reactos操作系统实现(123)

 目前，Reactos主要使用FAT的文件系统，因此下面就先来分析这个文件系统，以便了解这个文件系统的功能。这个文件系统的实现是在驱动程序FASTFAT.SYS里实现的，所以来分析这个驱动程序的源码，就可以了解FAT文件系统了。

 

6.2.1 FAT文件系统驱动程序入口函数

FAT的文件系统是当作一个驱动程序来加载到系统里，因此它也有驱动程序的形式了，也就是它的入口点函数，还是DriverEntry函数，它的实现代码如下：

#001  NTSTATUS NTAPI

#002  DriverEntry(PDRIVER_OBJECTDriverObject,

#003         PUNICODE_STRINGRegistryPath)

#004  /*

#005   * FUNCTION: Called by thesystem to initialize the driver

#006   * ARGUMENTS:

#007   *           DriverObject = object describingthis driver

#008   *           RegistryPath = path to ourconfiguration entries

#009   * RETURNS: Success orfailure

#010   */

#011  {

#012     PDEVICE_OBJECTDeviceObject;

 

FAT作为设备名称。

#013     UNICODE_STRING DeviceName= RTL_CONSTANT_STRING(L"//Fat");

#014     NTSTATUS Status;

#015 

 

创建文件系统设备对象。

#016     Status =IoCreateDevice(DriverObject,

#017                sizeof(VFAT_GLOBAL_DATA),

#018                &DeviceName,

#019                FILE_DEVICE_DISK_FILE_SYSTEM,

#020                0,

#021                FALSE,

#022                &DeviceObject);

#023 

 

如果创建这个设备名称已经存在，就使用RosFat的名称来创建设备。

#024     if (Status ==STATUS_OBJECT_NAME_EXISTS ||

#025         Status ==STATUS_OBJECT_NAME_COLLISION)

#026       {

#027         /* Try an other name,if 'Fat' is already in use. 'Fat' is also used by fastfat.sys on W2K */

#028        RtlInitUnicodeString(&DeviceName, L"//RosFat");

#029         Status =IoCreateDevice(DriverObject,

#030                                sizeof(VFAT_GLOBAL_DATA),

#031                                &DeviceName,

#032                                FILE_DEVICE_DISK_FILE_SYSTEM,

#033                                0,

#034                                FALSE,

#035                                &DeviceObject);

#036       }

#037 

#038 

#039 

#040     if (!NT_SUCCESS(Status))

#041       {

#042         return (Status);

#043       }

#044 

 

获取FAT全局数据区的指针。

#045     VfatGlobalData =DeviceObject->DeviceExtension;

 

清空FAT全局数据区。

#046     RtlZeroMemory (VfatGlobalData,sizeof(VFAT_GLOBAL_DATA));

#047    VfatGlobalData->DriverObject = DriverObject;

#048    VfatGlobalData->DeviceObject = DeviceObject;

#049 

 

设置设备是直接访问IO的方式。

#050     DeviceObject->Flags |=DO_DIRECT_IO;

 

设置驱动程序的IRP消息处理函数。

#051     DriverObject->MajorFunction[IRP_MJ_CLOSE]= VfatBuildRequest;

#052    DriverObject->MajorFunction[IRP_MJ_CREATE] = VfatBuildRequest;

#053    DriverObject->MajorFunction[IRP_MJ_READ] = VfatBuildRequest;

#054    DriverObject->MajorFunction[IRP_MJ_WRITE] = VfatBuildRequest;

#055    DriverObject->MajorFunction[IRP_MJ_FILE_SYSTEM_CONTROL] =VfatBuildRequest;

#056    DriverObject->MajorFunction[IRP_MJ_QUERY_INFORMATION] =VfatBuildRequest;

#057    DriverObject->MajorFunction[IRP_MJ_SET_INFORMATION] =VfatBuildRequest;

#058    DriverObject->MajorFunction[IRP_MJ_DIRECTORY_CONTROL] =VfatBuildRequest;

#059    DriverObject->MajorFunction[IRP_MJ_QUERY_VOLUME_INFORMATION] =

#060       VfatBuildRequest;

#061    DriverObject->MajorFunction[IRP_MJ_SET_VOLUME_INFORMATION] =

#062       VfatBuildRequest;

#063    DriverObject->MajorFunction[IRP_MJ_SHUTDOWN] = VfatShutdown;

#064    DriverObject->MajorFunction[IRP_MJ_LOCK_CONTROL] = VfatBuildRequest;

#065    DriverObject->MajorFunction[IRP_MJ_CLEANUP] = VfatBuildRequest;

#066     DriverObject->MajorFunction[IRP_MJ_FLUSH_BUFFERS]= VfatBuildRequest;

#067 

#068    DriverObject->DriverUnload = NULL;

#069 

 

缓存管理函数。

#070     /* Cache manager */

#071    VfatGlobalData->CacheMgrCallbacks.AcquireForLazyWrite =VfatAcquireForLazyWrite;

#072    VfatGlobalData->CacheMgrCallbacks.ReleaseFromLazyWrite =VfatReleaseFromLazyWrite;

#073    VfatGlobalData->CacheMgrCallbacks.AcquireForReadAhead =VfatAcquireForReadAhead;

#074    VfatGlobalData->CacheMgrCallbacks.ReleaseFromReadAhead = VfatReleaseFromReadAhead;

#075 

 

快速的I/O操作函数。

#076     /* Fast I/O */

#077    VfatInitFastIoRoutines(&VfatGlobalData->FastIoDispatch);

#078    DriverObject->FastIoDispatch =&VfatGlobalData->FastIoDispatch;

#079 

 

后备列表，以便提高速度。

#080     /* Private lists */

#081     ExInitializeNPagedLookasideList(&VfatGlobalData->FcbLookasideList,

#082                                    NULL, NULL, 0, sizeof(VFATFCB), TAG_FCB, 0);

#083    ExInitializeNPagedLookasideList(&VfatGlobalData->CcbLookasideList,

#084                                    NULL, NULL, 0, sizeof(VFATCCB), TAG_CCB, 0);

#085    ExInitializeNPagedLookasideList(&VfatGlobalData->IrpContextLookasideList,

#086                                    NULL, NULL, 0, sizeof(VFAT_IRP_CONTEXT), TAG_IRP, 0);

#087 

 

初始化资源列表。

#088    ExInitializeResourceLite(&VfatGlobalData->VolumeListLock);

#089    InitializeListHead(&VfatGlobalData->VolumeListHead);

 

注册文件系统到系统列表里。

#090    IoRegisterFileSystem(DeviceObject);

#091     return(STATUS_SUCCESS);

#092  }