retry.c

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/*++
 
Copyright (C) Microsoft Corporation, 1991 - 2010
 
Module Name:
 
    retry.c
 
Abstract:
 
    Packet retry routines for CLASSPNP
 
Environment:
 
    kernel mode only
 
Notes:
 
 
Revision History:
 
--*/
 
#include "classp.h"
#include "debug.h"
 
#ifdef DEBUG_USE_WPP
#include "retry.tmh"
#endif
 
 
/*
 *  InterpretTransferPacketError
 *
 *      Interpret the SRB error into a meaningful IRP status.
 *      ClassInterpretSenseInfo also may modify the SRB for the retry.
 *
 *      Return TRUE iff packet should be retried.
 */
BOOLEAN InterpretTransferPacketError(PTRANSFER_PACKET Pkt)
{
    PFUNCTIONAL_DEVICE_EXTENSION fdoExtension = Pkt->Fdo->DeviceExtension;
    PCLASS_PRIVATE_FDO_DATA fdoData = fdoExtension->PrivateFdoData;
    ULONG timesAlreadyRetried;
    BOOLEAN shouldRetry = FALSE;
    PCDB pCdb = ClasspTransferPacketGetCdb(Pkt);
 
    /*
     *  Interpret the error using the returned sense info first.
     */
    Pkt->RetryIn100nsUnits = 0;
 
 
    /*
     *  Pre-calculate the number of times the IO has already been
     *  retried, so that all InterpretSenseInfo routines get the right value.
     */
    if (ClasspTransferPacketGetNumberOfRetriesDone(Pkt, pCdb, &timesAlreadyRetried) == FALSE)
    {
        TracePrint((TRACE_LEVEL_ERROR, TRACE_FLAG_GENERAL, "Unhandled SRB Function %xh in error path for packet %p (did miniport change Srb.Cdb.OperationCode ?)", (ULONG)pCdb->CDB10.OperationCode, Pkt));
    }
 
    if (fdoData->InterpretSenseInfo != NULL) {
 
        SCSI_REQUEST_BLOCK tempSrb = { 0 };
        PSCSI_REQUEST_BLOCK srbPtr = (PSCSI_REQUEST_BLOCK)Pkt->Srb;
 
        // SAL annotation and ClassInitializeEx() both validate this
        NT_ASSERT(fdoData->InterpretSenseInfo->Interpret != NULL);
 
        //
        // If class driver does not support extended SRB and this is
        // an extended SRB, convert to legacy SRB and pass to class
        // driver.
        //
        if ((Pkt->Srb->Function == SRB_FUNCTION_STORAGE_REQUEST_BLOCK) &&
            ((fdoExtension->CommonExtension.DriverExtension->SrbSupport &
            CLASS_SRB_STORAGE_REQUEST_BLOCK) == 0)) {
            ClasspConvertToScsiRequestBlock(&tempSrb, (PSTORAGE_REQUEST_BLOCK)Pkt->Srb);
            srbPtr = &tempSrb;
        }
 
        shouldRetry = fdoData->InterpretSenseInfo->Interpret(Pkt->Fdo,
                                                             Pkt->OriginalIrp,
                                                             srbPtr,
                                                             IRP_MJ_SCSI,
                                                             0,
                                                             timesAlreadyRetried,
                                                             Pkt->RetryHistory,
                                                             &Pkt->Irp->IoStatus.Status,
                                                             &Pkt->RetryIn100nsUnits);
 
 
    } else {
 
        //
        // In this case, fdoData->InterpretSenseInfo == NULL so we must do our
        // own error code and sense info processing.
        //
 
        PVOID senseInfoBuffer = ClasspTransferPacketGetSenseInfoBuffer(Pkt);
        UCHAR senseInfoBufferLength = ClasspTransferPacketGetSenseInfoBufferLength(Pkt);
        BOOLEAN validSense = FALSE;
        UCHAR senseKey = 0;
        UCHAR additionalSenseCode = 0;
        UCHAR additionalSenseQual = 0;
 
