volinfo.c File Reference

#include "fatprocs.h"

Include dependency graph for volinfo.c:

Go to the source code of this file.

Macros
#define	Dbg   (DEBUG_TRACE_VOLINFO)

Functions
NTSTATUS	FatQueryFsVolumeInfo (IN PIRP_CONTEXT IrpContext, IN PVCB Vcb, IN PFILE_FS_VOLUME_INFORMATION Buffer, IN OUT PULONG Length)
NTSTATUS	FatQueryFsSizeInfo (IN PIRP_CONTEXT IrpContext, IN PVCB Vcb, IN PFILE_FS_SIZE_INFORMATION Buffer, IN OUT PULONG Length)
NTSTATUS	FatQueryFsDeviceInfo (IN PIRP_CONTEXT IrpContext, IN PVCB Vcb, IN PFILE_FS_DEVICE_INFORMATION Buffer, IN OUT PULONG Length)
NTSTATUS	FatQueryFsAttributeInfo (IN PIRP_CONTEXT IrpContext, IN PVCB Vcb, IN PFILE_FS_ATTRIBUTE_INFORMATION Buffer, IN OUT PULONG Length)
NTSTATUS	FatQueryFsFullSizeInfo (IN PIRP_CONTEXT IrpContext, IN PVCB Vcb, IN PFILE_FS_FULL_SIZE_INFORMATION Buffer, IN OUT PULONG Length)
NTSTATUS	FatSetFsLabelInfo (IN PIRP_CONTEXT IrpContext, IN PVCB Vcb, IN PFILE_FS_LABEL_INFORMATION Buffer)
NTSTATUS	FatQueryFsSectorSizeInfo (_In_ PIRP_CONTEXT IrpContext, _In_ PVCB Vcb, _Out_writes_bytes_(*Length) PFILE_FS_SECTOR_SIZE_INFORMATION Buffer, _Inout_ PULONG Length)
	_Function_class_ (IRP_MJ_QUERY_VOLUME_INFORMATION)
	_Function_class_ (IRP_MJ_SET_VOLUME_INFORMATION)
	_Requires_lock_held_ (_Global_critical_region_)

Macro Definition Documentation

Dbg

#define Dbg   (DEBUG_TRACE_VOLINFO)

Definition at line 23 of file volinfo.c.

Function Documentation

_Function_class_() [1/2]

_Function_class_

(

IRP_MJ_QUERY_VOLUME_INFORMATION

)

Definition at line 99 of file volinfo.c.

{
    NTSTATUS Status;
    PIRP_CONTEXT IrpContext = NULL;
 
    BOOLEAN TopLevel;
 
    PAGED_CODE();
 
    DebugTrace(+1, Dbg, "FatFsdQueryVolumeInformation\n", 0);
 
    //
    //  Call the common query routine, with blocking allowed if synchronous
    //
 
    FsRtlEnterFileSystem();
 
    TopLevel = FatIsIrpTopLevel( Irp );
 
    _SEH2_TRY {
 
        IrpContext = FatCreateIrpContext( Irp, CanFsdWait( Irp ) );
 
        Status = FatCommonQueryVolumeInfo( IrpContext, Irp );
 
    } _SEH2_EXCEPT(FatExceptionFilter( IrpContext, _SEH2_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
        //  exception code
        //
 
        Status = FatProcessException( IrpContext, Irp, _SEH2_GetExceptionCode() );
    } _SEH2_END;
 
    if (TopLevel) { IoSetTopLevelIrp( NULL ); }
 
    FsRtlExitFileSystem();
 
    //
    //  And return to our caller
    //
 
    DebugTrace(-1, Dbg, "FatFsdQueryVolumeInformation -> %08lx\n", Status);
 
    UNREFERENCED_PARAMETER( VolumeDeviceObject );
 
    return Status;
}

_Function_class_() [2/2]

_Function_class_

(

IRP_MJ_SET_VOLUME_INFORMATION

)

Definition at line 180 of file volinfo.c.

