        {
+            WorkItem->FileSystem = FileSystem;
+            memcpy(WorkItem->RequestBuf, Request, Request->Size);
+
+            if (QueueUserWorkItem(FspFileSystemPoolDispatcherWorker, WorkItem, WT_EXECUTEDEFAULT))
+                DispatcherResult = STATUS_SUCCESS;
+            else
+            {
+                DispatcherResult = FspNtStatusFromWin32(GetLastError());
+                MemFree(WorkItem);
+            }
+        }
     }
 
-    return STATUS_SUCCESS;
+    FspFileSystemSetDispatcherResult(FileSystem, DispatcherResult);
 }
 
 FSP_API NTSTATUS FspSendResponse(FSP_FILE_SYSTEM *FileSystem,