        NT_ASSERT(senseInfoBuffer);
 
        validSense = ScsiGetSenseKeyAndCodes(senseInfoBuffer,
                                             senseInfoBufferLength,
                                             SCSI_SENSE_OPTIONS_FIXED_FORMAT_IF_UNKNOWN_FORMAT_INDICATED,
                                             &senseKey,
                                             &additionalSenseCode,
                                             &additionalSenseQual);
 
        if (pCdb->MEDIA_REMOVAL.OperationCode == SCSIOP_MEDIUM_REMOVAL) {
 
            ULONG retryIntervalSeconds = 0;
            /*
             *  This is an Ejection Control SRB.  Interpret its sense info specially.
             */
            shouldRetry = ClassInterpretSenseInfo(
                Pkt->Fdo,
                (PSCSI_REQUEST_BLOCK)Pkt->Srb,
                IRP_MJ_SCSI,
                0,
                timesAlreadyRetried,
                &Pkt->Irp->IoStatus.Status,
                &retryIntervalSeconds);
 
            if (shouldRetry) {
                /*
                 *  If the device is not ready, wait at least 2 seconds before retrying.
                 */
                BOOLEAN setRetryIntervalSeconds = FALSE;
 
                if (validSense) {
 
                    if ((Pkt->Irp->IoStatus.Status == STATUS_DEVICE_NOT_READY) &&
                        (additionalSenseCode == SCSI_ADSENSE_LUN_NOT_READY)) {
                        setRetryIntervalSeconds = TRUE;
                    }
                }
 
                if (!setRetryIntervalSeconds && (SRB_STATUS(Pkt->Srb->SrbStatus) == SRB_STATUS_SELECTION_TIMEOUT)) {
                    setRetryIntervalSeconds = TRUE;
                }
 
                if (setRetryIntervalSeconds) {
                    retryIntervalSeconds = MAX(retryIntervalSeconds, 2);
                }
            }
 
            if (shouldRetry)
            {
                Pkt->RetryIn100nsUnits = retryIntervalSeconds;
                Pkt->RetryIn100nsUnits *= 1000 * 1000 * 10;
            }
 
        }
        else if ((pCdb->MODE_SENSE.OperationCode == SCSIOP_MODE_SENSE) ||
                 (pCdb->MODE_SENSE.OperationCode == SCSIOP_MODE_SENSE10)) {
 
            ULONG retryIntervalSeconds = 0;
            /*
             *  This is an Mode Sense SRB.  Interpret its sense info specially.
             */
            shouldRetry = ClassInterpretSenseInfo(
                Pkt->Fdo,
                (PSCSI_REQUEST_BLOCK)Pkt->Srb,
                IRP_MJ_SCSI,
                0,
                timesAlreadyRetried,
                &Pkt->Irp->IoStatus.Status,
                &retryIntervalSeconds);
            if (shouldRetry) {
                /*
                 *  If the device is not ready, wait at least 2 seconds before retrying.
                 */
                BOOLEAN setRetryIntervalSeconds = FALSE;
 
                if (validSense) {
                    if ((Pkt->Irp->IoStatus.Status == STATUS_DEVICE_NOT_READY) &&
                        (additionalSenseCode == SCSI_ADSENSE_LUN_NOT_READY)) {
                        setRetryIntervalSeconds = TRUE;
                    }
                }
 
                if (!setRetryIntervalSeconds && (SRB_STATUS(Pkt->Srb->SrbStatus) == SRB_STATUS_SELECTION_TIMEOUT)) {
                    setRetryIntervalSeconds = TRUE;
                }
 
                if (setRetryIntervalSeconds) {
                    retryIntervalSeconds = MAX(retryIntervalSeconds, 2);
                }
            }
 