{
    NTSTATUS Status;
    PIRP_CONTEXT IrpContext = NULL;
 
    BOOLEAN TopLevel;
 
    PAGED_CODE();
 
    DebugTrace(+1, Dbg, "FatFsdSetVolumeInformation\n", 0);
 
    //
    //  Call the common set routine
    //
 
    FsRtlEnterFileSystem();
 
    TopLevel = FatIsIrpTopLevel( Irp );
 
    _SEH2_TRY {
 
        IrpContext = FatCreateIrpContext( Irp, CanFsdWait( Irp ) );
 
        Status = FatCommonSetVolumeInfo( IrpContext, Irp );
 
    } _SEH2_EXCEPT(FatExceptionFilter( IrpContext, _SEH2_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
        //  exception code
        //
 
        Status = FatProcessException( IrpContext, Irp, _SEH2_GetExceptionCode() );
    } _SEH2_END;
 
    if (TopLevel) { IoSetTopLevelIrp( NULL ); }
 
    FsRtlExitFileSystem();
 
    //
    //  And return to our caller
    //
 
    DebugTrace(-1, Dbg, "FatFsdSetVolumeInformation -> %08lx\n", Status);
 
    UNREFERENCED_PARAMETER( VolumeDeviceObject );
 
    return Status;
}

_Requires_lock_held_()

_Requires_lock_held_

(

_Global_critical_region_

)

Definition at line 261 of file volinfo.c.

{
    NTSTATUS Status = STATUS_SUCCESS;
    PIO_STACK_LOCATION IrpSp;
 
    PVCB Vcb;
    PFCB Fcb;
    PCCB Ccb;
 
    ULONG Length;
    FS_INFORMATION_CLASS FsInformationClass;
    PVOID Buffer;
 
    BOOLEAN WeAcquiredVcb = FALSE;
 
    PAGED_CODE();
 
    //
    //  Get the current stack location
    //
 
    IrpSp = IoGetCurrentIrpStackLocation( Irp );
 
    DebugTrace(+1, Dbg, "FatCommonQueryVolumeInfo...\n", 0);
    DebugTrace( 0, Dbg, "Irp                  = %p\n", Irp );
    DebugTrace( 0, Dbg, "->Length             = %08lx\n", IrpSp->Parameters.QueryVolume.Length);
    DebugTrace( 0, Dbg, "->FsInformationClass = %08lx\n", IrpSp->Parameters.QueryVolume.FsInformationClass);
    DebugTrace( 0, Dbg, "->Buffer             = %p\n", Irp->AssociatedIrp.SystemBuffer);
 
    //
    //  Reference our input parameters to make things easier
    //
 
    Length = IrpSp->Parameters.QueryVolume.Length;
    FsInformationClass = IrpSp->Parameters.QueryVolume.FsInformationClass;
    Buffer = Irp->AssociatedIrp.SystemBuffer;
 
    //
    //  Decode the file object to get the Vcb
    //
 
    (VOID) FatDecodeFileObject( IrpSp->FileObject, &Vcb, &Fcb, &Ccb );
 
    NT_ASSERT( Vcb != NULL );
    _Analysis_assume_( Vcb != NULL );
 
    _SEH2_TRY {
 
        //
        //  Make sure the vcb is in a usable condition.  This will raise
        //  an error condition if the volume is unusable
        //
        //  Also verify the Root Dcb since we need info from there.
        //
 
        FatVerifyFcb( IrpContext, Vcb->RootDcb );
 
        //
        //  Based on the information class we'll do different actions.  Each
        //  of the procedures that we're calling fills up the output buffer
        //  if possible and returns true if it successfully filled the buffer
        //  and false if it couldn't wait for any I/O to complete.
        //
 
        switch (FsInformationClass) {
 
        case FileFsVolumeInformation:
 
            //
            //  This is the only routine we need the Vcb shared because of
            //  copying the volume label.  All other routines copy fields that
            //  cannot change or are just manifest constants.
            //
 
            if (!FatAcquireSharedVcb( IrpContext, Vcb )) {
 
                DebugTrace(0, Dbg, "Cannot acquire Vcb\n", 0);
 
                Status = FatFsdPostRequest( IrpContext, Irp );
                IrpContext = NULL;
                Irp = NULL;
 
            } else {
 
                WeAcquiredVcb = TRUE;
 
                Status = FatQueryFsVolumeInfo( IrpContext, Vcb, Buffer, &Length );
            }
 
            break;
 
        case FileFsSizeInformation:
 
