[reactos] 03/72: [NTFS] When writing to a file, increase the file size if trying to write past the end. *FindAttribute() has been given an optional pointer to a ULONG that will receive the offset of the found attribute from the beginning of the record. This is to allow for found attributes to be written back into their file records. +SetAttributeDataLength() +UpdateFileRecord() - Updates a file record in the master file table at a given index. +AddFixupArray() - Prepares a file record or directo

[Trevor Thompson]

https://git.reactos.org/?p=reactos.git;a=commitdiff;h=ba33b9faac9457359efac…

commit ba33b9faac9457359efac140b28cc17c7f664eb4
Author: Trevor Thompson <tmt256(a)email.vccs.edu>
AuthorDate: Wed Jun 22 21:20:50 2016 +0000

    [NTFS]
    When writing to a file, increase the file size if trying to write past the end.
    *FindAttribute() has been given an optional pointer to a ULONG that will receive the
offset of the found attribute from the beginning of the record. This is to allow for found
attributes to be written back into their file records.
    +SetAttributeDataLength()
    +UpdateFileRecord() - Updates a file record in the master file table at a given
index.
    +AddFixupArray() - Prepares a file record or directory index for writing to the disk.
    
    svn path=/branches/GSoC_2016/NTFS/; revision=71660
---
 drivers/filesystems/ntfs/attrib.c  |  20 ++++--
 drivers/filesystems/ntfs/dirctl.c  |   2 +-
 drivers/filesystems/ntfs/fcb.c     |   4 +-
 drivers/filesystems/ntfs/fsctl.c   |   8 +--
 drivers/filesystems/ntfs/mft.c     | 141 +++++++++++++++++++++++++++++++++++--
 drivers/filesystems/ntfs/ntfs.h    |  30 +++++++-
 drivers/filesystems/ntfs/rw.c      |  48 ++++++++++---
 drivers/filesystems/ntfs/volinfo.c |   2 +-
 8 files changed, 226 insertions(+), 29 deletions(-)

diff --git a/drivers/filesystems/ntfs/attrib.c b/drivers/filesystems/ntfs/attrib.c
index 1883951c44..12474f6c81 100644
--- a/drivers/filesystems/ntfs/attrib.c
+++ b/drivers/filesystems/ntfs/attrib.c
@@ -150,6 +150,8 @@ static
 PNTFS_ATTR_RECORD
 InternalGetNextAttribute(PFIND_ATTR_CONTXT Context)
 {
+    PNTFS_ATTR_RECORD NextAttribute;
+
     if (Context->CurrAttr == (PVOID)-1)
     {
         return NULL;
@@ -165,7 +167,10 @@ InternalGetNextAttribute(PFIND_ATTR_CONTXT Context)
             return NULL;
         }
 
-        Context->CurrAttr = (PNTFS_ATTR_RECORD)((ULONG_PTR)Context->CurrAttr +
Context->CurrAttr->Length);
+        NextAttribute = (PNTFS_ATTR_RECORD)((ULONG_PTR)Context->CurrAttr +
Context->CurrAttr->Length);
+        Context->Offset += ((ULONG_PTR)NextAttribute -
(ULONG_PTR)Context->CurrAttr);
+        Context->CurrAttr = NextAttribute;
+
         if (Context->CurrAttr < Context->LastAttr &&
             Context->CurrAttr->Type != AttributeEnd)
         {
@@ -186,7 +191,9 @@ InternalGetNextAttribute(PFIND_ATTR_CONTXT Context)
     }
     else if (Context->CurrAttr->Length != 0)
     {
-        Context->CurrAttr = (PNTFS_ATTR_RECORD)((ULONG_PTR)Context->CurrAttr +
Context->CurrAttr->Length);
+        NextAttribute = (PNTFS_ATTR_RECORD)((ULONG_PTR)Context->CurrAttr +
Context->CurrAttr->Length);
+        Context->Offset += ((ULONG_PTR)NextAttribute -
(ULONG_PTR)Context->CurrAttr);
+        Context->CurrAttr = NextAttribute;
     }
     else
     {
@@ -223,6 +230,7 @@ FindFirstAttribute(PFIND_ATTR_CONTXT Context,
     Context->LastAttr = (PNTFS_ATTR_RECORD)((ULONG_PTR)FileRecord +
FileRecord->BytesInUse);
     Context->NonResidentStart = NULL;
     Context->NonResidentEnd = NULL;
+    Context->Offset = FileRecord->AttributeOffset;
 
