diff --git a/src/sys/cleanup.c b/src/sys/cleanup.c
index 48c27882..694bec47 100644
--- a/src/sys/cleanup.c
+++ b/src/sys/cleanup.c
@@ -94,7 +94,11 @@ static NTSTATUS FspFsvolCleanup(
      * from our perspective, because they mean that the file system is going
      * away and should correctly tear things down.
      */
-    return STATUS_PENDING;
+
+    if (FspIoqPostIrpNoCap(FsvolDeviceExtension->Ioq, Irp, 0))
+        return STATUS_PENDING;
+    else
+        return STATUS_SUCCESS;
 }
 
 VOID FspFsvolCleanupComplete(
diff --git a/src/sys/close.c b/src/sys/close.c
index eed7ab56..b10bb5d2 100644
--- a/src/sys/close.c
+++ b/src/sys/close.c
@@ -62,7 +62,7 @@ static NTSTATUS FspFsvolClose(
     FspFileContextRelease(FsContext);
 
     /* create the user-mode file system request; MustSucceed because IRP_MJ_CLOSE cannot fail */
-    FspIopCreateRequestMustSucceed(Irp, FileNameRequired ? &FsContext->FileName : 0, 0, &Request);
+    FspIopCreateRequestMustSucceed(0, FileNameRequired ? &FsContext->FileName : 0, 0, &Request);
 
     /* populate the Close request */
     Request->Kind = FspFsctlTransactCloseKind;
@@ -70,10 +70,10 @@ static NTSTATUS FspFsvolClose(
     Request->Req.Close.UserContext2 = UserContext2;
 
     /*
-     * Post as a MustSucceed work request. This allows us to complete our own IRP
+     * Post as a BestEffort work request. This allows us to complete our own IRP
      * and return immediately.
      */
-    FspIopPostWorkRequestMustSucceed(FsvolDeviceObject, Request);
+    FspIopPostWorkRequestBestEffort(FsvolDeviceObject, Request);
 
     /*
      * Note that it is still possible for this request to not be delivered,
diff --git a/src/sys/driver.h b/src/sys/driver.h
index 89ab6e3b..0ecb5a7e 100644
--- a/src/sys/driver.h
+++ b/src/sys/driver.h
@@ -377,6 +377,8 @@ PIRP FspIoqEndProcessingIrp(FSP_IOQ *Ioq, UINT_PTR IrpHint);
 /* I/O processing */
 #define FSP_FSCTL_WORK                  \
     CTL_CODE(FILE_DEVICE_FILE_SYSTEM, 0x800 + 'W', METHOD_NEITHER, FILE_ANY_ACCESS)
+#define FSP_FSCTL_WORK_BEST_EFFORT      \
+    CTL_CODE(FILE_DEVICE_FILE_SYSTEM, 0x800 + 'w', METHOD_NEITHER, FILE_ANY_ACCESS)
 #define FspIopCreateRequest(I, F, E, P) \
     FspIopCreateRequestFunnel(I, F, E, 0, FALSE, P)
 #define FspIopCreateRequestMustSucceed(I, F, E, P)\
@@ -386,7 +388,7 @@ PIRP FspIoqEndProcessingIrp(FSP_IOQ *Ioq, UINT_PTR IrpHint);
 #define FspIopRequestContext(Request, I)\
     (*FspIopRequestContextAddress(Request, I))
 #define FspIopPostWorkRequest(D, R)     FspIopPostWorkRequestFunnel(D, R, FALSE)
-#define FspIopPostWorkRequestMustSucceed(D, R)\
+#define FspIopPostWorkRequestBestEffort(D, R)\
     FspIopPostWorkRequestFunnel(D, R, TRUE)
 #define FspIopCompleteIrp(I, R)         FspIopCompleteIrpEx(I, R, TRUE)
 typedef VOID FSP_IOP_REQUEST_FINI(PVOID Context[3]);
@@ -397,7 +399,7 @@ NTSTATUS FspIopCreateRequestFunnel(
 VOID FspIopDeleteRequest(FSP_FSCTL_TRANSACT_REQ *Request);
 PVOID *FspIopRequestContextAddress(FSP_FSCTL_TRANSACT_REQ *Request, ULONG I);
 NTSTATUS FspIopPostWorkRequestFunnel(PDEVICE_OBJECT DeviceObject,
-    FSP_FSCTL_TRANSACT_REQ *Request, BOOLEAN AllocateIrpMustSucceed);
+    FSP_FSCTL_TRANSACT_REQ *Request, BOOLEAN BestEffort);
 VOID FspIopCompleteIrpEx(PIRP Irp, NTSTATUS Result, BOOLEAN DeviceRelease);
 VOID FspIopCompleteCanceledIrp(PIRP Irp);
 NTSTATUS FspIopDispatchPrepare(PIRP Irp, FSP_FSCTL_TRANSACT_REQ *Request);
diff --git a/src/sys/fsctl.c b/src/sys/fsctl.c
index b785caae..d9c57c8b 100644
--- a/src/sys/fsctl.c
+++ b/src/sys/fsctl.c
@@ -61,6 +61,7 @@ static NTSTATUS FspFsvolFileSystemControl(
         switch (IrpSp->Parameters.FileSystemControl.FsControlCode)
         {
         case FSP_FSCTL_WORK:
+        case FSP_FSCTL_WORK_BEST_EFFORT:
             Result = FspVolumeWork(DeviceObject, Irp, IrpSp);
             break;
         }
diff --git a/src/sys/volume.c b/src/sys/volume.c
index 2e2c4230..e4cb25a0 100644
--- a/src/sys/volume.c
+++ b/src/sys/volume.c
@@ -606,7 +606,9 @@ NTSTATUS FspVolumeWork(
 