            Status = FatQueryFsSizeInfo( IrpContext, Vcb, Buffer, &Length );
            break;
 
        case FileFsDeviceInformation:
 
            Status = FatQueryFsDeviceInfo( IrpContext, Vcb, Buffer, &Length );
            break;
 
        case FileFsAttributeInformation:
 
            Status = FatQueryFsAttributeInfo( IrpContext, Vcb, Buffer, &Length );
            break;
 
        case FileFsFullSizeInformation:
 
            Status = FatQueryFsFullSizeInfo( IrpContext, Vcb, Buffer, &Length );
            break;
 
#if (NTDDI_VERSION >= NTDDI_WIN8)
        case FileFsSectorSizeInformation:
 
            Status = FatQueryFsSectorSizeInfo( IrpContext, Vcb, Buffer, &Length );
            break;
#endif
 
        default:
 
            Status = STATUS_INVALID_PARAMETER;
            break;
        }
 
        //
        //  Set the information field to the number of bytes actually filled in.
        //
 
        if (Irp != NULL) {
 
            Irp->IoStatus.Information = IrpSp->Parameters.QueryVolume.Length - Length;
        }
 
    } _SEH2_FINALLY {
 
        DebugUnwind( FatCommonQueryVolumeInfo );
 
        if (WeAcquiredVcb) {
 
            FatReleaseVcb( IrpContext, Vcb );
        }
 
        if (!_SEH2_AbnormalTermination()) {
 
            FatCompleteRequest( IrpContext, Irp, Status );
        }
 
        DebugTrace(-1, Dbg, "FatCommonQueryVolumeInfo -> %08lx\n", Status);
    } _SEH2_END;
 
    return Status;
}

FatQueryFsAttributeInfo()

NTSTATUS FatQueryFsAttributeInfo	(	IN PIRP_CONTEXT	IrpContext,
		IN PVCB	Vcb,
		IN PFILE_FS_ATTRIBUTE_INFORMATION	Buffer,
		IN OUT PULONG	Length
	)

Definition at line 809 of file volinfo.c.

{
    ULONG BytesToCopy;
 
    NTSTATUS Status;
 
    PAGED_CODE();
 
    DebugTrace(0, Dbg, "FatQueryFsAttributeInfo...\n", 0);
 
    //
    //  Set the output buffer
    //
 
    Buffer->FileSystemAttributes = FILE_CASE_PRESERVED_NAMES |
                                   FILE_UNICODE_ON_DISK;
 
    if (FlagOn( Vcb->VcbState, VCB_STATE_FLAG_WRITE_PROTECTED )) {
 
        SetFlag( Buffer->FileSystemAttributes, FILE_READ_ONLY_VOLUME );
    }
 
 
    Buffer->MaximumComponentNameLength = FatData.ChicagoMode ? 255 : 12;
 
    if (FatIsFat32(Vcb)) {
 
        //
        //  Determine how much of the file system name will fit.
        //
 
        if ( (*Length - FIELD_OFFSET( FILE_FS_ATTRIBUTE_INFORMATION,
                                      FileSystemName[0] )) >= 10 ) {
 
            BytesToCopy = 10;
            *Length -= FIELD_OFFSET( FILE_FS_ATTRIBUTE_INFORMATION,
                                     FileSystemName[0] ) + 10;
            Status = STATUS_SUCCESS;
 
        } else {
 
            BytesToCopy = *Length - FIELD_OFFSET( FILE_FS_ATTRIBUTE_INFORMATION,
                                                  FileSystemName[0]);
            *Length = 0;
 
            Status = STATUS_BUFFER_OVERFLOW;
        }
 
        RtlCopyMemory( &Buffer->FileSystemName[0], L"FAT32", BytesToCopy );
 
    } else {
 
        //
        //  Determine how much of the file system name will fit.
        //
 
        if ( (*Length - FIELD_OFFSET( FILE_FS_ATTRIBUTE_INFORMATION,
                                      FileSystemName[0] )) >= 6 ) {
 
            BytesToCopy = 6;
            *Length -= FIELD_OFFSET( FILE_FS_ATTRIBUTE_INFORMATION,
                                     FileSystemName[0] ) + 6;
            Status = STATUS_SUCCESS;
 
