diff --git a/src/sys/callbacks.c b/src/sys/callbacks.c
index 9f486f56..1ad363a4 100644
--- a/src/sys/callbacks.c
+++ b/src/sys/callbacks.c
@@ -131,12 +131,23 @@ NTSTATUS FspAcquireForCcFlush(
 
     FSP_FILE_NODE *FileNode = FileObject->FsContext;
     PIRP TopLevelIrp = IoGetTopLevelIrp();
+    ULONG TopFlags;
 
     ASSERT(0 == TopLevelIrp ||
         (PIRP)FSRTL_MAX_TOP_LEVEL_IRP_FLAG < TopLevelIrp);
-    FspFileNodeAcquireExclusive(FileNode, Full);
     if (0 == TopLevelIrp)
+    {
+        FspFileNodeAcquireExclusive(FileNode, Full);
         IoSetTopLevelIrp((PIRP)FSRTL_CACHE_TOP_LEVEL_IRP);
+    }
+    else
+    {
+        TopFlags = FspIrpTopFlags(TopLevelIrp);
+        FspIrpSetTopFlags(TopLevelIrp, FspIrpFlags(TopLevelIrp));
+        FspFileNodeAcquireExclusive(FileNode, Full);
+        ASSERT(0 == FileNode->Tls.TopFlags);
+        FileNode->Tls.TopFlags = TopFlags;
+    }
 
     FSP_LEAVE("FileObject=%p", FileObject);
 }
@@ -149,12 +160,22 @@ NTSTATUS FspReleaseForCcFlush(
 
     FSP_FILE_NODE *FileNode = FileObject->FsContext;
     PIRP TopLevelIrp = IoGetTopLevelIrp();
+    ULONG TopFlags;
 
     ASSERT((PIRP)FSRTL_CACHE_TOP_LEVEL_IRP == TopLevelIrp ||
         (PIRP)FSRTL_MAX_TOP_LEVEL_IRP_FLAG < TopLevelIrp);
     if ((PIRP)FSRTL_CACHE_TOP_LEVEL_IRP == TopLevelIrp)
+    {
         IoSetTopLevelIrp(0);
-    FspFileNodeRelease(FileNode, Full);
+        FspFileNodeRelease(FileNode, Full);
+    }
+    else
+    {
+        TopFlags = FileNode->Tls.TopFlags;
+        FileNode->Tls.TopFlags = 0;
+        FspFileNodeRelease(FileNode, Full);
+        FspIrpSetTopFlags(TopLevelIrp, TopFlags);
+    }
 
     FSP_LEAVE("FileObject=%p", FileObject);
 }
@@ -175,7 +196,8 @@ BOOLEAN FspAcquireForLazyWrite(
     Result = FspFileNodeTryAcquireExclusiveF(FileNode, FspFileNodeAcquireFull, Wait);
     if (Result)
     {
-        FileNode->LazyWriteThread = PsGetCurrentThread();
+        ASSERT(0 == FileNode->Tls.LazyWriteThread);
+        FileNode->Tls.LazyWriteThread = PsGetCurrentThread();
         IoSetTopLevelIrp((PIRP)FSRTL_CACHE_TOP_LEVEL_IRP);
     }
 
@@ -194,8 +216,9 @@ VOID FspReleaseFromLazyWrite(
     FSP_FILE_NODE *FileNode = Context;
 
     ASSERT((PIRP)FSRTL_CACHE_TOP_LEVEL_IRP == IoGetTopLevelIrp());
+    ASSERT(PsGetCurrentThread() == FileNode->Tls.LazyWriteThread);
     IoSetTopLevelIrp(0);
-    FileNode->LazyWriteThread = 0;
+    FileNode->Tls.LazyWriteThread = 0;
     FspFileNodeRelease(FileNode, Full);
 