     ASSERT(IRP_MJ_FILE_SYSTEM_CONTROL == IrpSp->MajorFunction);
     ASSERT(IRP_MN_USER_FS_REQUEST == IrpSp->MinorFunction);
-    ASSERT(FSP_FSCTL_TRANSACT == IrpSp->Parameters.FileSystemControl.FsControlCode);
+    ASSERT(
+        FSP_FSCTL_WORK == IrpSp->Parameters.FileSystemControl.FsControlCode ||
+        FSP_FSCTL_WORK_BEST_EFFORT == IrpSp->Parameters.FileSystemControl.FsControlCode);
 
     if (KernelMode != Irp->RequestorMode)
         return STATUS_INVALID_DEVICE_REQUEST;
@@ -614,6 +616,7 @@ NTSTATUS FspVolumeWork(
     NTSTATUS Result;
     FSP_FSVOL_DEVICE_EXTENSION *FsvolDeviceExtension = FspFsvolDeviceExtension(FsvolDeviceObject);
     FSP_FSCTL_TRANSACT_REQ *Request = IrpSp->Parameters.FileSystemControl.Type3InputBuffer;
+    BOOLEAN BestEffort = FSP_FSCTL_WORK_BEST_EFFORT == IrpSp->Parameters.FileSystemControl.FsControlCode;
 
     ASSERT(0 == Request->Hint);
 
@@ -622,11 +625,11 @@ NTSTATUS FspVolumeWork(
     FspIrpRequest(Irp) = Request;
 
     /*
-     * Post the IRP to our Ioq; we do this here instead of at IRP_LEAVE_MJ time,
+     * Post the IRP to our Ioq; we do this here instead of at FSP_LEAVE_MJ time,
      * so that we can disassociate the Request on failure and release ownership
      * back to the caller.
      */
-    if (!FspIoqPostIrp(FsvolDeviceExtension->Ioq, Irp, &Result))
+    if (!FspIoqPostIrpEx(FsvolDeviceExtension->Ioq, Irp, !BestEffort, &Result))
     {
         Request->Hint = 0;
         FspIrpRequest(Irp) = 0;