            /*
             *  Some special cases for mode sense.
             */
            if (Pkt->Irp->IoStatus.Status == STATUS_VERIFY_REQUIRED) {
                shouldRetry = TRUE;
            }
            else if (SRB_STATUS(Pkt->Srb->SrbStatus) == SRB_STATUS_DATA_OVERRUN) {
                /*
                 *  This is a HACK.
                 *  Atapi returns SRB_STATUS_DATA_OVERRUN when it really means
                 *  underrun (i.e. success, and the buffer is longer than needed).
                 *  So treat this as a success.
                 *  When the caller of this function sees that the status was changed to success,
                 *  it will add the transferred length to the original irp.
                 */
                Pkt->Irp->IoStatus.Status = STATUS_SUCCESS;
                shouldRetry = FALSE;
            }
 
            if (shouldRetry)
            {
                Pkt->RetryIn100nsUnits = retryIntervalSeconds;
                Pkt->RetryIn100nsUnits *= 1000 * 1000 * 10;
            }
 
        }
        else if ((pCdb->CDB10.OperationCode == SCSIOP_READ_CAPACITY) ||
                 (pCdb->CDB16.OperationCode == SCSIOP_READ_CAPACITY16)) {
 
            ULONG retryIntervalSeconds = 0;
 
            /*
             *  This is a Drive Capacity SRB.  Interpret its sense info specially.
             */
            shouldRetry = ClassInterpretSenseInfo(
                Pkt->Fdo,
                (PSCSI_REQUEST_BLOCK)Pkt->Srb,
                IRP_MJ_SCSI,
                0,
                timesAlreadyRetried,
                &Pkt->Irp->IoStatus.Status,
                &retryIntervalSeconds);
            if (Pkt->Irp->IoStatus.Status == STATUS_VERIFY_REQUIRED) {
                shouldRetry = TRUE;
            }
#if (NTDDI_VERSION >= NTDDI_WINBLUE)
            else if (ClasspSrbTimeOutStatus(Pkt->Srb)) {
 
                Pkt->TimedOut = TRUE;
 
                if (shouldRetry) {
                    //
                    // For requests that have timed-out we may only perform a limited
                    // number of retries.  This is typically less than the general
                    // number of retries allowed.
                    //
                    if (Pkt->NumIoTimeoutRetries == 0) {
                        shouldRetry = FALSE;
                    } else {
                        Pkt->NumIoTimeoutRetries--;
                        //
                        // We expect to be able to retry if there are some general retries remaining.
                        //
                    }
                }
            }
#endif
 
            if (shouldRetry)
            {
                Pkt->RetryIn100nsUnits = retryIntervalSeconds;
                Pkt->RetryIn100nsUnits *= 1000 * 1000 * 10;
            }
 
        }
        else if (IS_SCSIOP_READWRITE(pCdb->CDB10.OperationCode)) {
 
            ULONG retryIntervalSeconds = 0;
            /*
             *  This is a Read/Write Data packet.
             */
            PIO_STACK_LOCATION origCurrentSp = IoGetCurrentIrpStackLocation(Pkt->OriginalIrp);
 
            shouldRetry = ClassInterpretSenseInfo(Pkt->Fdo,
                                                  (PSCSI_REQUEST_BLOCK)Pkt->Srb,
                                                  origCurrentSp->MajorFunction,
                                                  0,
                                                  timesAlreadyRetried,
                                                  &Pkt->Irp->IoStatus.Status,
                                                  &retryIntervalSeconds);
 
            /*
             *  Deal with some special cases.
             */
            if (Pkt->Irp->IoStatus.Status == STATUS_INSUFFICIENT_RESOURCES) {
                /*
                 *  We are in extreme low-memory stress.
                 *  We will retry in smaller chunks.
                 */
                shouldRetry = TRUE;
            }
            else if (TEST_FLAG(origCurrentSp->Flags, SL_OVERRIDE_VERIFY_VOLUME) &&
                     (Pkt->Irp->IoStatus.Status == STATUS_VERIFY_REQUIRED)) {
                /*
                 *  We are still verifying a (possibly) reloaded disk/cdrom.
                 *  So retry the request.
                 */
                Pkt->Irp->IoStatus.Status = STATUS_IO_DEVICE_ERROR;
                shouldRetry = TRUE;
 
            }
#if (NTDDI_VERSION >= NTDDI_WINBLUE)
            else if (ClasspSrbTimeOutStatus(Pkt->Srb)) {
 
