flush.c

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/*++
 
Copyright (c) 1989-2000 Microsoft Corporation
 
Module Name:
 
    Flush.c
 
Abstract:
 
    This module implements the File Flush buffers routine for Fat called by the
    dispatch driver.
 
 
--*/
 
#include "fatprocs.h"
 
//
//  The Bug check file id for this module
//
 
#define BugCheckFileId                   (FAT_BUG_CHECK_FLUSH)
 
//
//  The local debug trace level
//
 
#define Dbg                              (DEBUG_TRACE_FLUSH)
 
#ifdef ALLOC_PRAGMA
#pragma alloc_text(PAGE, FatCommonFlushBuffers)
#pragma alloc_text(PAGE, FatFlushDirectory)
#pragma alloc_text(PAGE, FatFlushFat)
#pragma alloc_text(PAGE, FatFlushFile)
#pragma alloc_text(PAGE, FatFlushVolume)
#pragma alloc_text(PAGE, FatFsdFlushBuffers)
#pragma alloc_text(PAGE, FatFlushDirentForFile)
#pragma alloc_text(PAGE, FatFlushFatEntries)
#pragma alloc_text(PAGE, FatHijackIrpAndFlushDevice)
#endif
 
//
//  Local procedure prototypes
//
 
IO_COMPLETION_ROUTINE FatFlushCompletionRoutine;
 
NTSTATUS
NTAPI
FatFlushCompletionRoutine (
    _In_ PDEVICE_OBJECT DeviceObject,
    _In_ PIRP Irp,
    _In_reads_opt_(_Inexpressible_("varies")) PVOID Contxt
    );
 
IO_COMPLETION_ROUTINE FatHijackCompletionRoutine;
 
NTSTATUS
NTAPI
FatHijackCompletionRoutine (
    _In_ PDEVICE_OBJECT DeviceObject,
    _In_ PIRP Irp,
    _In_reads_opt_(_Inexpressible_("varies")) PVOID Contxt
    );
 
 
_Function_class_(IRP_MJ_FLUSH_BUFFERS)
_Function_class_(DRIVER_DISPATCH)
NTSTATUS
NTAPI
FatFsdFlushBuffers (
    _In_ PVOLUME_DEVICE_OBJECT VolumeDeviceObject,
    _Inout_ PIRP Irp
    )
 
/*++
 
Routine Description:
 
    This routine implements the FSD part of Flush buffers.
 
Arguments:
 
    VolumeDeviceObject - Supplies the volume device object where the
        file being flushed exists
 
    Irp - Supplies the Irp being processed
 
Return Value:
 
    NTSTATUS - The FSD status for the IRP
 
--*/
 
{
    NTSTATUS Status;
    PIRP_CONTEXT IrpContext = NULL;
 
    BOOLEAN TopLevel;
 
    PAGED_CODE();
 
    DebugTrace(+1, Dbg, "FatFsdFlushBuffers\n", 0);
 
    //
    //  Call the common Cleanup routine, with blocking allowed if synchronous
    //
 
    FsRtlEnterFileSystem();
 
    TopLevel = FatIsIrpTopLevel( Irp );
 
    _SEH2_TRY {
 
        IrpContext = FatCreateIrpContext( Irp, CanFsdWait( Irp ) );
 
        Status = FatCommonFlushBuffers( 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
        //  execption code
        //
 
        Status = FatProcessException( IrpContext, Irp, _SEH2_GetExceptionCode() );
    } _SEH2_END;
 
    if (TopLevel) { IoSetTopLevelIrp( NULL ); }
 
    FsRtlExitFileSystem();
 
    //
    //  And return to our caller
    //
 
    DebugTrace(-1, Dbg, "FatFsdFlushBuffers -> %08lx\n", Status);
 
    UNREFERENCED_PARAMETER( VolumeDeviceObject );
 
    return Status;
}
 
 
_Requires_lock_held_(_Global_critical_region_)
NTSTATUS
FatCommonFlushBuffers (
    IN PIRP_CONTEXT IrpContext,
    IN PIRP Irp
    )
 
/*++
 
Routine Description:
 
    This is the common routine for flushing a buffer.
 
