注只用于自己上班坐地铁看，不要转发。
NTSTATUSFatFsdCreate (IN PVOLUME_DEVICE_OBJECT VolumeDeviceObject,IN PIRP Irp)/*++Routine Description:This routine implements the FSD part of the NtCreateFile and NtOpenFileAPI calls.Arguments:VolumeDeviceObject - Supplies the volume device object where thefile/directory exists that we are trying to open/createIrp - Supplies the Irp being processedReturn Value:NTSTATUS - The Fsd status for the Irp--*/{NTSTATUS Status;PIRP_CONTEXT IrpContext = NULL;BOOLEAN TopLevel;//// If we were called with our file system device object instead of a// volume device object, just complete this request with STATUS_SUCCESS//if ( FatDeviceIsFatFsdo( VolumeDeviceObject)) {Irp->IoStatus.Status = STATUS_SUCCESS;Irp->IoStatus.Information = FILE_OPENED;IoCompleteRequest( Irp, IO_DISK_INCREMENT );return STATUS_SUCCESS;}TimerStart(Dbg);DebugTrace(+1, Dbg, "FatFsdCreaten", 0);//// Call the common create routine, with block allowed if the operation// is synchronous.//FsRtlEnterFileSystem();TopLevel = FatIsIrpTopLevel( Irp );try {IrpContext = FatCreateIrpContext( Irp, TRUE );Status = FatCommonCreate( IrpContext, Irp );} except(FatExceptionFilter( IrpContext, GetExceptionInformation() )) {//// We had some trouble trying to perform the requested// operation, so we'll abort the I/O request with// the error status that we get back from the// execption code//Status = FatProcessException( IrpContext, Irp, GetExceptionCode() );}if (TopLevel) { IoSetTopLevelIrp( NULL ); }FsRtlExitFileSystem();//// And return to our caller//DebugTrace(-1, Dbg, "FatFsdCreate -> %08lxn", Status );TimerStop(Dbg,"FatFsdCreate");UNREFERENCED_PARAMETER( VolumeDeviceObject );return Status;}// FatFsdCreate是FAT文件系统驱动程序的一部分，用于实现NtCreateFile和NtOpenFile API调用的文件系统驱动程序部分。// 函数的作用是处理文件的创建和打开操作。// 函数接受两个参数：// VolumeDeviceObject：表示文件所在的卷设备对象。// Irp：表示正在处理的IRP（I/O请求包）。// 函数返回一个NTSTATUS值，表示处理IRP的文件系统驱动程序的状态。// 函数的主要逻辑如下：// 首先检查VolumeDeviceObject是否是FAT文件系统设备对象，如果是，则直接将IRP的状态设置为STATUS_SUCCESS，// 信息设置为FILE_OPENED，然后完成IRP请求并返回STATUS_SUCCESS。// 如果VolumeDeviceObject不是FAT文件系统设备对象，则开始处理创建和打开操作。// 进入文件系统。// 检查IRP是否处于顶层（TopLevel）。// 创建一个IRP上下文（IrpContext）结构。// 调用FatCommonCreate函数进行公共的创建操作。// 如果发生异常，通过异常过滤器处理异常，并将异常代码转换为适当的错误状态。// 在处理完毕后，离开文件系统。// 返回处理结果的状态。NTSTATUSFatCommonCreate (IN PIRP_CONTEXT IrpContext,IN PIRP Irp)/*++Routine Description:This is the common routine for creating/opening a file called byboth the fsd and fsp threads.Arguments:Irp - Supplies the Irp to processReturn Value:NTSTATUS - the return status for the operation--*/{NTSTATUS Status;IO_STATUS_BLOCK Iosb;PIO_STACK_LOCATION IrpSp;PFILE_OBJECT FileObject;PFILE_OBJECT RelatedFileObject;UNICODE_STRING FileName;ULONG AllocationSize;PFILE_FULL_EA_INFORMATION EaBuffer;PACCESS_MASK DesiredAccess;ULONG Options;UCHAR FileAttributes;USHORT ShareAccess;ULONG EaLength;BOOLEAN CreateDirectory;BOOLEAN SequentialOnly;BOOLEAN NoIntermediateBuffering;BOOLEAN OpenDirectory;BOOLEAN IsPagingFile;BOOLEAN OpenTargetDirectory;BOOLEAN DirectoryFile;BOOLEAN NonDirectoryFile;BOOLEAN NoEaKnowledge;BOOLEAN DeleteOnClose;BOOLEAN TemporaryFile;BOOLEAN FileNameOpenedDos = FALSE;ULONG CreateDisposition;// PVCB（Volume Control Block）：卷控制块，用于表示文件系统的卷（卷是文件系统中的逻辑存储单元）。Vcb结构包含与特定卷相关的信息，如卷标、簇大小、簇位图等。// PFCB（File Control Block）：文件控制块，用于表示打开的文件对象。Fcb结构包含有关特定文件的信息，如文件大小、时间戳、文件属性等。// PCCB（Context Control Block）：上下文控制块，用于表示打开的文件的上下文信息。Ccb结构包含与文件相关的上下文数据，如当前文件指针位置、缓冲区等。// PDCB（Directory Control Block）：目录控制块，用于表示目录（文件夹）。Dcb结构包含与特定目录相关的信息，如目录的文件列表、子目录列表等。PVCB Vcb;// typedef struct _VCB {// //// // This is a common head for the FAT volume file// //// FSRTL_ADVANCED_FCB_HEADER VolumeFileHeader;// //// // The links for the device queue off of FatData.VcbQueue// //// LIST_ENTRY VcbLinks;// //// // A pointer the device object passed in by the I/O system on a mount// // This is the target device object that the file system talks to when it// // needs to do any I/O (e.g., the disk stripper device object).// //// //// //// // 在挂载时由I/O系统传递的设备对象的指针// // 这是文件系统在需要进行任何I/O操作时与之通信的目标设备对象（例如，磁盘分割设备对象）。// //// PDEVICE_OBJECT TargetDeviceObject;// //// // A pointer to the VPB for the volume passed in by the I/O system on// // a mount.// //// PVPB Vpb;// //// // The internal state of the device. This is a collection of fsd device// // state flags.// //// ULONG VcbState;// VCB_CONDITION VcbCondition;// //// // A pointer to the root DCB for this volume// //// struct _FCB *RootDcb;// //// // If the FAT has so many entries that the free cluster bitmap would// // be too large, we split the FAT into buckets, and only one bucket's// // worth of bits are kept in the bitmap.// //// //// // 如果FAT表的条目太多，使得空闲簇位图过大，我们将FAT分割成多个桶(bucket)，// // 位图中仅保留一个桶的位(bit)信息。// //// ULONG NumberOfWindows;// PFAT_WINDOW Windows;// PFAT_WINDOW CurrentWindow;// //// // A count of the number of file objects that have opened the volume// // for direct access, and their share access state.// //// CLONG DirectAccessOpenCount;// SHARE_ACCESS ShareAccess;// //// // A count of the number of file objects that have any file/directory// // opened on this volume, not including direct access. And also the// // count of the number of file objects that have a file opened for// // only read access (i.e., they cannot be modifying the disk).// ////// // 记录在该卷上打开的所有文件/目录的文件对象数目，不包括直接访问。// // 同时也记录只以读方式打开的文件对象数目（即它们不能修改磁盘）。// //// CLONG OpenFileCount;// CLONG ReadOnlyCount;// //// // The bios parameter block field contains// // an unpacked copy of the bpb for the volume, it is initialized// // during mount time and can be read by everyone else after that.// //// BIOS_PARAMETER_BLOCK Bpb;// PUCHAR First0x24BytesOfBootSector;// //// // The following structure contains information useful to the// // allocation support routines. Many of them are computed from// // elements of the Bpb, but are too involved to recompute every time// // they are needed.// //// struct {// LBO RootDirectoryLbo; // Lbo of beginning of root directory// LBO FileAreaLbo; // Lbo of beginning of file area// ULONG RootDirectorySize; // size of root directory in bytes// ULONG NumberOfClusters; // total number of clusters on the volume// ULONG NumberOfFreeClusters; // number of free clusters on the volume// UCHAR FatIndexBitSize; // indicates if 12, 16, or 32 bit fat table// UCHAR LogOfBytesPerSector; // Log(Bios->BytesPerSector)// UCHAR LogOfBytesPerCluster; // Log(Bios->SectorsPerCluster)// } AllocationSupport;// //// // The following Mcb is used to keep track of dirty sectors in the Fat.// // Runs of holes denote clean sectors while runs of LBO == VBO denote// // dirty sectors. The VBOs are that of the volume file, starting at// // 0. The granuality of dirt is one sectors, and additions are only// // made in sector chunks to prevent problems with several simultaneous// // updaters.// //// //// // 下面的 Mcb 用于跟踪 FAT 中的脏扇区。连续的空洞表示干净的扇区，而 LBO == VBO 的连续块表示脏扇区。// // VBO 是卷文件的偏移量，从 0 开始。脏扇区的粒度为一个扇区，只能以扇区块为单位进行添加，// // 以防止多个同时更新程序引起的问题。// //// LARGE_MCB DirtyFatMcb;// //// // The FreeClusterBitMap keeps track of all the clusters in the fat.// // A 1 means occupied while a 0 means free. It allows quick location// // of contiguous runs of free clusters. It is initialized on mount// // or verify.// //// //// // FreeClusterBitMap 用于跟踪 FAT 中的所有簇。// // 1 表示已被占用，0 表示空闲。它可以快速定位连续的空闲簇。// // 在挂载或验证时进行初始化。// //// RTL_BITMAP FreeClusterBitMap;// //// // The following fast mutex controls access to the free cluster bit map// // and the buckets.// //// //// // 下面的快速互斥锁控制对于空闲簇位图和存储桶的访问。// //// FAST_MUTEX FreeClusterBitMapMutex;// //// // A resource variable to control access to the volume specific data// // structures// //// //// // 一个资源变量，用于控制对于卷特定数据结构的访问。// //// ERESOURCE Resource;// //// // A resource to make sure no one changes the volume bitmap while// // you're using it. Only for volumes with NumberOfWindows > 1.// //// //// // 一个资源，确保在使用卷位图时没有人更改它。仅适用于NumberOfWindows > 1的卷。// //// ERESOURCE ChangeBitMapResource;// //// // The following field points to the file object used to do I/O to// // the virtual volume file. The virtual volume file maps sectors// // 0 through the end of fat and is of a fixed size (determined during// // mount)// //// //// // 下面的字段指向用于与虚拟卷文件进行 I/O 的文件对象。// // 虚拟卷文件映射从 0 扇区到 FAT 的末尾，并具有固定大小（在挂载时确定）。// //// PFILE_OBJECT VirtualVolumeFile;// //// // The following field contains a record of special pointers used by// // MM and Cache to manipluate section objects. Note that the values// // are set outside of the file system. However the file system on an// // open/create will set the file object's SectionObject field to point// // to this field// //// //// // 下面的字段包含了由 MM（内存管理器）和 Cache（缓存）用于操作分区对象的特殊指针的记录。// // 注意，这些值是在文件系统之外设置的。但是，在打开/创建操作时，文件系统会将文件对象的// // SectionObject 字段设置为指向这个字段。// //// SECTION_OBJECT_POINTERS SectionObjectPointers;// //// // The following fields is a hint cluster index used by the file system// // when allocating a new cluster.// //// ULONG ClusterHint;// //// // This field contains the "DeviceObject" that this volume is// // currently mounted on. Note Vcb->Vpb->RealDevice is constant.