                Pkt->TimedOut = TRUE;
 
                if (shouldRetry) {
                    //
                    // For requests that have timed-out we may only perform a limited
                    // number of retries.  This is typically less than the general
                    // number of retries allowed.
                    //
                    if (Pkt->NumIoTimeoutRetries == 0) {
                        shouldRetry = FALSE;
                    } else {
                        Pkt->NumIoTimeoutRetries--;
                        //
                        // We expect to be able to retry if there are some general retries remaining.
                        //
                    }
                }
            }
#endif
 
            if (shouldRetry)
            {
                Pkt->RetryIn100nsUnits = retryIntervalSeconds;
                Pkt->RetryIn100nsUnits *= 1000 * 1000 * 10;
            }
 
        } else if (ClasspIsOffloadDataTransferCommand(pCdb)) {
 
            ULONG retryIntervalSeconds = 0;
 
            Pkt->TransferCount = 0;
 
            shouldRetry = ClassInterpretSenseInfo(
                Pkt->Fdo,
                (PSCSI_REQUEST_BLOCK)Pkt->Srb,
                IRP_MJ_SCSI,
                0,
                timesAlreadyRetried,
                &Pkt->Irp->IoStatus.Status,
                &retryIntervalSeconds);
 
            if (shouldRetry) {
 
                Pkt->RetryIn100nsUnits = retryIntervalSeconds;
                Pkt->RetryIn100nsUnits *= 1000 * 1000 * 10;
 
            } else {
 
                if (ClasspIsTokenOperation(pCdb)) {
 
                    BOOLEAN isInformationValid = FALSE;
                    ULONGLONG information = 0;
 
                    if (validSense) {
 
                        //
                        // If this is a data underrun condition (i.e. target truncated the offload data transfer),
                        // the SenseData's Information field may have the TransferCount.
                        //
                        if ((senseKey == SCSI_SENSE_COPY_ABORTED || senseKey == SCSI_SENSE_ABORTED_COMMAND) &&
                            (additionalSenseCode == SCSI_ADSENSE_COPY_TARGET_DEVICE_ERROR && additionalSenseQual == SCSI_SENSEQ_DATA_UNDERRUN)) {
 
                            //
                            // Sense data in Descriptor format
                            //
                            if (IsDescriptorSenseDataFormat(senseInfoBuffer)) {
 
                                PVOID startBuffer = NULL;
                                UCHAR startBufferLength = 0;
 
 
                                if (ScsiGetSenseDescriptor(senseInfoBuffer,
                                                            SrbGetSenseInfoBufferLength(Pkt->Srb),
                                                            &startBuffer,
                                                            &startBufferLength)) {
                                    UCHAR outType;
                                    PVOID outBuffer = NULL;
                                    UCHAR outBufferLength = 0;
 
                                    UCHAR typeList[1] = { SCSI_SENSE_DESCRIPTOR_TYPE_INFORMATION };
 
                                    if (ScsiGetNextSenseDescriptorByType(startBuffer,
                                        startBufferLength,
                                        typeList,
                                        ARRAYSIZE(typeList),
                                        &outType,
                                        &outBuffer,
                                        &outBufferLength)) {
 
                                        if (outType == SCSI_SENSE_DESCRIPTOR_TYPE_INFORMATION) {
 
                                            if (ScsiValidateInformationSenseDescriptor(outBuffer, outBufferLength)) {
                                                REVERSE_BYTES_QUAD(&information, &(((PSCSI_SENSE_DESCRIPTOR_INFORMATION)outBuffer)->Information));
                                                isInformationValid = TRUE;
                                            }
 
                                        } else {
 
                                            //
                                            // ScsiGetNextDescriptorByType should only return a type that is specified by us.
                                            //
                                            NT_ASSERT(FALSE);
                                        }
                                    }
                                }
                            } else {
 
                                //
                                // Sense data in Fixed format
                                //
                                REVERSE_BYTES(&information, &(((PFIXED_SENSE_DATA)senseInfoBuffer)->Information));
                                isInformationValid = TRUE;
                            }
 