Arguments:
 
    Irp - Supplies the Irp to process
 
Return Value:
 
    NTSTATUS - The return status for the operation
 
--*/
 
{
    NTSTATUS Status;
 
    PIO_STACK_LOCATION IrpSp;
 
    PFILE_OBJECT FileObject;
 
    TYPE_OF_OPEN TypeOfOpen;
    PVCB Vcb;
    PFCB Fcb;
    PFCB NextFcb;
    PCCB Ccb;
 
    BOOLEAN VcbAcquired = FALSE;
    BOOLEAN FcbAcquired = FALSE;
    BOOLEAN FatFlushRequired = FALSE;
 
    PAGED_CODE();
 
    IrpSp = IoGetCurrentIrpStackLocation( Irp );
 
    DebugTrace(+1, Dbg, "FatCommonFlushBuffers\n", 0);
    DebugTrace( 0, Dbg, "Irp           = %p\n", Irp);
    DebugTrace( 0, Dbg, "->FileObject  = %p\n", IrpSp->FileObject);
 
    //
    //  Extract and decode the file object
    //
 
    FileObject = IrpSp->FileObject;
    TypeOfOpen = FatDecodeFileObject( FileObject, &Vcb, &Fcb, &Ccb );
 
    //
    //  CcFlushCache is always synchronous, so if we can't wait enqueue
    //  the irp to the Fsp.
    //
 
    if ( !FlagOn(IrpContext->Flags, IRP_CONTEXT_FLAG_WAIT) ) {
 
        Status = FatFsdPostRequest( IrpContext, Irp );
 
        DebugTrace(-1, Dbg, "FatCommonFlushBuffers -> %08lx\n", Status );
        return Status;
    }
 
    Status = STATUS_SUCCESS;
 
    _SEH2_TRY {
 
#if (NTDDI_VERSION >= NTDDI_WIN8)
 
        if (FatDiskAccountingEnabled) {
 
            PETHREAD OriginatingThread = NULL;
 
            //
            //  Charge the flush to the originating thread.
            //  Try the Thread in Irp's tail first, if that is NULL, then charge
            //  the flush to current thread.
            //
 
            if ((Irp->Tail.Overlay.Thread != NULL) &&
                !IoIsSystemThread( Irp->Tail.Overlay.Thread )) {
 
                OriginatingThread = Irp->Tail.Overlay.Thread;
 
            } else {
 
                OriginatingThread = PsGetCurrentThread();
            }
 
            NT_ASSERT( OriginatingThread != NULL );
 
            PsUpdateDiskCounters( PsGetThreadProcess( OriginatingThread ),
                                  0,
                                  0,
                                  0,
                                  0,
                                  1 );
        }
 
#endif
 
        //
        //  Case on the type of open that we are trying to flush
        //
 
        switch (TypeOfOpen) {
 
        case VirtualVolumeFile:
        case EaFile:
        case DirectoryFile:
            DebugTrace(0, Dbg, "Flush that does nothing\n", 0);
            break;
 
        case UserFileOpen:
 
            DebugTrace(0, Dbg, "Flush User File Open\n", 0);
 
            (VOID)FatAcquireExclusiveFcb( IrpContext, Fcb );
 
            FcbAcquired = TRUE;
 
            FatVerifyFcb( IrpContext, Fcb );
 
            //
            //  If the file is cached then flush its cache
            //
 
            Status = FatFlushFile( IrpContext, Fcb, Flush );
 
            //
            //  Also flush the file's dirent in the parent directory if the file
            //  flush worked.
            //
 
            if (NT_SUCCESS( Status )) {
 
                //
                //  Insure that we get the filesize to disk correctly.  This is
                //  benign if it was already good.
                //
 
                SetFlag(FileObject->Flags, FO_FILE_SIZE_CHANGED);
 
 
                FatUpdateDirentFromFcb( IrpContext, FileObject, Fcb, Ccb );
 
                if (FlagOn(Fcb->FcbState, FCB_STATE_FLUSH_FAT)) {
 
                    FatFlushRequired = TRUE;
                }
 
                //
                //  Flush the parent Dcb's to get any dirent updates to disk.
                //
 
                NextFcb = Fcb->ParentDcb;
 
                while (NextFcb != NULL) {
 
                    //
                    //  Make sure the Fcb is OK.
                    //
 
                    _SEH2_TRY {
 
                        FatVerifyFcb( IrpContext, NextFcb );
 
                    } _SEH2_EXCEPT( FsRtlIsNtstatusExpected(_SEH2_GetExceptionCode()) ?
                              EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH ) {
 
                        FatResetExceptionState( IrpContext );
                    } _SEH2_END;
 
                    if (NextFcb->FcbCondition == FcbGood) {
 
                        NTSTATUS LocalStatus;
 
                        LocalStatus = FatFlushFile( IrpContext, NextFcb, Flush );
 
                        if (!NT_SUCCESS(LocalStatus)) {
 
                            Status = LocalStatus;
                        }
 
                        if (FlagOn(NextFcb->FcbState, FCB_STATE_FLUSH_FAT)) {
 
                            FatFlushRequired = TRUE;
                        }
                    }
 
                    NextFcb = NextFcb->ParentDcb;
                }
 
                //
                //  Flush the volume file to get any allocation information
                //  updates to disk.
                //
 
                if (FatFlushRequired) {
 
                    Status = FatFlushFat( IrpContext, Vcb );
 