// //// PDEVICE_OBJECT CurrentDevice;// //// // This is a pointer to the file object and the Fcb which represent the ea data.// //// PFILE_OBJECT VirtualEaFile;// struct _FCB *EaFcb;// //// // The following field is a pointer to the file object that has the// // volume locked. if the VcbState has the locked flag set.// //// PFILE_OBJECT FileObjectWithVcbLocked;// //// // The following is the head of a list of notify Irps.// //// LIST_ENTRY DirNotifyList;// //// // The following is used to synchronize the dir notify list.// //// PNOTIFY_SYNC NotifySync;// //// // The following fast mutex is used to synchronize directory stream// // file object creation.// //// FAST_MUTEX DirectoryFileCreationMutex;// //// // This field holds the thread address of the current (or most recent// // depending on VcbState) thread doing a verify operation on this volume.// //// PKTHREAD VerifyThread;// //// // The following two structures are used for CleanVolume callbacks.// //// KDPC CleanVolumeDpc;// KTIMER CleanVolumeTimer;// //// // This field records the last time FatMarkVolumeDirty was called, and// // avoids excessive calls to push the CleanVolume forward in time.// //// LARGE_INTEGER LastFatMarkVolumeDirtyCall;// //// // The following fields holds a pointer to a struct which is used to// // hold performance counters.// //// struct _FILE_SYSTEM_STATISTICS *Statistics;// //// // The property tunneling cache for this volume// //// TUNNEL Tunnel;// //// // The media change count is returned by IOCTL_CHECK_VERIFY and// // is used to verify that no user-mode app has swallowed a media change// // notification. This is only meaningful for removable media.// //// //// // 媒体更改计数是由 IOCTL_CHECK_VERIFY 返回的，用于验证没有用户模式应用程序吞噬了媒体更改通知。// // 这仅对可移动介质有意义。// //// ULONG ChangeCount;// //// // Preallocated VPB for swapout, so we are not forced to consider// // must succeed pool.// //// PVPB SwapVpb;// //// // Per volume threading of the close queues.// //// LIST_ENTRY AsyncCloseList;// LIST_ENTRY DelayedCloseList;// //// // Fast mutex used by the ADVANCED FCB HEADER in this structure// //// FAST_MUTEX AdvancedFcbHeaderMutex;// //// // This is the close context associated with the Virtual Volume File.// //// PCLOSE_CONTEXT CloseContext;// //// // How many close contexts were preallocated on this Vcb// //// #if DBG// ULONG CloseContextCount;// #endif// } VCB;// VolumeFileHeader：文件系统高级文件控制块头部，用于表示FAT卷的文件头部信息。// VcbLinks：设备队列的链表项，用于将Vcb结构连接到全局Vcb队列。// TargetDeviceObject：目标设备对象指针，表示文件系统与之通信的目标设备对象（例如磁盘驱动器设备对象）。// Vpb：卷参数块指针，表示通过挂载传递给文件系统的卷参数块。// VcbState：设备的内部状态，是一组FSD设备状态标志。// VcbCondition：VCB的状态条件。// RootDcb：指向根目录DCB（目录控制块）的指针。// NumberOfWindows：FAT表的窗口数目，用于处理FAT表过大时的情况。// Windows：FAT窗口的指针数组。// CurrentWindow：当前FAT窗口的指针。// DirectAccessOpenCount：以直接访问方式打开卷的文件对象数量。// ShareAccess：共享访问状态。// OpenFileCount：在该卷上打开的文件/目录的文件对象数量（不包括直接访问方式）。// ReadOnlyCount：只读访问的文件对象数量（不能对磁盘进行修改）。// Bpb：BIOS参数块，存储了解包后的卷的BIOS参数块信息。// First0x24BytesOfBootSector：引导扇区的前24字节。// AllocationSupport：用于分配支持的结构体，包含了从BPB计算得出的一些信息。// DirtyFatMcb：用于跟踪FAT中的脏扇区的Mcb结构。// FreeClusterBitMap：空闲簇位图，用于快速定位连续的空闲簇。// FreeClusterBitMapMutex：用于控制对空闲簇位图和窗口的访问的快速互斥锁。// Resource：控制对卷特定数据结构的访问的资源变量。// ChangeBitMapResource：用于防止在使用卷位图时更改它的资源。// VirtualVolumeFile：用于对虚拟卷文件进行I/O的文件对象指针。// SectionObjectPointers：用于操作段对象的指针，由MM和Cache使用。// ClusterHint：分配新簇时使用的提示簇索引。// CurrentDevice：当前挂载该卷的设备对象。// VirtualEaFile：指向EA数据的文件对象指针。// EaFcb：指向表示EA数据的文件控制块。// FileObjectWithVcbLocked：如果VcbState中设置了锁定标志，则指向具有锁定该卷的文件对象。// DirNotifyList：通知IRP的链表头，用于管理目录通知。// NotifySync：用于同步目录通知列表的同步对象。// DirectoryFileCreationMutex：用于同步目录流文件对象创建的快速互斥锁。// VerifyThread：正在对该卷执行验证操作的线程的地址。// CleanVolumeDpc和CleanVolumeTimer：用于CleanVolume回调的DPC和定时器。// LastFatMarkVolumeDirtyCall：记录上次调用FatMarkVolumeDirty的时间，避免过多地推进CleanVolume的时间。// Statistics：用于存储性能计数器的结构体指针。// Tunnel：用于该卷的属性隧道缓存。// ChangeCount：由IOCTL_CHECK_VERIFY返回的媒体更改计数，用于验证没有用户模式应用程序忽略了媒体更改通知。仅对可移动介质有意义。// SwapVpb：用于换出的预分配VPB，以避免考虑必须成功分配的内存池。// AsyncCloseList和DelayedCloseList：用于异步关闭队列的每卷线程。// AdvancedFcbHeaderMutex：用于该结构中的高级FCB HEADER的快速互斥锁。// CloseContext：与虚拟卷文件关联的关闭上下文。// CloseContextCount：在该VCB上预分配的关闭上下文数量。PFCB Fcb;// typedef struct _FCB {// //// // The following field is used for fast I/O// //// // The following comments refer to the use of the AllocationSize field// // of the FsRtl-defined header to the nonpaged Fcb.// //// // For a directory when we create a Dcb we will not immediately// // initialize the cache map, instead we will postpone it until our first// // call to FatReadDirectoryFile or FatPrepareWriteDirectoryFile.// // At that time we will search the Fat to find out the current allocation// // size (by calling FatLookupFileAllocationSize) and then initialize the// // cache map to this allocation size.// //// // For a file when we create an Fcb we will not immediately initialize// // the cache map, instead we will postpone it until we need it and// // then we determine the allocation size from either searching the// // fat to determine the real file allocation, or from the allocation// // that we've just allocated if we're creating a file.// //// // A value of -1 indicates that we do not know what the current allocation// // size really is, and need to examine the fat to find it. A value// // of than -1 is the real file/directory allocation size.// //// // Whenever we need to extend the allocation size we call// // FatAddFileAllocation which (if we're really extending the allocation)// // will modify the Fat, Mcb, and update this field. The caller// // of FatAddFileAllocation is then responsible for altering the Cache// // map size.// //// // We are now using the ADVANCED fcb header to support filter contexts// // at the stream level// ////// 以下字段用于快速I/O//// 下面的注释是针对非分页的Fcb的FsRtl定义头部中的AllocationSize字段的使用。//// 对于目录，在创建Dcb时，我们不会立即初始化缓存映射，而是将其推迟到我们第一次调用FatReadDirectoryFile或FatPrepareWriteDirectoryFile时。// 在那时，我们将搜索FAT以找出当前的分配大小（通过调用FatLookupFileAllocationSize），然后将缓存映射初始化为此分配大小。//// 对于文件，在创建Fcb时，我们也不会立即初始化缓存映射，而是将其推迟到需要时才初始化，并且从搜索FAT以确定实际文件分配还是从刚刚分配的分配获取分配大小（如果我们正在创建文件）。//// 值为-1表示我们不知道当前的分配大小是多少，需要检查FAT来查找。大于-1的值是真正的文件/目录分配大小。//// 每当我们需要扩展分配大小时，我们调用FatAddFileAllocation，它（如果我们真的扩展了分配）将修改FAT、Mcb，并更新此字段。然后，调用FatAddFileAllocation的调用者负责更改缓存映射的大小。//// 我们现在使用高级的Fcb头部来支持流级别的过滤上下文//// FSRTL_ADVANCED_FCB_HEADER Header;// //// // This structure contains fields which must be in non-paged pool.// ////// 这个结构包含必须在非分页池中的字段。//// PNON_PAGED_FCB NonPaged;// //// // The head of the fat alloaction chain. FirstClusterOfFile == 0// // means that the file has no current allocation.// ////// FAT分配链的头部。FirstClusterOfFile == 0表示文件没有当前的分配。//// ULONG FirstClusterOfFile;// //// // The links for the queue of all fcbs for a specific dcb off of// // Dcb.ParentDcbQueue. For the root directory this queue is empty// // For a non-existent fcb this queue is off of the non existent// // fcb queue entry in the vcb.// ////// 链接到特定Dcb的所有Fcb的队列，通过Dcb.ParentDcbQueue进行链接。对于根目录，此队列为空。对于不存在的Fcb，此队列位于Vcb的不存在的Fcb队列条目处。//// LIST_ENTRY ParentDcbLinks;// //// // A pointer to the Dcb that is the parent directory containing// // this fcb. If this record itself is the root dcb then this field// // is null.// ////// 指向包含此Fcb的Dcb的指针。如果此记录本身是根Dcb，则此字段为空。//// struct _FCB *ParentDcb;// //// // A pointer to the Vcb containing this Fcb// ////// 指向包含此Fcb的Vcb//// PVCB Vcb;// //// // The internal state of the Fcb. This is a collection Fcb state flags.// // Also the shared access for each time this file/directory is opened.// ////// Fcb的内部状态。这是一组Fcb状态标志。还有每次打开此文件/目录时的共享访问。//// ULONG FcbState;// FCB_CONDITION FcbCondition;// SHARE_ACCESS ShareAccess;// #ifdef SYSCACHE_COMPILE// //// // For syscache we keep a bitmask that tells us if we have dispatched IO for// // the page aligned chunks of the stream.// ////// 对于syscache，我们保留一个位掩码，告诉我们是否已经为流的页面对齐的块调度了IO。//// PULONG WriteMask;// ULONG WriteMaskData;// #endif// //// // A count of the number of file objects that have been opened for// // this file/directory, but not yet been cleaned up yet. This count// // is only used for data file objects, not for the Acl or Ea stream// // file objects. This count gets decremented in FatCommonCleanup,// // while the OpenCount below gets decremented in FatCommonClose.// //// // 这是已经打开但尚未清理的文件对象的数量。该计数仅用于数据文件对象，而不用于Acl或Ea流文件对象。// // 在FatCommonCleanup中递减该计数，而在下面的OpenCount中递减。// CLONG UncleanCount;// //// // A count of the number of file objects that have opened// // this file/directory. For files & directories the FsContext of the// // file object points to this record.// //// 打开了该文件/目录的文件对象数量计数。对于文件和目录，文件对象的FsContext指向该记录// CLONG OpenCount;// //// // A count of how many of "UncleanCount" handles were opened for// // non-cached I/O.// //// CLONG NonCachedUncleanCount;// //// // The following field is used to locate the dirent for this fcb/dcb.// // All directory are opened as mapped files so the only additional// // information we need to locate this dirent (beside its parent directory)// // is the byte offset for the dirent. Note that for the root dcb// // this field is not used.// //// VBO DirentOffsetWithinDirectory;// //// // The following field is filled in when there is an Lfn associated// // with this file. It is the STARTING offset of the Lfn.