     FSP_LEAVE_VOID("Context=%p", Context);
diff --git a/src/sys/driver.h b/src/sys/driver.h
index 171da557..37aae1e1 100644
--- a/src/sys/driver.h
+++ b/src/sys/driver.h
@@ -793,7 +793,11 @@ typedef struct
     UINT64 Security;
     ULONG SecurityChangeNumber;
     BOOLEAN TruncateOnClose;
-    PVOID LazyWriteThread;
+    union
+    {
+        PVOID LazyWriteThread;
+        UINT32 TopFlags;
+    } Tls;
     /* read-only after creation (and insertion in the ContextTable) */
     PDEVICE_OBJECT FsvolDeviceObject;
     UINT64 UserContext;
diff --git a/src/sys/file.c b/src/sys/file.c
index 77b3e0e0..5709c5a6 100644
--- a/src/sys/file.c
+++ b/src/sys/file.c
@@ -64,15 +64,19 @@ VOID FspFileDescDelete(FSP_FILE_DESC *FileDesc);
 #define FSP_FILE_NODE_GET_FLAGS()       \
     PIRP Irp = IoGetTopLevelIrp();      \
     BOOLEAN IrpValid = (PIRP)FSRTL_MAX_TOP_LEVEL_IRP_FLAG < Irp &&\
-        IO_TYPE_IRP == Irp->Type;\
+        IO_TYPE_IRP == Irp->Type;       \
     if (IrpValid)                       \
-        Flags &= ~FspIrpTopFlags(Irp);
+        Flags &= ~FspIrpTopFlags(Irp)
+#define FSP_FILE_NODE_ASSERT_FLAGS_CLR()\
+    ASSERT(IrpValid ? (0 == (FspIrpFlags(Irp) & Flags)) : TRUE)
+#define FSP_FILE_NODE_ASSERT_FLAGS_SET()\
+    ASSERT(IrpValid ? (Flags == (FspIrpFlags(Irp) & Flags)) : TRUE)
 #define FSP_FILE_NODE_SET_FLAGS()       \
     if (IrpValid)                       \
-        FspIrpSetFlags(Irp, FspIrpFlags(Irp) | Flags);
+        FspIrpSetFlags(Irp, FspIrpFlags(Irp) | Flags)
 #define FSP_FILE_NODE_CLR_FLAGS()       \
     if (IrpValid)                       \
-        FspIrpSetFlags(Irp, FspIrpFlags(Irp) & (~Flags & 3));
+        FspIrpSetFlags(Irp, FspIrpFlags(Irp) & (~Flags & 3))
 
 NTSTATUS FspFileNodeCreate(PDEVICE_OBJECT DeviceObject,
     ULONG ExtraSize, FSP_FILE_NODE **PFileNode)
@@ -145,6 +149,7 @@ VOID FspFileNodeAcquireSharedF(FSP_FILE_NODE *FileNode, ULONG Flags)
     PAGED_CODE();
 
     FSP_FILE_NODE_GET_FLAGS();
+    FSP_FILE_NODE_ASSERT_FLAGS_CLR();
 
     if (Flags & FspFileNodeAcquireMain)
         ExAcquireResourceSharedLite(FileNode->Header.Resource, TRUE);
@@ -160,6 +165,7 @@ BOOLEAN FspFileNodeTryAcquireSharedF(FSP_FILE_NODE *FileNode, ULONG Flags, BOOLE
     PAGED_CODE();
 
     FSP_FILE_NODE_GET_FLAGS();
+    FSP_FILE_NODE_ASSERT_FLAGS_CLR();
 
     BOOLEAN Result = TRUE;
 
@@ -192,6 +198,7 @@ VOID FspFileNodeAcquireExclusiveF(FSP_FILE_NODE *FileNode, ULONG Flags)
     PAGED_CODE();
 
     FSP_FILE_NODE_GET_FLAGS();
+    FSP_FILE_NODE_ASSERT_FLAGS_CLR();
 
     if (Flags & FspFileNodeAcquireMain)
         ExAcquireResourceExclusiveLite(FileNode->Header.Resource, TRUE);
@@ -207,6 +214,7 @@ BOOLEAN FspFileNodeTryAcquireExclusiveF(FSP_FILE_NODE *FileNode, ULONG Flags, BO
     PAGED_CODE();
 
     FSP_FILE_NODE_GET_FLAGS();
+    FSP_FILE_NODE_ASSERT_FLAGS_CLR();
 
     BOOLEAN Result = TRUE;
 
@@ -254,6 +262,7 @@ VOID FspFileNodeReleaseF(FSP_FILE_NODE *FileNode, ULONG Flags)
     PAGED_CODE();
 
     FSP_FILE_NODE_GET_FLAGS();
+    FSP_FILE_NODE_ASSERT_FLAGS_SET();
 
     if (Flags & FspFileNodeAcquirePgio)
         ExReleaseResourceLite(FileNode->Header.PagingIoResource);
@@ -269,6 +278,7 @@ VOID FspFileNodeReleaseOwnerF(FSP_FILE_NODE *FileNode, ULONG Flags, PVOID Owner)
     PAGED_CODE();
 
     FSP_FILE_NODE_GET_FLAGS();
+    FSP_FILE_NODE_ASSERT_FLAGS_SET();
 
     Owner = (PVOID)((UINT_PTR)Owner | 3);
 
diff --git a/src/sys/write.c b/src/sys/write.c
index aa88e6bb..1a7eb7f2 100644
--- a/src/sys/write.c
+++ b/src/sys/write.c
@@ -285,7 +285,7 @@ static NTSTATUS FspFsvolWriteNonCached(
 
     /* if we are called by the lazy writer we must constrain writes */
     if (FlagOn(FspIrpTopFlags(Irp), FspFileNodeAcquireMain) &&  /* if TopLevelIrp has acquired Main */
-        FileNode->LazyWriteThread == PsGetCurrentThread())      /* and this is a lazy writer thread */
+        FileNode->Tls.LazyWriteThread == PsGetCurrentThread())  /* and this is a lazy writer thread */
     {
         ASSERT(PagingIo);
         ASSERT(FspTimeoutInfinity32 ==