     if (Context->FirstAttr->Type == AttributeEnd)
     {
@@ -246,6 +254,7 @@ FindFirstAttribute(PFIND_ATTR_CONTXT Context,
     else
     {
         *Attribute = Context->CurrAttr;
+        Context->Offset = (UCHAR*)Context->CurrAttr - (UCHAR*)FileRecord;
     }
 
     return STATUS_SUCCESS;
@@ -307,7 +316,8 @@ NtfsDumpFileNameAttribute(PNTFS_ATTR_RECORD Attribute)
 
     FileNameAttr = (PFILENAME_ATTRIBUTE)((ULONG_PTR)Attribute +
Attribute->Resident.ValueOffset);
     DbgPrint(" (%x) '%.*S' ", FileNameAttr->NameType,
FileNameAttr->NameLength, FileNameAttr->Name);
-    DbgPrint(" '%x' ", FileNameAttr->FileAttributes);
+    DbgPrint(" '%x' \n", FileNameAttr->FileAttributes);
+    DbgPrint(" AllocatedSize: %I64u\nDataSize: %I64u\n",
FileNameAttr->AllocatedSize, FileNameAttr->DataSize);
 }
 
 
@@ -481,8 +491,8 @@ NtfsDumpAttribute(PDEVICE_EXTENSION Vcb,
         {
             FindRun(Attribute,0,&lcn, &runcount);
 
-            DbgPrint("  AllocatedSize %I64u  DataSize %I64u\n",
-                     Attribute->NonResident.AllocatedSize,
Attribute->NonResident.DataSize);
+            DbgPrint("  AllocatedSize %I64u  DataSize %I64u InitilizedSize
%I64u\n",
+                     Attribute->NonResident.AllocatedSize,
Attribute->NonResident.DataSize, Attribute->NonResident.InitializedSize);
             DbgPrint("  logical clusters: %I64u - %I64u\n",
                      lcn, lcn + runcount - 1);
         }
diff --git a/drivers/filesystems/ntfs/dirctl.c b/drivers/filesystems/ntfs/dirctl.c
index 82b8a7cb1b..aaa6dfcb87 100644
--- a/drivers/filesystems/ntfs/dirctl.c
+++ b/drivers/filesystems/ntfs/dirctl.c
@@ -47,7 +47,7 @@ NtfsGetFileSize(PDEVICE_EXTENSION DeviceExt,
     NTSTATUS Status;
     PNTFS_ATTR_CONTEXT DataContext;
 
-    Status = FindAttribute(DeviceExt, FileRecord, AttributeData, Stream, StreamLength,
&DataContext);
+    Status = FindAttribute(DeviceExt, FileRecord, AttributeData, Stream, StreamLength,
&DataContext, NULL);
     if (NT_SUCCESS(Status))
     {
         Size = AttributeDataLength(&DataContext->Record);
diff --git a/drivers/filesystems/ntfs/fcb.c b/drivers/filesystems/ntfs/fcb.c
index e88944c334..111660288a 100644
--- a/drivers/filesystems/ntfs/fcb.c
+++ b/drivers/filesystems/ntfs/fcb.c
@@ -568,7 +568,7 @@ NtfsDirFindFile(PNTFS_VCB Vcb,
     }
     else if (Colon != 0)
     {
-        Status = FindAttribute(Vcb, FileRecord, AttributeData, Colon, wcslen(Colon),
&DataContext);
+        Status = FindAttribute(Vcb, FileRecord, AttributeData, Colon, wcslen(Colon),
&DataContext, NULL);
         if (!NT_SUCCESS(Status))
         {
             return STATUS_OBJECT_NAME_NOT_FOUND;
@@ -741,7 +741,7 @@ NtfsReadFCBAttribute(PNTFS_VCB Vcb,
         return Status;
     }
 