// //// VBO LfnOffsetWithinDirectory;// //// // Thess entries is kept in ssync with the dirent. It allows a more// // accurate verify capability and speeds up FatFastQueryBasicInfo().// //// LARGE_INTEGER CreationTime;// LARGE_INTEGER LastAccessTime;// LARGE_INTEGER LastWriteTime;// //// // Valid data to disk// //// ULONG ValidDataToDisk;// //// // The following field contains the retrieval mapping structure// // for the file/directory. Note that for the Root Dcb this// // structure is set at mount time. Also note that in this// // implementation of Fat the Mcb really maps VBOs to LBOs and not// // VBNs to LBNs.// //// LARGE_MCB Mcb;// //// // The following union is cased off of the node type code for the fcb.// // There is a seperate case for the directory versus file fcbs.// //// union {// //// // A Directory Control Block (Dcb)// //// struct {// //// // A queue of all the fcbs/dcbs that are opened under this// // Dcb.// //// LIST_ENTRY ParentDcbQueue;// //// // The following field points to the file object used to do I/O to// // the directory file for this dcb. The directory file maps the// // sectors for the directory. This field is initialized by// // CreateRootDcb but is left null by CreateDcb. It isn't// // until we try to read/write the directory file that we// // create the stream file object for non root dcbs.// //// ULONG DirectoryFileOpenCount;// PFILE_OBJECT DirectoryFile;// //// // If the UnusedDirentVbo is != 0xffffffff, then the dirent at this// // offset is guarenteed to unused. A value of 0xffffffff means// // it has yet to be initialized. Note that a value beyond the// // end of allocation means that there an unused dirent, but we// // will have to allocate another cluster to use it.// //// // DeletedDirentHint contains lowest possible VBO of a deleted// // dirent (assuming as above that it is not 0xffffffff).// //// VBO UnusedDirentVbo;// VBO DeletedDirentHint;// //// // The following two entries links together all the Fcbs// // opened under this Dcb sorted in a splay tree by name.// //// // I'd like to go into why we have (and must have) two separate// // splay trees within the current fastfat architecture. I will// // provide some insight into what would have to change if we// // wanted to have a single UNICODE tree.// //// // What makes FAT unique is that both Oem and Unicode names sit// // side by side on disk. Several unique UNICODE names coming// // into fastfat can match a single OEM on-disk name, and there// // is really no way to enumerate all the possible UNICODE// // source strings that can map to a given OEM name. This argues// // for converting the incomming UNICODE name into OEM, and then// // running through an OEM splay tree of the open files. This// // works well when there are only OEM names on disk.// //// // The UNICODE name on disk can be VERY different from the short// // name in the DIRENT and not even representable in the OEM code// // page. Even if it were representable in OEM, it is possible// // that a case varient of the original UNICODE name would match// // a different OEM name, causing us to miss the Fcb in the// // prefix lookup phase. In these cases, we must put UNICODE// // name in the splay to guarentee that we find any case varient// // of the input UNICODE name. See the routine description of// // FatConstructNamesInFcb() for a detailed analysis of how we// // detect this case.// //// // The fundamental limitation we are imposing here is that if// // an Fcb exists for an open file, we MUST find it during the// // prefix stage. This is a basic premise of the create path// // in fastfat. In fact if we later find it gravelling through// // the disk (but not the splay tree), we will bug check if we// // try to add a duplicate entry to the splay tree (not to// // mention having two Fcbs). If we had some mechanism to deal// // with cases (and they would be rare) that we don't find the// // entry in the splay tree, but the Fcb is actually in there,// // then we could go to a single UNICODE splay tree. While// // this uses more pool for the splay tree, and makes string// // compares maybe take a bit as longer, it would eliminate the// // need for any NLS conversion during the prefix phase, so it// // might really be a net win.// //// // The current scheme was optimized for non-extended names// // (i.e. US names). As soon as you start using extended// // characters, then it is clearly a win as many code paths// // become active that would otherwise not be needed if we// // only had a single UNICODE splay tree.// //// // We may think about changing this someday.// //// // 下面的两个条目将所有在此Dcb下打开的Fcbs按名称在一个Splay树中排序连接在一起。// //// // 我想解释一下为什么我们在当前的Fastfat架构中必须有（并且必须有）两个独立的Splay树。// // 我将提供一些关于如果我们想要一个单一的UNICODE树会有什么改变的见解。// //// // FAT的独特之处在于OEM和Unicode名称在磁盘上并排存在。几个不同的UNICODE名称// // 进入fastfat时可以匹配一个单独的OEM磁盘名称，并且真的没有办法列举出所有可能的// // UNICODE源字符串，可以映射到给定的OEM名称。这就说明了将输入的UNICODE名称转换// // 为OEM名称，然后通过一个OEM的Splay树来处理打开的文件的方式。当磁盘上只有OEM名称时，// // 这种方法很有效。// //// // 磁盘上的UNICODE名称可以与DIRENT中的短名称非常不同，甚至不能在OEM代码页中表示。// // 即使它可以在OEM中表示，也有可能原始UNICODE名称的大小写变体会与不同的OEM名称匹配，// // 导致我们在前缀查找阶段错过Fcb。在这些情况下，我们必须将UNICODE名称放入Splay中，// // 以确保我们找到输入UNICODE名称的任何大小写变体。请参阅FatConstructNamesInFcb()// // 的例程描述，详细分析了我们如何检测这种情况。// //// // 我们在这里施加的根本限制是，如果一个Fcb存在于打开的文件中，我们必须在前缀阶段// // 找到它。这是fastfat中创建路径的基本前提。事实上，如果我们稍后通过磁盘（而不是// // Splay树）找到它，如果尝试向Splay树添加重复条目，我们将引发bug检查（更不用说有两个// // Fcb了）。如果我们有一些机制来处理我们在Splay树中找不到条目但实际上Fcb确实在其中的// // 情况（尽管它们很少见），那么我们可以转向单个UNICODE的Splay树。虽然这会在Splay树// // 中使用更多的池，并且可能使字符串比较稍微变长，但它消除了前缀阶段中的任何NLS转换的需要，因此可能真的是一个净收益。//// 当前的方案针对非扩展名称（即美国名称）进行了优化。一旦开始使用扩展字符，那么它显然是一种优势，// 因为许多代码路径将变得活跃，否则在只有单个UNICODE的Splay树的情况下是不需要的。//// 也许有一天我们会考虑改变这一点。// PRTL_SPLAY_LINKS RootOemNode;// PRTL_SPLAY_LINKS RootUnicodeNode;// //// // The following field keeps track of free dirents, i.e.,// // dirents that are either unallocated for deleted.// //// //// // 以下字段跟踪空闲的目录项，即未分配或已删除的目录项。// //// RTL_BITMAP FreeDirentBitmap;// //// // Since the FCB specific part of this union is larger, use// // the slack here for an initial bitmap buffer. Currently// // there is enough space here for an 8K cluster.// //// //// // 由于此联合中 FCB 特定部分较大，因此在此处使用剩余空间作为初始位图缓冲区。当前这里有足够的空间容纳一个8K簇。// //// ULONG FreeDirentBitmapBuffer[1];// } Dcb;// //// // A File Control Block (Fcb)// //// struct {// //// // The following field is used by the filelock module// // to maintain current byte range locking information.// //// //// // 以下字段由 filelock 模块用于维护当前的字节范围锁定信息。// //// FILE_LOCK FileLock;// //// // The following field is used by the oplock module// // to maintain current oplock information.// ////// // 以下字段由 oplock 模块用于维护当前的 oplock 信息。// //// OPLOCK Oplock;// //// // This pointer is used to detect writes that eminated in the// // cache manager's lazywriter. It prevents lazy writer threads,// // who already have the Fcb shared, from trying to acquire it// // exclusive, and thus causing a deadlock.// //// //// // 此指针用于检测源自缓存管理器的惰性写入的写操作。它防止已共享 Fcb 的惰性写入线程试图以独占方式获取它，从而导致死锁。// //// PVOID LazyWriteThread;// } Fcb;// } Specific;// //// // The following field is used to verify that the Ea's for a file// // have not changed between calls to query for Ea's. It is compared// // with a similar field in a Ccb.// //// // IMPORTANT!! **** DO NOT MOVE THIS FIELD ****// //// // The slack space in the union above is computed from// // the field offset of the EaModificationCount.// //// //// // 以下字段用于验证文件的扩展属性（Ea）在查询 Ea 时未发生更改。它与 Ccb 中的类似字段进行比较。// //// // 重要提示！！**** 不要移动此字段 ****// //// // 上述联合体中的空闲空间是根据 EaModificationCount 字段的偏移量计算的。// //// ULONG EaModificationCount;// //// // The following field is the fully qualified file name for this FCB/DCB// // starting from the root of the volume, and last file name in the// // fully qualified name.// //// // 以下字段是该 FCB/DCB 的完全限定文件名，从卷的根目录开始，以及完全限定名中的最后一个文件名。// FILE_NAME_NODE ShortName;// //// // The following field is only filled in if it is needed with the user's// // opened path// //// // 如果需要，以下字段将仅填充用户打开的路径// UNICODE_STRING FullFileName;// USHORT FinalNameLength;// //// // To make life simpler we also keep in the Fcb/Dcb a current copy of// // the fat attribute byte for the file/directory. This field must// // also be updated when we create the Fcb, modify the File, or verify// // the Fcb// ////为了简化操作，我们还在Fcb/Dcb中保留了文件/目录的当前FAT属性字节的副本。当创建Fcb、修改文件或验证Fcb时，这个字段也必须进行更新。// UCHAR DirentFatFlags;// //// // The case preserved long filename// //// // 保留大小写的长文件名// UNICODE_STRING ExactCaseLongName;// //// // If the UNICODE Lfn is fully expressible in the system Oem code// // page, then we will store it in a prefix table, otherwise we will// // store the last UNICODE name in the Fcb. In both cases the name// // has been upcased.// //// // Note that we may need neither of these fields if an LFN was strict// // 8.3 or differed only in case. Indeed if there wasn't an LFN, we// // don't need them at all.// //// //// // 如果UNICODE Lfn完全可表示为系统Oem代码页中的字符，则我们将其存储在前缀表中，否则将将最后一个UNICODE名称存储在Fcb中。在这两种情况下，名称都已经被大写处理。// //// // 需要注意的是，如果LFN是严格的8.3格式，或者只是大小写不同，那么我们可能都不需要这些字段。实际上，如果没有LFN，我们根本不需要它们。// //// union {// //// // This first field is present if FCB_STATE_HAS_OEM_LONG_NAME// // is set in the FcbState.