                    ClearFlag(Fcb->FcbState, FCB_STATE_FLUSH_FAT);
                }
 
                //
                //  Set the write through bit so that these modifications
                //  will be completed with the request.
                //
 
                SetFlag(IrpContext->Flags, IRP_CONTEXT_FLAG_WRITE_THROUGH);
            }
 
            break;
 
        case UserDirectoryOpen:
 
            //
            //  If the user had opened the root directory then we'll
            //  oblige by flushing the volume.
            //
 
            if (NodeType(Fcb) != FAT_NTC_ROOT_DCB) {
 
                DebugTrace(0, Dbg, "Flush a directory does nothing\n", 0);
                break;
            }
 
        case UserVolumeOpen:
 
            DebugTrace(0, Dbg, "Flush User Volume Open, or root dcb\n", 0);
 
            //
            //  Acquire exclusive access to the Vcb.
            //
 
            {
                BOOLEAN Finished;
#ifdef _MSC_VER
#pragma prefast( suppress:28931, "needed for debug build" )
#endif
                Finished = FatAcquireExclusiveVcb( IrpContext, Vcb );
                NT_ASSERT( Finished );
            }
 
            VcbAcquired = TRUE;
 
            //
            //  Mark the volume clean and then flush the volume file,
            //  and then all directories
            //
 
            Status = FatFlushVolume( IrpContext, Vcb, Flush );
 
            //
            //  If the volume was dirty, do the processing that the delayed
            //  callback would have done.
            //
 
            if (FlagOn(Vcb->VcbState, VCB_STATE_FLAG_VOLUME_DIRTY)) {
 
                //
                //  Cancel any pending clean volumes.
                //
 
                (VOID)KeCancelTimer( &Vcb->CleanVolumeTimer );
                (VOID)KeRemoveQueueDpc( &Vcb->CleanVolumeDpc );
 
                //
                //  The volume is now clean, note it.
                //
 
                if (!FlagOn(Vcb->VcbState, VCB_STATE_FLAG_MOUNTED_DIRTY)) {
 
                    FatMarkVolume( IrpContext, Vcb, VolumeClean );
                    ClearFlag( Vcb->VcbState, VCB_STATE_FLAG_VOLUME_DIRTY );
                }
 
                //
                //  Unlock the volume if it is removable.
                //
 
                if (FlagOn(Vcb->VcbState, VCB_STATE_FLAG_REMOVABLE_MEDIA) &&
                    !FlagOn(Vcb->VcbState, VCB_STATE_FLAG_BOOT_OR_PAGING_FILE)) {
 
                    FatToggleMediaEjectDisable( IrpContext, Vcb, FALSE );
                }
            }
 
            break;
 
        default:
 
#ifdef _MSC_VER
#pragma prefast( suppress:28159, "things are seriously wrong if we get here" )
#endif
            FatBugCheck( TypeOfOpen, 0, 0 );
        }
 
        FatUnpinRepinnedBcbs( IrpContext );
 
    } _SEH2_FINALLY {
 
        DebugUnwind( FatCommonFlushBuffers );
 
        if (VcbAcquired) { FatReleaseVcb( IrpContext, Vcb ); }
 
        if (FcbAcquired) { FatReleaseFcb( IrpContext, Fcb ); }
 
        //
        //  If this is a normal termination then pass the request on
        //  to the target device object.
        //
 
        if (!_SEH2_AbnormalTermination()) {
 
#if (NTDDI_VERSION >= NTDDI_WIN8)
            if ((IrpSp->MinorFunction != IRP_MN_FLUSH_DATA_ONLY) &&
                (IrpSp->MinorFunction != IRP_MN_FLUSH_NO_SYNC)) {
#endif
 
                NTSTATUS DriverStatus;
 
                //
                //  Get the next stack location, and copy over the stack location
                //
 
                IoCopyCurrentIrpStackLocationToNext(Irp);
 
                //
                //  Set up the completion routine
                //
 
                IoSetCompletionRoutine( Irp,
                                        FatFlushCompletionRoutine,
                                        ULongToPtr( Status ),
                                        TRUE,
                                        TRUE,
                                        TRUE );
 
                //
                //  Send the request.
                //
 
                DriverStatus = IoCallDriver(Vcb->TargetDeviceObject, Irp);
 
                if ((DriverStatus == STATUS_PENDING) ||
                    (!NT_SUCCESS(DriverStatus) &&
                     (DriverStatus != STATUS_INVALID_DEVICE_REQUEST))) {
 
                    Status = DriverStatus;
                }
 
                Irp = NULL;
 
#if (NTDDI_VERSION >= NTDDI_WIN8)
            }
#endif
 
            //
            //  Complete the Irp if necessary and return to the caller.
            //
 
            FatCompleteRequest( IrpContext, Irp, Status );
 
        }
 
        DebugTrace(-1, Dbg, "FatCommonFlushBuffers -> %08lx\n", Status);
    } _SEH2_END;
 
    return Status;
}
 
 
_Requires_lock_held_(_Global_critical_region_)
NTSTATUS
FatFlushDirectory (
    IN PIRP_CONTEXT IrpContext,
    IN PDCB Dcb,
    IN FAT_FLUSH_TYPE FlushType
    )
 
/*++
 
Routine Description:
 
    This routine non-recursively flushes a dcb tree.
 