                            if (isInformationValid) {
                                Pkt->TransferCount = information;
                            }
                        }
                    }
                }
            }
 
        }
        else {
            TracePrint((TRACE_LEVEL_ERROR, TRACE_FLAG_GENERAL, "Unhandled SRB Function %xh in error path for packet %p (did miniport change Srb.Cdb.OperationCode ?)", (ULONG)pCdb->CDB10.OperationCode, Pkt));
        }
    }
 
    return shouldRetry;
}
 
 
/*
 *  RetryTransferPacket
 *
 *      Retry sending a TRANSFER_PACKET.
 *
 *      Return TRUE iff the packet is complete.
 *          (if so the status in pkt->irp is the final status).
 */
BOOLEAN RetryTransferPacket(PTRANSFER_PACKET Pkt)
{
    BOOLEAN packetDone;
    BOOLEAN scaleDown = FALSE;
    PFUNCTIONAL_DEVICE_EXTENSION fdoExtension = (PFUNCTIONAL_DEVICE_EXTENSION)Pkt->Fdo->DeviceExtension;
    PCLASS_PRIVATE_FDO_DATA fdoData = fdoExtension->PrivateFdoData;
    PCDB pCdb = SrbGetCdb(Pkt->Srb);
 
#if !defined(__REACTOS__) && NTDDI_VERSION >= NTDDI_WINBLUE
    if(ClasspIsThinProvisioningError((PSCSI_REQUEST_BLOCK)Pkt->Srb) &&
        (pCdb != NULL) && IS_SCSIOP_READWRITE(pCdb->CDB10.OperationCode)) {
 
        if(Pkt->NumThinProvisioningRetries >= NUM_THIN_PROVISIONING_RETRIES) {
            //We've already retried this the maximum times.  Bail out.
            return TRUE;
        }
        Pkt->NumThinProvisioningRetries++;
    }
    else {
        NT_ASSERT(Pkt->NumRetries > 0 || Pkt->RetryHistory);
        Pkt->NumRetries--;
    }
#else
    NT_ASSERT(Pkt->NumRetries > 0 || Pkt->RetryHistory);
    Pkt->NumRetries--;
#endif
 
    TracePrint((TRACE_LEVEL_INFORMATION, TRACE_FLAG_GENERAL, "retrying failed transfer (pkt=%ph, op=%s)", Pkt, DBGGETSCSIOPSTR(Pkt->Srb)));
 
    if (!fdoData->DisableThrottling) {
 
        //
        // If this is the last retry, then turn off disconnect, sync transfer,
        // and tagged queuing.  On all other retries, leave the original settings.
        // Do not apply this for thin provisioning soft threshold errors, since
        // they should succeed as soon as they're retried on the right IT nexus.
        //
        if ((Pkt->NumRetries == 0) && !ClasspIsThinProvisioningError((PSCSI_REQUEST_BLOCK)Pkt->Srb)) {
            scaleDown = TRUE;
        }
 
#if (NTDDI_VERSION >= NTDDI_WINBLUE)
        //
        // If this request previously timed-out and there are no more retries left
        // for timed-out requests, then we should also apply the scale down.
        //
        if (Pkt->TimedOut && Pkt->NumIoTimeoutRetries == 0) {
            scaleDown = TRUE;
        }
#endif
    }
 
 
    if (scaleDown) {
        /*
         *  Tone down performance on the retry.
         *  This increases the chance for success on the retry.
         *  We've seen instances of drives that fail consistently but then start working
         *  once this scale-down is applied.
         */
        SrbSetSrbFlags(Pkt->Srb, SRB_FLAGS_DISABLE_DISCONNECT);
        SrbSetSrbFlags(Pkt->Srb, SRB_FLAGS_DISABLE_SYNCH_TRANSFER);
        SrbClearSrbFlags(Pkt->Srb, SRB_FLAGS_QUEUE_ACTION_ENABLE);
        SrbSetRequestTag(Pkt->Srb, SP_UNTAGGED);
    }
 
