drivers/filesystems/ntfs/rw.c

   1 /*
   2  *  ReactOS kernel
   3  *  Copyright (C) 2002, 2014 ReactOS Team
   4  *
   5  *  This program is free software; you can redistribute it and/or modify
   6  *  it under the terms of the GNU General Public License as published by
   7  *  the Free Software Foundation; either version 2 of the License, or
   8  *  (at your option) any later version.
   9  *
  10  *  This program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU General Public License
  16  *  along with this program; if not, write to the Free Software
  17  *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
  18  *
  19  * COPYRIGHT:        See COPYING in the top level directory
  20  * PROJECT:          ReactOS kernel
  21  * FILE:             drivers/filesystem/ntfs/rw.c
  22  * PURPOSE:          NTFS filesystem driver
  23  * PROGRAMMERS:      Art Yerkes
  24  *                   Pierre Schweitzer (pierre@reactos.org)
  25  *                   Trevor Thompson
  26  */
  27
  28 /* INCLUDES *****************************************************************/
  29
  30 #include <ntddk.h>
  31 #include "ntfs.h"
  32
  33 #define NDEBUG
  34 #include <debug.h>
  35
  36 /* FUNCTIONS ****************************************************************/
  37
  38 /*
  39  * FUNCTION: Reads data from a file
  40  */
  41 static
  42 NTSTATUS
  43 NtfsReadFile(PDEVICE_EXTENSION DeviceExt,
  44              PFILE_OBJECT FileObject,
  45              PUCHAR Buffer,
  46              ULONG Length,
  47              ULONG ReadOffset,
  48              ULONG IrpFlags,
  49              PULONG LengthRead)
  50 {
  51     NTSTATUS Status = STATUS_SUCCESS;
  52     PNTFS_FCB Fcb;
  53     PFILE_RECORD_HEADER FileRecord;
  54     PNTFS_ATTR_CONTEXT DataContext;
  55     ULONG RealLength;
  56     ULONG RealReadOffset;
  57     ULONG RealLengthRead;
  58     ULONG ToRead;
  59     BOOLEAN AllocatedBuffer = FALSE;
  60     PCHAR ReadBuffer = (PCHAR)Buffer;
  61     ULONGLONG StreamSize;
  62
  63     DPRINT1("NtfsReadFile(%p, %p, %p, %u, %u, %x, %p)\n", DeviceExt, FileObject, Buffer, Length, ReadOffset, IrpFlags, LengthRead);
  64
  65     *LengthRead = 0;
  66
  67     if (Length == 0)
  68     {
  69         DPRINT1("Null read!\n");
  70         return STATUS_SUCCESS;
  71     }
  72
  73     Fcb = (PNTFS_FCB)FileObject->FsContext;
  74
  75     if (NtfsFCBIsCompressed(Fcb))
  76     {
  77         DPRINT1("Compressed file!\n");
  78         UNIMPLEMENTED;
  79         return STATUS_NOT_IMPLEMENTED;
  80     }
  81
  82     FileRecord = ExAllocatePoolWithTag(NonPagedPool, DeviceExt->NtfsInfo.BytesPerFileRecord, TAG_NTFS);
  83     if (FileRecord == NULL)
  84     {
  85         DPRINT1("Not enough memory!\n");
  86         return STATUS_INSUFFICIENT_RESOURCES;
  87     }
  88
  89     Status = ReadFileRecord(DeviceExt, Fcb->MFTIndex, FileRecord);
  90     if (!NT_SUCCESS(Status))
  91     {
  92         DPRINT1("Can't find record!\n");
  93         ExFreePoolWithTag(FileRecord, TAG_NTFS);
  94         return Status;
  95     }
  96
  97
  98     Status = FindAttribute(DeviceExt, FileRecord, AttributeData, Fcb->Stream, wcslen(Fcb->Stream), &DataContext, NULL);
