write.c File Reference

#include "fatprocs.h"

Include dependency graph for write.c:

Go to the source code of this file.

Macros
#define	BugCheckFileId   (FAT_BUG_CHECK_WRITE)
#define	Dbg   (DEBUG_TRACE_WRITE)
#define	CollectWriteStats(VCB, OPEN_TYPE, BYTE_COUNT)

Functions
VOID NTAPI	FatDeferredFlushDpc (_In_ PKDPC Dpc, _In_opt_ PVOID DeferredContext, _In_opt_ PVOID SystemArgument1, _In_opt_ PVOID SystemArgument2)
VOID NTAPI	FatDeferredFlush (_In_ PVOID Parameter)
	_Function_class_ (IRP_MJ_WRITE)
	_Requires_lock_held_ (_Global_critical_region_)

Variables
BOOLEAN	FatNoAsync = FALSE
KDEFERRED_ROUTINE	FatDeferredFlushDpc
WORKER_THREAD_ROUTINE	FatDeferredFlush

Macro Definition Documentation

BugCheckFileId

#define BugCheckFileId   (FAT_BUG_CHECK_WRITE)

Definition at line 23 of file write.c.

CollectWriteStats

#define CollectWriteStats	(		VCB,
			OPEN_TYPE,
			BYTE_COUNT
	)

Value:

{                                        \
    PFILESYSTEM_STATISTICS Stats = &(VCB)->Statistics[KeGetCurrentProcessorNumber() % FatData.NumberProcessors].Common; \
    if (((OPEN_TYPE) == UserFileOpen)) {                                                     \
        Stats->UserFileWrites += 1;                                                          \
        Stats->UserFileWriteBytes += (ULONG)(BYTE_COUNT);                                    \
    } else if (((OPEN_TYPE) == VirtualVolumeFile || ((OPEN_TYPE) == DirectoryFile))) {       \
        Stats->MetaDataWrites += 1;                                                          \
        Stats->MetaDataWriteBytes += (ULONG)(BYTE_COUNT);                                    \
    }                                                                                        \
}

Definition at line 35 of file write.c.

Dbg

#define Dbg   (DEBUG_TRACE_WRITE)

Definition at line 29 of file write.c.

Function Documentation

_Function_class_()

_Function_class_

(

IRP_MJ_WRITE

)

Definition at line 77 of file write.c.

{
    PFCB Fcb;
    NTSTATUS Status;
    PIRP_CONTEXT IrpContext = NULL;

    BOOLEAN ModWriter = FALSE;
    BOOLEAN TopLevel = FALSE;

    DebugTrace(+1, Dbg, "FatFsdWrite\n", 0);

    //
    //  Call the common Write routine, with blocking allowed if synchronous
    //

    FsRtlEnterFileSystem();

    //
    //  We are first going to do a quick check for paging file IO.  Since this
    //  is a fast path, we must replicate the check for the fsdo.
    //

    if (!FatDeviceIsFatFsdo( IoGetCurrentIrpStackLocation(Irp)->DeviceObject))  {

        Fcb = (PFCB)(IoGetCurrentIrpStackLocation(Irp)->FileObject->FsContext);

        if ((NodeType(Fcb) == FAT_NTC_FCB) &&
            FlagOn(Fcb->FcbState, FCB_STATE_PAGING_FILE)) {

            //
            //  Do the usual STATUS_PENDING things.
            //

            IoMarkIrpPending( Irp );

            //
            //  Perform the actual IO, it will be completed when the io finishes.
            //

            FatPagingFileIo( Irp, Fcb );

            FsRtlExitFileSystem();

            return STATUS_PENDING;
        }
    }

    _SEH2_TRY {

        TopLevel = FatIsIrpTopLevel( Irp );

        IrpContext = FatCreateIrpContext( Irp, CanFsdWait( Irp ) );

        //
        //  This is a kludge for the mod writer case.  The correct state
        //  of recursion is set in IrpContext, however, we much with the
        //  actual top level Irp field to get the correct WriteThrough
        //  behaviour.
        //

        if (IoGetTopLevelIrp() == (PIRP)FSRTL_MOD_WRITE_TOP_LEVEL_IRP) {

            ModWriter = TRUE;

            IoSetTopLevelIrp( Irp );
        }

        //
        //  If this is an Mdl complete request, don't go through
        //  common write.
        //

        if (FlagOn( IrpContext->MinorFunction, IRP_MN_COMPLETE )) {

            DebugTrace(0, Dbg, "Calling FatCompleteMdl\n", 0 );
            Status = FatCompleteMdl( IrpContext, Irp );

        } else {

            Status = FatCommonWrite( 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;

//  NT_ASSERT( !(ModWriter && (Status == STATUS_CANT_WAIT)) );

    NT_ASSERT( !(ModWriter && TopLevel) );

    if (ModWriter) { IoSetTopLevelIrp((PIRP)FSRTL_MOD_WRITE_TOP_LEVEL_IRP); }

    if (TopLevel) { IoSetTopLevelIrp( NULL ); }

    FsRtlExitFileSystem();

    //
    //  And return to our caller
    //

    DebugTrace(-1, Dbg, "FatFsdWrite -> %08lx\n", Status);

    UNREFERENCED_PARAMETER( VolumeDeviceObject );

    return Status;
}

_Requires_lock_held_()

_Requires_lock_held_

(

_Global_critical_region_

)

Definition at line 220 of file write.c.

{
    PVCB Vcb;
    PFCB FcbOrDcb;
    PCCB Ccb;

    VBO StartingVbo;
    ULONG ByteCount;
    ULONG FileSize = 0;
    ULONG InitialFileSize = 0;
    ULONG InitialValidDataLength = 0;

    PIO_STACK_LOCATION IrpSp;
    PFILE_OBJECT FileObject;
    TYPE_OF_OPEN TypeOfOpen;

    BOOLEAN PostIrp = FALSE;
    BOOLEAN OplockPostIrp = FALSE;
    BOOLEAN ExtendingFile = FALSE;
    BOOLEAN FcbOrDcbAcquired = FALSE;
    BOOLEAN SwitchBackToAsync = FALSE;
    BOOLEAN CalledByLazyWriter = FALSE;
    BOOLEAN ExtendingValidData = FALSE;
    BOOLEAN FcbAcquiredExclusive = FALSE;
    BOOLEAN FcbCanDemoteToShared = FALSE;
    BOOLEAN WriteFileSizeToDirent = FALSE;
    BOOLEAN RecursiveWriteThrough = FALSE;
    BOOLEAN UnwindOutstandingAsync = FALSE;
    BOOLEAN PagingIoResourceAcquired = FALSE;
    BOOLEAN SuccessfulPurge = FALSE;

    BOOLEAN SynchronousIo;
    BOOLEAN WriteToEof;
    BOOLEAN PagingIo;
    BOOLEAN NonCachedIo;
    BOOLEAN Wait;
    NTSTATUS Status = STATUS_SUCCESS;

    FAT_IO_CONTEXT StackFatIoContext;

    //
    // A system buffer is only used if we have to access the buffer directly
    // from the Fsp to clear a portion or to do a synchronous I/O, or a
    // cached transfer.  It is possible that our caller may have already
    // mapped a system buffer, in which case we must remember this so
    // we do not unmap it on the way out.
    //

    PVOID SystemBuffer = (PVOID) NULL;

    LARGE_INTEGER StartingByte;

    PAGED_CODE();

    //
    // Get current Irp stack location and file object
    //

    IrpSp = IoGetCurrentIrpStackLocation( Irp );
    FileObject = IrpSp->FileObject;


    DebugTrace(+1, Dbg, "FatCommonWrite\n", 0);
    DebugTrace( 0, Dbg, "Irp                 = %p\n", Irp);
    DebugTrace( 0, Dbg, "ByteCount           = %8lx\n", IrpSp->Parameters.Write.Length);
    DebugTrace( 0, Dbg, "ByteOffset.LowPart  = %8lx\n", IrpSp->Parameters.Write.ByteOffset.LowPart);
    DebugTrace( 0, Dbg, "ByteOffset.HighPart = %8lx\n", IrpSp->Parameters.Write.ByteOffset.HighPart);

    //
    // Initialize the appropriate local variables.
    //

    Wait          = BooleanFlagOn(IrpContext->Flags, IRP_CONTEXT_FLAG_WAIT);
    PagingIo      = BooleanFlagOn(Irp->Flags, IRP_PAGING_IO);
    NonCachedIo   = BooleanFlagOn(Irp->Flags,IRP_NOCACHE);
    SynchronousIo = BooleanFlagOn(FileObject->Flags, FO_SYNCHRONOUS_IO);

    //NT_ASSERT( PagingIo || FileObject->WriteAccess );

    //
    //  Extract the bytecount and do our noop/throttle checking.
    //

    ByteCount = IrpSp->Parameters.Write.Length;