        } else {
 
            BytesToCopy = *Length - FIELD_OFFSET( FILE_FS_ATTRIBUTE_INFORMATION,
                                                  FileSystemName[0]);
            *Length = 0;
 
            Status = STATUS_BUFFER_OVERFLOW;
        }
 
 
        RtlCopyMemory( &Buffer->FileSystemName[0], L"FAT", BytesToCopy );
    }
 
    Buffer->FileSystemNameLength       = BytesToCopy;
 
    //
    //  And return success to our caller
    //
 
    UNREFERENCED_PARAMETER( IrpContext );
    UNREFERENCED_PARAMETER( Vcb );
 
    return Status;
}

Referenced by _Requires_lock_held_().

FatQueryFsDeviceInfo()

NTSTATUS FatQueryFsDeviceInfo	(	IN PIRP_CONTEXT	IrpContext,
		IN PVCB	Vcb,
		IN PFILE_FS_DEVICE_INFORMATION	Buffer,
		IN OUT PULONG	Length
	)

Definition at line 744 of file volinfo.c.

{
    PAGED_CODE();
 
    DebugTrace(0, Dbg, "FatQueryFsDeviceInfo...\n", 0);
 
    RtlZeroMemory( Buffer, sizeof(FILE_FS_DEVICE_INFORMATION) );
 
    //
    //  Set the output buffer
    //
 
    Buffer->DeviceType = FILE_DEVICE_DISK;
 
    Buffer->Characteristics = Vcb->TargetDeviceObject->Characteristics;
 
    //
    //  Adjust the length variable
    //
 
    *Length -= sizeof(FILE_FS_DEVICE_INFORMATION);
 
    //
    //  And return success to our caller
    //
 
    UNREFERENCED_PARAMETER( IrpContext );
 
    return STATUS_SUCCESS;
}

Referenced by _Requires_lock_held_().

FatQueryFsFullSizeInfo()

NTSTATUS FatQueryFsFullSizeInfo	(	IN PIRP_CONTEXT	IrpContext,
		IN PVCB	Vcb,
		IN PFILE_FS_FULL_SIZE_INFORMATION	Buffer,
		IN OUT PULONG	Length
	)

Definition at line 932 of file volinfo.c.

{
    PAGED_CODE();
 
    DebugTrace(0, Dbg, "FatQueryFsSizeInfo...\n", 0);
 
    RtlZeroMemory( Buffer, sizeof(FILE_FS_FULL_SIZE_INFORMATION) );
 
    Buffer->TotalAllocationUnits.LowPart =
                                Vcb->AllocationSupport.NumberOfClusters;
    Buffer->CallerAvailableAllocationUnits.LowPart =
                                Vcb->AllocationSupport.NumberOfFreeClusters;
    Buffer->ActualAvailableAllocationUnits.LowPart =
        Buffer->CallerAvailableAllocationUnits.LowPart;
    Buffer->SectorsPerAllocationUnit = Vcb->Bpb.SectorsPerCluster;
    Buffer->BytesPerSector = Vcb->Bpb.BytesPerSector;
 
    //
    //  Adjust the length variable
    //
 
    *Length -= sizeof(FILE_FS_FULL_SIZE_INFORMATION);
 
    //
    //  And return success to our caller
    //
 
    UNREFERENCED_PARAMETER( IrpContext );
 
    return STATUS_SUCCESS;
}

Referenced by _Requires_lock_held_().

FatQueryFsSectorSizeInfo()

NTSTATUS FatQueryFsSectorSizeInfo	(	_In_ PIRP_CONTEXT	IrpContext,
		_In_ PVCB	Vcb,
		_Out_writes_bytes_ *Length PFILE_FS_SECTOR_SIZE_INFORMATION	Buffer,
		_Inout_ PULONG	Length
	)

Definition at line 1317 of file volinfo.c.

{
    NTSTATUS Status;
 
    PAGED_CODE();
    UNREFERENCED_PARAMETER( IrpContext );
 
    //
    //  Sufficient buffer size is guaranteed by the I/O manager or the
    //  originating kernel mode driver.
    //
 
    ASSERT( *Length >= sizeof( FILE_FS_SECTOR_SIZE_INFORMATION ));
    _Analysis_assume_( *Length >= sizeof( FILE_FS_SECTOR_SIZE_INFORMATION ));
 
    //
    //  Retrieve the sector size information
    //
 
    Status = FsRtlGetSectorSizeInformation( Vcb->Vpb->RealDevice,
                                            Buffer );
 
    //
    //  Adjust the length variable
    //
 
    if (NT_SUCCESS( Status )) {
 
        *Length -= sizeof( FILE_FS_SECTOR_SIZE_INFORMATION );
    }
 
    return Status;
}

Referenced by _Requires_lock_held_().