// //// // 如果FcbState中设置了FCB_STATE_HAS_OEM_LONG_NAME，则存在此字段。// FILE_NAME_NODE Oem;// //// // This first field is present if FCB_STATE_HAS_UNICODE_LONG_NAME// // is set in the FcbState.// //// // 如果FcbState中设置了FCB_STATE_HAS_UNICODE_LONG_NAME，则存在此字段。// FILE_NAME_NODE Unicode;// } LongName;// //// // Defragmentation / ReallocateOnWrite synchronization object. This// // is filled in by FatMoveFile() and affects the read and write paths.// ///// 碎片整理/重分配同步对象。由FatMoveFile()填充，影响读取和写入路径。// PKEVENT MoveFileEvent;// } FCB, *PFCB;// Header：用于快速I/O的字段。// NonPaged：指向非分页池中的字段。// FirstClusterOfFile：文件分配链的头部。// ParentDcbLinks：用于在特定DCB的所有FCB队列上链接的队列。// ParentDcb：指向包含此FCB的父目录DCB的指针。// Vcb：指向包含此FCB的VCB的指针。// FcbState：FCB的内部状态和共享访问。// UncleanCount：已打开但尚未清理的文件对象数目。// OpenCount：已打开此文件/目录的文件对象数目。// NonCachedUncleanCount：以非缓存I/O打开的 "UncleanCount" 句柄数目。// DirentOffsetWithinDirectory：在目录中定位此FCB/Dcb的目录项的字节偏移量。// LfnOffsetWithinDirectory：与此文件关联的长文件名的起始偏移量。// CreationTime、LastAccessTime、LastWriteTime：用于验证目录项的时间戳。// ValidDataToDisk：要写入磁盘的有效数据。// Mcb：文件/目录的检索映射结构。// Specific：针对FCB和DCB的联合体，包含相应的字段。// EaModificationCount：用于验证文件的扩展属性是否在查询期间发生更改。// ShortName：FCB/DCB的完全限定文件名。// FullFileName：用户打开的路径的Unicode字符串。// DirentFatFlags：文件/目录的FAT属性字节的当前副本。// ExactCaseLongName：区分大小写的长文件名。// LongName：存储长文件名的结构体。// MoveFileEvent：用于碎片整理/重写分配的同步对象。PCCB Ccb;//typedef struct _CCB {// //// // Type and size of this record (must be FAT_NTC_CCB)// //// NODE_TYPE_CODE NodeTypeCode; // 记录类型代码// NODE_BYTE_SIZE NodeByteSize; // 记录字节大小// //// // Define a 24bit wide field for Flags, but a UCHAR for Wild Cards Present// // since it is used so often. Line these up on byte boundaries for grins.// //// ULONG Flags:24; // 标志位，占用24位// BOOLEAN ContainsWildCards; // 是否包含通配符// //// // Overlay a close context on the data of the CCB. The remaining// // fields are not useful during close, and we would like to avoid// // paying extra pool for it.// //// //// // 在CCB的数据上叠加一个关闭上下文。在关闭过程中，其余的字段是无用的，我们希望避免额外的内存池开销。// //// union {// struct {// //// // Save the offset to start search from.// //// VBO OffsetToStartSearchFrom; // 保存起始搜索偏移量// //// // The query template is used to filter directory query requests.// // It originally is set to null and on the first call to NtQueryDirectory// // it is set to the input filename or "*" if the name is not supplied.// // All subsequent queries then use this template.// //// // The Oem structure is a union because if the name is wild, we store// // the arbitrary length string, while if the name is constant, we store// // the 8.3 representation for fast comparison.// ////// // 查询模板用于过滤目录查询请求。// // 最初设置为空，在第一次调用NtQueryDirectory时，// // 如果输入文件名存在，则设置为输入文件名，否则设置为"*"。// // 后续的查询都使用这个模板。// //// // Oem结构体是一个联合体，因为如果名称是通配符，我们会存储任意长度的字符串，// // 而如果名称是常量，我们会存储用于快速比较的8.3表示。// //// union {// //// // If the template contains a wild card, use this.// //// //// // 如果查询模板包含通配符，使用此字段。// //// OEM_STRING Wild; // 通配符模板// //// // If the name is constant, use this part.// //// FAT8DOT3 Constant; // 常量名称// } OemQueryTemplate;// UNICODE_STRING UnicodeQueryTemplate; // Unicode查询模板// //// // The field is compared with the similar field in the Fcb to determine// // if the Ea's for a file have been modified.// //// //// // 该字段与Fcb中的相似字段进行比较，以确定文件的扩展属性（Ea）是否已被修改。// //// ULONG EaModificationCount; // EA修改计数// //// // The following field is used as an offset into the Eas for a// // particular file. This will be the offset for the next// // Ea to return. A value of 0xffffffff indicates that the// // Ea's are exhausted.// //// //// // 下面的字段用作特定文件的扩展属性（Ea）的偏移量。// // 这将是下一个要返回的扩展属性的偏移量。// // 值为0xffffffff表示扩展属性已经耗尽。// //// ULONG OffsetOfNextEaToReturn; // 下一个要返回的EA的偏移量// };// CLOSE_CONTEXT CloseContext; // 关闭上下文// };//} CCB;PDCB ParentDcb;//typedef FCB DCB;PDCB FinalDcb = NULL;// PVCB（Volume Control Block）：卷控制块，用于表示文件系统的卷（卷是文件系统中的逻辑存储单元）。Vcb结构包含与特定卷相关的信息，如卷标、簇大小、簇位图等。// PFCB（File Control Block）：文件控制块，用于表示打开的文件对象。Fcb结构包含有关特定文件的信息，如文件大小、时间戳、文件属性等。// PCCB（Context Control Block）：上下文控制块，用于表示打开的文件的上下文信息。Ccb结构包含与文件相关的上下文数据，如当前文件指针位置、缓冲区等。// PDCB（Directory Control Block）：目录控制块，用于表示目录（文件夹）。Dcb结构包含与特定目录相关的信息，如目录的文件列表、子目录列表等。UNICODE_STRING FinalName;UNICODE_STRING RemainingPart;UNICODE_STRING NextRemainingPart;UNICODE_STRING UpcasedFinalName;WCHAR UpcasedBuffer[ FAT_CREATE_INITIAL_NAME_BUF_SIZE];OEM_STRING OemFinalName;UCHAR OemBuffer[ FAT_CREATE_INITIAL_NAME_BUF_SIZE*2];BOOLEAN FreeOemBuffer;BOOLEAN FreeUpcasedBuffer;PDIRENT Dirent;PBCB DirentBcb = NULL;ULONG LfnByteOffset;ULONG DirentByteOffset;BOOLEAN PostIrp = FALSE;BOOLEAN OplockPostIrp = FALSE;BOOLEAN TrailingBackslash;BOOLEAN FirstLoop = TRUE;CCB LocalCcb;UNICODE_STRING Lfn;WCHAR LfnBuffer[ FAT_CREATE_INITIAL_NAME_BUF_SIZE];//// Get the current IRP stack location//IrpSp = IoGetCurrentIrpStackLocation( Irp );//获取当前的irpDebugTrace(+1, Dbg, "FatCommonCreaten", 0 );DebugTrace( 0, Dbg, "Irp = %08lxn", Irp );DebugTrace( 0, Dbg, "->Flags = %08lxn", Irp->Flags );DebugTrace( 0, Dbg, "->FileObject = %08lxn", IrpSp->FileObject );DebugTrace( 0, Dbg, " ->RelatedFileObject = %08lxn", IrpSp->FileObject->RelatedFileObject );DebugTrace( 0, Dbg, " ->FileName = %Zn", &IrpSp->FileObject->FileName );DebugTrace( 0, Dbg, "->AllocationSize.LowPart = %08lxn", Irp->Overlay.AllocationSize.LowPart );DebugTrace( 0, Dbg, "->AllocationSize.HighPart = %08lxn", Irp->Overlay.AllocationSize.HighPart );DebugTrace( 0, Dbg, "->SystemBuffer = %08lxn", Irp->AssociatedIrp.SystemBuffer );DebugTrace( 0, Dbg, "->DesiredAccess = %08lxn", IrpSp->Parameters.Create.SecurityContext->DesiredAccess );DebugTrace( 0, Dbg, "->Options = %08lxn", IrpSp->Parameters.Create.Options );DebugTrace( 0, Dbg, "->FileAttributes = %04xn", IrpSp->Parameters.Create.FileAttributes );DebugTrace( 0, Dbg, "->ShareAccess = %04xn", IrpSp->Parameters.Create.ShareAccess );DebugTrace( 0, Dbg, "->EaLength = %08lxn", IrpSp->Parameters.Create.EaLength );//// This is here because the Win32 layer can't avoid sending me double// beginning backslashes.//if ((IrpSp->FileObject->FileName.Length > sizeof(WCHAR)) &&(IrpSp->FileObject->FileName.Buffer[1] == L'\') &&(IrpSp->FileObject->FileName.Buffer[0] == L'\')) {IrpSp->FileObject->FileName.Length -= sizeof(WCHAR);RtlMoveMemory( &IrpSp->FileObject->FileName.Buffer[0],&IrpSp->FileObject->FileName.Buffer[1],IrpSp->FileObject->FileName.Length );//// If there are still two beginning backslashes, the name is bogus.//if ((IrpSp->FileObject->FileName.Length > sizeof(WCHAR)) &&(IrpSp->FileObject->FileName.Buffer[1] == L'\') &&(IrpSp->FileObject->FileName.Buffer[0] == L'\')) {FatCompleteRequest( IrpContext, Irp, STATUS_OBJECT_NAME_INVALID );DebugTrace(-1, Dbg, "FatCommonCreate -> STATUS_OBJECT_NAME_INVALIDn", 0);return STATUS_OBJECT_NAME_INVALID;}}//// Reference our input parameters to make things easier//ASSERT( IrpSp->Parameters.Create.SecurityContext != NULL );FileObject = IrpSp->FileObject;FileName = FileObject->FileName;RelatedFileObject = FileObject->RelatedFileObject;AllocationSize = Irp->Overlay.AllocationSize.LowPart;EaBuffer = Irp->AssociatedIrp.SystemBuffer;DesiredAccess = &IrpSp->Parameters.Create.SecurityContext->DesiredAccess;Options = IrpSp->Parameters.Create.Options;FileAttributes = (UCHAR)(IrpSp->Parameters.Create.FileAttributes & ~FILE_ATTRIBUTE_NORMAL);ShareAccess = IrpSp->Parameters.Create.ShareAccess;EaLength = IrpSp->Parameters.Create.EaLength;//// Set up the file object's Vpb pointer in case anything happens.// This will allow us to get a reasonable pop-up.//if ( RelatedFileObject != NULL ) {FileObject->Vpb = RelatedFileObject->Vpb;}//// Force setting the archive bit in the attributes byte to follow OS/2,// & DOS semantics. Also mask out any extraneous bits, note that// we can't use the ATTRIBUTE_VALID_FLAGS constant because that has// the control and normal flags set.//// Delay setting ARCHIVE in case this is a directory: DavidGoe 2/16/95//FileAttributes &= (FILE_ATTRIBUTE_READONLY |FILE_ATTRIBUTE_HIDDEN |FILE_ATTRIBUTE_SYSTEM |FILE_ATTRIBUTE_ARCHIVE );//// Locate the volume device object and Vcb that we are trying to access//Vcb = &((PVOLUME_DEVICE_OBJECT)IrpSp->DeviceObject)->Vcb;// 首先，通过IoGetCurrentIrpStackLocation获取当前IRP堆栈位置的指针IrpSp，然后输出一些调试信息，包括相关的IRP和参数的值。// 接下来，代码检查文件名是否以双斜杠开头。这段注释中提到的问题是，Windows Win32层有时无法避免发送带有双斜杠开头的文件名给文件系统驱动。如果检测到文件名以双斜杠开头，//代码会将第一个斜杠去除，并继续检查是否还有两个斜杠，如果是，则认为文件名无效，完成请求并返回STATUS_OBJECT_NAME_INVALID表示对象名无效。// 然后，代码引用输入参数以便后续操作。例如，FileObject表示文件对象，FileName表示文件名，AllocationSize表示文件的分配大小，等等。// 接着，代码设置文件对象的Vpb字段，以便在发生错误时能够获取适当的弹出窗口。// 接下来，代码强制将文件属性中的存档位（Archive）设置为1，以符合OS/2和DOS的语义。此外，还将文件属性掩码为有效的属性标志，包括只读、隐藏、系统和存档。// 最后，代码定位要访问的卷设备对象和Vcb（卷控制块），并将其赋值给变量Vcb，以便后续使用。///--------------------------------//// Decipher Option flags and values////// If this is an open by fileid operation, just fail it explicitly. FAT's// source of fileids is not reversible for open operations.