sfilter中的写文件出错.

我写了一个小的文件过滤驱动,作用是把当前写的这个文件的内容保存下来.
现在能成功取到写的内容了.
不过,输出的长度好像长于当前的内容.我在保存时,写文件总是不成功,提示错误0xc00054

代码如下:请各位帮我看一下.谢谢..
_inline NTSTATUS  SaveFile (UNICODE_STRING filename,LARGE_INTEGER offset,
                    ULONG length,PVOID m_buffer)
{
    HANDLE FileHandle;
    OBJECT_ATTRIBUTES ObjectAttributes;
    IO_STATUS_BLOCK IoStatus;
    NTSTATUS Status;
    UNICODE_STRING m_save_filename,m_temp;
    WCHAR        m_file_buffer[260];
    PVOID        m_save_buffer;

    if(KeGetCurrentIrql() != PASSIVE_LEVEL)
    {
        DbgPrint("Irp is not PASSIVE_LEVEL\n");
        return FALSE;
    }

    UNREFERENCED_PARAMETER(offset);
    UNREFERENCED_PARAMETER(length);
    RtlInitEmptyUnicodeString(&m_save_filename,m_file_buffer,260);
    RtlInitUnicodeString(&m_temp,L"\\??\\C:");////只临时D盘,所以把当前的东西保存在C盘,这样,就不会重入了.
    RtlCopyUnicodeString(&m_save_filename,&m_temp);
    RtlAppendUnicodeStringToString(&m_save_filename,&filename);

    m_save_buffer=ExAllocatePoolWithTag(NonPagedPool,length,SF_POOL_TAG);
    
    RtlZeroMemory(m_save_buffer,length);
    RtlCopyMemory(m_save_buffer, m_buffer,length);

    InitializeObjectAttributes(&ObjectAttributes,
        &m_save_filename,
        OBJ_CASE_INSENSITIVE|OBJ_KERNEL_HANDLE,
        NULL,
        NULL
        );
//    
    Status = ZwCreateFile(&FileHandle,
            FILE_WRITE_DATA | SYNCHRONIZE,
            &ObjectAttributes,
            &IoStatus,
            NULL,
            FILE_ATTRIBUTE_NORMAL,
            0,
            FILE_OVERWRITE_IF,
            FILE_SYNCHRONOUS_IO_NONALERT,
            NULL,
            0
            );
    if (!NT_SUCCESS(Status))
    {
        ExFreePool(m_save_buffer);
        return Status;
    }
    Status = ZwWriteFile(FileHandle,
        NULL,
        NULL,
        NULL,
        &IoStatus,
        m_save_buffer,
        length,///写入长度,我发现总是写入的4096,不管这个文件改了多少,只要小于4096,就会直接写入这么多.
//这个函数,就会返回错误信息,0xc000054
//如果把写入长度变得短点,就没有问题了.比如:100字节
        NULL,
        NULL
        );
    ZwClose(FileHandle);
    ExFreePool(m_save_buffer);
    if (!NT_SUCCESS(Status))
    {
        DbgPrint("save is  :%x \r\n",Status);
    }
    return Status;
}

//////////这里是在IRP_MJ_WRITE中的调用代码..请帮忙看一下,有没有错误..谢谢
if(irpSp->Parameters.Write.Length!=0&&Irp->MdlAddress)
       {
           mdl = MmGetSystemAddressForMdl( Irp->MdlAddress );
           if(mdl)
           {//
     SaveFile(name,irpSp->Parameters.Write.ByteOffset,irpSp->Parameters.Write.Length,mdl);

            
           }
          
       }

0xC0000054 = STATUS_FILE_LOCK_CONFLICT.
I believe the problem is that the temporary file you try to write is on the same volume as the original file where the volume has been locked by FSD already. If your write length is less than 4K then FSD may cache the data first so there is no lock conflict, but eventually you'll get lock conflict. One solution I can think of to solve your problem is to pend your requests into a system thread.