  99     if (!NT_SUCCESS(Status))
 100     {
 101         NTSTATUS BrowseStatus;
 102         FIND_ATTR_CONTXT Context;
 103         PNTFS_ATTR_RECORD Attribute;
 104
 105         DPRINT1("No '%S' data stream associated with file!\n", Fcb->Stream);
 106
 107         BrowseStatus = FindFirstAttribute(&Context, DeviceExt, FileRecord, FALSE, &Attribute);
 108         while (NT_SUCCESS(BrowseStatus))
 109         {
 110             if (Attribute->Type == AttributeData)
 111             {
 112                 UNICODE_STRING Name;
 113
 114                 Name.Length = Attribute->NameLength * sizeof(WCHAR);
 115                 Name.MaximumLength = Name.Length;
 116                 Name.Buffer = (PWCHAR)((ULONG_PTR)Attribute + Attribute->NameOffset);
 117                 DPRINT1("Data stream: '%wZ' available\n", &Name);
 118             }
 119
 120             BrowseStatus = FindNextAttribute(&Context, &Attribute);
 121         }
 122         FindCloseAttribute(&Context);
 123
 124         ReleaseAttributeContext(DataContext);
 125         ExFreePoolWithTag(FileRecord, TAG_NTFS);
 126         return Status;
 127     }
 128
 129     StreamSize = AttributeDataLength(&DataContext->Record);
 130     if (ReadOffset >= StreamSize)
 131     {
 132         DPRINT1("Reading beyond stream end!\n");
 133         ReleaseAttributeContext(DataContext);
 134         ExFreePoolWithTag(FileRecord, TAG_NTFS);
 135         return STATUS_END_OF_FILE;
 136     }
 137
 138     ToRead = Length;
 139     if (ReadOffset + Length > StreamSize)
 140         ToRead = StreamSize - ReadOffset;
 141
 142     RealReadOffset = ReadOffset;
 143     RealLength = ToRead;
 144
 145     if ((ReadOffset % DeviceExt->NtfsInfo.BytesPerSector) != 0 || (ToRead % DeviceExt->NtfsInfo.BytesPerSector) != 0)
 146     {
 147         RealReadOffset = ROUND_DOWN(ReadOffset, DeviceExt->NtfsInfo.BytesPerSector);
 148         RealLength = ROUND_UP(ToRead, DeviceExt->NtfsInfo.BytesPerSector);
 149         /* do we need to extend RealLength by one sector? */
 150         if (RealLength + RealReadOffset < ReadOffset + Length)
 151         {
 152             if (RealReadOffset + RealLength + DeviceExt->NtfsInfo.BytesPerSector <= AttributeAllocatedLength(&DataContext->Record))
 153                 RealLength += DeviceExt->NtfsInfo.BytesPerSector;
 154         }
 155
 156
 157         ReadBuffer = ExAllocatePoolWithTag(NonPagedPool, RealLength, TAG_NTFS);
 158         if (ReadBuffer == NULL)
 159         {
 160             DPRINT1("Not enough memory!\n");
 161             ReleaseAttributeContext(DataContext);
 162             ExFreePoolWithTag(FileRecord, TAG_NTFS);
 163             return STATUS_INSUFFICIENT_RESOURCES;
 164         }
 165         AllocatedBuffer = TRUE;
 166     }
 167
 168     DPRINT1("Effective read: %lu at %lu for stream '%S'\n", RealLength, RealReadOffset, Fcb->Stream);
 169     RealLengthRead = ReadAttribute(DeviceExt, DataContext, RealReadOffset, (PCHAR)ReadBuffer, RealLength);
 170     if (RealLengthRead == 0)
 171     {
 172         DPRINT1("Read failure!\n");
 173         ReleaseAttributeContext(DataContext);
 174         ExFreePoolWithTag(FileRecord, TAG_NTFS);
 175         if (AllocatedBuffer)
 176         {