    if (Pkt->Irp->IoStatus.Status == STATUS_INSUFFICIENT_RESOURCES) {
 
        UCHAR cdbOpcode = 0;
        BOOLEAN isReadWrite = FALSE;
 
        if (pCdb) {
            cdbOpcode = pCdb->CDB10.OperationCode;
            isReadWrite = IS_SCSIOP_READWRITE(cdbOpcode);
        }
 
        if ((Pkt->DriverUsesStartIO) &&
            ( (cdbOpcode == SCSIOP_WRITE6 ) ||
              (cdbOpcode == SCSIOP_WRITE  ) ||
              (cdbOpcode == SCSIOP_WRITE12) ||
              (cdbOpcode == SCSIOP_WRITE16) )) {
 
            /* don't retry writes in super-low-memory conditions if the
             * driver must serialize against StartIO.  This is because
             * some write methods used in such drivers cannot accept
             * random-sized writes. (i.e CD-RW in packet writing mode)
             * Reads, however, are always safe to split up.
             */
            SET_FLAG(fdoData->TrackingFlags, TRACKING_FORWARD_PROGRESS_PATH1);
            packetDone = TRUE;
        }
        else if (Pkt->InLowMemRetry || !isReadWrite){
            /*
             *  This should never happen under normal circumstances.
             *  The memory manager guarantees that at least four pages will
             *  be available to allow forward progress in the port driver.
             *  So a one-page transfer should never fail with insufficient resources.
             *
             *  However, it is possible to get in here with virtual storage
             *  or thin provisioned storage for example.
             *  A single sector write can trigger an allocation request and
             *  presently a forward progress guarantee is not provided.
             *  VHD also may have some limitations in forward progress guarantee.
             *  And USB too might also fall into this category.
             */
            SET_FLAG(fdoData->TrackingFlags, TRACKING_FORWARD_PROGRESS_PATH2);
            packetDone = TRUE;
        }
        else {
            /*
             *  We are in low-memory stress.
             *  Start the low-memory retry state machine, which tries to
             *  resend the packet in little one-page chunks.
             */
            SET_FLAG(fdoData->TrackingFlags, TRACKING_FORWARD_PROGRESS_PATH3);
            InitLowMemRetry(Pkt,
                            Pkt->BufPtrCopy,
                            Pkt->BufLenCopy,
                            Pkt->TargetLocationCopy);
            StepLowMemRetry(Pkt);
            packetDone = FALSE;
        }
    }
    else {
        /*
         *  Retry the packet by simply resending it after a delay.
         *  Put the packet back in the pending queue and
         *  schedule a timer to retry the transfer.
         *
         *  Do not call SetupReadWriteTransferPacket again because:
         *  (1)  The minidriver may have set some bits
         *       in the SRB that it needs again and
         *  (2)  doing so would reset numRetries.
         *
         *  BECAUSE we do not call SetupReadWriteTransferPacket again,
         *  we have to reset a couple fields in the SRB that
         *  some miniports overwrite when they fail an SRB.
         */
 
        SrbSetDataBuffer(Pkt->Srb, Pkt->BufPtrCopy);
        SrbSetDataTransferLength(Pkt->Srb, Pkt->BufLenCopy);
 
        TransferPacketQueueRetryDpc(Pkt);
 
        packetDone = FALSE;
    }
 
    return packetDone;
}
 
 
VOID TransferPacketQueueRetryDpc(PTRANSFER_PACKET Pkt)
{
    KeInitializeDpc(&Pkt->RetryTimerDPC, TransferPacketRetryTimerDpc, Pkt);
 
    if (Pkt->RetryIn100nsUnits == 0){
        KeInsertQueueDpc(&Pkt->RetryTimerDPC, NULL, NULL);
    }
    else {
        LARGE_INTEGER timerPeriod;
 
        NT_ASSERT(Pkt->RetryIn100nsUnits < 100 * 1000 * 1000 * 10); // sanity check -- 100 seconds is normally too long
        timerPeriod.QuadPart = -(Pkt->RetryIn100nsUnits);
        KeInitializeTimer(&Pkt->RetryTimer);
        KeSetTimer(&Pkt->RetryTimer, timerPeriod, &Pkt->RetryTimerDPC);
    }
}
 