    //
    //  If there is nothing to write, return immediately.
    //

    if (ByteCount == 0) {

        Irp->IoStatus.Information = 0;
        FatCompleteRequest( IrpContext, Irp, STATUS_SUCCESS );
        return STATUS_SUCCESS;
    }

    //
    //  See if we have to defer the write.
    //

    if (!NonCachedIo &&
        !CcCanIWrite(FileObject,
                     ByteCount,
                     (BOOLEAN)(Wait && !BooleanFlagOn(IrpContext->Flags, IRP_CONTEXT_FLAG_IN_FSP)),
                     BooleanFlagOn(IrpContext->Flags, IRP_CONTEXT_FLAG_DEFERRED_WRITE))) {

        BOOLEAN Retrying = BooleanFlagOn(IrpContext->Flags, IRP_CONTEXT_FLAG_DEFERRED_WRITE);

        FatPrePostIrp( IrpContext, Irp );

        SetFlag( IrpContext->Flags, IRP_CONTEXT_FLAG_DEFERRED_WRITE );

        CcDeferWrite( FileObject,
                      (PCC_POST_DEFERRED_WRITE)FatAddToWorkque,
                      IrpContext,
                      Irp,
                      ByteCount,
                      Retrying );

        return STATUS_PENDING;
    }

    //
    //  Determine our starting position and type.  If we are writing
    //  at EOF, then we will need additional synchronization before
    //  the IO is issued to determine where the data will go.
    //

    StartingByte = IrpSp->Parameters.Write.ByteOffset;
    StartingVbo = StartingByte.LowPart;

    WriteToEof = ( (StartingByte.LowPart == FILE_WRITE_TO_END_OF_FILE) &&
                   (StartingByte.HighPart == -1) );

    //
    //  Extract the nature of the write from the file object, and case on it
    //

    TypeOfOpen = FatDecodeFileObject(FileObject, &Vcb, &FcbOrDcb, &Ccb);

    NT_ASSERT( Vcb != NULL );

    //
    //  Save callers who try to do cached IO to the raw volume from themselves.
    //

    if (TypeOfOpen == UserVolumeOpen) {

        NonCachedIo = TRUE;
    }

    NT_ASSERT(!(NonCachedIo == FALSE && TypeOfOpen == VirtualVolumeFile));

    //
    //  Collect interesting statistics.  The FLAG_USER_IO bit will indicate
    //  what type of io we're doing in the FatNonCachedIo function.
    //

    if (PagingIo) {
        CollectWriteStats(Vcb, TypeOfOpen, ByteCount);

        if (TypeOfOpen == UserFileOpen) {
            SetFlag(IrpContext->Flags, IRP_CONTEXT_FLAG_USER_IO);
        } else {
            ClearFlag(IrpContext->Flags, IRP_CONTEXT_FLAG_USER_IO);
        }
    }

    //
    //  We must disallow writes to regular objects that would require us
    //  to maintain an AllocationSize of greater than 32 significant bits.
    //
    //  If this is paging IO, this is simply a case where we need to trim.
    //  This will occur in due course.
    //

    if (!PagingIo && !WriteToEof && (TypeOfOpen != UserVolumeOpen)) {


        if (!FatIsIoRangeValid( Vcb, StartingByte, ByteCount)) {


            Irp->IoStatus.Information = 0;
            FatCompleteRequest( IrpContext, Irp, STATUS_DISK_FULL );

            return STATUS_DISK_FULL;
        }
    }

    //
    //  Allocate if necessary and initialize a FAT_IO_CONTEXT block for
    //  all non cached Io.  For synchronous Io
    //  we use stack storage, otherwise we allocate pool.
    //

    if (NonCachedIo) {

        if (IrpContext->FatIoContext == NULL) {

            if (!Wait) {

                IrpContext->FatIoContext =
#ifndef __REACTOS__
                    FsRtlAllocatePoolWithTag( NonPagedPoolNx,
#else
                    FsRtlAllocatePoolWithTag( NonPagedPool,
#endif
                                              sizeof(FAT_IO_CONTEXT),
                                              TAG_FAT_IO_CONTEXT );

            } else {

                IrpContext->FatIoContext = &StackFatIoContext;

                SetFlag( IrpContext->Flags, IRP_CONTEXT_STACK_IO_CONTEXT );
            }
        }

        RtlZeroMemory( IrpContext->FatIoContext, sizeof(FAT_IO_CONTEXT) );

        if (Wait) {

            KeInitializeEvent( &IrpContext->FatIoContext->Wait.SyncEvent,
                               NotificationEvent,
                               FALSE );

        } else {

            if (PagingIo) {

                IrpContext->FatIoContext->Wait.Async.ResourceThreadId =
                    ExGetCurrentResourceThread();

            } else {

                IrpContext->FatIoContext->Wait.Async.ResourceThreadId =
                    ((ULONG_PTR)IrpContext->FatIoContext) | 3;
            }

            IrpContext->FatIoContext->Wait.Async.RequestedByteCount =
                ByteCount;

            IrpContext->FatIoContext->Wait.Async.FileObject = FileObject;
        }
        
    }

    //
    //  Check if this volume has already been shut down.  If it has, fail
    //  this write request.
    //

    if ( FlagOn(Vcb->VcbState, VCB_STATE_FLAG_SHUTDOWN) ) {

        Irp->IoStatus.Information = 0;
        FatCompleteRequest( IrpContext, Irp, STATUS_TOO_LATE );
        return STATUS_TOO_LATE;
    }

    //
    //  This case corresponds to a write of the volume file (only the first
    //  fat allowed, the other fats are written automatically in parallel).
    //
    //  We use an Mcb keep track of dirty sectors.  Actual entries are Vbos
    //  and Lbos (ie. bytes), though they are all added in sector chunks.
    //  Since Vbo == Lbo for the volume file, the Mcb entries
    //  alternate between runs of Vbo == Lbo, and holes (Lbo == 0).  We use
    //  the prior to represent runs of dirty fat sectors, and the latter
    //  for runs of clean fat.  Note that since the first part of the volume
    //  file (boot sector) is always clean (a hole), and an Mcb never ends in
    //  a hole, there must always be an even number of runs(entries) in the Mcb.
    //
    //  The strategy is to find the first and last dirty run in the desired
    //  write range (which will always be a set of pages), and write from the
    //  former to the later.  The may result in writing some clean data, but
    //  will generally be more efficient than writing each runs seperately.
    //

    if (TypeOfOpen == VirtualVolumeFile) {

        LBO DirtyLbo;
        LBO CleanLbo;

        VBO DirtyVbo;
        VBO StartingDirtyVbo;

        ULONG DirtyByteCount;
        ULONG CleanByteCount;

        ULONG WriteLength;

        BOOLEAN MoreDirtyRuns = TRUE;

        IO_STATUS_BLOCK RaiseIosb;

        DebugTrace(0, Dbg, "Type of write is Virtual Volume File\n", 0);

        //
        //  If we can't wait we have to post this.
        //

        if (!Wait) {

            DebugTrace( 0, Dbg, "Passing request to Fsp\n", 0 );

            Status = FatFsdPostRequest(IrpContext, Irp);

            return Status;
        }

        //
        //  If we weren't called by the Lazy Writer, then this write
        //  must be the result of a write-through or flush operation.
        //  Setting the IrpContext flag, will cause DevIoSup.c to
        //  write-through the data to the disk.
        //

        if (!FlagOn((ULONG_PTR)IoGetTopLevelIrp(), FSRTL_CACHE_TOP_LEVEL_IRP)) {

            SetFlag( IrpContext->Flags, IRP_CONTEXT_FLAG_WRITE_THROUGH );
        }

        //
        //  Assert an even number of entries in the Mcb, an odd number would
        //  mean that the Mcb is corrupt.
        //

        NT_ASSERT( (FsRtlNumberOfRunsInLargeMcb( &Vcb->DirtyFatMcb ) & 1) == 0);

        //
        //  We need to skip over any clean sectors at the start of the write.
        //
        //  Also check the two cases where there are no dirty fats in the
        //  desired write range, and complete them with success.
        //
        //      1) There is no Mcb entry corresponding to StartingVbo, meaning
        //         we are beyond the end of the Mcb, and thus dirty fats.
        //
        //      2) The run at StartingVbo is clean and continues beyond the
        //         desired write range.
        //

        if (!FatLookupMcbEntry( Vcb, &Vcb->DirtyFatMcb,
                                StartingVbo,
                                &DirtyLbo,
                                &DirtyByteCount,
                                NULL )

          || ( (DirtyLbo == 0) && (DirtyByteCount >= ByteCount) ) ) {

            DebugTrace(0, DEBUG_TRACE_DEBUG_HOOKS,
                       "No dirty fat sectors in the write range.\n", 0);