 177             ExFreePoolWithTag(ReadBuffer, TAG_NTFS);
 178         }
 179         return Status;
 180     }
 181
 182     ReleaseAttributeContext(DataContext);
 183     ExFreePoolWithTag(FileRecord, TAG_NTFS);
 184
 185     *LengthRead = ToRead;
 186
 187     DPRINT1("%lu got read\n", *LengthRead);
 188
 189     if (AllocatedBuffer)
 190     {
 191         RtlCopyMemory(Buffer, ReadBuffer + (ReadOffset - RealReadOffset), ToRead);
 192     }
 193
 194     if (ToRead != Length)
 195     {
 196         RtlZeroMemory(Buffer + ToRead, Length - ToRead);
 197     }
 198
 199     if (AllocatedBuffer)
 200     {
 201         ExFreePoolWithTag(ReadBuffer, TAG_NTFS);
 202     }
 203
 204     return STATUS_SUCCESS;
 205 }
 206
 207
 208 NTSTATUS
 209 NtfsRead(PNTFS_IRP_CONTEXT IrpContext)
 210 {
 211     PDEVICE_EXTENSION DeviceExt;
 212     PIO_STACK_LOCATION Stack;
 213     PFILE_OBJECT FileObject;
 214     PVOID Buffer;
 215     ULONG ReadLength;
 216     LARGE_INTEGER ReadOffset;
 217     ULONG ReturnedReadLength = 0;
 218     NTSTATUS Status = STATUS_SUCCESS;
 219     PIRP Irp;
 220     PDEVICE_OBJECT DeviceObject;
 221
 222     DPRINT("NtfsRead(IrpContext %p)\n", IrpContext);
 223
 224     DeviceObject = IrpContext->DeviceObject;
 225     Irp = IrpContext->Irp;
 226     Stack = IrpContext->Stack;
 227     FileObject = IrpContext->FileObject;
 228
 229     DeviceExt = DeviceObject->DeviceExtension;
 230     ReadLength = Stack->Parameters.Read.Length;
 231     ReadOffset = Stack->Parameters.Read.ByteOffset;
 232     Buffer = NtfsGetUserBuffer(Irp, BooleanFlagOn(Irp->Flags, IRP_PAGING_IO));
 233
 234     Status = NtfsReadFile(DeviceExt,
 235                           FileObject,
 236                           Buffer,
 237                           ReadLength,
 238                           ReadOffset.u.LowPart,
 239                           Irp->Flags,
 240                           &ReturnedReadLength);
 241     if (NT_SUCCESS(Status))
 242     {
 243         if (FileObject->Flags & FO_SYNCHRONOUS_IO)
 244         {
 245             FileObject->CurrentByteOffset.QuadPart =
 246                 ReadOffset.QuadPart + ReturnedReadLength;
 247         }
 248
 249         Irp->IoStatus.Information = ReturnedReadLength;
 250     }
 251     else
 252     {
 253         Irp->IoStatus.Information = 0;
 254     }
 255
 256     return Status;
 257 }
 258
 259 /**
 260 * @name NtfsWriteFile
 261 * @implemented
 262 *
 263 * Writes a file to the disk. It presently borrows a lot of code from NtfsReadFile() and
 264 * VFatWriteFileData(). It needs some more work before it will be complete; it won't handle
 265 * page files, asnyc io, cached writes, etc.
 266 *
 267 * @param DeviceExt
 268 * Points to the target disk's DEVICE_EXTENSION
 269 *
 270 * @param FileObject
 271 * Pointer to a FILE_OBJECT describing the target file
 272 *
 273 * @param Buffer
 274 * The data that's being written to the file
 275 *
 276 * @Param Length
 277 * The size of the data buffer being written, in bytes
 278 *
 279 * @param WriteOffset
 280 * Offset, in bytes, from the beginning of the file. Indicates where to start
 281 * writing data.
 282 *
 283 * @param IrpFlags
 284 * TODO: flags are presently ignored in code.