FatQueryFsSizeInfo()

NTSTATUS FatQueryFsSizeInfo	(	IN PIRP_CONTEXT	IrpContext,
		IN PVCB	Vcb,
		IN PFILE_FS_SIZE_INFORMATION	Buffer,
		IN OUT PULONG	Length
	)

Definition at line 675 of file volinfo.c.

{
    PAGED_CODE();
 
    DebugTrace(0, Dbg, "FatQueryFsSizeInfo...\n", 0);
 
    RtlZeroMemory( Buffer, sizeof(FILE_FS_SIZE_INFORMATION) );
 
    //
    //  Set the output buffer.
    //
 
    Buffer->TotalAllocationUnits.LowPart =
                                    Vcb->AllocationSupport.NumberOfClusters;
    Buffer->AvailableAllocationUnits.LowPart =
                                    Vcb->AllocationSupport.NumberOfFreeClusters;
 
    Buffer->SectorsPerAllocationUnit = Vcb->Bpb.SectorsPerCluster;
    Buffer->BytesPerSector = Vcb->Bpb.BytesPerSector;
 
    //
    //  Adjust the length variable
    //
 
    *Length -= sizeof(FILE_FS_SIZE_INFORMATION);
 
    //
    //  And return success to our caller
    //
 
    UNREFERENCED_PARAMETER( IrpContext );
 
    return STATUS_SUCCESS;
}

Referenced by _Requires_lock_held_().

FatQueryFsVolumeInfo()

NTSTATUS FatQueryFsVolumeInfo	(	IN PIRP_CONTEXT	IrpContext,
		IN PVCB	Vcb,
		IN PFILE_FS_VOLUME_INFORMATION	Buffer,
		IN OUT PULONG	Length
	)

Definition at line 581 of file volinfo.c.

{
    ULONG BytesToCopy;
 
    NTSTATUS Status;
 
    PAGED_CODE();
 
    DebugTrace(0, Dbg, "FatQueryFsVolumeInfo...\n", 0);
 
    //
    //  Zero out the buffer, then extract and fill up the non zero fields.
    //
 
    RtlZeroMemory( Buffer, sizeof(FILE_FS_VOLUME_INFORMATION) );
 
    Buffer->VolumeSerialNumber = Vcb->Vpb->SerialNumber;
 
    Buffer->SupportsObjects = FALSE;
 
    *Length -= FIELD_OFFSET(FILE_FS_VOLUME_INFORMATION, VolumeLabel[0]);
 
    //
    //  Check if the buffer we're given is long enough
    //
 
    if ( *Length >= (ULONG)Vcb->Vpb->VolumeLabelLength ) {
 
        BytesToCopy = Vcb->Vpb->VolumeLabelLength;
 
        Status = STATUS_SUCCESS;
 
    } else {
 
        BytesToCopy = *Length;
 
        Status = STATUS_BUFFER_OVERFLOW;
    }
 
    //
    //  Copy over what we can of the volume label, and adjust *Length
    //
 
    Buffer->VolumeLabelLength = Vcb->Vpb->VolumeLabelLength;
 
    RtlCopyMemory( &Buffer->VolumeLabel[0],
                   &Vcb->Vpb->VolumeLabel[0],
                   BytesToCopy );
 
    *Length -= BytesToCopy;
 
    //
    //  Set our status and return to our caller
    //
 
    UNREFERENCED_PARAMETER( IrpContext );
 
    return Status;
}

Referenced by _Requires_lock_held_().

FatSetFsLabelInfo()

NTSTATUS FatSetFsLabelInfo	(	IN PIRP_CONTEXT	IrpContext,
		IN PVCB	Vcb,
		IN PFILE_FS_LABEL_INFORMATION	Buffer
	)

Definition at line 998 of file volinfo.c.