Arguments:
 
    Dcb - Supplies the Dcb being flushed
 
    FlushType - Specifies the kind of flushing to perform
 
Return Value:
 
    VOID
 
--*/
 
{
    PFCB Fcb;
    PVCB Vcb;
    PFCB NextFcb;
 
    PDIRENT Dirent;
    PBCB DirentBcb = NULL;
 
    NTSTATUS Status;
    NTSTATUS ReturnStatus = STATUS_SUCCESS;
 
    BOOLEAN ClearWriteThroughOnExit = FALSE;
    BOOLEAN ClearWaitOnExit = FALSE;
 
    ULONG CorrectedFileSize = 0;
 
    PAGED_CODE();
 
    NT_ASSERT( FatVcbAcquiredExclusive(IrpContext, Dcb->Vcb) );
 
    DebugTrace(+1, Dbg, "FatFlushDirectory, Dcb = %p\n", Dcb);
 
    //
    //  First flush all the files, then the directories, to make sure all the
    //  file sizes and times get sets correctly on disk.
    //
    //  We also have to check here if the "Ea Data. Sf" fcb really
    //  corressponds to an existing file.
    //
 
    if (!FlagOn(IrpContext->Flags, IRP_CONTEXT_FLAG_WRITE_THROUGH)) {
 
        ClearWriteThroughOnExit = TRUE;
        SetFlag(IrpContext->Flags, IRP_CONTEXT_FLAG_WRITE_THROUGH);
    }
 
    if (!FlagOn(IrpContext->Flags, IRP_CONTEXT_FLAG_WAIT)) {
 
        ClearWaitOnExit = TRUE;
        SetFlag(IrpContext->Flags, IRP_CONTEXT_FLAG_WAIT);
    }
 
    Vcb = Dcb->Vcb;
    Fcb = Dcb;
 
    while (Fcb != NULL) {
 
        NextFcb = FatGetNextFcbTopDown(IrpContext, Fcb, Dcb);
 
        if ( (NodeType( Fcb ) == FAT_NTC_FCB) &&
             (Vcb->EaFcb != Fcb) &&
             !IsFileDeleted(IrpContext, Fcb)) {
 
            (VOID)FatAcquireExclusiveFcb( IrpContext, Fcb );
 
            ClearFlag( Vcb->VcbState, VCB_STATE_FLAG_DELETED_FCB );
 
            //
            //  Exception handler to catch and commute errors encountered
            //  doing the flush dance.  We may encounter corruption, and
            //  should continue flushing the volume as much as possible.
            //
 
            _SEH2_TRY {
 
                //
                //  Standard handler to release resources, etc.
                //
 
                _SEH2_TRY {
 
                    //
                    //  Make sure the Fcb is OK.
                    //
 
                    _SEH2_TRY {
 
                        FatVerifyFcb( IrpContext, Fcb );
 
                    } _SEH2_EXCEPT( FsRtlIsNtstatusExpected(_SEH2_GetExceptionCode()) ?
                              EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH ) {
 
                        FatResetExceptionState( IrpContext );
                    } _SEH2_END;
 
                    //
                    //  If this Fcb is not good skip it.  Note that a 'continue'
                    //  here would be very expensive as we inside a try{} body.
                    //
 
                    if (Fcb->FcbCondition != FcbGood) {
 
                        try_leave( NOTHING);
                    }
 
                    //
                    //  In case a handle was never closed and the FS and AS are more
                    //  than a cluster different, do this truncate.
                    //
 
                    if ( FlagOn(Fcb->FcbState, FCB_STATE_TRUNCATE_ON_CLOSE) ) {
 
 
                        FatTruncateFileAllocation( IrpContext,
                                                   Fcb,
                                                   Fcb->Header.FileSize.LowPart );
 
 
                    }
 
                    //
                    //  Also compare the file's dirent in the parent directory
                    //  with the size information in the Fcb and update
                    //  it if neccessary.  Note that we don't mark the Bcb dirty
                    //  because we will be flushing the file object presently, and
                    //  Mm knows what's really dirty.
                    //
 
                    FatGetDirentFromFcbOrDcb( IrpContext,
                                              Fcb,
                                              FALSE,
                                              &Dirent,
                                              &DirentBcb );
 