 285 *
 286 * @param LengthWritten
 287 * Pointer to a ULONG. This ULONG will be set to the number of bytes successfully written.
 288 *
 289 * @return
 290 * STATUS_SUCCESS if successful, STATUS_NOT_IMPLEMENTED if a required feature isn't implemented,
 291 * STATUS_INSUFFICIENT_RESOURCES if an allocation failed, STATUS_ACCESS_DENIED if the write itself fails,
 292 * STATUS_PARTIAL_COPY or STATUS_UNSUCCESSFUL if ReadFileRecord() fails, or
 293 * STATUS_OBJECT_NAME_NOT_FOUND if the file's data stream could not be found.
 294 *
 295 * @remarks Called by NtfsWrite(). It may perform a read-modify-write operation if the requested write is
 296 * not sector-aligned. LengthWritten only refers to how much of the requested data has been written;
 297 * extra data that needs to be written to make the write sector-aligned will not affect it.
 298 *
 299 */
 300 NTSTATUS NtfsWriteFile(PDEVICE_EXTENSION DeviceExt,
 301                        PFILE_OBJECT FileObject,
 302                        const PUCHAR Buffer,
 303                        ULONG Length,
 304                        ULONG WriteOffset,
 305                        ULONG IrpFlags,
 306                        PULONG LengthWritten)
 307 {
 308     NTSTATUS Status = STATUS_NOT_IMPLEMENTED;
 309     PNTFS_FCB Fcb;
 310     PFILE_RECORD_HEADER FileRecord;
 311     PNTFS_ATTR_CONTEXT DataContext;
 312     ULONG AttributeOffset;
 313     ULONGLONG StreamSize;
 314
 315     DPRINT("NtfsWriteFile(%p, %p, %p, %u, %u, %x, %p)\n", DeviceExt, FileObject, Buffer, Length, WriteOffset, IrpFlags, LengthWritten);
 316
 317     *LengthWritten = 0;
 318
 319     ASSERT(DeviceExt);
 320
 321     if (Length == 0)
 322     {
 323         if (Buffer == NULL)
 324             return STATUS_SUCCESS;
 325         else
 326             return STATUS_INVALID_PARAMETER;
 327     }
 328
 329     // get the File control block
 330     Fcb = (PNTFS_FCB)FileObject->FsContext;
 331     ASSERT(Fcb);
 332
 333     DPRINT("Fcb->PathName: %wS\n", Fcb->PathName);
 334     DPRINT("Fcb->ObjectName: %wS\n", Fcb->ObjectName);
 335
 336     // we don't yet handle compression
 337     if (NtfsFCBIsCompressed(Fcb))
 338     {
 339         DPRINT("Compressed file!\n");
 340         UNIMPLEMENTED;
 341         return STATUS_NOT_IMPLEMENTED;
 342     }
 343
 344     // allocate non-paged memory for the FILE_RECORD_HEADER
 345     FileRecord = ExAllocatePoolWithTag(NonPagedPool, DeviceExt->NtfsInfo.BytesPerFileRecord, TAG_NTFS);
 346     if (FileRecord == NULL)
 347     {
 348         DPRINT1("Not enough memory! Can't write %wS!\n", Fcb->PathName);
 349         return STATUS_INSUFFICIENT_RESOURCES;
 350     }
 351
 352     // read the FILE_RECORD_HEADER from the drive (or cache)
 353     DPRINT("Reading file record...\n");
 354     Status = ReadFileRecord(DeviceExt, Fcb->MFTIndex, FileRecord);
 355     if (!NT_SUCCESS(Status))
 356     {
 357         // We couldn't get the file's record. Free the memory and return the error
 358         DPRINT1("Can't find record for %wS!\n", Fcb->ObjectName);
 359         ExFreePoolWithTag(FileRecord, TAG_NTFS);
 360         return Status;
 361     }
 362
 363     DPRINT("Found record for %wS\n", Fcb->ObjectName);
 364
 365     // Find the attribute with the data stream for our file
 366     DPRINT("Finding Data Attribute...\n");
 367     Status = FindAttribute(DeviceExt, FileRecord, AttributeData, Fcb->Stream, wcslen(Fcb->Stream), &DataContext,
 368                            &AttributeOffset);
 369
 370     // Did we fail to find the attribute?