            FatCompleteRequest( IrpContext, Irp, STATUS_SUCCESS );
            return STATUS_SUCCESS;
        }

        DirtyVbo = (VBO)DirtyLbo;

        //
        //  If the last run was a hole (clean), up DirtyVbo to the next
        //  run, which must be dirty.
        //

        if (DirtyVbo == 0) {

            DirtyVbo = StartingVbo + DirtyByteCount;
        }

        //
        //  This is where the write will start.
        //

        StartingDirtyVbo = DirtyVbo;

        //
        //
        //  Now start enumerating the dirty fat sectors spanning the desired
        //  write range, this first one of which is now DirtyVbo.
        //

        while ( MoreDirtyRuns ) {

            //
            //  Find the next dirty run, if it is not there, the Mcb ended
            //  in a hole, or there is some other corruption of the Mcb.
            //

            if (!FatLookupMcbEntry( Vcb, &Vcb->DirtyFatMcb,
                                    DirtyVbo,
                                    &DirtyLbo,
                                    &DirtyByteCount,
                                    NULL )) {

#ifdef _MSC_VER
#pragma prefast( suppress:28931, "needed for debug build" )
#endif
                DirtyVbo = (VBO)DirtyLbo;

                DebugTrace(0, Dbg, "Last dirty fat Mcb entry was a hole: corrupt.\n", 0);
                
#ifdef _MSC_VER
#pragma prefast( suppress:28159, "things are seriously wrong if we get here" )                
#endif
                FatBugCheck( 0, 0, 0 );

            } else {

                DirtyVbo = (VBO)DirtyLbo;

                //
                //  This has to correspond to a dirty run, and must start
                //  within the write range since we check it at entry to,
                //  and at the bottom of this loop.
                //

                NT_ASSERT((DirtyVbo != 0) && (DirtyVbo < StartingVbo + ByteCount));

                //
                //  There are three ways we can know that this was the
                //  last dirty run we want to write.
                //
                //      1)  The current dirty run extends beyond or to the
                //          desired write range.
                //
                //      2)  On trying to find the following clean run, we
                //          discover that this is the last run in the Mcb.
                //
                //      3)  The following clean run extend beyond the
                //          desired write range.
                //
                //  In any of these cases we set MoreDirtyRuns = FALSE.
                //

                //
                //  If the run is larger than we are writing, we also
                //  must truncate the WriteLength.  This is benign in
                //  the equals case.
                //

                if (DirtyVbo + DirtyByteCount >= StartingVbo + ByteCount) {

                    DirtyByteCount = StartingVbo + ByteCount - DirtyVbo;

                    MoreDirtyRuns = FALSE;

                } else {

                    //
                    //  Scan the clean hole after this dirty run.  If this
                    //  run was the last, prepare to exit the loop
                    //

                    if (!FatLookupMcbEntry( Vcb, &Vcb->DirtyFatMcb,
                                            DirtyVbo + DirtyByteCount,
                                            &CleanLbo,
                                            &CleanByteCount,
                                            NULL )) {

                        MoreDirtyRuns = FALSE;

                    } else {

                        //
                        //  Assert that we actually found a clean run.
                        //  and compute the start of the next dirty run.
                        //

                        NT_ASSERT (CleanLbo == 0);

                        //
                        //  If the next dirty run starts beyond the desired
                        //  write, we have found all the runs we need, so
                        //  prepare to exit.
                        //

                        if (DirtyVbo + DirtyByteCount + CleanByteCount >=
                                                    StartingVbo + ByteCount) {

                            MoreDirtyRuns = FALSE;

                        } else {

                            //
                            //  Compute the start of the next dirty run.
                            //

                            DirtyVbo += DirtyByteCount + CleanByteCount;
                        }
                    }
                }
            }
        } // while ( MoreDirtyRuns )

        //
        //  At this point DirtyVbo and DirtyByteCount correctly reflect the
        //  final dirty run, constrained to the desired write range.
        //
        //  Now compute the length we finally must write.
        //

        WriteLength = (DirtyVbo + DirtyByteCount) - StartingDirtyVbo;

        //
        // We must now assume that the write will complete with success,
        // and initialize our expected status in RaiseIosb.  It will be
        // modified below if an error occurs.
        //

        RaiseIosb.Status = STATUS_SUCCESS;
        RaiseIosb.Information = ByteCount;

        //
        //  Loop through all the fats, setting up a multiple async to
        //  write them all.  If there are more than FAT_MAX_PARALLEL_IOS
        //  then we do several muilple asyncs.
        //

        {
            ULONG Fat;
            ULONG BytesPerFat;
            IO_RUN StackIoRuns[2];
            PIO_RUN IoRuns;

            BytesPerFat = FatBytesPerFat( &Vcb->Bpb );

            if ((ULONG)Vcb->Bpb.Fats > 2) {

                IoRuns = FsRtlAllocatePoolWithTag( PagedPool,
                                                   (ULONG)(Vcb->Bpb.Fats*sizeof(IO_RUN)),
                                                   TAG_IO_RUNS );

            } else {

                IoRuns = StackIoRuns;
            }

            for (Fat = 0; Fat < (ULONG)Vcb->Bpb.Fats; Fat++) {

                IoRuns[Fat].Vbo = StartingDirtyVbo;
                IoRuns[Fat].Lbo = Fat * BytesPerFat + StartingDirtyVbo;
                IoRuns[Fat].Offset = StartingDirtyVbo - StartingVbo;
                IoRuns[Fat].ByteCount = WriteLength;
            }

            //
            //  Keep track of meta-data disk ios.
            //

            Vcb->Statistics[KeGetCurrentProcessorNumber() % FatData.NumberProcessors].Common.MetaDataDiskWrites += Vcb->Bpb.Fats;

            _SEH2_TRY {

                FatMultipleAsync( IrpContext,
                                  Vcb,
                                  Irp,
                                  (ULONG)Vcb->Bpb.Fats,
                                  IoRuns );

            } _SEH2_FINALLY {

                if (IoRuns != StackIoRuns) {

                    ExFreePool( IoRuns );
                }
            } _SEH2_END;

#if (NTDDI_VERSION >= NTDDI_WIN8)

            //
            //  Account for DASD Ios
            //

            if (FatDiskAccountingEnabled) {

                PETHREAD ThreadIssuingIo = PsGetCurrentThread();

                PsUpdateDiskCounters( PsGetThreadProcess( ThreadIssuingIo ),
                                      0,
                                      WriteLength,
                                      0,
                                      1,
                                      0 );
            }

#endif
            //
            //  Wait for all the writes to finish
            //

            FatWaitSync( IrpContext );

            //
            //  If we got an error, or verify required, remember it.
            //

            if (!NT_SUCCESS( Irp->IoStatus.Status )) {

                DebugTrace( 0,
                            Dbg,
                            "Error %X while writing volume file.\n",
                            Irp->IoStatus.Status );

                RaiseIosb = Irp->IoStatus;
            }
        }

        //
        //  If the writes were a success, set the sectors clean, else
        //  raise the error status and mark the volume as needing
        //  verification.  This will automatically reset the volume
        //  structures.
        //
        //  If not, then mark this volume as needing verification to
        //  automatically cause everything to get cleaned up.
        //

        Irp->IoStatus = RaiseIosb;

        if ( NT_SUCCESS( Status = Irp->IoStatus.Status )) {

            FatRemoveMcbEntry( Vcb, &Vcb->DirtyFatMcb,
                               StartingDirtyVbo,
                               WriteLength );

        } else {

            FatNormalizeAndRaiseStatus( IrpContext, Status );
        }

        DebugTrace(-1, Dbg, "CommonWrite -> %08lx\n", Status );

        FatCompleteRequest( IrpContext, Irp, Status );
        return Status;
    }

    //
    //  This case corresponds to a general opened volume (DASD), ie.
    //  open ("a:").
    //

    if (TypeOfOpen == UserVolumeOpen) {

        LBO StartingLbo;
        LBO VolumeSize;

        //
        //  Precalculate the volume size since we're nearly always going
        //  to be wanting to use it.
        //

        VolumeSize = (LBO) Int32x32To64( Vcb->Bpb.BytesPerSector,
                                         (Vcb->Bpb.Sectors != 0 ? Vcb->Bpb.Sectors :
                                                                  Vcb->Bpb.LargeSectors));

        StartingLbo = StartingByte.QuadPart;

        DebugTrace(0, Dbg, "Type of write is User Volume.\n", 0);