//if (BooleanFlagOn( Options, FILE_OPEN_BY_FILE_ID )) {FatCompleteRequest( IrpContext, Irp, STATUS_NOT_IMPLEMENTED );return STATUS_NOT_IMPLEMENTED;}DirectoryFile = BooleanFlagOn( Options, FILE_DIRECTORY_FILE );NonDirectoryFile = BooleanFlagOn( Options, FILE_NON_DIRECTORY_FILE );SequentialOnly = BooleanFlagOn( Options, FILE_SEQUENTIAL_ONLY );NoIntermediateBuffering = BooleanFlagOn( Options, FILE_NO_INTERMEDIATE_BUFFERING );NoEaKnowledge = BooleanFlagOn( Options, FILE_NO_EA_KNOWLEDGE );DeleteOnClose = BooleanFlagOn( Options, FILE_DELETE_ON_CLOSE );TemporaryFile = BooleanFlagOn( IrpSp->Parameters.Create.FileAttributes,FILE_ATTRIBUTE_TEMPORARY );CreateDisposition = (Options >> 24) & 0x000000ff;IsPagingFile = BooleanFlagOn( IrpSp->Flags, SL_OPEN_PAGING_FILE );OpenTargetDirectory = BooleanFlagOn( IrpSp->Flags, SL_OPEN_TARGET_DIRECTORY );CreateDirectory = (BOOLEAN)(DirectoryFile &&((CreateDisposition == FILE_CREATE) ||(CreateDisposition == FILE_OPEN_IF)));OpenDirectory = (BOOLEAN)(DirectoryFile &&((CreateDisposition == FILE_OPEN) ||(CreateDisposition == FILE_OPEN_IF)));//// Make sure the input large integer is valid and that the dir/nondir// indicates a storage type we understand.//if (Irp->Overlay.AllocationSize.HighPart != 0 ||(DirectoryFile && NonDirectoryFile)) {FatCompleteRequest( IrpContext, Irp, STATUS_INVALID_PARAMETER );DebugTrace(-1, Dbg, "FatCommonCreate -> STATUS_INVALID_PARAMETERn", 0);return STATUS_INVALID_PARAMETER;}// 首先，代码检查是否是通过文件ID进行打开的操作，如果是，则返回STATUS_NOT_IMPLEMENTED，表示不支持通过文件ID打开文件的操作。// 接下来，根据传入的选项参数进行标志位的设置，这些标志位包括：// DirectoryFile: 是否是目录文件// NonDirectoryFile: 是否是非目录文件// SequentialOnly: 是否仅支持顺序访问// NoIntermediateBuffering: 是否禁用中间缓冲// NoEaKnowledge: 是否不需要EA（扩展属性）的相关信息// DeleteOnClose: 是否在关闭时删除文件// 然后，根据文件属性判断是否是临时文件。// 接下来，解析Options参数中的CreateDisposition，确定文件的创建或打开方式。// 然后，根据IrpSp->Flags中的标志位判断是否是分页文件或目标目录的打开操作。// 最后，代码进行一些简单的验证。它检查输入的AllocationSize是否有效（高32位必须为0）以及DirectoryFile和NonDirectoryFile是否同时设置（两者互斥）。//如果验证失败，将返回STATUS_INVALID_PARAMETER表示参数无效。////----------------------------------//// Acquire exclusive access to the vcb, and enqueue the Irp if// we didn't get it.//if (!FatAcquireExclusiveVcb( IrpContext, Vcb )) {DebugTrace(0, Dbg, "Cannot acquire Vcbn", 0);Iosb.Status = FatFsdPostRequest( IrpContext, Irp );DebugTrace(-1, Dbg, "FatCommonCreate -> %08lxn", Iosb.Status );return Iosb.Status;}//// Initialize the DirentBcb to null//DirentBcb = NULL;//// Initialize our temp strings with their stack buffers.//OemFinalName.Length = 0;OemFinalName.MaximumLength = sizeof( OemBuffer);OemFinalName.Buffer = OemBuffer;UpcasedFinalName.Length = 0;UpcasedFinalName.MaximumLength = sizeof( UpcasedBuffer);UpcasedFinalName.Buffer = UpcasedBuffer;Lfn.Length = 0;Lfn.MaximumLength = sizeof( LfnBuffer);Lfn.Buffer = LfnBuffer;// 首先尝试获取卷控制块（Vcb）的排它访问权，通过调用FatAcquireExclusiveVcb函数。如果无法获取Vcb的排它访问权，说明当前无法处理IRP，因此将IRP提交到延迟队列中，并返回相应的状态。// 接下来，对一些临时字符串进行初始化，这些字符串用于存储文件名的不同形式。具体而言：// OemFinalName是一个ANSI字符串，用于存储转换为OEM字符集的文件名。// UpcasedFinalName是一个Unicode字符串，用于存储转换为大写形式的文件名。// Lfn是一个Unicode字符串，用于存储长文件名（Long File Name）。// 这些字符串都使用了栈上的缓冲区作为存储空间。try {//// Make sure the vcb is in a usable condition. This will raise// and error condition if the volume is unusable//FatVerifyVcb( IrpContext, Vcb );//// If the Vcb is locked then we cannot open another file//if (FlagOn(Vcb->VcbState, VCB_STATE_FLAG_LOCKED)) {DebugTrace(0, Dbg, "Volume is lockedn", 0);Status = STATUS_ACCESS_DENIED;if (Vcb->VcbCondition != VcbGood) {Status = STATUS_VOLUME_DISMOUNTED;}try_return( Iosb.Status = Status );}//// Don't allow the DELETE_ON_CLOSE option if the volume is// write-protected.//if (DeleteOnClose && FlagOn(Vcb->VcbState, VCB_STATE_FLAG_WRITE_PROTECTED)) {//// Set the real device for the pop-up info, and set the verify// bit in the device object, so that we will force a verify// in case the user put the correct media back in.//IoSetHardErrorOrVerifyDevice( IrpContext->OriginatingIrp,Vcb->Vpb->RealDevice );SetFlag(Vcb->Vpb->RealDevice->Flags, DO_VERIFY_VOLUME);FatRaiseStatus( IrpContext, STATUS_MEDIA_WRITE_PROTECTED );}//// If this is a fat32 volume, EA's are not supported.//if (EaBuffer != NULL &&FatIsFat32(Vcb)) {try_return( Iosb.Status = STATUS_EAS_NOT_SUPPORTED );}//// Check if we are opening the volume and not a file/directory.// We are opening the volume if the name is empty and there// isn't a related file object. If there is a related file object// then it is the Vcb itself.//if (FileName.Length == 0) {PVCB DecodeVcb;if (RelatedFileObject == NULL ||FatDecodeFileObject( RelatedFileObject,&DecodeVcb,&Fcb,&Ccb ) == UserVolumeOpen) {ASSERT( RelatedFileObject == NULL || Vcb == DecodeVcb );//// Check if we were to open a directory//if (DirectoryFile) {DebugTrace(0, Dbg, "Cannot open volume as a directoryn", 0);try_return( Iosb.Status = STATUS_NOT_A_DIRECTORY );}//// Can't open the TargetDirectory of the DASD volume.//if (OpenTargetDirectory) {try_return( Iosb.Status = STATUS_INVALID_PARAMETER );}DebugTrace(0, Dbg, "Opening the volume, Vcb = %08lxn", Vcb);CollectCreateHitStatistics(Vcb);Iosb = FatOpenVolume( IrpContext,FileObject,Vcb,DesiredAccess,ShareAccess,CreateDisposition );Irp->IoStatus.Information = Iosb.Information;try_return( Iosb.Status );}}// 首先，通过调用FatVerifyVcb函数，确保Vcb（卷控制块）处于可用状态。如果发现卷不可用，则会引发错误条件，并根据卷的状态设置相应的错误状态。// 接下来，检查Vcb是否已被锁定。如果Vcb的状态标志中设置了VCB_STATE_FLAG_LOCKED，表示卷已被锁定，此时无法打开其他文件。如果发现卷已被锁定，则将返回适当的错误状态。// 然后，检查是否允许使用DELETE_ON_CLOSE选项。如果Vcb的状态标志中设置了VCB_STATE_FLAG_WRITE_PROTECTED（表示卷为只读），且指定了DELETE_ON_CLOSE选项，则无法执行删除操作。//在此情况下，将设置硬错误和验证设备，以便在用户将正确的介质放回时触发验证，并引发相应的错误状态。// 接下来，对于FAT32卷，不支持扩展属性（EA），因此如果EaBuffer不为空且卷是FAT32卷，则返回STATUS_EAS_NOT_SUPPORTED。// 然后，检查是否正在打开卷而不是文件/目录。如果文件名长度为0且不存在相关的文件对象（RelatedFileObject为空），则表示正在打开卷。在这种情况下，//首先解码文件对象以获取相关的Vcb，并进行一些检查。如果指定了打开目录的选项，则返回STATUS_NOT_A_DIRECTORY；如果指定了打开目标目录的选项，//则返回STATUS_INVALID_PARAMETER。如果通过了这些检查，则调用FatOpenVolume函数打开卷。// 最后，将Iosb结构中的信息（如打开的文件大小等）传递给Irp的IoStatus字段，并返回对应的Iosb.Status。//// If there is a related file object then this is a relative open.// The related file object is the directory to start our search at.// Return an error if it is not a directory.//if (RelatedFileObject != NULL) {PVCB RelatedVcb;PDCB RelatedDcb;PCCB RelatedCcb;TYPE_OF_OPEN TypeOfOpen;TypeOfOpen = FatDecodeFileObject( RelatedFileObject,&RelatedVcb,&RelatedDcb,&RelatedCcb );if (TypeOfOpen != UserFileOpen &&TypeOfOpen != UserDirectoryOpen) {DebugTrace(0, Dbg, "Invalid related file objectn", 0);try_return( Iosb.Status = STATUS_OBJECT_PATH_NOT_FOUND );}//// A relative open must be via a relative path.//if (FileName.Length != 0 &&FileName.Buffer[0] == L'\') {try_return( Iosb.Status = STATUS_OBJECT_NAME_INVALID );}//// Set up the file object's Vpb pointer in case anything happens.//ASSERT( Vcb == RelatedVcb );FileObject->Vpb = RelatedFileObject->Vpb;//// Now verify the related Fcb so we don't get in trouble later// by assuming its in good shape.//FatVerifyFcb( IrpContext, RelatedDcb );ParentDcb = RelatedDcb;} else {//// This is not a relative open, so check if we're// opening the root dcb//if ((FileName.Length == sizeof(WCHAR)) &&(FileName.Buffer[0] == L'\')) {//// Check if we were not supposed to open a directory//if (NonDirectoryFile) {DebugTrace(0, Dbg, "Cannot open root directory as a filen", 0);try_return( Iosb.Status = STATUS_FILE_IS_A_DIRECTORY );}//// Can't open the TargetDirectory of the root directory.//if (OpenTargetDirectory) {try_return( Iosb.Status = STATUS_INVALID_PARAMETER );}//// Not allowed to delete root directory.//if (DeleteOnClose) {try_return( Iosb.Status = STATUS_CANNOT_DELETE );}DebugTrace(0, Dbg, "Opening root dcbn", 0);CollectCreateHitStatistics(Vcb);Iosb = FatOpenRootDcb( IrpContext,FileObject,Vcb,DesiredAccess,ShareAccess,CreateDisposition );Irp->IoStatus.Information = Iosb.Information;try_return( Iosb.Status );}//// Nope, we will be opening relative to the root directory.//ParentDcb = Vcb->RootDcb;}////// 如果存在相关的文件对象（RelatedFileObject不为空），则表示这是一个相对路径的打开操作。相关的文件对象是要开始搜索的目录。//如果相关的文件对象不是一个目录（既不是文件打开，也不是目录打开），则返回STATUS_OBJECT_PATH_NOT_FOUND错误。// 接下来，检查文件名是否为空（FileName.Length != 0）且文件名的第一个字符为反斜杠（）。如果是这种情况，//表示相对打开应该是通过相对路径进行的，因此返回STATUS_OBJECT_NAME_INVALID错误。// 然后，设置文件对象的Vpb指针，以防发生任何意外情况。并调用FatVerifyFcb函数验证相关的DCB（目录控制块），以确保它处于良好状态。// 如果没有相关的文件对象，即不是相对路径的打开操作，则检查是否正在打开根目录（通过检查文件名是否为单个反斜杠 ）。//如果是这种情况，则进行一些检查：如果指定了打开非目录文件的选项，则返回STATUS_FILE_IS_A_DIRECTORY错误；如果指定了打开目标目录的选项，//则返回STATUS_INVALID_PARAMETER错误；如果指定了DeleteOnClose选项，则返回STATUS_CANNOT_DELETE错误。然后，//调用FatOpenRootDcb函数打开根目录的DCB。// 最后，设置ParentDcb变量为相应的目录控制块，用于后续的文件创建操作。//// FatCommonCreate(): trailing backslash check//if ((FileName.Length != 0) &&(FileName.Buffer[FileName.Length/sizeof(WCHAR)-1] == L'\')) {FileName.Length -= sizeof(WCHAR);TrailingBackslash = TRUE;} else {TrailingBackslash = FALSE;}//// Check for max path. We might want to tighten this down to DOS MAX_PATH// for maximal interchange with non-NT platforms, but for now defer to the// possibility of something depending on it.//if (ParentDcb->FullFileName.Buffer == NULL) {FatSetFullFileNameInFcb( IrpContext, ParentDcb );}if ((USHORT) (ParentDcb->FullFileName.Length + sizeof(WCHAR) + FileName.Length) <= FileName.Length) {try_return( Iosb.Status = STATUS_OBJECT_NAME_INVALID );}//// 首先，检查文件名的长度是否不为零，并且文件名的最后一个字符是否为反斜杠（）。如果满足条件，则将文件名长度减去一个字符的大小（sizeof(WCHAR)），//并将TrailingBackslash标记设置为TRUE，表示存在尾部反斜杠。// 接下来，检查父目录的完整文件名的缓冲区是否为NULL，如果是，则调用FatSetFullFileNameInFcb函数为父目录的DCB设置完整文件名。