 
                    CorrectedFileSize = Fcb->Header.FileSize.LowPart;
 
 
                    if (Dirent->FileSize != CorrectedFileSize) {
 
                        Dirent->FileSize = CorrectedFileSize;
 
 
                    }
 
                    //
                    //  We must unpin the Bcb before the flush since we recursively tear up
                    //  the tree if Mm decides that the data section is no longer referenced
                    //  and the final close comes in for this file. If this parent has no
                    //  more children as a result, we will try to initiate teardown on it
                    //  and Cc will deadlock against the active count of this Bcb.
                    //
 
                    FatUnpinBcb( IrpContext, DirentBcb );
 
                    //
                    //  Now flush the file.  Note that this may make the Fcb
                    //  go away if Mm dereferences its file object.
                    //
 
                    Status = FatFlushFile( IrpContext, Fcb, FlushType );
 
                    if (!NT_SUCCESS(Status)) {
 
                        ReturnStatus = Status;
                    }
 
                } _SEH2_FINALLY {
 
                    FatUnpinBcb( IrpContext, DirentBcb );
 
                    //
                    //  Since we have the Vcb exclusive we know that if any closes
                    //  come in it is because the CcPurgeCacheSection caused the
                    //  Fcb to go away.
                    //
 
                    if ( !FlagOn(Vcb->VcbState, VCB_STATE_FLAG_DELETED_FCB) ) {
 
                        FatReleaseFcb( (IRPCONTEXT), Fcb );
                    }
                } _SEH2_END;
            } _SEH2_EXCEPT( (FsRtlIsNtstatusExpected( ReturnStatus = _SEH2_GetExceptionCode() ) != 0 ) ?
                       EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH ) {
                   FatResetExceptionState( IrpContext );
             } _SEH2_END;
 
        }
 
        Fcb = NextFcb;
    }
 
    //
    //  OK, now flush the directories.
    //
 
    Fcb = Dcb;
 
    while (Fcb != NULL) {
 
        NextFcb = FatGetNextFcbTopDown(IrpContext, Fcb, Dcb);
 
        if ( (NodeType( Fcb ) != FAT_NTC_FCB) &&
             !IsFileDeleted(IrpContext, Fcb) ) {
 
            //
            //  Make sure the Fcb is OK.
            //
 
            _SEH2_TRY {
 
                FatVerifyFcb( IrpContext, Fcb );
 
            } _SEH2_EXCEPT( FsRtlIsNtstatusExpected(_SEH2_GetExceptionCode()) ?
                      EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH ) {
 
                FatResetExceptionState( IrpContext );
            } _SEH2_END;
 
            if (Fcb->FcbCondition == FcbGood) {
 
                Status = FatFlushFile( IrpContext, Fcb, FlushType );
 
                if (!NT_SUCCESS(Status)) {
 
                    ReturnStatus = Status;
                }
            }
        }
 
        Fcb = NextFcb;
    }
 
    _SEH2_TRY {
 
        FatUnpinRepinnedBcbs( IrpContext );
 
    } _SEH2_EXCEPT(FatExceptionFilter( IrpContext, _SEH2_GetExceptionInformation() )) {
 
        ReturnStatus = IrpContext->ExceptionStatus;
    } _SEH2_END;
 
    if (ClearWriteThroughOnExit) {
 
        ClearFlag(IrpContext->Flags, IRP_CONTEXT_FLAG_WRITE_THROUGH);
    }
    if (ClearWaitOnExit) {
 
        ClearFlag(IrpContext->Flags, IRP_CONTEXT_FLAG_WAIT);
    }
 
    DebugTrace(-1, Dbg, "FatFlushDirectory -> 0x%08lx\n", ReturnStatus);
 
    return ReturnStatus;
}
 
 
NTSTATUS
FatFlushFat (
    IN PIRP_CONTEXT IrpContext,
    IN PVCB Vcb
    )
 
/*++
 
Routine Description:
 
    The function carefully flushes the entire FAT for a volume.  It is
    nessecary to dance around a bit because of complicated synchronization
    reasons.
 
Arguments:
 
    Vcb - Supplies the Vcb whose FAT is being flushed
 
Return Value:
 
    VOID
 
--*/
 
{
    PBCB Bcb;
    PVOID DontCare;
    IO_STATUS_BLOCK Iosb;
    LARGE_INTEGER Offset;
 
    NTSTATUS ReturnStatus = STATUS_SUCCESS;
 
    PAGED_CODE();
 
    //
    //  If this volume is write protected, no need to flush.
    //
 
    if (FlagOn(Vcb->VcbState, VCB_STATE_FLAG_WRITE_PROTECTED)) {
 
        return STATUS_SUCCESS;
    }
 
    //
    //  Make sure the Vcb is OK.
    //
 
    _SEH2_TRY {
 
        FatVerifyVcb( IrpContext, Vcb );
 