        //
        //  If this is a write on a disk-based volume that is not locked, we need to limit
        //  the sectors we allow to be written within the volume.  Specifically, we only
        //  allow writes to the reserved area.  Note that extended DASD can still be used
        //  to write past the end of the volume.  We also allow kernel mode callers to force
        //  access via a flag in the IRP.  A handle that issued a dismount can write anywhere
        //  as well.
        //

        if ((Vcb->TargetDeviceObject->DeviceType == FILE_DEVICE_DISK) &&
            !FlagOn( Vcb->VcbState, VCB_STATE_FLAG_LOCKED ) &&
            !FlagOn( IrpSp->Flags, SL_FORCE_DIRECT_WRITE ) &&
            !FlagOn( Ccb->Flags, CCB_FLAG_COMPLETE_DISMOUNT )) {

            //
            //  First check for a write beyond the end of the volume.
            //

            if (!WriteToEof && (StartingLbo < VolumeSize)) {

                //
                //  This write is within the volume.  Make sure it is not beyond the reserved section.
                //

                if ((StartingLbo >= FatReservedBytes( &(Vcb->Bpb) )) ||
                    (ByteCount > (FatReservedBytes( &(Vcb->Bpb) ) - StartingLbo))) {

                    FatCompleteRequest( IrpContext, Irp, STATUS_ACCESS_DENIED );
                    return STATUS_ACCESS_DENIED;
                }
            }
        }

        //
        //  Verify that the volume for this handle is still valid, permitting
        //  operations to proceed on dismounted volumes via the handle which
        //  performed the dismount or sent a format unit command.
        //

        if (!FlagOn( Ccb->Flags, CCB_FLAG_COMPLETE_DISMOUNT | CCB_FLAG_SENT_FORMAT_UNIT )) {

            FatQuickVerifyVcb( IrpContext, Vcb );
        }

        //
        //  If the caller previously sent a format unit command, then we will allow
        //  their read/write requests to ignore the verify flag on the device, since some
        //  devices send a media change event after format unit, but we don't want to 
        //  process it yet since we're probably in the process of formatting the
        //  media.
        //
        
        if (FlagOn( Ccb->Flags, CCB_FLAG_SENT_FORMAT_UNIT )) {
        
            SetFlag( IrpContext->Flags, IRP_CONTEXT_FLAG_OVERRIDE_VERIFY );
        }

        if (!FlagOn( Ccb->Flags, CCB_FLAG_DASD_PURGE_DONE )) {

            BOOLEAN PreviousWait = BooleanFlagOn( IrpContext->Flags, IRP_CONTEXT_FLAG_WAIT );

            //
            //  Grab the entire volume so that even the normally unsafe action
            //  of writing to an unlocked volume won't open us to a race between
            //  the flush and purge of the FAT below.
            //
            //  I really don't think this is particularly important to worry about,
            //  but a repro case for another bug happens to dance into this race
            //  condition pretty easily. Eh.
            //
            
            SetFlag( IrpContext->Flags, IRP_CONTEXT_FLAG_WAIT );
            FatAcquireExclusiveVolume( IrpContext, Vcb );

            _SEH2_TRY {

                //
                //  If the volume isn't locked, flush and purge it.
                //

                if (!FlagOn(Vcb->VcbState, VCB_STATE_FLAG_LOCKED)) {

                    FatFlushFat( IrpContext, Vcb );
                    CcPurgeCacheSection( &Vcb->SectionObjectPointers,
                                         NULL,
                                         0,
                                         FALSE );

                    FatPurgeReferencedFileObjects( IrpContext, Vcb->RootDcb, Flush );
                }

            } _SEH2_FINALLY {

                FatReleaseVolume( IrpContext, Vcb );
                if (!PreviousWait) {
                    ClearFlag( IrpContext->Flags, IRP_CONTEXT_FLAG_WAIT );
                }
            } _SEH2_END;

            SetFlag( Ccb->Flags, CCB_FLAG_DASD_PURGE_DONE |
                                 CCB_FLAG_DASD_FLUSH_DONE );
        }

        if (!FlagOn( Ccb->Flags, CCB_FLAG_ALLOW_EXTENDED_DASD_IO )) {

            //
            //  Make sure we don't try to write past end of volume,
            //  reducing the requested byte count if necessary.
            //

            if (WriteToEof || StartingLbo >= VolumeSize) {
                FatCompleteRequest( IrpContext, Irp, STATUS_SUCCESS );
                return STATUS_SUCCESS;
            }

            if (ByteCount > VolumeSize - StartingLbo) {

                ByteCount = (ULONG) (VolumeSize - StartingLbo);

                //
                //  For async writes we had set the byte count in the FatIoContext
                //  above, so fix that here.
                //

                if (!Wait) {

                    IrpContext->FatIoContext->Wait.Async.RequestedByteCount =
                        ByteCount;
                }
            }
        } else {

            //
            //  This has a peculiar interpretation, but just adjust the starting
            //  byte to the end of the visible volume.
            //

            if (WriteToEof) {

                StartingLbo = VolumeSize;
            }
        }

        //
        // For DASD we have to probe and lock the user's buffer
        //

        FatLockUserBuffer( IrpContext, Irp, IoReadAccess, ByteCount );

        //
        //  Set the FO_MODIFIED flag here to trigger a verify when this
        //  handle is closed.  Note that we can err on the conservative
        //  side with no problem, i.e. if we accidently do an extra
        //  verify there is no problem.
        //

        SetFlag( FileObject->Flags, FO_FILE_MODIFIED );

        //
        //  Write the data and wait for the results
        //

        FatSingleAsync( IrpContext,
                        Vcb,
                        StartingLbo,
                        ByteCount,
                        Irp );

#if (NTDDI_VERSION >= NTDDI_WIN8)

        //
        //  Account for DASD Ios
        //

        if (FatDiskAccountingEnabled) {

            PETHREAD ThreadIssuingIo = PsGetCurrentThread();

            PsUpdateDiskCounters( PsGetThreadProcess( ThreadIssuingIo ),
                                  0,
                                  ByteCount,
                                  0,
                                  1,
                                  0 );
        }

#endif

        if (!Wait) {

            //
            //  We, nor anybody else, need the IrpContext any more.
            //

            IrpContext->FatIoContext = NULL;

            FatDeleteIrpContext( IrpContext );

            DebugTrace(-1, Dbg, "FatNonCachedIo -> STATUS_PENDING\n", 0);

            return STATUS_PENDING;
        }

        FatWaitSync( IrpContext );

        //
        //  If the call didn't succeed, raise the error status
        //
        //  Also mark this volume as needing verification to automatically
        //  cause everything to get cleaned up.
        //

        if (!NT_SUCCESS( Status = Irp->IoStatus.Status )) {

            FatNormalizeAndRaiseStatus( IrpContext, Status );
        }

        //
        //  Update the current file position.  We assume that
        //  open/create zeros out the CurrentByteOffset field.
        //

        if (SynchronousIo && !PagingIo) {
            FileObject->CurrentByteOffset.QuadPart =
                StartingLbo + Irp->IoStatus.Information;
        }

        DebugTrace(-1, Dbg, "FatCommonWrite -> %08lx\n", Status );

        FatCompleteRequest( IrpContext, Irp, Status );
        return Status;
    }

    //
    //  At this point we know there is an Fcb/Dcb.
    //

    NT_ASSERT( FcbOrDcb != NULL );

    //
    //  Use a try-finally to free Fcb/Dcb and buffers on the way out.
    //

    _SEH2_TRY {

        //
        // This case corresponds to a normal user write file.
        //

        if ( TypeOfOpen == UserFileOpen
            ) {

            ULONG ValidDataLength;
            ULONG ValidDataToDisk;
            ULONG ValidDataToCheck;

            DebugTrace(0, Dbg, "Type of write is user file open\n", 0);

            //
            //  If this is a noncached transfer and is not a paging I/O, and
            //  the file has been opened cached, then we will do a flush here
            //  to avoid stale data problems.  Note that we must flush before
            //  acquiring the Fcb shared since the write may try to acquire
            //  it exclusive.
            //
            //  The Purge following the flush will guarentee cache coherency.
            //

            if (NonCachedIo && !PagingIo &&
                (FileObject->SectionObjectPointer->DataSectionObject != NULL)) {

#ifndef __REACTOS__
                IO_STATUS_BLOCK IoStatus = {0};
#else
                IO_STATUS_BLOCK IoStatus = {{0}};
#endif

                //
                //  We need the Fcb exclsuive to do the CcPurgeCache
                //

                if (!FatAcquireExclusiveFcb( IrpContext, FcbOrDcb )) {

                    DebugTrace( 0, Dbg, "Cannot acquire FcbOrDcb = %p shared without waiting\n", FcbOrDcb );

                    try_return( PostIrp = TRUE );
                }

                FcbOrDcbAcquired = TRUE;
                FcbAcquiredExclusive = TRUE;

                //
                //  Preacquire pagingio for the flush.
                //

                ExAcquireResourceExclusiveLite( FcbOrDcb->Header.PagingIoResource, TRUE );