// 然后，计算父目录的完整文件名长度加上一个字符大小和文件名长度的和，并将其转换为USHORT类型进行比较。如果长度超过了文件名长度，说明路径名过长，返回STATUS_OBJECT_NAME_INVALID错误。//// We loop here until we land on an Fcb that is in a good// condition. This way we can reopen files that have stale handles// to files of the same name but are now different.//最后，通过一个循环，找到一个处于良好状态的FCB（文件控制块）。这样可以重新打开具有陈旧句柄的同名文件，而现在它们是不同的文件。while ( TRUE ) {Fcb = ParentDcb;RemainingPart = FileName;//// Now walk down the Dcb tree looking for the longest prefix.// This one exit condition in the while() is to handle a// special case condition (relative NULL name open), the main// exit conditions are at the bottom of the loop.//while (RemainingPart.Length != 0) {PFCB NextFcb;FsRtlDissectName( RemainingPart,&FinalName,&NextRemainingPart );//// If RemainingPart starts with a backslash the name is// invalid.// Check for no more than 255 characters in FinalName//if (((NextRemainingPart.Length != 0) && (NextRemainingPart.Buffer[0] == L'\')) ||(FinalName.Length > 255*sizeof(WCHAR))) {try_return( Iosb.Status = STATUS_OBJECT_NAME_INVALID );}//// Now, try to convert this one component into Oem and search// the splay tree. If it works then that's great, otherwise// we have to try with the UNICODE name instead.//FatEnsureStringBufferEnough( &OemFinalName,FinalName.Length);Status = RtlUpcaseUnicodeStringToCountedOemString( &OemFinalName, &FinalName, FALSE );if (NT_SUCCESS(Status)) {NextFcb = FatFindFcb( IrpContext,&Fcb->Specific.Dcb.RootOemNode,(PSTRING)&OemFinalName,&FileNameOpenedDos );} else {NextFcb = NULL;OemFinalName.Length = 0;if (Status != STATUS_UNMAPPABLE_CHARACTER) {try_return( Iosb.Status = Status );}}//// If we didn't find anything searching the Oem space, we// have to try the Unicode space. To save cycles in the// common case that this tree is empty, we do a quick check// here.//if ((NextFcb == NULL) && Fcb->Specific.Dcb.RootUnicodeNode) {//// First downcase, then upcase the string, because this// is what happens when putting names into the tree (see// strucsup.c, FatConstructNamesInFcb()).//FatEnsureStringBufferEnough( &UpcasedFinalName,FinalName.Length);Status = RtlDowncaseUnicodeString(&UpcasedFinalName, &FinalName, FALSE );ASSERT( NT_SUCCESS( Status ));Status = RtlUpcaseUnicodeString( &UpcasedFinalName, &UpcasedFinalName, FALSE );ASSERT( NT_SUCCESS( Status ));NextFcb = FatFindFcb( IrpContext,&Fcb->Specific.Dcb.RootUnicodeNode,(PSTRING)&UpcasedFinalName,&FileNameOpenedDos );}//// If we got back an Fcb then we consumed the FinalName// legitimately, so the remaining name is now RemainingPart.//if (NextFcb != NULL) {Fcb = NextFcb;RemainingPart = NextRemainingPart;}if ((NextFcb == NULL) ||(NodeType(NextFcb) == FAT_NTC_FCB) ||(NextRemainingPart.Length == 0)) {break;}}//// Remaining name cannot start with a backslash//if (RemainingPart.Length && (RemainingPart.Buffer[0] == L'\')) {RemainingPart.Length -= sizeof(WCHAR);RemainingPart.Buffer += 1;}//// Now verify that everybody up to the longest found prefix is valid.//try {FatVerifyFcb( IrpContext, Fcb );} except( (GetExceptionCode() == STATUS_FILE_INVALID) ?EXCEPTION_EXECUTE_HANDLER :EXCEPTION_CONTINUE_SEARCH ) {FatResetExceptionState( IrpContext );}if ( Fcb->FcbCondition == FcbGood ) {//// If we are trying to open a paging file and have happened// upon the DelayedCloseFcb, make it go away, and try again.//if (IsPagingFile && FirstLoop &&(NodeType(Fcb) == FAT_NTC_FCB) &&(!IsListEmpty( &FatData.AsyncCloseList ) ||!IsListEmpty( &FatData.DelayedCloseList ))) {FatFspClose(Vcb);FirstLoop = FALSE;continue;} else {break;}} else {FatRemoveNames( IrpContext, Fcb );}}// 循环中逐级遍历文件路径，寻找最长的前缀匹配的文件控制块（FCB）。// 首先，将Fcb设置为ParentDcb，RemainingPart设置为FileName。然后进入一个while循环，直到满足特定条件才会退出循环。// 在循环中，首先使用FsRtlDissectName函数将RemainingPart分解为最后一个路径分量FinalName和剩余部分NextRemainingPart。// 接下来，进行一些检查。如果NextRemainingPart不为空且以反斜杠（）开头，或者FinalName的长度超过255个字符，就返回STATUS_OBJECT_NAME_INVALID错误。// 然后，尝试将FinalName转换为OEM字符串，并在OEM节点的空间中搜索相应的FCB。如果成功找到，则将NextFcb设置为找到的FCB，并更新Fcb和RemainingPart。// 如果OEM搜索未找到匹配的FCB，或者Fcb->Specific.Dcb.RootUnicodeNode不为空（即Unicode节点的空间不为空），则进行Unicode搜索。// 首先进行大小写转换，并在Unicode节点的空间中搜索相应的FCB。如果找到，则将NextFcb设置为找到的FCB，并更新Fcb和RemainingPart。// 最后，检查RemainingPart是否以反斜杠开头，如果是，则将长度减去一个字符大小并将缓冲区指针向前移动一个字符。// 接下来，通过FatVerifyFcb函数验证路径中每个级别的FCB的有效性。// 如果Fcb的状态为FcbGood，表示找到了有效的FCB，可以退出循环。// 如果尝试打开的是分页文件且是第一次循环，并且存在延迟关闭的FCB，那么将执行延迟关闭操作，并重新开始循环。// 如果Fcb的状态不为FcbGood，则调用FatRemoveNames函数，将路径中已经访问的名称从FCB中移除。// 整个过程将会逐级遍历路径，直到找到最长的前缀匹配的FCB或无法继续遍历为止。ASSERT( Fcb->FcbCondition == FcbGood );//// If there is already an Fcb for a paging file open and// it was not already opened as a paging file, we cannot// continue as it is too difficult to move a live Fcb to// non-paged pool.//if (IsPagingFile) {if (NodeType(Fcb) == FAT_NTC_FCB &&!FlagOn( Fcb->FcbState, FCB_STATE_PAGING_FILE )) {try_return( Iosb.Status = STATUS_SHARING_VIOLATION );}//// Check for a system file.//} else if (FlagOn( Fcb->FcbState, FCB_STATE_SYSTEM_FILE )) {try_return( Iosb.Status = STATUS_ACCESS_DENIED );}//// If the longest prefix is pending delete (either the file or// some higher level directory), we cannot continue.//if (FlagOn( Fcb->FcbState, FCB_STATE_DELETE_ON_CLOSE )) {try_return( Iosb.Status = STATUS_DELETE_PENDING );}//// Now that we've found the longest matching prefix we'll// check if there isn't any remaining part because that means// we've located an existing fcb/dcb to open and we can do the open// without going to the disk//if (RemainingPart.Length == 0) {//// First check if the user wanted to open the target directory// and if so then call the subroutine to finish the open.//if (OpenTargetDirectory) {CollectCreateHitStatistics(Vcb);Iosb = FatOpenTargetDirectory( IrpContext,FileObject,Fcb->ParentDcb,DesiredAccess,ShareAccess,TRUE );Irp->IoStatus.Information = Iosb.Information;try_return( Iosb.Status );}//// We can open an existing fcb/dcb, now we only need to case// on which type to open.//if (NodeType(Fcb) == FAT_NTC_DCB || NodeType(Fcb) == FAT_NTC_ROOT_DCB) {//// This is a directory we're opening up so check if// we were not to open a directory//if (NonDirectoryFile) {DebugTrace(0, Dbg, "Cannot open directory as a filen", 0);try_return( Iosb.Status = STATUS_FILE_IS_A_DIRECTORY );}DebugTrace(0, Dbg, "Open existing dcb, Dcb = %08lxn", Fcb);CollectCreateHitStatistics(Vcb);Iosb = FatOpenExistingDcb( IrpContext,FileObject,Vcb,(PDCB)Fcb,DesiredAccess,ShareAccess,CreateDisposition,NoEaKnowledge,DeleteOnClose );Irp->IoStatus.Information = Iosb.Information;try_return( Iosb.Status );}//// Check if we're trying to open an existing Fcb and that// the user didn't want to open a directory. Note that this// call might actually come back with status_pending because// the user wanted to supersede or overwrite the file and we// cannot block. If it is pending then we do not complete the// request, and we fall through the bottom to the code that// dispatches the request to the fsp.//if (NodeType(Fcb) == FAT_NTC_FCB) {//// Check if we were only to open a directory//if (OpenDirectory) {DebugTrace(0, Dbg, "Cannot open file as directoryn", 0);try_return( Iosb.Status = STATUS_NOT_A_DIRECTORY );}DebugTrace(0, Dbg, "Open existing fcb, Fcb = %08lxn", Fcb);if ( TrailingBackslash ) {try_return( Iosb.Status = STATUS_OBJECT_NAME_INVALID );}CollectCreateHitStatistics(Vcb);Iosb = FatOpenExistingFcb( IrpContext,FileObject,Vcb,Fcb,DesiredAccess,ShareAccess,AllocationSize,EaBuffer,EaLength,FileAttributes,CreateDisposition,NoEaKnowledge,DeleteOnClose,FileNameOpenedDos,&OplockPostIrp );if (Iosb.Status != STATUS_PENDING) {//// Check if we need to set the cache support flag in// the file object//if (NT_SUCCESS( Iosb.Status) && !NoIntermediateBuffering) {FileObject->Flags |= FO_CACHE_SUPPORTED;}Irp->IoStatus.Information = Iosb.Information;} else {DebugTrace(0, Dbg, "Enqueue Irp to FSPn", 0);PostIrp = TRUE;}try_return( Iosb.Status );}//// Not and Fcb or a Dcb so we bug check//FatBugCheck( NodeType(Fcb), (ULONG_PTR) Fcb, 0 );}// 在找到最长匹配的前缀后，检查文件控制块（FCB）的状态和执行相应的操作。// 首先，使用断言语句ASSERT( Fcb->FcbCondition == FcbGood )检查FCB的状态是否为FcbGood。这是一个额外的检查，用于确保FCB的状态是良好的。// 接下来，根据打开的是分页文件还是普通文件，执行不同的检查和操作。// 如果打开的是分页文件（IsPagingFile为真），并且找到的FCB类型是FAT_NTC_FCB且没有设置FCB_STATE_PAGING_FILE标志，则返回STATUS_SHARING_VIOLATION错误，表示无法继续打开。// 如果打开的不是分页文件，并且找到的FCB有FCB_STATE_SYSTEM_FILE标志，则返回STATUS_ACCESS_DENIED错误，表示无法访问系统文件。// 接下来，检查找到的最长匹配前缀的FCB是否具有FCB_STATE_DELETE_ON_CLOSE标志。如果有，则返回STATUS_DELETE_PENDING错误，表示该文件或其某个上级目录已被标记为删除。// 如果没有剩余路径（RemainingPart.Length == 0），则说明找到了一个现有的FCB或DCB，可以直接打开而无需访问磁盘。// 如果OpenTargetDirectory为真，则调用FatOpenTargetDirectory子例程来完成打开操作。// 如果找到的是DCB或RootDCB类型的FCB，则检查是否允许打开目录。如果NonDirectoryFile为真，则返回STATUS_FILE_IS_A_DIRECTORY错误，表示无法将目录作为文件打开。// 如果找到的是FCB类型的FCB，则检查是否允许打开文件。如果OpenDirectory为真，则返回STATUS_NOT_A_DIRECTORY错误，表示无法将文件作为目录打开。// 如果TrailingBackslash为真，则返回STATUS_OBJECT_NAME_INVALID错误，表示无效的对象名称。// 最后，调用FatOpenExistingFcb函数来打开现有的FCB，并根据返回的状态执行相应的操作。如果操作不是挂起状态（Iosb.Status != STATUS_PENDING），// 则将结果信息和状态保存在Irp结构中。如果需要启用中间缓存，则将文件对象的标志设置为FO_CACHE_SUPPORTED。// 如果返回的状态是挂起状态，表示需要将IRP排队到文件系统进程（FSP）中处理，设置PostIrp为真。// 如果找到的FCB既不是DCB也不是FCB，则调用FatBugCheck函数引发系统错误，用于调试和错误分析。