    } _SEH2_EXCEPT( FsRtlIsNtstatusExpected(_SEH2_GetExceptionCode()) ?
              EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH ) {
 
        FatResetExceptionState( IrpContext );
    } _SEH2_END;
 
    if (Vcb->VcbCondition != VcbGood) {
 
        return STATUS_FILE_INVALID;
    }
 
    //
    //  The only way we have to correctly synchronize things is to
    //  repin stuff, and then unpin repin it.
    //
    //  With NT 5.0, we can use some new cache manager support to make
    //  this a lot more efficient (important for FAT32).  Since we're
    //  only worried about ranges that are dirty - and since we're a
    //  modified-no-write stream - we can assume that if there is no
    //  BCB, there is no work to do in the range. I.e., the lazy writer
    //  beat us to it.
    //
    //  This is much better than reading the entire FAT in and trying
    //  to punch it out (see the test in the write path to blow
    //  off writes that don't correspond to dirty ranges of the FAT).
    //  For FAT32, this would be a *lot* of reading.
    //
 
    if (Vcb->AllocationSupport.FatIndexBitSize != 12) {
 
        //
        //  Walk through the Fat, one page at a time.
        //
 
        ULONG NumberOfPages;
        ULONG Page;
 
        NumberOfPages = ( FatReservedBytes(&Vcb->Bpb) +
                          FatBytesPerFat(&Vcb->Bpb) +
                          (PAGE_SIZE - 1) ) / PAGE_SIZE;
 
 
        for ( Page = 0, Offset.QuadPart = 0;
              Page < NumberOfPages;
              Page++, Offset.LowPart += PAGE_SIZE ) {
 
            _SEH2_TRY {
 
                if (CcPinRead( Vcb->VirtualVolumeFile,
                               &Offset,
                               PAGE_SIZE,
                               PIN_WAIT | PIN_IF_BCB,
                               &Bcb,
                               &DontCare )) {
 
                    CcSetDirtyPinnedData( Bcb, NULL );
                    CcRepinBcb( Bcb );
                    CcUnpinData( Bcb );
                    CcUnpinRepinnedBcb( Bcb, TRUE, &Iosb );
 
                    if (!NT_SUCCESS(Iosb.Status)) {
 
                        ReturnStatus = Iosb.Status;
                    }
                }
 
            } _SEH2_EXCEPT(FatExceptionFilter(IrpContext, _SEH2_GetExceptionInformation())) {
 
                ReturnStatus = IrpContext->ExceptionStatus;
                continue;
            } _SEH2_END;
        }
 
    } else {
 
        //
        //  We read in the entire fat in the 12 bit case.
        //
 
        Offset.QuadPart = FatReservedBytes( &Vcb->Bpb );
 
        _SEH2_TRY {
 
            if (CcPinRead( Vcb->VirtualVolumeFile,
                           &Offset,
                           FatBytesPerFat( &Vcb->Bpb ),
                           PIN_WAIT | PIN_IF_BCB,
                           &Bcb,
                           &DontCare )) {
 
                CcSetDirtyPinnedData( Bcb, NULL );
                CcRepinBcb( Bcb );
                CcUnpinData( Bcb );
                CcUnpinRepinnedBcb( Bcb, TRUE, &Iosb );
 
                if (!NT_SUCCESS(Iosb.Status)) {
 
                    ReturnStatus = Iosb.Status;
                }
            }
 
        } _SEH2_EXCEPT(FatExceptionFilter(IrpContext, _SEH2_GetExceptionInformation())) {
 
            ReturnStatus = IrpContext->ExceptionStatus;
        } _SEH2_END;
    }
 
    return ReturnStatus;
}
 
 
_Requires_lock_held_(_Global_critical_region_)
NTSTATUS
FatFlushVolume (
    IN PIRP_CONTEXT IrpContext,
    IN PVCB Vcb,
    IN FAT_FLUSH_TYPE FlushType
    )
 
/*++
 
Routine Description:
 
    The following routine is used to flush a volume to disk, including the
    volume file, and ea file.
 
Arguments:
 
    Vcb - Supplies the volume being flushed
 
    FlushType - Specifies the kind of flushing to perform
 
Return Value:
 
    NTSTATUS - The Status from the flush.
 