#if (NTDDI_VERSION >= NTDDI_WIN7)

                //
                //  Remember that we are holding the paging I/O resource.
                //

                PagingIoResourceAcquired = TRUE;

                //
                //  We hold so that we will prevent a pagefault from occuring and seeing
                //  soon-to-be stale data from the disk. We used to believe this was
                //  something to be left to the app to synchronize; we now realize that
                //  noncached IO on a fileserver is doomed without the filesystem forcing
                //  the coherency issue. By only penalizing noncached coherency when
                //  needed, this is about the best we can do.
                //

                //
                // Now perform the coherency flush and purge operation. This version of the call
                // will try to invalidate mapped pages to prevent data corruption.
                //

                CcCoherencyFlushAndPurgeCache(  FileObject->SectionObjectPointer,
                                                WriteToEof ? &FcbOrDcb->Header.FileSize : &StartingByte,
                                                ByteCount,
                                                &IoStatus,
                                                0 );

                SuccessfulPurge = NT_SUCCESS( IoStatus.Status );

#else

                CcFlushCache( FileObject->SectionObjectPointer,
                              WriteToEof ? &FcbOrDcb->Header.FileSize : &StartingByte,
                              ByteCount,
                              &IoStatus );

                if (!NT_SUCCESS( IoStatus.Status )) {

                    ExReleaseResourceLite( FcbOrDcb->Header.PagingIoResource );
                    try_return( IoStatus.Status );
                }

                //
                //  Remember that we are holding the paging I/O resource.
                //

                PagingIoResourceAcquired = TRUE;

                //
                //  We hold so that we will prevent a pagefault from occuring and seeing
                //  soon-to-be stale data from the disk. We used to believe this was
                //  something to be left to the app to synchronize; we now realize that
                //  noncached IO on a fileserver is doomed without the filesystem forcing
                //  the coherency issue. By only penalizing noncached coherency when
                //  needed, this is about the best we can do.
                //

                SuccessfulPurge = CcPurgeCacheSection( FileObject->SectionObjectPointer,
                                                       WriteToEof ? &FcbOrDcb->Header.FileSize : &StartingByte,
                                                       ByteCount,
                                                       FALSE );

#endif

                if (!SuccessfulPurge && (FcbOrDcb->PurgeFailureModeEnableCount > 0)) {

                    //
                    //  Purge failure mode only applies to user files.
                    //
                    
                    NT_ASSERT( TypeOfOpen == UserFileOpen );

                    //
                    //  Do not swallow the purge failure if in purge failure
                    //  mode. Someone outside the file system intends to handle
                    //  the error and prevent any application compatibilty 
                    //  issue.
                    //
                    //  NOTE: If the file system were not preventing a pagefault
                    //  from processing while this write is in flight, which it does
                    //  by holding the paging resource across the write, it would
                    //  need to fail the operation even if a purge succeeded. If
                    //  not a memory mapped read could bring in a stale page before
                    //  the write makes it to disk.
                    //
                    
                    try_return( Status = STATUS_PURGE_FAILED );                
                }

                //
                //  Indicate we're OK with the fcb being demoted to shared access
                //  if that turns out to be possible later on after VDL extension
                //  is checked for.
                //
                //  PagingIo must be held all the way through.
                //
                
                FcbCanDemoteToShared = TRUE;
            }

            //
            //  We assert that Paging Io writes will never WriteToEof.
            //

            NT_ASSERT( WriteToEof ? !PagingIo : TRUE );
            
            //
            //  First let's acquire the Fcb shared.  Shared is enough if we
            //  are not writing beyond EOF.
            //

            if ( PagingIo ) {

                (VOID)ExAcquireResourceSharedLite( FcbOrDcb->Header.PagingIoResource, TRUE );
                PagingIoResourceAcquired = TRUE;

                if (!Wait) {

                    IrpContext->FatIoContext->Wait.Async.Resource =
                        FcbOrDcb->Header.PagingIoResource;
                }

                //
                //  Check to see if we colided with a MoveFile call, and if
                //  so block until it completes.
                //

                if (FcbOrDcb->MoveFileEvent) {

                    (VOID)KeWaitForSingleObject( FcbOrDcb->MoveFileEvent,
                                                 Executive,
                                                 KernelMode,
                                                 FALSE,
                                                 NULL );
                }

            } else {

                //
                //  We may already have the Fcb due to noncached coherency
                //  work done just above; however, we may still have to extend
                //  valid data length.  We can't demote this to shared, matching
                //  what occured before, until we figure that out a bit later. 
                //
                //  We kept ahold of it since our lockorder is main->paging,
                //  and paging must now held across the noncached write from
                //  the purge on.
                //
                
                //
                //  If this is async I/O, we will wait if there is an exclusive
                //  waiter.
                //

                if (!Wait && NonCachedIo) {

                    if (!FcbOrDcbAcquired &&
                        !FatAcquireSharedFcbWaitForEx( IrpContext, FcbOrDcb )) {

                        DebugTrace( 0, Dbg, "Cannot acquire FcbOrDcb = %p shared without waiting\n", FcbOrDcb );
                        try_return( PostIrp = TRUE );
                    }

                    //
                    //  Note we will have to release this resource elsewhere.  If we came
                    //  out of the noncached coherency path, we will also have to drop
                    //  the paging io resource.
                    //

                    IrpContext->FatIoContext->Wait.Async.Resource = FcbOrDcb->Header.Resource;

                    if (FcbCanDemoteToShared) {
                        
                        IrpContext->FatIoContext->Wait.Async.Resource2 = FcbOrDcb->Header.PagingIoResource;
                    }
                } else {

                    if (!FcbOrDcbAcquired &&
                        !FatAcquireSharedFcb( IrpContext, FcbOrDcb )) {

                        DebugTrace( 0, Dbg, "Cannot acquire FcbOrDcb = %p shared without waiting\n", FcbOrDcb );
                        try_return( PostIrp = TRUE );
                    }
                }

                FcbOrDcbAcquired = TRUE;
            }

            //
            //  Get a first tentative file size and valid data length.
            //  We must get ValidDataLength first since it is always
            //  increased second (in case we are unprotected) and
            //  we don't want to capture ValidDataLength > FileSize.
            //

            ValidDataToDisk = FcbOrDcb->ValidDataToDisk;
            ValidDataLength = FcbOrDcb->Header.ValidDataLength.LowPart;
            FileSize = FcbOrDcb->Header.FileSize.LowPart;

            NT_ASSERT( ValidDataLength <= FileSize );

            //
            // If are paging io, then we do not want
            // to write beyond end of file.  If the base is beyond Eof, we will just
            // Noop the call.  If the transfer starts before Eof, but extends
            // beyond, we will truncate the transfer to the last sector
            // boundary.
            //

            //
            //  Just in case this is paging io, limit write to file size.
            //  Otherwise, in case of write through, since Mm rounds up
            //  to a page, we might try to acquire the resource exclusive
            //  when our top level guy only acquired it shared. Thus, =><=.
            //

            if ( PagingIo ) {

                if (StartingVbo >= FileSize) {

                    DebugTrace( 0, Dbg, "PagingIo started beyond EOF.\n", 0 );

                    Irp->IoStatus.Information = 0;

                    try_return( Status = STATUS_SUCCESS );
                }

                if (ByteCount > FileSize - StartingVbo) {

                    DebugTrace( 0, Dbg, "PagingIo extending beyond EOF.\n", 0 );

                    ByteCount = FileSize - StartingVbo;
                }
            }

            //
            //  Determine if we were called by the lazywriter.
            //  (see resrcsup.c)
            //

            if (FcbOrDcb->Specific.Fcb.LazyWriteThread == PsGetCurrentThread()) {

                CalledByLazyWriter = TRUE;

                if (FlagOn( FcbOrDcb->Header.Flags, FSRTL_FLAG_USER_MAPPED_FILE )) {

                    //
                    //  Fail if the start of this request is beyond valid data length.
                    //  Don't worry if this is an unsafe test.  MM and CC won't
                    //  throw this page away if it is really dirty.
                    //

                    if ((StartingVbo + ByteCount > ValidDataLength) &&
                        (StartingVbo < FileSize)) {

                        //
                        //  It's OK if byte range is within the page containing valid data length,
                        //  since we will use ValidDataToDisk as the start point.
                        //

                        if (StartingVbo + ByteCount > ((ValidDataLength + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1))) {

                            //
                            //  Don't flush this now.
                            //

                            try_return( Status = STATUS_FILE_LOCK_CONFLICT );
                        }
                    }
                }
            }

            //
            //  This code detects if we are a recursive synchronous page write
            //  on a write through file object.
            //

            if (FlagOn(Irp->Flags, IRP_SYNCHRONOUS_PAGING_IO) &&
                FlagOn(IrpContext->Flags, IRP_CONTEXT_FLAG_RECURSIVE_CALL)) {