{
    NTSTATUS Status;
 
    PDIRENT Dirent;
    PBCB DirentBcb = NULL;
    ULONG ByteOffset;
 
    WCHAR TmpBuffer[11];
    UCHAR OemBuffer[11];
    OEM_STRING OemLabel;
    UNICODE_STRING UnicodeString;
    UNICODE_STRING UpcasedLabel;
 
    PAGED_CODE();
 
    DebugTrace(+1, Dbg, "FatSetFsLabelInfo...\n", 0);
 
    //
    //  Setup our local variable
    //
 
    UnicodeString.Length = (USHORT)Buffer->VolumeLabelLength;
    UnicodeString.MaximumLength = UnicodeString.Length;
    UnicodeString.Buffer = (PWSTR) &Buffer->VolumeLabel[0];
 
    //
    //  Make sure the name can fit into the stack buffer
    //
 
    if ( UnicodeString.Length > 11*sizeof(WCHAR) ) {
 
        return STATUS_INVALID_VOLUME_LABEL;
    }
 
    //
    //  Upcase the name and convert it to the Oem code page.
    //
 
    OemLabel.Buffer = (PCHAR)&OemBuffer[0];
    OemLabel.Length = 0;
    OemLabel.MaximumLength = 11;
 
    Status = RtlUpcaseUnicodeStringToCountedOemString( &OemLabel,
                                                       &UnicodeString,
                                                       FALSE );
 
    //
    //  Volume label that fits in 11 unicode character length limit
    //  is not necessarily within 11 characters in OEM character set.
    //
 
    if (!NT_SUCCESS( Status )) {
 
        DebugTrace(-1, Dbg, "FatSetFsLabelInfo:  Label must be too long. %08lx\n", Status );
 
        return STATUS_INVALID_VOLUME_LABEL;
    }
 
    //
    //  Strip spaces off of the label.
    //
 
    if (OemLabel.Length > 0) {
 
        USHORT i;
        USHORT LastSpaceIndex = MAXUSHORT;
 
        //
        //  Check the label for illegal characters
        //
 
        for ( i = 0; i < (ULONG)OemLabel.Length; i += 1 ) {
 
            if ( FsRtlIsLeadDbcsCharacter( OemLabel.Buffer[i] ) ) {
 
                LastSpaceIndex = MAXUSHORT;
                i += 1;
                continue;
            }
 
            if (!FsRtlIsAnsiCharacterLegalFat(OemLabel.Buffer[i], FALSE) ||
                (OemLabel.Buffer[i] == '.')) {
 
                return STATUS_INVALID_VOLUME_LABEL;
            }
 
            //
            //  Watch for the last run of spaces, so we can strip them.
            //
 
            if (OemLabel.Buffer[i] == ' ' &&
                LastSpaceIndex == MAXUSHORT) {
                LastSpaceIndex = i;
            } else {
                LastSpaceIndex = MAXUSHORT;
            }
        }
 
        if (LastSpaceIndex != MAXUSHORT) {
            OemLabel.Length = LastSpaceIndex;
        }
    }
 
    //
    //  Get the Unicode upcased string to store in the VPB.
    //
 
    UpcasedLabel.Length = UnicodeString.Length;
    UpcasedLabel.MaximumLength = 11*sizeof(WCHAR);
    UpcasedLabel.Buffer = &TmpBuffer[0];
 
    Status = RtlOemStringToCountedUnicodeString( &UpcasedLabel,
                                                 &OemLabel,
                                                 FALSE );
 
    if (!NT_SUCCESS( Status )) {
 
        DebugTrace(-1, Dbg, "FatSetFsLabelInfo:  Label must be too long. %08lx\n", Status );
 
        return STATUS_INVALID_VOLUME_LABEL;
    }
 
    DirentBcb = NULL;
 
    //
    //  Make this look like a write through to disk.  This is important to
    //  avoid a unpleasant window where it looks like we have the wrong volume.
    //
 
    SetFlag( IrpContext->Flags, IRP_CONTEXT_FLAG_WRITE_THROUGH );
 