-    Status = FindAttribute(Vcb, FileRecord, Type, Name, NameLength, &AttrCtxt);
+    Status = FindAttribute(Vcb, FileRecord, Type, Name, NameLength, &AttrCtxt,
NULL);
     if (!NT_SUCCESS(Status))
     {
         ExFreePoolWithTag(FileRecord, TAG_NTFS);
diff --git a/drivers/filesystems/ntfs/fsctl.c b/drivers/filesystems/ntfs/fsctl.c
index 0ce93a58ea..a1f3048cd0 100644
--- a/drivers/filesystems/ntfs/fsctl.c
+++ b/drivers/filesystems/ntfs/fsctl.c
@@ -295,7 +295,7 @@ NtfsGetVolumeData(PDEVICE_OBJECT DeviceObject,
         return Status;
     }
 
-    Status = FindAttribute(DeviceExt, DeviceExt->MasterFileTable, AttributeData,
L"", 0, &DeviceExt->MFTContext);
+    Status = FindAttribute(DeviceExt, DeviceExt->MasterFileTable, AttributeData,
L"", 0, &DeviceExt->MFTContext, NULL);
     if (!NT_SUCCESS(Status))
     {
         DPRINT1("Can't find data attribute for Master File Table.\n");
@@ -333,7 +333,7 @@ NtfsGetVolumeData(PDEVICE_OBJECT DeviceObject,
     NtfsDumpFileAttributes(DeviceExt, VolumeRecord);
 
     /* Get volume name */
-    Status = FindAttribute(DeviceExt, VolumeRecord, AttributeVolumeName, L"",
0, &AttrCtxt);
+    Status = FindAttribute(DeviceExt, VolumeRecord, AttributeVolumeName, L"",
0, &AttrCtxt, NULL);
 
     if (NT_SUCCESS(Status) && AttrCtxt->Record.Resident.ValueLength != 0)
     {
@@ -374,7 +374,7 @@ NtfsGetVolumeData(PDEVICE_OBJECT DeviceObject,
     DeviceExt->VolumeFcb = VolumeFcb;
 
     /* Get volume information */
-    Status = FindAttribute(DeviceExt, VolumeRecord, AttributeVolumeInformation,
L"", 0, &AttrCtxt);
+    Status = FindAttribute(DeviceExt, VolumeRecord, AttributeVolumeInformation,
L"", 0, &AttrCtxt, NULL);
 
     if (NT_SUCCESS(Status) && AttrCtxt->Record.Resident.ValueLength != 0)
     {
@@ -804,7 +804,7 @@ GetVolumeBitmap(PDEVICE_EXTENSION DeviceExt,
         return Status;
     }
 
-    Status = FindAttribute(DeviceExt, BitmapRecord, AttributeData, L"", 0,
&DataContext);
+    Status = FindAttribute(DeviceExt, BitmapRecord, AttributeData, L"", 0,
&DataContext, NULL);
     if (!NT_SUCCESS(Status))
     {
         DPRINT1("Failed find $DATA for bitmap: %lx\n", Status);
diff --git a/drivers/filesystems/ntfs/mft.c b/drivers/filesystems/ntfs/mft.c
index 1294264e69..a53b37fb87 100644
--- a/drivers/filesystems/ntfs/mft.c
+++ b/drivers/filesystems/ntfs/mft.c
@@ -81,13 +81,24 @@ ReleaseAttributeContext(PNTFS_ATTR_CONTEXT Context)
 }
 
 
+/**
+* @name FindAttribute
+* @implemented
+* 
+* Searches a file record for an attribute matching the given type and name.
+*
+* @param Offset
+* Optional pointer to a ULONG that will receive the offset of the found attribute
+* from the beginning of the record. Can be set to NULL.
+*/
 NTSTATUS
 FindAttribute(PDEVICE_EXTENSION Vcb,
               PFILE_RECORD_HEADER MftRecord,
               ULONG Type,
               PCWSTR Name,
               ULONG NameLength,
-              PNTFS_ATTR_CONTEXT * AttrCtx)
+              PNTFS_ATTR_CONTEXT * AttrCtx,
+              PULONG Offset)
 {
     BOOLEAN Found;
     NTSTATUS Status;
@@ -123,6 +134,10 @@ FindAttribute(PDEVICE_EXTENSION Vcb,
                 /* Found it, fill up the context and return. */
                 DPRINT("Found context\n");
                 *AttrCtx = PrepareAttributeContext(Attribute);
+
+                if (Offset != NULL)
+                    *Offset = Context.Offset;
+
                 FindCloseAttribute(&Context);
                 return STATUS_SUCCESS;
             }
@@ -156,6 +171,61 @@ AttributeDataLength(PNTFS_ATTR_RECORD AttrRecord)
 }
 