 371     if (!NT_SUCCESS(Status))
 372     {
 373         NTSTATUS BrowseStatus;
 374         FIND_ATTR_CONTXT Context;
 375         PNTFS_ATTR_RECORD Attribute;
 376
 377         DPRINT1("No '%S' data stream associated with file!\n", Fcb->Stream);
 378
 379         // Couldn't find the requested data stream; print a list of streams available
 380         BrowseStatus = FindFirstAttribute(&Context, DeviceExt, FileRecord, FALSE, &Attribute);
 381         while (NT_SUCCESS(BrowseStatus))
 382         {
 383             if (Attribute->Type == AttributeData)
 384             {
 385                 UNICODE_STRING Name;
 386
 387                 Name.Length = Attribute->NameLength * sizeof(WCHAR);
 388                 Name.MaximumLength = Name.Length;
 389                 Name.Buffer = (PWCHAR)((ULONG_PTR)Attribute + Attribute->NameOffset);
 390                 DPRINT1("Data stream: '%wZ' available\n", &Name);
 391             }
 392
 393             BrowseStatus = FindNextAttribute(&Context, &Attribute);
 394         }
 395         FindCloseAttribute(&Context);
 396
 397         ReleaseAttributeContext(DataContext);
 398         ExFreePoolWithTag(FileRecord, TAG_NTFS);
 399         return Status;
 400     }
 401
 402     // Get the size of the stream on disk
 403     StreamSize = AttributeDataLength(&DataContext->Record);
 404
 405     DPRINT("WriteOffset: %lu\tStreamSize: %I64u\n", WriteOffset, StreamSize);
 406
 407     // Are we trying to write beyond the end of the stream?
 408     if (WriteOffset + Length > StreamSize)
 409     {
 410         // is increasing the stream size allowed?
 411         if (!(Fcb->Flags & FCB_IS_VOLUME) &&
 412             !(IrpFlags & IRP_PAGING_IO))
 413         {
 414             LARGE_INTEGER DataSize;
 415             ULONGLONG AllocationSize;
 416             PFILENAME_ATTRIBUTE fileNameAttribute;
 417             ULONGLONG ParentMFTId;
 418             UNICODE_STRING filename;
 419
 420             DataSize.QuadPart = WriteOffset + Length;
 421
 422             AllocationSize = ROUND_UP(DataSize.QuadPart, Fcb->Vcb->NtfsInfo.BytesPerCluster);
 423
 424             // set the attribute data length
 425             Status = SetAttributeDataLength(FileObject, Fcb, DataContext, AttributeOffset, FileRecord, &DataSize);
 426
 427             if (!NT_SUCCESS(Status))
 428             {
 429                 ReleaseAttributeContext(DataContext);
 430                 ExFreePoolWithTag(FileRecord, TAG_NTFS);
 431                 *LengthWritten = 0;
 432                 return Status;
 433             }
 434
 435             // at this point the record in DataContext may be stale, so we need to refresh it
 436             ReleaseAttributeContext(DataContext);
 437
 438             Status = FindAttribute(DeviceExt,
 439                                    FileRecord,
 440                                    AttributeData,
 441                                    Fcb->Stream,
 442                                    wcslen(Fcb->Stream),
 443                                    &DataContext,
 444                                    &AttributeOffset);
 445             if (!NT_SUCCESS(Status))
 446             {
 447                 DPRINT1("DRIVER ERROR: Couldn't find $DATA attribute after setting size!\n");
 448                 return Status;
 449             }
 450
 451             // now we need to update this file's size in every directory index entry that references it
 452             // TODO: put this code in its own function and adapt it to work with every filename / hardlink
 453             // stored in the file record.