--*/
 
{
    NTSTATUS Status;
    NTSTATUS ReturnStatus = STATUS_SUCCESS;
 
    PAGED_CODE();
 
    //
    //  If this volume is write protected, no need to flush.
    //
 
    if (FlagOn(Vcb->VcbState, VCB_STATE_FLAG_WRITE_PROTECTED)) {
 
        return STATUS_SUCCESS;
    }
 
    //
    //  Flush all the files and directories.
    //
 
    Status = FatFlushDirectory( IrpContext, Vcb->RootDcb, FlushType );
 
    if (!NT_SUCCESS(Status)) {
 
        ReturnStatus = Status;
    }
 
    //
    //  Now Flush the FAT
    //
 
    Status = FatFlushFat( IrpContext, Vcb );
 
    if (!NT_SUCCESS(Status)) {
 
        ReturnStatus = Status;
    }
 
    //
    //  Unlock the volume if it is removable.
    //
 
    if (FlagOn(Vcb->VcbState, VCB_STATE_FLAG_REMOVABLE_MEDIA) &&
        !FlagOn(Vcb->VcbState, VCB_STATE_FLAG_BOOT_OR_PAGING_FILE)) {
 
        FatToggleMediaEjectDisable( IrpContext, Vcb, FALSE );
    }
 
    return ReturnStatus;
}
 
 
_Requires_lock_held_(_Global_critical_region_)
NTSTATUS
FatFlushFile (
    IN PIRP_CONTEXT IrpContext,
    IN PFCB Fcb,
    IN FAT_FLUSH_TYPE FlushType
    )
 
/*++
 
Routine Description:
 
    This routine simply flushes the data section on a file.
 
Arguments:
 
    Fcb - Supplies the file being flushed
 
    FlushType - Specifies the kind of flushing to perform
 
Return Value:
 
    NTSTATUS - The Status from the flush.
 
--*/
 
{
    IO_STATUS_BLOCK Iosb;
    PVCB Vcb = Fcb->Vcb;
 
    PAGED_CODE();
 
    CcFlushCache( &Fcb->NonPaged->SectionObjectPointers, NULL, 0, &Iosb );
 
 
    if ( !FlagOn( Vcb->VcbState, VCB_STATE_FLAG_DELETED_FCB )) {
 
        //
        //  Grab and release PagingIo to serialize ourselves with the lazy writer.
        //  This will work to ensure that all IO has completed on the cached
        //  data.
        //
        //  If we are to invalidate the file, now is the right time to do it.  Do
        //  it non-recursively so we don't thump children before their time.
        //
 
        ExAcquireResourceExclusiveLite( Fcb->Header.PagingIoResource, TRUE);
 
        if (FlushType == FlushAndInvalidate) {
 
            FatMarkFcbCondition( IrpContext, Fcb, FcbBad, FALSE );
        }
 
        ExReleaseResourceLite( Fcb->Header.PagingIoResource );
    }
 
    return Iosb.Status;
}
 
 
NTSTATUS
FatHijackIrpAndFlushDevice (
    IN PIRP_CONTEXT IrpContext,
    IN PIRP Irp,
    IN PDEVICE_OBJECT TargetDeviceObject
    )
 
/*++
 
Routine Description:
 
    This routine is called when we need to send a flush to a device but
    we don't have a flush Irp.  What this routine does is make a copy
    of its current Irp stack location, but changes the Irp Major code
    to a IRP_MJ_FLUSH_BUFFERS amd then send it down, but cut it off at
    the knees in the completion routine, fix it up and return to the
    user as if nothing had happened.
 
Arguments:
 
    Irp - The Irp to hijack
 
    TargetDeviceObject - The device to send the request to.
 
Return Value:
 
    NTSTATUS - The Status from the flush in case anybody cares.
 
--*/
 
{
    KEVENT Event;
    NTSTATUS Status;
    PIO_STACK_LOCATION NextIrpSp;
 
    PAGED_CODE();
 
    UNREFERENCED_PARAMETER( IrpContext );
 
    //
    //  Get the next stack location, and copy over the stack location
    //
 
    IoCopyCurrentIrpStackLocationToNext(Irp);
 
    NextIrpSp = IoGetNextIrpStackLocation( Irp );
    NextIrpSp->MajorFunction = IRP_MJ_FLUSH_BUFFERS;
    NextIrpSp->MinorFunction = 0;
 
    //
    //  Set up the completion routine
    //
 
    KeInitializeEvent( &Event, NotificationEvent, FALSE );
 
    IoSetCompletionRoutine( Irp,
                            FatHijackCompletionRoutine,
                            &Event,
                            TRUE,
                            TRUE,
                            TRUE );
 
    //
    //  Send the request.
    //
 
    Status = IoCallDriver( TargetDeviceObject, Irp );
 
    if (Status == STATUS_PENDING) {
 
        KeWaitForSingleObject( &Event, Executive, KernelMode, FALSE, NULL );
 
        Status = Irp->IoStatus.Status;
    }
 
    //
    //  If the driver doesn't support flushes, return SUCCESS.
    //
 
    if (Status == STATUS_INVALID_DEVICE_REQUEST) {
        Status = STATUS_SUCCESS;
    }
 
    Irp->IoStatus.Status = 0;
    Irp->IoStatus.Information = 0;
 
    return Status;
}
 
 
VOID
FatFlushFatEntries (
    IN PIRP_CONTEXT IrpContext,
    IN PVCB Vcb,
    IN ULONG Cluster,
    IN ULONG Count
)
 
/*++
 
Routine Description:
 
    This macro flushes the FAT page(s) containing the passed in run.
 