 
VOID
NTAPI /* ReactOS Change: GCC Does not support STDCALL by default */
TransferPacketRetryTimerDpc(   IN PKDPC Dpc,
                                    IN PVOID DeferredContext,
                                    IN PVOID SystemArgument1,
                                    IN PVOID SystemArgument2)
{
    PTRANSFER_PACKET pkt;
    PDEVICE_OBJECT fdo;
    PFUNCTIONAL_DEVICE_EXTENSION fdoExtension;
 
    _Analysis_assume_(DeferredContext != NULL);
 
    pkt = (PTRANSFER_PACKET)DeferredContext;
 
    fdo = pkt->Fdo;
    fdoExtension = fdo->DeviceExtension;
 
    UNREFERENCED_PARAMETER(Dpc);
    UNREFERENCED_PARAMETER(SystemArgument1);
    UNREFERENCED_PARAMETER(SystemArgument2);
 
 
    /*
     *  Sometimes the port driver can allocates a new 'sense' buffer
     *  to report transfer errors, e.g. when the default sense buffer
     *  is too small.  If so, it is up to us to free it.
     *  Now that we're done using the sense info, free it if appropriate.
     *  Then clear the sense buffer so it doesn't pollute future errors returned in this packet.
     */
    if (PORT_ALLOCATED_SENSE_EX(fdoExtension, pkt->Srb)) {
        TracePrint((TRACE_LEVEL_INFORMATION, TRACE_FLAG_RW, "Freeing port-allocated sense buffer for pkt %ph.", pkt));
        FREE_PORT_ALLOCATED_SENSE_BUFFER_EX(fdoExtension, pkt->Srb);
        SrbSetSenseInfoBuffer(pkt->Srb, &pkt->SrbErrorSenseData);
        SrbSetSenseInfoBufferLength(pkt->Srb, sizeof(pkt->SrbErrorSenseData));
    }
    else {
        NT_ASSERT(SrbGetSenseInfoBuffer(pkt->Srb) == &pkt->SrbErrorSenseData);
        NT_ASSERT(SrbGetSenseInfoBufferLength(pkt->Srb) <= sizeof(pkt->SrbErrorSenseData));
    }
 
    RtlZeroMemory(&pkt->SrbErrorSenseData, sizeof(pkt->SrbErrorSenseData));
 
    SubmitTransferPacket(pkt);
 
}
 
 
VOID InitLowMemRetry(PTRANSFER_PACKET Pkt, PVOID BufPtr, ULONG Len, LARGE_INTEGER TargetLocation)
{
    NT_ASSERT(Len > 0);
    NT_ASSERT(!Pkt->InLowMemRetry);
 
    if (Pkt->DriverUsesStartIO)
    {
        /*
         * special case: StartIO-based writing must stay serialized for performance
         * and proper operations (i.e. sequential writing mode).  If need more than
         * one transfer to perform this operation, and it's a StartIO-based driver
         * (such as CDROM), then just use a single packet and use the retry logic
         * that's already built-in to the packet engine.  Note that low-mem retry
         * cannot be used directly because some write methods do not work if the
         * writes are only PAGE_SIZE (i.e. packet writing may corrupt data).
         */
        Pkt->InLowMemRetry = FALSE;
    }
    else
    {
        Pkt->InLowMemRetry = TRUE;
    }
    Pkt->LowMemRetry_remainingBufPtr = BufPtr;
    Pkt->LowMemRetry_remainingBufLen = Len;
    Pkt->LowMemRetry_nextChunkTargetLocation = TargetLocation;
}
 