 
+NTSTATUS
+SetAttributeDataLength(PFILE_OBJECT FileObject,
+                       PNTFS_FCB Fcb,
+                       PNTFS_ATTR_CONTEXT AttrContext,
+                       ULONG AttrOffset,
+                       PFILE_RECORD_HEADER FileRecord,
+                       PDEVICE_EXTENSION DeviceExt,
+                       PLARGE_INTEGER DataSize)
+{
+    if (AttrContext->Record.IsNonResident)
+    {
+        // do we need to increase the allocation size?
+        if (AttrContext->Record.NonResident.AllocatedSize < DataSize->QuadPart)
+        {            
+            DPRINT1("FixMe: Increasing allocation size is unimplemented!\n");
+            return STATUS_NOT_IMPLEMENTED;
+        }
+
+        // TODO: is the file compressed, encrypted, or sparse?
+
+        // NOTE: we need to have acquired the main resource exclusively, as well as(?)
the PagingIoResource
+
+        // TODO: update the allocated size on-disk
+        DPRINT("Allocated Size: %I64u\n",
AttrContext->Record.NonResident.AllocatedSize);
+
+        AttrContext->Record.NonResident.DataSize = DataSize->QuadPart;
+        AttrContext->Record.NonResident.InitializedSize = DataSize->QuadPart;
+
+        Fcb->RFCB.FileSize = *DataSize;
+        Fcb->RFCB.ValidDataLength = *DataSize;
+
+        DPRINT("Data Size: %I64u\n", Fcb->RFCB.FileSize.QuadPart);
+
+        //NtfsDumpFileAttributes(Fcb->Vcb, FileRecord);
+
+        // copy the attribute back into the FileRecord
+        RtlCopyMemory((PCHAR)FileRecord + AttrOffset, &AttrContext->Record,
AttrContext->Record.Length);
+
+        //NtfsDumpFileAttributes(Fcb->Vcb, FileRecord);
+
+        // write the updated file record back to disk
+        UpdateFileRecord(Fcb->Vcb, Fcb->MFTIndex, FileRecord);
+
+        CcSetFileSizes(FileObject, (PCC_FILE_SIZES)&Fcb->RFCB.AllocationSize);
+    }
+    else
+    {
+        // we can't yet handle resident attributes
+        DPRINT1("FixMe: Can't handle increasing length of resident
attribute\n");
+        return STATUS_NOT_IMPLEMENTED;
+    }
+
+    return STATUS_SUCCESS;
+}
+
 ULONG
 ReadAttribute(PDEVICE_EXTENSION Vcb,
               PNTFS_ATTR_CONTEXT Context,
@@ -612,8 +682,39 @@ ReadFileRecord(PDEVICE_EXTENSION Vcb,
     return FixupUpdateSequenceArray(Vcb, &file->Ntfs);
 }
 
+/**
+* UpdateFileRecord
+* @implemented
+* Writes a file record to the master file table, at a given index.
+*/
+NTSTATUS
+UpdateFileRecord(PDEVICE_EXTENSION Vcb,
+                 ULONGLONG index,
+                 PFILE_RECORD_HEADER file)
+{
+    ULONG BytesWritten;
+    NTSTATUS Status = STATUS_SUCCESS;
+
+    DPRINT("UpdateFileRecord(%p, %I64x, %p)\n", Vcb, index, file);
+
+    // Add the fixup array to prepare the data for writing to disk
+    AddFixupArray(Vcb, file);
+
+    // write the file record to the master file table
+    Status = WriteAttribute(Vcb, Vcb->MFTContext, index *
Vcb->NtfsInfo.BytesPerFileRecord, (const PUCHAR)file,
Vcb->NtfsInfo.BytesPerFileRecord, &BytesWritten);
+
+    // TODO: Update MFT mirror
+
+    if (!NT_SUCCESS(Status))
+    {
+        DPRINT1("UpdateFileRecord failed: %I64u written, %u expected\n",
BytesWritten, Vcb->NtfsInfo.BytesPerFileRecord);
+    }
+
+    return Status;
+}
+
 