Arguments:
 
    Vcb - Supplies the volume being flushed
 
    Cluster - The starting cluster
 
    Count -  The number of FAT entries in the run
 
Return Value:
 
    VOID
 
--*/
 
{
    ULONG ByteCount;
    LARGE_INTEGER FileOffset;
 
    IO_STATUS_BLOCK Iosb;
 
    PAGED_CODE();
 
    FileOffset.HighPart = 0;
    FileOffset.LowPart = FatReservedBytes( &Vcb->Bpb );
 
    if (Vcb->AllocationSupport.FatIndexBitSize == 12) {
 
        FileOffset.LowPart += Cluster * 3 / 2;
        ByteCount = (Count * 3 / 2) + 1;
 
    } else if (Vcb->AllocationSupport.FatIndexBitSize == 32) {
 
        FileOffset.LowPart += Cluster * sizeof(ULONG);
        ByteCount = Count * sizeof(ULONG);
 
    } else {
 
        FileOffset.LowPart += Cluster * sizeof( USHORT );
        ByteCount = Count * sizeof( USHORT );
 
    }
 
    CcFlushCache( &Vcb->SectionObjectPointers,
                  &FileOffset,
                  ByteCount,
                  &Iosb );
 
    if (NT_SUCCESS(Iosb.Status)) {
        Iosb.Status = FatHijackIrpAndFlushDevice( IrpContext,
                                                  IrpContext->OriginatingIrp,
                                                  Vcb->TargetDeviceObject );
    }
 
    if (!NT_SUCCESS(Iosb.Status)) {
        FatNormalizeAndRaiseStatus(IrpContext, Iosb.Status);
    }
}
 
 
VOID
FatFlushDirentForFile (
    IN PIRP_CONTEXT IrpContext,
    IN PFCB Fcb
)
 
/*++
 
Routine Description:
 
    This macro flushes the page containing a file's DIRENT in its parent.
 
Arguments:
 
    Fcb - Supplies the file whose DIRENT is being flushed
 
Return Value:
 
    VOID
 
--*/
 
{
    LARGE_INTEGER FileOffset;
    IO_STATUS_BLOCK Iosb;
 
    PAGED_CODE();
 
    FileOffset.QuadPart = Fcb->DirentOffsetWithinDirectory;
 
    CcFlushCache( &Fcb->ParentDcb->NonPaged->SectionObjectPointers,
                  &FileOffset,
                  sizeof( DIRENT ),
                  &Iosb );
 
    if (NT_SUCCESS(Iosb.Status)) {
        Iosb.Status = FatHijackIrpAndFlushDevice( IrpContext,
                                                  IrpContext->OriginatingIrp,
                                                  Fcb->Vcb->TargetDeviceObject );
    }
 
    if (!NT_SUCCESS(Iosb.Status)) {
        FatNormalizeAndRaiseStatus(IrpContext, Iosb.Status);
    }
}
 
 
//
//  Local support routine
//
 
NTSTATUS
NTAPI
FatFlushCompletionRoutine (
    IN PDEVICE_OBJECT DeviceObject,
    IN PIRP Irp,
    IN PVOID Contxt
    )
 
{
    NTSTATUS Status = (NTSTATUS) (ULONG_PTR) Contxt;
 
    if ( Irp->PendingReturned ) {
 
        IoMarkIrpPending( Irp );
    }
 
    //
    //  If the Irp got STATUS_INVALID_DEVICE_REQUEST, normalize it
    //  to STATUS_SUCCESS.
    //
 
    if (NT_SUCCESS(Irp->IoStatus.Status) ||
        (Irp->IoStatus.Status == STATUS_INVALID_DEVICE_REQUEST)) {
 
        Irp->IoStatus.Status = Status;
    }
 
    UNREFERENCED_PARAMETER( DeviceObject );
    UNREFERENCED_PARAMETER( Contxt );
 
    return STATUS_SUCCESS;
}
 
//
//  Local support routine
//
 
NTSTATUS
NTAPI
FatHijackCompletionRoutine (
    _In_ PDEVICE_OBJECT DeviceObject,
    _In_ PIRP Irp,
    _In_reads_opt_(_Inexpressible_("varies")) PVOID Contxt
    )
 
{
    //
    //  Set the event so that our call will wake up.
    //
 
    KeSetEvent( (PKEVENT)Contxt, 0, FALSE );
 
    UNREFERENCED_PARAMETER( DeviceObject );
    UNREFERENCED_PARAMETER( Irp );
 
    return STATUS_MORE_PROCESSING_REQUIRED;
}