sys: FspVolumeTransact: upper bound on loop guarantees forward progress!

src/sys/driver.h

@@ -571,7 +571,7 @@ typedef struct
     LIST_ENTRY PendingIrpList, ProcessIrpList, RetriedIrpList;
     IO_CSQ PendingIoCsq, ProcessIoCsq, RetriedIoCsq;
     ULONG IrpTimeout;
-    ULONG PendingIrpCapacity, PendingIrpCount;
+    ULONG PendingIrpCapacity, PendingIrpCount, ProcessIrpCount, RetriedIrpCount;
     VOID (*CompleteCanceledIrp)(PIRP Irp);
     ULONG ProcessIrpBucketCount;
     PVOID ProcessIrpBuckets[];
@@ -586,10 +586,13 @@ VOID FspIoqRemoveExpired(FSP_IOQ *Ioq, UINT64 InterruptTime);
 BOOLEAN FspIoqPostIrpEx(FSP_IOQ *Ioq, PIRP Irp, BOOLEAN BestEffort, NTSTATUS *PResult);
 PIRP FspIoqNextPendingIrp(FSP_IOQ *Ioq, PIRP BoundaryIrp, PLARGE_INTEGER Timeout,
     PIRP CancellableIrp);
+ULONG FspIoqPendingIrpCount(FSP_IOQ *Ioq);
 BOOLEAN FspIoqStartProcessingIrp(FSP_IOQ *Ioq, PIRP Irp);
 PIRP FspIoqEndProcessingIrp(FSP_IOQ *Ioq, UINT_PTR IrpHint);
+ULONG FspIoqProcessIrpCount(FSP_IOQ *Ioq);
 BOOLEAN FspIoqRetryCompleteIrp(FSP_IOQ *Ioq, PIRP Irp, NTSTATUS *PResult);
 PIRP FspIoqNextCompleteIrp(FSP_IOQ *Ioq, PIRP BoundaryIrp);
+ULONG FspIoqRetriedIrpCount(FSP_IOQ *Ioq);
 
 /* meta cache */
 typedef struct

src/sys/ioq.c

@@ -270,6 +270,7 @@ static NTSTATUS FspIoqProcessInsertIrpEx(PIO_CSQ IoCsq, PIRP Irp, PVOID InsertCo
     FSP_IOQ *Ioq = CONTAINING_RECORD(IoCsq, FSP_IOQ, ProcessIoCsq);
     if (Ioq->Stopped)
         return STATUS_CANCELLED;
+    Ioq->ProcessIrpCount++;
     InsertTailList(&Ioq->ProcessIrpList, &Irp->Tail.Overlay.ListEntry);
     ULONG Index = FspHashMixPointer(Irp) % Ioq->ProcessIrpBucketCount;
 #if DBG
@@ -296,6 +297,7 @@ static VOID FspIoqProcessRemoveIrp(PIO_CSQ IoCsq, PIRP Irp)
             break;
         }
     }
+    Ioq->ProcessIrpCount--;
     RemoveEntryList(&Irp->Tail.Overlay.ListEntry);
 }
 
@@ -360,12 +362,15 @@ static NTSTATUS FspIoqRetriedInsertIrpEx(PIO_CSQ IoCsq, PIRP Irp, PVOID InsertCo
     FSP_IOQ *Ioq = CONTAINING_RECORD(IoCsq, FSP_IOQ, RetriedIoCsq);
     if (Ioq->Stopped)
         return STATUS_CANCELLED;
+    Ioq->RetriedIrpCount++;
     InsertTailList(&Ioq->RetriedIrpList, &Irp->Tail.Overlay.ListEntry);
     return STATUS_SUCCESS;
 }
 
 static VOID FspIoqRetriedRemoveIrp(PIO_CSQ IoCsq, PIRP Irp)
 {
+    FSP_IOQ *Ioq = CONTAINING_RECORD(IoCsq, FSP_IOQ, RetriedIoCsq);
+    Ioq->RetriedIrpCount--;
     RemoveEntryList(&Irp->Tail.Overlay.ListEntry);
 }
 
@@ -583,6 +588,16 @@ PIRP FspIoqNextPendingIrp(FSP_IOQ *Ioq, PIRP BoundaryIrp, PLARGE_INTEGER Timeout
     return PendingIrp;
 }
 