                PIRP TopIrp;

                TopIrp = IoGetTopLevelIrp();

                //
                //  This clause determines if the top level request was
                //  in the FastIo path.  Gack.  Since we don't have a
                //  real sharing protocol for the top level IRP field ...
                //  yet ... if someone put things other than a pure IRP in
                //  there we best be careful.
                //

                if ((ULONG_PTR)TopIrp > FSRTL_MAX_TOP_LEVEL_IRP_FLAG &&
                    NodeType(TopIrp) == IO_TYPE_IRP) {

                    PIO_STACK_LOCATION IrpStack;

                    IrpStack = IoGetCurrentIrpStackLocation(TopIrp);

                    //
                    //  Finally this routine detects if the Top irp was a
                    //  cached write to this file and thus we are the writethrough.
                    //

                    if ((IrpStack->MajorFunction == IRP_MJ_WRITE) &&
                        (IrpStack->FileObject->FsContext == FileObject->FsContext) &&
                        !FlagOn(TopIrp->Flags,IRP_NOCACHE)) {

                        RecursiveWriteThrough = TRUE;
                        SetFlag( IrpContext->Flags, IRP_CONTEXT_FLAG_WRITE_THROUGH );
                    }
                }
            }

            //
            //  Here is the deal with ValidDataLength and FileSize:
            //
            //  Rule 1: PagingIo is never allowed to extend file size.
            //
            //  Rule 2: Only the top level requestor may extend Valid
            //          Data Length.  This may be paging IO, as when a
            //          a user maps a file, but will never be as a result
            //          of cache lazy writer writes since they are not the
            //          top level request.
            //
            //  Rule 3: If, using Rules 1 and 2, we decide we must extend
            //          file size or valid data, we take the Fcb exclusive.
            //

            //
            // Now see if we are writing beyond valid data length, and thus
            // maybe beyond the file size.  If so, then we must
            // release the Fcb and reacquire it exclusive.  Note that it is
            // important that when not writing beyond EOF that we check it
            // while acquired shared and keep the FCB acquired, in case some
            // turkey truncates the file.
            //

            //
            //  Note that the lazy writer must not be allowed to try and
            //  acquire the resource exclusive.  This is not a problem since
            //  the lazy writer is paging IO and thus not allowed to extend
            //  file size, and is never the top level guy, thus not able to
            //  extend valid data length.
            //

            if ( !CalledByLazyWriter &&

                 !RecursiveWriteThrough &&

                 (WriteToEof ||
                  StartingVbo + ByteCount > ValidDataLength)) {

                //
                //  If this was an asynchronous write, we are going to make
                //  the request synchronous at this point, but only kinda.
                //  At the last moment, before sending the write off to the
                //  driver, we may shift back to async.
                //
                //  The modified page writer already has the resources
                //  he requires, so this will complete in small finite
                //  time.
                //

                if (!Wait) {

                    Wait = TRUE;
                    SetFlag( IrpContext->Flags, IRP_CONTEXT_FLAG_WAIT );

                    if (NonCachedIo) {

                        NT_ASSERT( TypeOfOpen == UserFileOpen );

                        SwitchBackToAsync = TRUE;
                    }
                }

                //
                // We need Exclusive access to the Fcb/Dcb since we will
                // probably have to extend valid data and/or file.
                //

                //
                //  Y'know, the PagingIo case is a mapped page writer, and
                //  MmFlushSection or the mapped page writer itself already
                //  snatched up the main exclusive for us via the AcquireForCcFlush
                //  or AcquireForModWrite logic (the default logic parallels FAT's
                //  requirements since this order/model came first).  Should ASSERT
                //  this since it'll just go 1->2, and a few more unnecesary DPC
                //  transitions.
                //
                //  The preacquire is done to avoid inversion over the collided flush
                //  meta-resource in Mm.  The one time this is not true is at final
                //  system shutdown time, when Mm goes off and flushes all the dirty
                //  pages.  Since the callback is defined as Wait == FALSE he can't
                //  guarantee acquisition (though with clean process shutdown being
                //  enforced, it really should be now).  Permit this to float.
                //
                //  Note that since we're going to fall back on the acquisition aleady
                //  done for us, don't confuse things by thinking we did the work
                //  for it.
                //

                if ( PagingIo ) {

                    ExReleaseResourceLite( FcbOrDcb->Header.PagingIoResource );
                    PagingIoResourceAcquired = FALSE;

                } else {

                    //
                    //  The Fcb may already be acquired exclusive due to coherency
                    //  work performed earlier.  If so, obviously no work to do.
                    //
                    
                    if (!FcbAcquiredExclusive) {
                        
                        FatReleaseFcb( IrpContext, FcbOrDcb );
                        FcbOrDcbAcquired = FALSE;

                        if (!FatAcquireExclusiveFcb( IrpContext, FcbOrDcb )) {

                            DebugTrace( 0, Dbg, "Cannot acquire FcbOrDcb = %p shared without waiting\n", FcbOrDcb );

                            try_return( PostIrp = TRUE );
                        }

                        FcbOrDcbAcquired = TRUE;
                        
#ifdef _MSC_VER
#pragma prefast( suppress:28931, "convenient for debugging" )
#endif
                        FcbAcquiredExclusive = TRUE;
                    }
                }

                //
                //  Now that we have the Fcb exclusive, see if this write
                //  qualifies for being made async again.  The key point
                //  here is that we are going to update ValidDataLength in
                //  the Fcb before returning.  We must make sure this will
                //  not cause a problem.  One thing we must do is keep out
                //  the FastIo path.
                //

                if (SwitchBackToAsync) {

                    if ((FcbOrDcb->NonPaged->SectionObjectPointers.DataSectionObject != NULL) ||
                        (StartingVbo + ByteCount > FcbOrDcb->Header.ValidDataLength.LowPart) ||
                        FatNoAsync) {

                        RtlZeroMemory( IrpContext->FatIoContext, sizeof(FAT_IO_CONTEXT) );

                        KeInitializeEvent( &IrpContext->FatIoContext->Wait.SyncEvent,
                                           NotificationEvent,
                                           FALSE );

                        SwitchBackToAsync = FALSE;

                    } else {

                        if (!FcbOrDcb->NonPaged->OutstandingAsyncEvent) {

                            FcbOrDcb->NonPaged->OutstandingAsyncEvent =
#ifndef __REACTOS__
                                FsRtlAllocatePoolWithTag( NonPagedPoolNx,
#else
                                FsRtlAllocatePoolWithTag( NonPagedPool,
#endif
                                                          sizeof(KEVENT),
                                                          TAG_EVENT );

                            KeInitializeEvent( FcbOrDcb->NonPaged->OutstandingAsyncEvent,
                                               NotificationEvent,
                                               FALSE );
                        }

                        //
                        //  If we are transitioning from 0 to 1, reset the event.
                        //

                        if (ExInterlockedAddUlong( &FcbOrDcb->NonPaged->OutstandingAsyncWrites,
                                                   1,
                                                   &FatData.GeneralSpinLock ) == 0) {

                            KeClearEvent( FcbOrDcb->NonPaged->OutstandingAsyncEvent );
                        }

                        UnwindOutstandingAsync = TRUE;

                        IrpContext->FatIoContext->Wait.Async.NonPagedFcb = FcbOrDcb->NonPaged;
                    }
                }

                //
                //  Now that we have the Fcb exclusive, get a new batch of
                //  filesize and ValidDataLength.
                //

                ValidDataToDisk = FcbOrDcb->ValidDataToDisk;
                ValidDataLength = FcbOrDcb->Header.ValidDataLength.LowPart;
                FileSize = FcbOrDcb->Header.FileSize.LowPart;

                //
                //  If this is PagingIo check again if any pruning is
                //  required.  It is important to start from basic
                //  princples in case the file was *grown* ...
                //

                if ( PagingIo ) {

                    if (StartingVbo >= FileSize) {
                        Irp->IoStatus.Information = 0;
                        try_return( Status = STATUS_SUCCESS );
                    }
                    
                    ByteCount = IrpSp->Parameters.Write.Length;

                    if (ByteCount > FileSize - StartingVbo) {
                        ByteCount = FileSize - StartingVbo;
                    }
                }
            }

            //
            //  Remember the final requested byte count
            //

            if (NonCachedIo && !Wait) {

                IrpContext->FatIoContext->Wait.Async.RequestedByteCount =
                    ByteCount;
            }

            //
            //  Remember the initial file size and valid data length,
            //  just in case .....
            //

            InitialFileSize = FileSize;

            InitialValidDataLength = ValidDataLength;

            //
            //  Make sure the FcbOrDcb is still good
            //

            FatVerifyFcb( IrpContext, FcbOrDcb );