 454             fileNameAttribute = GetBestFileNameFromRecord(Fcb->Vcb, FileRecord);
 455             ASSERT(fileNameAttribute);
 456
 457             ParentMFTId = fileNameAttribute->DirectoryFileReferenceNumber & NTFS_MFT_MASK;
 458
 459             filename.Buffer = fileNameAttribute->Name;
 460             filename.Length = fileNameAttribute->NameLength * sizeof(WCHAR);
 461             filename.MaximumLength = filename.Length;
 462
 463             Status = UpdateFileNameRecord(Fcb->Vcb, ParentMFTId, &filename, FALSE, DataSize.QuadPart, AllocationSize);
 464
 465         }
 466         else
 467         {
 468             // TODO - just fail for now
 469             ReleaseAttributeContext(DataContext);
 470             ExFreePoolWithTag(FileRecord, TAG_NTFS);
 471             *LengthWritten = 0;
 472             return STATUS_ACCESS_DENIED;
 473         }
 474     }
 475
 476     DPRINT("Length: %lu\tWriteOffset: %lu\tStreamSize: %I64u\n", Length, WriteOffset, StreamSize);
 477
 478     // Write the data to the attribute
 479     Status = WriteAttribute(DeviceExt, DataContext, WriteOffset, Buffer, Length, LengthWritten);
 480
 481     // Did the write fail?
 482     if (!NT_SUCCESS(Status))
 483     {
 484         DPRINT1("Write failure!\n");
 485         ReleaseAttributeContext(DataContext);
 486         ExFreePoolWithTag(FileRecord, TAG_NTFS);
 487
 488         return Status;
 489     }
 490
 491     // This should never happen:
 492     if (*LengthWritten != Length)
 493     {
 494         DPRINT1("\a\tNTFS DRIVER ERROR: length written (%lu) differs from requested (%lu), but no error was indicated!\n",
 495             *LengthWritten, Length);
 496         Status = STATUS_UNEXPECTED_IO_ERROR;
 497     }
 498
 499     ReleaseAttributeContext(DataContext);
 500     ExFreePoolWithTag(FileRecord, TAG_NTFS);
 501
 502     return Status;
 503 }
 504
 505 /**
 506 * @name NtfsWrite
 507 * @implemented
 508 *
 509 * Handles IRP_MJ_WRITE I/O Request Packets for NTFS. This code borrows a lot from
 510 * VfatWrite, and needs a lot of cleaning up. It also needs a lot more of the code
 511 * from VfatWrite integrated.
 512 *
 513 * @param IrpContext
 514 * Points to an NTFS_IRP_CONTEXT which describes the write
 515 *
 516 * @return
 517 * STATUS_SUCCESS if successful,
 518 * STATUS_INSUFFICIENT_RESOURCES if an allocation failed,
 519 * STATUS_INVALID_DEVICE_REQUEST if called on the main device object,
 520 * STATUS_NOT_IMPLEMENTED or STATUS_ACCESS_DENIED if a required feature isn't implemented.
 521 * STATUS_PARTIAL_COPY, STATUS_UNSUCCESSFUL, or STATUS_OBJECT_NAME_NOT_FOUND if NtfsWriteFile() fails.
 522 *
 523 * @remarks Called by NtfsDispatch() in response to an IRP_MJ_WRITE request. Page files are not implemented.
 524 * Support for large files (>4gb) is not implemented. Cached writes, file locks, transactions, etc - not implemented.