+ULONG FspIoqPendingIrpCount(FSP_IOQ *Ioq)
+{
+    ULONG Result;
+    KIRQL Irql;
+    KeAcquireSpinLock(&Ioq->SpinLock, &Irql);
+    Result = Ioq->PendingIrpCount;
+    KeReleaseSpinLock(&Ioq->SpinLock, Irql);
+    return Result;
+}
+
 BOOLEAN FspIoqStartProcessingIrp(FSP_IOQ *Ioq, PIRP Irp)
 {
     NTSTATUS Result;
@@ -606,6 +621,16 @@ PIRP FspIoqEndProcessingIrp(FSP_IOQ *Ioq, UINT_PTR IrpHint)
     return FspCsqRemoveNextIrp(&Ioq->ProcessIoCsq, &PeekContext);
 }
 
+ULONG FspIoqProcessIrpCount(FSP_IOQ *Ioq)
+{
+    ULONG Result;
+    KIRQL Irql;
+    KeAcquireSpinLock(&Ioq->SpinLock, &Irql);
+    Result = Ioq->ProcessIrpCount;
+    KeReleaseSpinLock(&Ioq->SpinLock, Irql);
+    return Result;
+}
+
 BOOLEAN FspIoqRetryCompleteIrp(FSP_IOQ *Ioq, PIRP Irp, NTSTATUS *PResult)
 {
     NTSTATUS Result;
@@ -637,3 +662,13 @@ PIRP FspIoqNextCompleteIrp(FSP_IOQ *Ioq, PIRP BoundaryIrp)
     PeekContext.ExpirationTime = 0;
     return FspCsqRemoveNextIrp(&Ioq->RetriedIoCsq, &PeekContext);
 }
+
+ULONG FspIoqRetriedIrpCount(FSP_IOQ *Ioq)
+{
+    ULONG Result;
+    KIRQL Irql;
+    KeAcquireSpinLock(&Ioq->SpinLock, &Irql);
+    Result = Ioq->RetriedIrpCount;
+    KeReleaseSpinLock(&Ioq->SpinLock, Irql);
+    return Result;
+}

src/sys/volume.c

@@ -546,6 +546,7 @@ NTSTATUS FspVolumeTransact(
     FSP_FSCTL_TRANSACT_RSP *Response, *NextResponse;
     FSP_FSCTL_TRANSACT_REQ *Request, *PendingIrpRequest;
     PIRP ProcessIrp, PendingIrp, RetriedIrp, RepostedIrp;
+    ULONG LoopCount;
     LARGE_INTEGER Timeout;
     PIRP TopLevelIrp = IoGetTopLevelIrp();
 
@@ -587,7 +588,8 @@ NTSTATUS FspVolumeTransact(
     }
 
     /* process any retried IRP's */
-    for (;;)
+    LoopCount = FspIoqRetriedIrpCount(FsvolDeviceExtension->Ioq);
+    while (0 < LoopCount--) /* upper bound on loop guarantees forward progress! */
     {
         /* get the next retried IRP, but do not go beyond the first reposted IRP! */
         RetriedIrp = FspIoqNextCompleteIrp(FsvolDeviceExtension->Ioq, RepostedIrp);
@@ -656,6 +658,7 @@ NTSTATUS FspVolumeTransact(
     Request = OutputBuffer;
     BufferEnd = (PUINT8)OutputBuffer + OutputBufferLength;
     ASSERT(FspFsctlTransactCanProduceRequest(Request, BufferEnd));
+    LoopCount = FspIoqPendingIrpCount(FsvolDeviceExtension->Ioq);
     for (;;)
     {
         PendingIrpRequest = FspIrpRequest(PendingIrp);
@@ -701,6 +704,9 @@ NTSTATUS FspVolumeTransact(
                 break;
         }
         
+        if (0 >= LoopCount--) /* upper bound on loop guarantees forward progress! */
+            break;
+
         /* get the next pending IRP, but do not go beyond the first reposted IRP! */
         PendingIrp = FspIoqNextPendingIrp(FsvolDeviceExtension->Ioq, RepostedIrp, 0, Irp);
         if (0 == PendingIrp)