-NTSTATUS 
+NTSTATUS
 FixupUpdateSequenceArray(PDEVICE_EXTENSION Vcb,
                          PNTFS_RECORD_HEADER Record)
 {
@@ -627,6 +728,8 @@ FixupUpdateSequenceArray(PDEVICE_EXTENSION Vcb,
     USACount = Record->UsaCount - 1; /* Exclude the USA Number. */
     Block = (USHORT*)((PCHAR)Record + Vcb->NtfsInfo.BytesPerSector - 2);
 
+    DPRINT("FixupUpdateSequenceArray(%p, %p)\nUSANumber: %u\tUSACount: %u\n",
Vcb, Record, USANumber, USACount);
+
     while (USACount)
     {
         if (*Block != USANumber)
@@ -642,6 +745,36 @@ FixupUpdateSequenceArray(PDEVICE_EXTENSION Vcb,
     return STATUS_SUCCESS;
 }
 
+NTSTATUS
+AddFixupArray(PDEVICE_EXTENSION Vcb,
+              PFILE_RECORD_HEADER Record)
+{
+    USHORT *pShortToFixUp;
+    unsigned int ArrayEntryCount = Record->BytesAllocated /
Vcb->NtfsInfo.BytesPerSector;
+    unsigned int Offset = Vcb->NtfsInfo.BytesPerSector - 2;
+    int i;
+
+    PFIXUP_ARRAY fixupArray = (PFIXUP_ARRAY)((UCHAR*)Record +
Record->Ntfs.UsaOffset);
+
+    DPRINT("AddFixupArray(%p, %p)\n fixupArray->USN: %u, ArrayEntryCount:
%u\n", Vcb, Record, fixupArray->USN, ArrayEntryCount);
+
+    if (Record->BytesAllocated % Vcb->NtfsInfo.BytesPerSector != 0)
+        ArrayEntryCount++;
+
+    fixupArray->USN++;
+
+    for (i = 0; i < ArrayEntryCount; i++)
+    {
+        DPRINT("USN: %u\tOffset: %u\n", fixupArray->USN, Offset);
+
+        pShortToFixUp = (USHORT*)((UCHAR*)Record + Offset);
+        fixupArray->Array[i] = *pShortToFixUp;
+        *pShortToFixUp = fixupArray->USN;
+        Offset += Vcb->NtfsInfo.BytesPerSector;
+    }
+
+    return STATUS_SUCCESS;
+}
 
 NTSTATUS
 ReadLCN(PDEVICE_EXTENSION Vcb,
@@ -780,7 +913,7 @@ BrowseIndexEntries(PDEVICE_EXTENSION Vcb,
         return STATUS_OBJECT_PATH_NOT_FOUND; 
     }
 
-    Status = FindAttribute(Vcb, MftRecord, AttributeIndexAllocation, L"$I30",
4, &IndexAllocationCtx);
+    Status = FindAttribute(Vcb, MftRecord, AttributeIndexAllocation, L"$I30",
4, &IndexAllocationCtx, NULL);
     if (!NT_SUCCESS(Status))
     {
         DPRINT("Corrupted filesystem!\n");
@@ -850,7 +983,7 @@ NtfsFindMftRecord(PDEVICE_EXTENSION Vcb,
     }
 
     ASSERT(MftRecord->Ntfs.Type == NRH_FILE_TYPE);
-    Status = FindAttribute(Vcb, MftRecord, AttributeIndexRoot, L"$I30", 4,
&IndexRootCtx);
+    Status = FindAttribute(Vcb, MftRecord, AttributeIndexRoot, L"$I30", 4,
&IndexRootCtx, NULL);
     if (!NT_SUCCESS(Status))
     {
         ExFreePoolWithTag(MftRecord, TAG_NTFS);
diff --git a/drivers/filesystems/ntfs/ntfs.h b/drivers/filesystems/ntfs/ntfs.h
index f80bb973fe..6b9a86ed07 100644
--- a/drivers/filesystems/ntfs/ntfs.h
+++ b/drivers/filesystems/ntfs/ntfs.h
@@ -483,8 +483,15 @@ typedef struct _FIND_ATTR_CONTXT
     PNTFS_ATTR_RECORD LastAttr;
     PNTFS_ATTR_RECORD NonResidentStart;
     PNTFS_ATTR_RECORD NonResidentEnd;
+    ULONG Offset;
 } FIND_ATTR_CONTXT, *PFIND_ATTR_CONTXT;
 