//// There is more in the name to parse than we have in existing// fcbs/dcbs. So now make sure that fcb we got for the largest// matching prefix is really a dcb otherwise we can't go any// further//if ((NodeType(Fcb) != FAT_NTC_DCB) && (NodeType(Fcb) != FAT_NTC_ROOT_DCB)) {DebugTrace(0, Dbg, "Cannot open file as subdirectory, Fcb = %08lxn", Fcb);try_return( Iosb.Status = STATUS_OBJECT_PATH_NOT_FOUND );}//// Otherwise we continue on processing the Irp and allowing ourselves// to block for I/O as necessary. Find/create additional dcb's for// the one we're trying to open. We loop until either remaining part// is empty or we get a bad filename. When we exit FinalName is// the last name in the string we're after, and ParentDcb is the// parent directory that will contain the opened/created// file/directory.//// Make sure the rest of the name is valid in at least the LFN// character set (which just happens to be that of HPFS).//// If we are not in ChicagoMode, use FAT symantics.//ParentDcb = Fcb;FirstLoop = TRUE;while (TRUE) {//// We do one little optimization here on the first itterration of// the loop since we know that we have already tried to convert// FinalOemName from the original UNICODE.//if (FirstLoop) {FirstLoop = FALSE;RemainingPart = NextRemainingPart;Status = OemFinalName.Length ? STATUS_SUCCESS : STATUS_UNMAPPABLE_CHARACTER;} else {//// Dissect the remaining part.//DebugTrace(0, Dbg, "Dissecting the name %Zn", &RemainingPart);FsRtlDissectName( RemainingPart,&FinalName,&RemainingPart );//// If RemainingPart starts with a backslash the name is// invalid.// Check for no more than 255 characters in FinalName//if (((RemainingPart.Length != 0) && (RemainingPart.Buffer[0] == L'\')) ||(FinalName.Length > 255*sizeof(WCHAR))) {try_return( Iosb.Status = STATUS_OBJECT_NAME_INVALID );}//// Now, try to convert this one component into Oem. If it works// then that's great, otherwise we have to try with the UNICODE// name instead.//FatEnsureStringBufferEnough( &OemFinalName,FinalName.Length);Status = RtlUpcaseUnicodeStringToCountedOemString( &OemFinalName, &FinalName, FALSE );}if (NT_SUCCESS(Status)) {//// We'll start by trying to locate the dirent for the name. Note// that we already know that there isn't an Fcb/Dcb for the file// otherwise we would have found it when we did our prefix lookup.//if (FatIsNameShortOemValid( IrpContext, OemFinalName, FALSE, FALSE, FALSE )) {FatStringTo8dot3( IrpContext,OemFinalName,&LocalCcb.OemQueryTemplate.Constant );LocalCcb.Flags = 0;} else {LocalCcb.Flags = CCB_FLAG_SKIP_SHORT_NAME_COMPARE;}} else {LocalCcb.Flags = CCB_FLAG_SKIP_SHORT_NAME_COMPARE;if (Status != STATUS_UNMAPPABLE_CHARACTER) {try_return( Iosb.Status = Status );}}//// Now we know a lot about the final name, so do legal name// checking here.//if (FatData.ChicagoMode) {if (!FatIsNameLongUnicodeValid( IrpContext, &FinalName, FALSE, FALSE, FALSE )) {try_return( Iosb.Status = STATUS_OBJECT_NAME_INVALID );}} else {if (FlagOn(LocalCcb.Flags, CCB_FLAG_SKIP_SHORT_NAME_COMPARE)) {try_return( Iosb.Status = STATUS_OBJECT_NAME_INVALID );}}DebugTrace(0, Dbg, "FinalName is %Zn", &FinalName);DebugTrace(0, Dbg, "RemainingPart is %Zn", &RemainingPart);FatEnsureStringBufferEnough( &UpcasedFinalName,FinalName.Length);if (!NT_SUCCESS(Status = RtlUpcaseUnicodeString( &UpcasedFinalName, &FinalName, FALSE))) {try_return( Iosb.Status = Status );}LocalCcb.UnicodeQueryTemplate = UpcasedFinalName;LocalCcb.ContainsWildCards = FALSE;Lfn.Length = 0;FatLocateDirent( IrpContext,ParentDcb,&LocalCcb,0,&Dirent,&DirentBcb,&DirentByteOffset,&FileNameOpenedDos,&Lfn);//// Remember we read this Dcb for error recovery.//FinalDcb = ParentDcb;//// If the remaining part is now empty then this is the last name// in the string and the one we want to open//if (RemainingPart.Length == 0) { break; }//// We didn't find a dirent, bail.//if (Dirent == NULL) {Iosb.Status = STATUS_OBJECT_PATH_NOT_FOUND;try_return( Iosb.Status );}//// We now have a dirent, make sure it is a directory//if (!FlagOn( Dirent->Attributes, FAT_DIRENT_ATTR_DIRECTORY )) {Iosb.Status = STATUS_OBJECT_PATH_NOT_FOUND;try_return( Iosb.Status );}//// Compute the LfnByteOffset.//LfnByteOffset = DirentByteOffset -FAT_LFN_DIRENTS_NEEDED(&Lfn) * sizeof(LFN_DIRENT);//// Create a dcb for the new directory//ParentDcb = FatCreateDcb( IrpContext,Vcb,ParentDcb,LfnByteOffset,DirentByteOffset,Dirent,&Lfn );//// Remember we created this Dcb for error recovery.//FinalDcb = ParentDcb;FatSetFullNameInFcb( IrpContext, ParentDcb, &FinalName );}// 首先，代码检查最大匹配前缀对应的Fcb是否是一个目录控制块（DCB）。如果不是DCB，也不是根目录的DCB，那么无法继续打开文件或创建子目录，会返回错误状态码STATUS_OBJECT_PATH_NOT_FOUND。// 如果Fcb是DCB或根目录的DCB，那么代码会继续处理Irp，并允许根据需要进行I/O阻塞。接下来的任务是找到或创建要打开/创建的目录的附加DCB。// 代码会循环执行，直到剩余部分为空或获取到无效的文件名。在退出循环时，FinalName是要打开/创建的字符串中的最后一个名称，而ParentDcb是包含所打开/创建文件/目录的父目录。// 代码会检查剩余部分的名称在至少LFN（长文件名）字符集中是否有效（LFN字符集与HPFS字符集相同）。// 根据ChicagoMode的设置，在合法名称检查方面会有所不同。如果在ChicagoMode中，会检查FinalName是否为有效的长文件名（Unicode格式）。如果不在ChicagoMode中，则要求FinalName为有效的短文件名（OEM格式）。// 接下来，代码会对FinalName进行大写转换，并将结果存储在UpcasedFinalName中。// 然后，代码通过调用FatLocateDirent函数来定位与FinalName匹配的目录项。这里已经确定在进行前缀查找时，没有找到对应的Fcb/Dcb。// 如果剩余部分的长度为0，说明这是字符串中的最后一个名称，也是要打开的目标。// 如果没有找到目录项（Dirent为空），则返回STATUS_OBJECT_PATH_NOT_FOUND错误。// 确保找到的目录项是一个目录（通过检查Attributes属性）。// 计算LfnByteOffset，该值用于创建新目录的DCB。// 创建新目录的DCB（ParentDcb），并将其设置为下一次循环的父目录。// 在最后，将FinalName设置为ParentDcb的完整路径名。//// First check if the user wanted to open the target directory// and if so then call the subroutine to finish the open.//if (OpenTargetDirectory) {Iosb = FatOpenTargetDirectory( IrpContext,FileObject,ParentDcb,DesiredAccess,ShareAccess,Dirent ? TRUE : FALSE);Irp->IoStatus.Information = Iosb.Information;try_return( Iosb.Status );}if (Dirent != NULL) {//// Compute the LfnByteOffset.//LfnByteOffset = DirentByteOffset -FAT_LFN_DIRENTS_NEEDED(&Lfn) * sizeof(LFN_DIRENT);//// We were able to locate an existing dirent entry, so now// see if it is a directory that we're trying to open.//if (FlagOn( Dirent->Attributes, FAT_DIRENT_ATTR_DIRECTORY )) {//// Make sure its okay to open a directory//if (NonDirectoryFile) {DebugTrace(0, Dbg, "Cannot open directory as a filen", 0);try_return( Iosb.Status = STATUS_FILE_IS_A_DIRECTORY );}DebugTrace(0, Dbg, "Open existing directoryn", 0);Iosb = FatOpenExistingDirectory( IrpContext,FileObject,Vcb,ParentDcb,Dirent,LfnByteOffset,DirentByteOffset,&Lfn,DesiredAccess,ShareAccess,CreateDisposition,NoEaKnowledge,DeleteOnClose );Irp->IoStatus.Information = Iosb.Information;try_return( Iosb.Status );}//// Otherwise we're trying to open and existing file, and we// need to check if the user only wanted to open a directory.//if (OpenDirectory) {DebugTrace(0, Dbg, "Cannot open file as directoryn", 0);try_return( Iosb.Status = STATUS_NOT_A_DIRECTORY );}DebugTrace(0, Dbg, "Open existing filen", 0);if ( TrailingBackslash ) {try_return( Iosb.Status = STATUS_OBJECT_NAME_INVALID );}Iosb = FatOpenExistingFile( IrpContext,FileObject,Vcb,ParentDcb,Dirent,LfnByteOffset,DirentByteOffset,&Lfn,DesiredAccess,ShareAccess,AllocationSize,EaBuffer,EaLength,FileAttributes,CreateDisposition,IsPagingFile,NoEaKnowledge,DeleteOnClose,FileNameOpenedDos );//// Check if we need to set the cache support flag in// the file object//if (NT_SUCCESS(Iosb.Status) && !NoIntermediateBuffering) {FileObject->Flags |= FO_CACHE_SUPPORTED;}Irp->IoStatus.Information = Iosb.Information;try_return( Iosb.Status );}// 处理在已经定位到目标目录项的情况下，打开目标目录或目标文件的逻辑。// 如果OpenTargetDirectory标志被设置，表示用户希望打开目标目录，那么调用FatOpenTargetDirectory子例程完成打开操作。// 如果Dirent不为空，表示已经定位到一个现有的目录项。接下来，检查该目录项是否是一个目录。// a. 如果是目录且NonDirectoryFile标志没有设置，表示要打开一个现有的目录。调用FatOpenExistingDirectory子例程完成打开操作。// b. 如果是目录但NonDirectoryFile标志被设置，表示试图将目录作为文件打开，此时返回错误状态码STATUS_FILE_IS_A_DIRECTORY。// c. 如果不是目录，表示要打开一个现有的文件。此时需要检查是否只希望打开目录（OpenDirectory标志被设置）。// 如果OpenDirectory标志被设置，表示不允许将文件作为目录打开，返回错误状态码STATUS_NOT_A_DIRECTORY。// 如果OpenDirectory标志没有设置，调用FatOpenExistingFile子例程完成打开操作。// 最后，根据打开操作的结果更新Iosb结构和Irp的相关字段。//// We can't locate a dirent so this is a new file.////// Now check to see if we wanted to only open an existing file.// And then case on whether we wanted to create a file or a directory.//if ((CreateDisposition == FILE_OPEN) ||(CreateDisposition == FILE_OVERWRITE)) {DebugTrace( 0, Dbg, "Cannot open nonexisting filen", 0);try_return( Iosb.Status = STATUS_OBJECT_NAME_NOT_FOUND );}//// Skip a few cycles later if we know now that the Oem name is not// valid 8.3.//if (FlagOn(LocalCcb.Flags, CCB_FLAG_SKIP_SHORT_NAME_COMPARE)) {OemFinalName.Length = 0;}//// Determine the granted access for this operation now.//if (!NT_SUCCESS( Iosb.Status = FatCheckSystemSecurityAccess( IrpContext ))) {try_return( Iosb );}if (CreateDirectory) {DebugTrace(0, Dbg, "Create new directoryn", 0);//// If this media is write protected, don't even try the create.//if (FlagOn(Vcb->VcbState, VCB_STATE_FLAG_WRITE_PROTECTED)) {//// Set the real device for the pop-up info, and set the verify// bit in the device object, so that we will force a verify// in case the user put the correct media back in.