 525 *
 526 */
 527 NTSTATUS
 528 NtfsWrite(PNTFS_IRP_CONTEXT IrpContext)
 529 {
 530     PNTFS_FCB Fcb;
 531     PERESOURCE Resource = NULL;
 532     LARGE_INTEGER ByteOffset;
 533     PUCHAR Buffer;
 534     NTSTATUS Status = STATUS_SUCCESS;
 535     ULONG Length = 0;
 536     ULONG ReturnedWriteLength = 0;
 537     PDEVICE_OBJECT DeviceObject = NULL;
 538     PDEVICE_EXTENSION DeviceExt = NULL;
 539     PFILE_OBJECT FileObject = NULL;
 540     PIRP Irp = NULL;
 541     ULONG BytesPerSector;
 542
 543     DPRINT("NtfsWrite(IrpContext %p)\n", IrpContext);
 544     ASSERT(IrpContext);
 545
 546     // This request is not allowed on the main device object
 547     if (IrpContext->DeviceObject == NtfsGlobalData->DeviceObject)
 548     {
 549         DPRINT1("\t\t\t\tNtfsWrite is called with the main device object.\n");
 550
 551         Irp->IoStatus.Information = 0;
 552         return STATUS_INVALID_DEVICE_REQUEST;
 553     }
 554
 555     // get the I/O request packet
 556     Irp = IrpContext->Irp;
 557
 558     // get the File control block
 559     Fcb = (PNTFS_FCB)IrpContext->FileObject->FsContext;
 560     ASSERT(Fcb);
 561
 562     DPRINT("About to write %wS\n", Fcb->ObjectName);
 563     DPRINT("NTFS Version: %d.%d\n", Fcb->Vcb->NtfsInfo.MajorVersion, Fcb->Vcb->NtfsInfo.MinorVersion);
 564
 565     // setup some more locals
 566     FileObject = IrpContext->FileObject;
 567     DeviceObject = IrpContext->DeviceObject;
 568     DeviceExt = DeviceObject->DeviceExtension;
 569     BytesPerSector = DeviceExt->StorageDevice->SectorSize;
 570     Length = IrpContext->Stack->Parameters.Write.Length;
 571
 572     // get the file offset we'll be writing to
 573     ByteOffset = IrpContext->Stack->Parameters.Write.ByteOffset;
 574     if (ByteOffset.u.LowPart == FILE_WRITE_TO_END_OF_FILE &&
 575         ByteOffset.u.HighPart == -1)
 576     {
 577         ByteOffset.QuadPart = Fcb->RFCB.FileSize.QuadPart;
 578     }
 579
 580     DPRINT("ByteOffset: %I64u\tLength: %lu\tBytes per sector: %lu\n", ByteOffset.QuadPart,
 581         Length, BytesPerSector);
 582
 583     if (ByteOffset.u.HighPart && !(Fcb->Flags & FCB_IS_VOLUME))
 584     {
 585         // TODO: Support large files
 586         DPRINT1("FIXME: Writing to large files is not yet supported at this time.\n");
 587         return STATUS_INVALID_PARAMETER;
 588     }
 589
 590     // Is this a non-cached write? A non-buffered write?
 591     if (IrpContext->Irp->Flags & (IRP_PAGING_IO | IRP_NOCACHE) || (Fcb->Flags & FCB_IS_VOLUME) ||
 592         IrpContext->FileObject->Flags & FILE_NO_INTERMEDIATE_BUFFERING)
 593     {
 594         // non-cached and non-buffered writes must be sector aligned
 595         if (ByteOffset.u.LowPart % BytesPerSector != 0 || Length % BytesPerSector != 0)
 596         {
 597             DPRINT1("Non-cached writes and non-buffered writes must be sector aligned!\n");
 598             return STATUS_INVALID_PARAMETER;
 599         }
 600     }
 601
 602     if (Length == 0)
 603     {
 604         DPRINT1("Null write!\n");
 605
 606         IrpContext->Irp->IoStatus.Information = 0;
 607
 608         // FIXME: Doesn't accurately detect when a user passes NULL to WriteFile() for the buffer
 609         if (Irp->UserBuffer == NULL && Irp->MdlAddress == NULL)
 610         {
 611             // FIXME: Update last write time
 612             return STATUS_SUCCESS;