+typedef struct
+{
+    USHORT USN;
+    USHORT Array[];
+} FIXUP_ARRAY, *PFIXUP_ARRAY;
+
 extern PNTFS_GLOBAL_DATA NtfsGlobalData;
 
 FORCEINLINE
@@ -555,7 +562,7 @@ NtfsWriteDisk(IN PDEVICE_OBJECT DeviceObject,
               IN LONGLONG StartingOffset,
               IN ULONG Length,
               IN ULONG SectorSize,
-              IN PUCHAR Buffer);
+              IN const PUCHAR Buffer);
 
 NTSTATUS
 NtfsReadSectors(IN PDEVICE_OBJECT DeviceObject,
@@ -759,6 +766,15 @@ WriteAttribute(PDEVICE_EXTENSION Vcb,
 ULONGLONG
 AttributeDataLength(PNTFS_ATTR_RECORD AttrRecord);
 
+NTSTATUS
+SetAttributeDataLength(PFILE_OBJECT FileObject,
+                       PNTFS_FCB Fcb,
+                       PNTFS_ATTR_CONTEXT AttrContext,
+                       ULONG AttrOffset,
+                       PFILE_RECORD_HEADER FileRecord,
+                       PDEVICE_EXTENSION DeviceExt,
+                       PLARGE_INTEGER DataSize);
+
 ULONG
 AttributeAllocatedLength(PNTFS_ATTR_RECORD AttrRecord);
 
@@ -767,13 +783,19 @@ ReadFileRecord(PDEVICE_EXTENSION Vcb,
                ULONGLONG index,
                PFILE_RECORD_HEADER file);
 
+NTSTATUS
+UpdateFileRecord(PDEVICE_EXTENSION Vcb,
+                 ULONGLONG index,
+                 PFILE_RECORD_HEADER file);
+
 NTSTATUS
 FindAttribute(PDEVICE_EXTENSION Vcb,
               PFILE_RECORD_HEADER MftRecord,
               ULONG Type,
               PCWSTR Name,
               ULONG NameLength,
-              PNTFS_ATTR_CONTEXT * AttrCtx);
+              PNTFS_ATTR_CONTEXT * AttrCtx,
+              PULONG Offset);
 
 VOID
 ReadVCN(PDEVICE_EXTENSION Vcb,
@@ -787,6 +809,10 @@ NTSTATUS
 FixupUpdateSequenceArray(PDEVICE_EXTENSION Vcb,
                          PNTFS_RECORD_HEADER Record);
 
+NTSTATUS
+AddFixupArray(PDEVICE_EXTENSION Vcb,
+    PFILE_RECORD_HEADER Record);
+
 NTSTATUS
 ReadLCN(PDEVICE_EXTENSION Vcb,
         ULONGLONG lcn,
diff --git a/drivers/filesystems/ntfs/rw.c b/drivers/filesystems/ntfs/rw.c
index 076a3e8578..5d95300ae2 100644
--- a/drivers/filesystems/ntfs/rw.c
+++ b/drivers/filesystems/ntfs/rw.c
@@ -95,7 +95,7 @@ NtfsReadFile(PDEVICE_EXTENSION DeviceExt,
     }
 
 
-    Status = FindAttribute(DeviceExt, FileRecord, AttributeData, Fcb->Stream,
wcslen(Fcb->Stream), &DataContext);
+    Status = FindAttribute(DeviceExt, FileRecord, AttributeData, Fcb->Stream,
wcslen(Fcb->Stream), &DataContext, NULL);
     if (!NT_SUCCESS(Status))
     {
         NTSTATUS BrowseStatus;
@@ -309,6 +309,7 @@ NTSTATUS NtfsWriteFile(PDEVICE_EXTENSION DeviceExt,
     PNTFS_FCB Fcb;
     PFILE_RECORD_HEADER FileRecord;
     PNTFS_ATTR_CONTEXT DataContext;
+    ULONG AttributeOffset;
     ULONGLONG StreamSize;
 