//IoSetHardErrorOrVerifyDevice( IrpContext->OriginatingIrp,Vcb->Vpb->RealDevice );SetFlag(Vcb->Vpb->RealDevice->Flags, DO_VERIFY_VOLUME);FatRaiseStatus( IrpContext, STATUS_MEDIA_WRITE_PROTECTED );}//// Don't allow people to create directories with the// temporary bit set.//if (TemporaryFile) {try_return( Iosb.Status = STATUS_INVALID_PARAMETER );}Iosb = FatCreateNewDirectory( IrpContext,FileObject,Vcb,ParentDcb,&OemFinalName,&FinalName,DesiredAccess,ShareAccess,EaBuffer,EaLength,FileAttributes,NoEaKnowledge,DeleteOnClose );Irp->IoStatus.Information = Iosb.Information;try_return( Iosb.Status );}DebugTrace(0, Dbg, "Create new filen", 0);if ( TrailingBackslash ) {try_return( Iosb.Status = STATUS_OBJECT_NAME_INVALID );}//// If this media is write protected, don't even try the create.//if (FlagOn(Vcb->VcbState, VCB_STATE_FLAG_WRITE_PROTECTED)) {//// Set the real device for the pop-up info, and set the verify// bit in the device object, so that we will force a verify// in case the user put the correct media back in.//IoSetHardErrorOrVerifyDevice( IrpContext->OriginatingIrp,Vcb->Vpb->RealDevice );SetFlag(Vcb->Vpb->RealDevice->Flags, DO_VERIFY_VOLUME);FatRaiseStatus( IrpContext, STATUS_MEDIA_WRITE_PROTECTED );}Iosb = FatCreateNewFile( IrpContext,FileObject,Vcb,ParentDcb,&OemFinalName,&FinalName,DesiredAccess,ShareAccess,AllocationSize,EaBuffer,EaLength,FileAttributes,&Lfn,IsPagingFile,NoEaKnowledge,DeleteOnClose,TemporaryFile );//// Check if we need to set the cache support flag in// the file object//if (NT_SUCCESS(Iosb.Status) && !NoIntermediateBuffering) {FileObject->Flags |= FO_CACHE_SUPPORTED;}Irp->IoStatus.Information = Iosb.Information;try_exit: NOTHING;//// This is a Beta Fix. Do this at a better place later.//if (NT_SUCCESS(Iosb.Status) && !OpenTargetDirectory) {PFCB LocalFcb;//// If there is an Fcb/Dcb, set the long file name.//LocalFcb = FileObject->FsContext;if (LocalFcb &&((NodeType(LocalFcb) == FAT_NTC_FCB) ||(NodeType(LocalFcb) == FAT_NTC_DCB)) &&(LocalFcb->FullFileName.Buffer == NULL)) {FatSetFullNameInFcb( IrpContext, LocalFcb, &FinalName );}}} finally {DebugUnwind( FatCommonCreate );//// There used to be a test here - the ASSERT replaces it. We will// never have begun enumerating directories if we post the IRP for// oplock reasons.//ASSERT( !OplockPostIrp || DirentBcb == NULL );FatUnpinBcb( IrpContext, DirentBcb );//// If we are in an error path, check for any created subdir Dcbs that// have to be unwound. Don't whack the root directory.//// Note this will leave a branch of Dcbs dangling if the directory file// had not been built on the leaf (case: opening path which has an// element containing an invalid character name).//if ((AbnormalTermination() || !NT_SUCCESS(Iosb.Status)) &&(FinalDcb != NULL) &&(NodeType(FinalDcb) == FAT_NTC_DCB) &&IsListEmpty(&FinalDcb->Specific.Dcb.ParentDcbQueue) &&(FinalDcb->OpenCount == 0) &&(FinalDcb->Specific.Dcb.DirectoryFile != NULL)) {PFILE_OBJECT DirectoryFileObject;ULONG SavedFlags;//// Before doing the uninitialize, we have to unpin anything// that has been repinned, but disable writethrough first. We// disable raise from unpin-repin since we're already failing.//SavedFlags = IrpContext->Flags;SetFlag( IrpContext->Flags, IRP_CONTEXT_FLAG_DISABLE_RAISE |IRP_CONTEXT_FLAG_DISABLE_WRITE_THROUGH );FatUnpinRepinnedBcbs( IrpContext );DirectoryFileObject = FinalDcb->Specific.Dcb.DirectoryFile;FinalDcb->Specific.Dcb.DirectoryFile = NULL;CcUninitializeCacheMap( DirectoryFileObject, NULL, NULL );ObDereferenceObject( DirectoryFileObject );IrpContext->Flags = SavedFlags;}if (AbnormalTermination()) {FatReleaseVcb( IrpContext, Vcb );}//// Free up any string buffers we allocated//FatFreeStringBuffer( &OemFinalName);FatFreeStringBuffer( &UpcasedFinalName);FatFreeStringBuffer( &Lfn);}// 处理无法定位到目标目录项的情况，即需要创建一个新文件或目录的逻辑。// 首先检查是否只想打开一个现有文件，然后根据CreateDisposition的值分别处理文件和目录的创建：// a. 如果CreateDisposition是FILE_OPEN或FILE_OVERWRITE，表示不允许打开不存在的文件，返回错误状态码STATUS_OBJECT_NAME_NOT_FOUND。// 如果LocalCcb.Flags的CCB_FLAG_SKIP_SHORT_NAME_COMPARE标志被设置，表示不需要进行8.3格式的短文件名比较，将OemFinalName的长度设置为0。// 调用FatCheckSystemSecurityAccess函数确定此操作的授权访问权限。// 如果CreateDirectory标志被设置，表示要创建一个新目录。// a. 如果存储介质是只读的（VCB_STATE_FLAG_WRITE_PROTECTED标志被设置），则不执行创建操作，引发状态码STATUS_MEDIA_WRITE_PROTECTED。// b. 如果TemporaryFile标志被设置，表示不允许创建带有临时标志的目录，返回错误状态码STATUS_INVALID_PARAMETER。// c. 调用FatCreateNewDirectory子例程创建新目录。// 否则，表示要创建一个新文件。// a. 如果TrailingBackslash标志被设置，表示文件名无效，返回错误状态码STATUS_OBJECT_NAME_INVALID。// b. 如果存储介质是只读的，不执行创建操作，引发状态码STATUS_MEDIA_WRITE_PROTECTED。// c. 调用FatCreateNewFile子例程创建新文件。// 如果操作成功且NoIntermediateBuffering标志未设置，则设置文件对象的FO_CACHE_SUPPORTED标志，以指示支持缓存。// 更新Irp的相关字段和Iosb结构。// 在try_exit块中的Beta Fix代码段中进行额外的处理。如果存在Fcb/Dcb（文件/目录控制块），并且FullName.Buffer为空，则将FullName设置到Fcb中。// finally块中进行清理和释放操作。// a. 解除DirentBcb的锁定。// b. 如果存在FinalDcb且不为空且不是根目录（FinalDcb是目标目录的父目录），并且没有打开的子目录，并且Specific.Dcb.DirectoryFile不为空，则进行一些额外的清理操作，包括解除映射缓存、取消引用DirectoryFileObject，并进行BCB的解锁。// c. 如果发生异常终止，释放Vcb资源。// d. 释放分配的字符串缓冲区。//// The following code is only executed if we are exiting the// procedure through a normal termination. We complete the request// and if for any reason that bombs out then we need to unreference// and possibly delete the fcb and ccb.//try {if (PostIrp) {//// If the Irp hasn't already been posted, do it now.//if (!OplockPostIrp) {Iosb.Status = FatFsdPostRequest( IrpContext, Irp );}} else {FatUnpinRepinnedBcbs( IrpContext );}} finally {DebugUnwind( FatCommonCreate-in-FatCompleteRequest );if (AbnormalTermination()) {PVCB LocalVcb;PFCB LocalFcb;PCCB LocalCcb2;//// Unwind all of our counts. Note that if a write failed, then// the volume has been marked for verify, and all volume// structures will be cleaned up automatically.//(VOID) FatDecodeFileObject( FileObject, &LocalVcb, &LocalFcb, &LocalCcb2 );LocalFcb->UncleanCount -= 1;LocalFcb->OpenCount -= 1;LocalVcb->OpenFileCount -= 1;if (IsFileObjectReadOnly(FileObject)) { LocalVcb->ReadOnlyCount -= 1; }//// If we leafed out on a new Fcb we should get rid of it at this point.//// Since the object isn't being opened, we have to do all of the teardown// here. Our close path will not occur for this fileobject. Note this// will leave a branch of Dcbs dangling since we do it by hand and don't// chase to the root.//if (LocalFcb->OpenCount == 0 &&(NodeType( LocalFcb ) == FAT_NTC_FCB ||IsListEmpty(&LocalFcb->Specific.Dcb.ParentDcbQueue))) {ASSERT( NodeType( LocalFcb ) != FAT_NTC_ROOT_DCB );if ( (NodeType( LocalFcb ) == FAT_NTC_DCB) &&(LocalFcb->Specific.Dcb.DirectoryFile != NULL) ) {FatSyncUninitializeCacheMap( IrpContext,LocalFcb->Specific.Dcb.DirectoryFile );InterlockedDecrement( &LocalFcb->Specific.Dcb.DirectoryFileOpenCount );FatSetFileObject( LocalFcb->Specific.Dcb.DirectoryFile,UnopenedFileObject,NULL,NULL );ObDereferenceObject( LocalFcb->Specific.Dcb.DirectoryFile );LocalFcb->Specific.Dcb.DirectoryFile = NULL;ExFreePool( FatAllocateCloseContext(Vcb));}FatDeleteFcb( IrpContext, LocalFcb );}FatDeleteCcb( IrpContext, LocalCcb2 );FatReleaseVcb( IrpContext, LocalVcb );} else {FatReleaseVcb( IrpContext, Vcb );if ( !PostIrp ) {//// If this request is successful and the file was opened// for FILE_EXECUTE access, then set the FileObject bit.//ASSERT( IrpSp->Parameters.Create.SecurityContext != NULL );if (FlagOn( *DesiredAccess, FILE_EXECUTE )) {SetFlag( FileObject->Flags, FO_FILE_FAST_IO_READ );}//// Lock volume in drive if we opened a paging file, allocating a// reserve MDL to guarantee paging file operations can always// go forward.//if (IsPagingFile && NT_SUCCESS(Iosb.Status)) {if (!FatReserveMdl) {PMDL ReserveMdl = IoAllocateMdl( NULL,FAT_RESERVE_MDL_SIZE * PAGE_SIZE,TRUE,FALSE,NULL );//// Stash the MDL, and if it turned out there was already one there// just free what we got.//InterlockedCompareExchangePointer( &FatReserveMdl, ReserveMdl, NULL );if (FatReserveMdl != ReserveMdl) {IoFreeMdl( ReserveMdl );}}SetFlag(Vcb->VcbState, VCB_STATE_FLAG_BOOT_OR_PAGING_FILE);if (FlagOn(Vcb->VcbState, VCB_STATE_FLAG_REMOVABLE_MEDIA)) {FatToggleMediaEjectDisable( IrpContext, Vcb, TRUE );}}//// Complete the request.//FatCompleteRequest( IrpContext, Irp, Iosb.Status );}}DebugTrace(-1, Dbg, "FatCommonCreate -> %08lxn", Iosb.Status);}CollectCreateStatistics(Vcb, Iosb.Status);return Iosb.Status;// 用于处理在FAT文件系统中创建文件或目录的操作。// 代码的作用是在正常终止的情况下完成请求，并进行必要的清理操作。// try块开始执行，包含以下两种可能的路径：// 如果PostIrp为真，则检查IRP是否已经被发送。如果没有发送，则立即发送IRP以进行异步处理。// 如果PostIrp为假，则调用FatUnpinRepinnedBcbs函数对缓存进行解除固定操作。// finally块开始执行，其中包含以下两种情况的处理逻辑：// 如果程序异常终止，则执行清理操作：// 解码文件对象(FileObject)，获取相关的卷控制块(LocalVcb)、文件控制块(LocalFcb)和文件控制块(LocalCcb2)。// 减少文件控制块(LocalFcb)的未清除计数(UncleanCount)、打开计数(OpenCount)和卷控制块(LocalVcb)的打开文件计数(OpenFileCount)。// 如果文件对象(FileObject)是只读的，减少卷控制块(LocalVcb)的只读计数(ReadOnlyCount)。// 如果文件控制块(LocalFcb)的打开计数(OpenCount)为零，并且是新的文件控制块(Fcb)，或者其父级目录队列(ParentDcbQueue)为空，则删除该文件控制块(Fcb)。// 注意：此处将会删除文件控制块(Fcb)及其相关的目录控制块(Dcb)，但不会沿着树状结构删除其它相关的目录控制块(Dcb)。// 如果程序正常终止，则执行以下操作：// 释放卷控制块(Vcb)。// 如果PostIrp为假，则执行以下操作：// 如果请求成功，并且文件以FILE_EXECUTE访问模式打开，则设置文件对象(FileObject)的相应标志位。// 如果打开的是分页文件，并且I/O操作状态为成功，则锁定驱动器上的卷，分配一个保留的内存描述符列表(MDL)来确保分页文件的操作能够进行。// 完成请求，调用FatCompleteRequest函数。// 最后，代码收集创建统计信息，然后返回Iosb.Status的值。}
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