            //
            //  Check for writing to end of File.  If we are, then we have to
            //  recalculate a number of fields.
            //

            if ( WriteToEof ) {

                StartingVbo = FileSize;
                StartingByte = FcbOrDcb->Header.FileSize;

                //
                //  Since we couldn't know this information until now, perform the
                //  necessary bounds checking that we ommited at the top because
                //  this is a WriteToEof operation.
                //

                
                if (!FatIsIoRangeValid( Vcb, StartingByte, ByteCount)) {
                    
                    Irp->IoStatus.Information = 0;
                    try_return( Status = STATUS_DISK_FULL );
                }


            }

            //
            //  If this is a non paging write to a data stream object we have to
            //  check for access according to the current state op/filelocks.
            //
            //  Note that after this point, operations will be performed on the file.
            //  No modifying activity can occur prior to this point in the write
            //  path.
            //

            if (!PagingIo && TypeOfOpen == UserFileOpen) {

                Status = FsRtlCheckOplock( FatGetFcbOplock(FcbOrDcb),
                                           Irp,
                                           IrpContext,
                                           FatOplockComplete,
                                           FatPrePostIrp );

                if (Status != STATUS_SUCCESS) {

                    OplockPostIrp = TRUE;
                    PostIrp = TRUE;
                    try_return( NOTHING );
                }

                //
                //  This oplock call can affect whether fast IO is possible.
                //  We may have broken an oplock to no oplock held.  If the
                //  current state of the file is FastIoIsNotPossible then
                //  recheck the fast IO state.
                //

                if (FcbOrDcb->Header.IsFastIoPossible == FastIoIsNotPossible) {

                    FcbOrDcb->Header.IsFastIoPossible = FatIsFastIoPossible( FcbOrDcb );
                }

                //
                //  And finally check the regular file locks.
                //

                if (!FsRtlCheckLockForWriteAccess( &FcbOrDcb->Specific.Fcb.FileLock, Irp )) {

                    try_return( Status = STATUS_FILE_LOCK_CONFLICT );
                }
            }

            //
            //  Determine if we will deal with extending the file. Note that
            //  this implies extending valid data, and so we already have all
            //  of the required synchronization done.
            //

            if (!PagingIo && (StartingVbo + ByteCount > FileSize)) {

                ExtendingFile = TRUE;
            }

            if ( ExtendingFile ) {


                //
                //  EXTENDING THE FILE
                //

                //
                //  For an extending write on hotplug media, we are going to defer the metadata
                //  updates via Cc's lazy writer. They will also be flushed when the handle is closed.
                //

                if (FlagOn(Vcb->VcbState, VCB_STATE_FLAG_DEFERRED_FLUSH)) {
                    
                    SetFlag(IrpContext->Flags, IRP_CONTEXT_FLAG_DISABLE_WRITE_THROUGH);
                }

                //
                //  Update our local copy of FileSize
                //

                FileSize = StartingVbo + ByteCount;


                if (FcbOrDcb->Header.AllocationSize.QuadPart == FCB_LOOKUP_ALLOCATIONSIZE_HINT) {

                    FatLookupFileAllocationSize( IrpContext, FcbOrDcb );
                }

                //
                //  If the write goes beyond the allocation size, add some
                //  file allocation.
                //


                if ( (FileSize) > FcbOrDcb->Header.AllocationSize.LowPart ) {


                    BOOLEAN AllocateMinimumSize = TRUE;

                    //
                    //  Only do allocation chuncking on writes if this is
                    //  not the first allocation added to the file.
                    //

                    if (FcbOrDcb->Header.AllocationSize.LowPart != 0 ) {

                        ULONGLONG ApproximateClusterCount;
                        ULONGLONG TargetAllocation;
                        ULONGLONG AddedAllocation;                        
                        ULONGLONG Multiplier;
                        ULONG BytesPerCluster;
                        ULONG ClusterAlignedFileSize;

                        //
                        //  We are going to try and allocate a bigger chunk than
                        //  we actually need in order to maximize FastIo usage.
                        //
                        //  The multiplier is computed as follows:
                        //
                        //
                        //            (FreeDiskSpace            )
                        //  Mult =  ( (-------------------------) / 32 ) + 1
                        //            (FileSize - AllocationSize)
                        //
                        //          and max out at 32.
                        //
                        //  With this formula we start winding down chunking
                        //  as we get near the disk space wall.
                        //
                        //  For instance on an empty 1 MEG floppy doing an 8K
                        //  write, the multiplier is 6, or 48K to allocate.
                        //  When this disk is half full, the multipler is 3,
                        //  and when it is 3/4 full, the mupltiplier is only 1.
                        //
                        //  On a larger disk, the multiplier for a 8K read will
                        //  reach its maximum of 32 when there is at least ~8 Megs
                        //  available.
                        //

                        //
                        //  Small write performance note, use cluster aligned
                        //  file size in above equation.
                        //

                        //
                        //  We need to carefully consider what happens when we approach
                        //  a 2^32 byte filesize.  Overflows will cause problems.
                        //

                        BytesPerCluster = 1 << Vcb->AllocationSupport.LogOfBytesPerCluster;

                        //
                        //  This can overflow if the target filesize is in the last cluster.
                        //  In this case, we can obviously skip over all of this fancy
                        //  logic and just max out the file right now.
                        //


                        ClusterAlignedFileSize = ((FileSize) + (BytesPerCluster - 1)) &
                                                 ~(BytesPerCluster - 1);


                        if (ClusterAlignedFileSize != 0) {

                            //
                            //  This actually has a chance but the possibility of overflowing
                            //  the numerator is pretty unlikely, made more unlikely by moving
                            //  the divide by 32 up to scale the BytesPerCluster. However, even if it does the
                            //  effect is completely benign.
                            //
                            //  FAT32 with a 64k cluster and over 2^21 clusters would do it (and
                            //  so forth - 2^(16 - 5 + 21) == 2^32).  Since this implies a partition
                            //  of 32gb and a number of clusters (and cluster size) we plan to
                            //  disallow in format for FAT32, the odds of this happening are pretty
                            //  low anyway.    
                            Multiplier = ((Vcb->AllocationSupport.NumberOfFreeClusters *
                                           (BytesPerCluster >> 5)) /
                                          (ClusterAlignedFileSize -
                                           FcbOrDcb->Header.AllocationSize.LowPart)) + 1;
    
                            if (Multiplier > 32) { Multiplier = 32; }

                            // These computations will never overflow a ULONGLONG because a file is capped at 4GB, and 
                            // a single write can be a max of 4GB.
                            AddedAllocation = Multiplier * (ClusterAlignedFileSize - FcbOrDcb->Header.AllocationSize.LowPart);

                            TargetAllocation = FcbOrDcb->Header.AllocationSize.LowPart + AddedAllocation;
    
                            //
                            //  We know that TargetAllocation is in whole clusters. Now
                            //  we check if it exceeded the maximum valid FAT file size.
                            //  If it did, we fall back to allocating up to the maximum legal size.
                            //
    
                            if (TargetAllocation > ~BytesPerCluster + 1) {
    
                                TargetAllocation = ~BytesPerCluster + 1;
                                AddedAllocation = TargetAllocation - FcbOrDcb->Header.AllocationSize.LowPart;
                            }
    
                            //
                            //  Now do an unsafe check here to see if we should even
                            //  try to allocate this much.  If not, just allocate
                            //  the minimum size we need, if so so try it, but if it
                            //  fails, just allocate the minimum size we need.
                            //
    
                            ApproximateClusterCount = (AddedAllocation / BytesPerCluster);
    
                            if (ApproximateClusterCount <= Vcb->AllocationSupport.NumberOfFreeClusters) {
    
                                _SEH2_TRY {
    
                                    FatAddFileAllocation( IrpContext,
                                                          FcbOrDcb,
                                                          FileObject,
                                                          (ULONG)TargetAllocation );
    
                                    AllocateMinimumSize = FALSE;
                                    SetFlag( FcbOrDcb->FcbState, FCB_STATE_TRUNCATE_ON_CLOSE );
    
                                } _SEH2_EXCEPT( _SEH2_GetExceptionCode() == STATUS_DISK_FULL ?
                                          EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH ) {
    
                                      FatResetExceptionState( IrpContext );
                                } _SEH2_END;
                            }
                        }
                    }

                    if ( AllocateMinimumSize ) {


                        FatAddFileAllocation( IrpContext,
                                              FcbOrDcb,
                                              FileObject,
                                              FileSize );


                    }

                    //
                    //  Assert that the allocation worked
                    //


                    NT_ASSERT( FcbOrDcb->Header.AllocationSize.LowPart >= FileSize );


                }

                //
                //  Set the new file size in the Fcb
                //


                NT_ASSERT( FileSize <= FcbOrDcb->Header.AllocationSize.LowPart );