 
/*
 *  StepLowMemRetry
 *
 *      During extreme low-memory stress, this function retries
 *      a packet in small one-page chunks, sent serially.
 *
 *      Returns TRUE iff the packet is done.
 */
BOOLEAN StepLowMemRetry(PTRANSFER_PACKET Pkt)
{
    BOOLEAN packetDone;
 
    if (Pkt->LowMemRetry_remainingBufLen == 0){
        packetDone = TRUE;
    }
    else {
        ULONG thisChunkLen;
        if (Pkt->DriverUsesStartIO)
        {
            /*
             * Need the fdoData for the HwMaxXferLen
             */
            PFUNCTIONAL_DEVICE_EXTENSION fdoExt = Pkt->Fdo->DeviceExtension;
            PCLASS_PRIVATE_FDO_DATA fdoData = fdoExt->PrivateFdoData;
 
            /*
             * Need the adapterDesc to limit transfers based on byte count
             */
            PCOMMON_DEVICE_EXTENSION commonExtension = Pkt->Fdo->DeviceExtension;
            PSTORAGE_ADAPTER_DESCRIPTOR adapterDesc = commonExtension->PartitionZeroExtension->AdapterDescriptor;
 
            ULONG hwMaxXferLen;
 
            /*
             * special case: StartIO-based writing must stay serialized for performance
             * and proper operations (i.e. sequential writing mode).  If need more than
             * one transfer to perform this operation, and it's a StartIO-based driver
             * (such as CDROM), then just use a single packet and use the retry logic
             * that's already built-in to the packet engine.  Note that low-mem retry
             * cannot be used directly because some write methods do not work if the
             * writes are only PAGE_SIZE (i.e. packet writing may corrupt data).
             */
            NT_ASSERT(!Pkt->InLowMemRetry);
 
            /*
             *  We precomputed fdoData->HwMaxXferLen using (MaximumPhysicalPages-1).
             *  If the buffer is page-aligned, that's one less page crossing so we can add the page back in.
             *  Note: adapters that return MaximumPhysicalPages=0x10 depend on this to
             *           transfer aligned 64K requests in one piece.
             *  Also note:  make sure adding PAGE_SIZE back in doesn't wrap to zero.
             */
 
            if (((ULONG_PTR)(Pkt->LowMemRetry_remainingBufPtr) & (PAGE_SIZE-1)) || (fdoData->HwMaxXferLen > 0xffffffff-PAGE_SIZE)){
                hwMaxXferLen = fdoData->HwMaxXferLen;
            }
            else {
                NT_ASSERT((PAGE_SIZE%fdoExt->DiskGeometry.BytesPerSector) == 0);
                hwMaxXferLen = min(fdoData->HwMaxXferLen+PAGE_SIZE, adapterDesc->MaximumTransferLength);
            }
            thisChunkLen = MIN(Pkt->LowMemRetry_remainingBufLen, hwMaxXferLen);
        }
        else {
            /*
             *  Make sure the little chunk we send is <= a page length
             *  AND that it does not cross any page boundaries.
             */
            ULONG bytesToNextPageBoundary;
            bytesToNextPageBoundary = PAGE_SIZE-(ULONG)((ULONG_PTR)Pkt->LowMemRetry_remainingBufPtr%PAGE_SIZE);
            thisChunkLen = MIN(Pkt->LowMemRetry_remainingBufLen, bytesToNextPageBoundary);
            NT_ASSERT(Pkt->InLowMemRetry);
        }
 
 
        /*
         *  Set up the transfer packet for the new little chunk.
         *  This will reset numRetries so that we retry each chunk as required.
         */
        SetupReadWriteTransferPacket(Pkt,
                                     Pkt->LowMemRetry_remainingBufPtr,
                                     thisChunkLen,
                                     Pkt->LowMemRetry_nextChunkTargetLocation,
                                     Pkt->OriginalIrp);
 
        Pkt->LowMemRetry_remainingBufPtr += thisChunkLen;
        Pkt->LowMemRetry_remainingBufLen -= thisChunkLen;
        Pkt->LowMemRetry_nextChunkTargetLocation.QuadPart += thisChunkLen;
 
        //
        // When running in low-memory stress, always use a partial MDL.
        // This allows lower drivers to potentially map a smaller buffer.
        //
        Pkt->UsePartialMdl = TRUE;
 
        TransferPacketQueueRetryDpc(Pkt);
 
        packetDone = FALSE;
    }
 
    return packetDone;
}