     DPRINT("NtfsWriteFile(%p, %p, %p, %u, %u, %x, %p)\n", DeviceExt,
FileObject, Buffer, Length, WriteOffset, IrpFlags, LengthWritten);
@@ -361,9 +362,10 @@ NTSTATUS NtfsWriteFile(PDEVICE_EXTENSION DeviceExt,
 
     DPRINT("Found record for %wS\n", Fcb->ObjectName);
 
-    // Find the attribute (in the NTFS sense of the word) with the data stream for our
file
+    // Find the attribute with the data stream for our file
     DPRINT("Finding Data Attribute...\n");
-    Status = FindAttribute(DeviceExt, FileRecord, AttributeData, Fcb->Stream,
wcslen(Fcb->Stream), &DataContext);
+    Status = FindAttribute(DeviceExt, FileRecord, AttributeData, Fcb->Stream,
wcslen(Fcb->Stream), &DataContext,
+                           &AttributeOffset);
 
     // Did we fail to find the attribute?
     if (!NT_SUCCESS(Status))
@@ -405,13 +407,39 @@ NTSTATUS NtfsWriteFile(PDEVICE_EXTENSION DeviceExt,
     // Are we trying to write beyond the end of the stream?
     if (WriteOffset + Length > StreamSize)
     {
-        // TODO: allocate additional clusters as needed and expand stream
-        DPRINT1("WriteOffset: %lu\tLength: %lu\tStreamSize: %I64u\n",
WriteOffset, Length, StreamSize);
-        DPRINT1("TODO: Stream embiggening (appending files) is not yet
supported!\n");
-        ReleaseAttributeContext(DataContext);
-        ExFreePoolWithTag(FileRecord, TAG_NTFS);
-        *LengthWritten = 0;             // We didn't write anything
-        return STATUS_ACCESS_DENIED;    // temporarily; we don't change file sizes
yet
+        // is increasing the stream size allowed?
+        if (!(Fcb->Flags & FCB_IS_VOLUME) &&
+            !(IrpFlags & IRP_PAGING_IO))
+        {
+            LARGE_INTEGER DataSize;
+            ULONGLONG AllocationSize;
+
+            DataSize.QuadPart = WriteOffset + Length;
+
+            AllocationSize = ROUND_UP(DataSize.QuadPart,
Fcb->Vcb->NtfsInfo.BytesPerCluster);
+
+            // set the attribute data length
+            Status = SetAttributeDataLength(FileObject, Fcb, DataContext,
AttributeOffset, FileRecord, DeviceExt, &DataSize);
+            
+            if (!NT_SUCCESS(Status))
+            {
+                ReleaseAttributeContext(DataContext);
+                ExFreePoolWithTag(FileRecord, TAG_NTFS);
+                *LengthWritten = 0;
+                return Status;
+            }
+
+            // now we need to update this file's size in every directory index entry
that references it
+            // (saved for a later commit)
+        }
+        else
+        {
+            // TODO - just fail for now
+            ReleaseAttributeContext(DataContext);
+            ExFreePoolWithTag(FileRecord, TAG_NTFS);
+            *LengthWritten = 0;
+            return STATUS_ACCESS_DENIED;
+        }
     }
 
     DPRINT("Length: %lu\tWriteOffset: %lu\tStreamSize: %I64u\n", Length,
WriteOffset, StreamSize);
diff --git a/drivers/filesystems/ntfs/volinfo.c b/drivers/filesystems/ntfs/volinfo.c
index ddf7f6c58d..13a3b7af7f 100644
--- a/drivers/filesystems/ntfs/volinfo.c
+++ b/drivers/filesystems/ntfs/volinfo.c
@@ -62,7 +62,7 @@ NtfsGetFreeClusters(PDEVICE_EXTENSION DeviceExt)
         return 0;
     }
 
-    Status = FindAttribute(DeviceExt, BitmapRecord, AttributeData, L"", 0,
&DataContext);
+    Status = FindAttribute(DeviceExt, BitmapRecord, AttributeData, L"", 0,
&DataContext, NULL);
     if (!NT_SUCCESS(Status))
     {
         ExFreePoolWithTag(BitmapRecord, TAG_NTFS);