 613         }
 614
 615         return STATUS_INVALID_PARAMETER;
 616     }
 617
 618     // get the Resource
 619     if (Fcb->Flags & FCB_IS_VOLUME)
 620     {
 621         Resource = &DeviceExt->DirResource;
 622     }
 623     else if (IrpContext->Irp->Flags & IRP_PAGING_IO)
 624     {
 625         Resource = &Fcb->PagingIoResource;
 626     }
 627     else
 628     {
 629         Resource = &Fcb->MainResource;
 630     }
 631
 632     // acquire exclusive access to the Resource
 633     if (!ExAcquireResourceExclusiveLite(Resource, BooleanFlagOn(IrpContext->Flags, IRPCONTEXT_CANWAIT)))
 634     {
 635         return STATUS_CANT_WAIT;
 636     }
 637
 638     /* From VfatWrite(). Todo: Handle file locks
 639     if (!(IrpContext->Irp->Flags & IRP_PAGING_IO) &&
 640     FsRtlAreThereCurrentFileLocks(&Fcb->FileLock))
 641     {
 642     if (!FsRtlCheckLockForWriteAccess(&Fcb->FileLock, IrpContext->Irp))
 643     {
 644     Status = STATUS_FILE_LOCK_CONFLICT;
 645     goto ByeBye;
 646     }
 647     }*/
 648
 649     // Is this an async request to a file?
 650     if (!(IrpContext->Flags & IRPCONTEXT_CANWAIT) && !(Fcb->Flags & FCB_IS_VOLUME))
 651     {
 652         DPRINT1("FIXME: Async writes not supported in NTFS!\n");
 653
 654         ExReleaseResourceLite(Resource);
 655         return STATUS_NOT_IMPLEMENTED;
 656     }
 657
 658     // get the buffer of data the user is trying to write
 659     Buffer = NtfsGetUserBuffer(Irp, BooleanFlagOn(Irp->Flags, IRP_PAGING_IO));
 660     ASSERT(Buffer);
 661
 662     // lock the buffer
 663     Status = NtfsLockUserBuffer(Irp, Length, IoReadAccess);
 664
 665     // were we unable to lock the buffer?
 666     if (!NT_SUCCESS(Status))
 667     {
 668         DPRINT1("Unable to lock user buffer!\n");
 669
 670         ExReleaseResourceLite(Resource);
 671         return Status;
 672     }
 673
 674     DPRINT("Existing File Size(Fcb->RFCB.FileSize.QuadPart): %I64u\n", Fcb->RFCB.FileSize.QuadPart);
 675     DPRINT("About to write the data. Length: %lu\n", Length);
 676
 677     // TODO: handle HighPart of ByteOffset (large files)
 678
 679     // write the file
 680     Status = NtfsWriteFile(DeviceExt,
 681                            FileObject,
 682                            Buffer,
 683                            Length,
 684                            ByteOffset.LowPart,
 685                            Irp->Flags,
 686                            &ReturnedWriteLength);
 687
 688     IrpContext->Irp->IoStatus.Status = Status;
 689
 690     // was the write successful?
 691     if (NT_SUCCESS(Status))
 692     {
 693         // TODO: Update timestamps
 694
 695         if (FileObject->Flags & FO_SYNCHRONOUS_IO)
 696         {
 697             // advance the file pointer
 698             FileObject->CurrentByteOffset.QuadPart = ByteOffset.QuadPart + ReturnedWriteLength;
 699         }
 700
 701         IrpContext->PriorityBoost = IO_DISK_INCREMENT;
 702     }
 703     else
 704     {
 705         DPRINT1("Write not Succesful!\tReturned length: %lu\n", ReturnedWriteLength);
 706     }
 707
 708     Irp->IoStatus.Information = ReturnedWriteLength;
 709
 710     // Note: We leave the user buffer that we locked alone, it's up to the I/O manager to unlock and free it
 711
 712     ExReleaseResourceLite(Resource);
 713
 714     return Status;
 715 }
 716
 717 /* EOF */