    _SEH2_TRY {
 
        //
        //  Are we setting or removing the label?  Note that shaving spaces could
        //  make this different than wondering if the input buffer is non-zero length.
        //
 
        if (OemLabel.Length > 0) {
 
            //
            //  Translate the first character from 0xe5 to 0x5.
            //
 
            if ((UCHAR)OemLabel.Buffer[0] == 0xe5) {
 
                OemLabel.Buffer[0] = FAT_DIRENT_REALLY_0E5;
            }
 
            //
            //  Locate the volume label if there already is one
            //
 
            FatLocateVolumeLabel( IrpContext,
                                  Vcb,
                                  &Dirent,
                                  &DirentBcb,
                                  (PVBO)&ByteOffset );
 
            //
            //  Check that we really got one, if not then we need to create
            //  a new one.  The procedure we call will raise an appropriate
            //  status if we are not able to allocate a new dirent
            //
 
            if (Dirent == NULL) {
 
                ByteOffset = FatCreateNewDirent( IrpContext,
                                                 Vcb->RootDcb,
                                                 1,
                                                 FALSE );
 
                FatPrepareWriteDirectoryFile( IrpContext,
                                              Vcb->RootDcb,
                                              ByteOffset,
                                              sizeof(DIRENT),
                                              &DirentBcb,
#ifndef __REACTOS__
                                              &Dirent,
#else
                                              (PVOID *)&Dirent,
#endif
                                              FALSE,
                                              TRUE,
                                              &Status );
 
                NT_ASSERT( NT_SUCCESS( Status ));
 
            } else {
 
                //
                //  Just mark this guy dirty now.
                //
 
                FatSetDirtyBcb( IrpContext, DirentBcb, Vcb, TRUE );
            }
 
            //
            //  Now reconstruct the volume label dirent.
            //
 
            FatConstructLabelDirent( IrpContext,
                                     Dirent,
                                     &OemLabel );
 
            //
            //  Unpin the Bcb here so that we will get any IO errors
            //  here before changing the VPB label.
            //
 
            FatUnpinBcb( IrpContext, DirentBcb );
            FatUnpinRepinnedBcbs( IrpContext );
 
            //
            //  Now set the upcased label in the VPB
            //
 
            RtlCopyMemory( &Vcb->Vpb->VolumeLabel[0],
                           &UpcasedLabel.Buffer[0],
                           UpcasedLabel.Length );
 
            Vcb->Vpb->VolumeLabelLength = UpcasedLabel.Length;
 
        } else {
 
            //
            //  Otherwise we're trying to delete the label
            //  Locate the current volume label if there already is one
            //
 
            FatLocateVolumeLabel( IrpContext,
                                  Vcb,
                                  &Dirent,
                                  &DirentBcb,
                                  (PVBO)&ByteOffset );
 
            //
            //  Check that we really got one
            //
 
            if (Dirent == NULL) {
 
                try_return( Status = STATUS_SUCCESS );
            }
 
            //
            //  Now delete the current label.
            //
 
            Dirent->FileName[0] = FAT_DIRENT_DELETED;
 
            NT_ASSERT( (Vcb->RootDcb->Specific.Dcb.UnusedDirentVbo == 0xffffffff) ||
                    RtlAreBitsSet( &Vcb->RootDcb->Specific.Dcb.FreeDirentBitmap,
                                   ByteOffset / sizeof(DIRENT),
                                   1 ) );
 
            RtlClearBits( &Vcb->RootDcb->Specific.Dcb.FreeDirentBitmap,
                          ByteOffset / sizeof(DIRENT),
                          1 );
 
            FatSetDirtyBcb( IrpContext, DirentBcb, Vcb, TRUE );
 
            //
            //  Unpin the Bcb here so that we will get any IO errors
            //  here before changing the VPB label.
            //
 
            FatUnpinBcb( IrpContext, DirentBcb );
            FatUnpinRepinnedBcbs( IrpContext );
 
            //
            //  Now set the label in the VPB
            //
 
            Vcb->Vpb->VolumeLabelLength = 0;
        }
 
        Status = STATUS_SUCCESS;
 
    try_exit: NOTHING;
    } _SEH2_FINALLY {
 
        DebugUnwind( FatSetFsALabelInfo );
 
        FatUnpinBcb( IrpContext, DirentBcb );
 
        DebugTrace(-1, Dbg, "FatSetFsALabelInfo -> STATUS_SUCCESS\n", 0);
    } _SEH2_END;
 
    return Status;
}