                
                FcbOrDcb->Header.FileSize.LowPart = FileSize;

                //
                //  Extend the cache map, letting mm knows the new file size.
                //  We only have to do this if the file is cached.
                //

                if (CcIsFileCached(FileObject)) {
                    CcSetFileSizes( FileObject, (PCC_FILE_SIZES)&FcbOrDcb->Header.AllocationSize );
                }
            }

            //
            //  Determine if we will deal with extending valid data.
            //

            if ( !CalledByLazyWriter &&
                 !RecursiveWriteThrough &&
                 (StartingVbo + ByteCount > ValidDataLength) ) {

                ExtendingValidData = TRUE;
            
            } else {

                //
                //  If not extending valid data, and we otherwise believe we
                //  could demote from exclusive to shared, do so.  This will
                //  occur when we synchronize tight for noncached coherency
                //  but must defer the demotion until after we decide about
                //  valid data length, which requires it exclusive.  Since we
                //  can't drop/re-pick the resources without letting a pagefault
                //  squirt through, the resource decision was kept up in the air
                //  until now.
                //
                //  Note that we've still got PagingIo exclusive in these cases.
                //
                
                if (FcbCanDemoteToShared) {

                    NT_ASSERT( FcbAcquiredExclusive && ExIsResourceAcquiredExclusiveLite( FcbOrDcb->Header.Resource ));
                    ExConvertExclusiveToSharedLite( FcbOrDcb->Header.Resource );
                    FcbAcquiredExclusive = FALSE;
                }
            }
            
            if (ValidDataToDisk > ValidDataLength) {
                
                ValidDataToCheck = ValidDataToDisk;
            
            } else {
                
                ValidDataToCheck = ValidDataLength;
            }



            //
            // HANDLE THE NON-CACHED CASE
            //

            if ( NonCachedIo ) {

                //
                // Declare some local variables for enumeration through the
                // runs of the file, and an array to store parameters for
                // parallel I/Os
                //

                ULONG SectorSize;

                ULONG BytesToWrite;

                DebugTrace(0, Dbg, "Non cached write.\n", 0);

                //
                //  Round up to sector boundry.  The end of the write interval
                //  must, however, be beyond EOF.
                //

                SectorSize = (ULONG)Vcb->Bpb.BytesPerSector;

                BytesToWrite = (ByteCount + (SectorSize - 1))
                                         & ~(SectorSize - 1);

                //
                //  All requests should be well formed and
                //  make sure we don't wipe out any data
                //

                if (((StartingVbo & (SectorSize - 1)) != 0) ||

                        ((BytesToWrite != ByteCount) &&
                         (StartingVbo + ByteCount < ValidDataLength))) {

                    NT_ASSERT( FALSE );

                    DebugTrace( 0, Dbg, "FatCommonWrite -> STATUS_NOT_IMPLEMENTED\n", 0);
                    try_return( Status = STATUS_NOT_IMPLEMENTED );
                }

                //
                // If this noncached transfer is at least one sector beyond
                // the current ValidDataLength in the Fcb, then we have to
                // zero the sectors in between.  This can happen if the user
                // has opened the file noncached, or if the user has mapped
                // the file and modified a page beyond ValidDataLength.  It
                // *cannot* happen if the user opened the file cached, because
                // ValidDataLength in the Fcb is updated when he does the cached
                // write (we also zero data in the cache at that time), and
                // therefore, we will bypass this test when the data
                // is ultimately written through (by the Lazy Writer).
                //
                //  For the paging file we don't care about security (ie.
                //  stale data), do don't bother zeroing.
                //
                //  We can actually get writes wholly beyond valid data length
                //  from the LazyWriter because of paging Io decoupling.
                //

                if (!CalledByLazyWriter &&
                    !RecursiveWriteThrough &&
                    (StartingVbo > ValidDataToCheck)) {

                    FatZeroData( IrpContext,
                                 Vcb,
                                 FileObject,
                                 ValidDataToCheck,
                                 StartingVbo - ValidDataToCheck );
                }

                //
                // Make sure we write FileSize to the dirent if we
                // are extending it and we are successful.  (This may or
                // may not occur Write Through, but that is fine.)
                //

                WriteFileSizeToDirent = TRUE;

                //
                //  Perform the actual IO
                //

                if (SwitchBackToAsync) {

                    Wait = FALSE;
                    ClearFlag( IrpContext->Flags, IRP_CONTEXT_FLAG_WAIT );
                }

#ifdef SYSCACHE_COMPILE

#define MY_SIZE 0x1000000
#define LONGMAP_COUNTER

#ifdef BITMAP
                //
                //  Maintain a bitmap of IO started on this file.
                //

                {
                    PULONG WriteMask = FcbOrDcb->WriteMask;

                    if (NULL == WriteMask) {

                        WriteMask = FsRtlAllocatePoolWithTag( NonPagedPoolNx,
                                                              (MY_SIZE/PAGE_SIZE) / 8,
                                                              'wtaF' );

                        FcbOrDcb->WriteMask = WriteMask;
                        RtlZeroMemory(WriteMask, (MY_SIZE/PAGE_SIZE) / 8);
                    }

                    if (StartingVbo < MY_SIZE) {

                        ULONG Off = StartingVbo;
                        ULONG Len = BytesToWrite;

                        if (Off + Len > MY_SIZE) {
                            Len = MY_SIZE - Off;
                        }

                        while (Len != 0) {
                            WriteMask[(Off/PAGE_SIZE) / 32] |=
                                1 << (Off/PAGE_SIZE) % 32;

                            Off += PAGE_SIZE;
                            if (Len <= PAGE_SIZE) {
                                break;
                            }
                            Len -= PAGE_SIZE;
                        }
                    }
                }
#endif

#ifdef LONGMAP_COUNTER
                //
                //  Maintain a longmap of IO started on this file, each ulong containing
                //  the value of an ascending counter per write (gives us order information).
                //
                //  Unlike the old bitmask stuff, this is mostly well synchronized.
                //

                {
                    PULONG WriteMask = (PULONG)FcbOrDcb->WriteMask;

                    if (NULL == WriteMask) {

                        WriteMask = FsRtlAllocatePoolWithTag( NonPagedPoolNx,
                                                              (MY_SIZE/PAGE_SIZE) * sizeof(ULONG),
                                                              'wtaF' );

                        FcbOrDcb->WriteMask = WriteMask;
                        RtlZeroMemory(WriteMask, (MY_SIZE/PAGE_SIZE) * sizeof(ULONG));
                    }

                    if (StartingVbo < MY_SIZE) {

                        ULONG Off = StartingVbo;
                        ULONG Len = BytesToWrite;
                        ULONG Tick = InterlockedIncrement( &FcbOrDcb->WriteMaskData );

                        if (Off + Len > MY_SIZE) {
                            Len = MY_SIZE - Off;
                        }

                        while (Len != 0) {
                            InterlockedExchange( WriteMask + Off/PAGE_SIZE, Tick );

                            Off += PAGE_SIZE;
                            if (Len <= PAGE_SIZE) {
                                break;
                            }
                            Len -= PAGE_SIZE;
                        }
                    }
                }
#endif

#endif


                if (FatNonCachedIo( IrpContext,
                                    Irp,
                                    FcbOrDcb,
                                    StartingVbo,
                                    BytesToWrite,
                                    BytesToWrite,
                                    0) == STATUS_PENDING) {


                    UnwindOutstandingAsync = FALSE;

#ifdef _MSC_VER
#pragma prefast( suppress:28931, "convenient for debugging" )
#endif
                    Wait = TRUE;
                    SetFlag( IrpContext->Flags, IRP_CONTEXT_FLAG_WAIT );

                    IrpContext->FatIoContext = NULL;
                    Irp = NULL;

                    //
                    //  As a matter of fact, if we hit this we are in deep trouble
                    //  if VDL is being extended. We are no longer attached to the
                    //  IRP, and have thus lost synchronization.  Note that we should
                    //  not hit this case anymore since we will not re-async vdl extension.
                    //
                    
                    NT_ASSERT( !ExtendingValidData );

                    try_return( Status = STATUS_PENDING );
                }

                //
                //  If the call didn't succeed, raise the error status
                //

                if (!NT_SUCCESS( Status = Irp->IoStatus.Status )) {

                    FatNormalizeAndRaiseStatus( IrpContext, Status );

                } else {

                    ULONG NewValidDataToDisk;

                    //
                    //  Else set the context block to reflect the entire write
                    //  Also assert we got how many bytes we asked for.
                    //

                    NT_ASSERT( Irp->IoStatus.Information == BytesToWrite );

                    Irp->IoStatus.Information = ByteCount;

                    //
                    //  Take this opportunity to update ValidDataToDisk.
                    //

                    NewValidDataToDisk = StartingVbo + ByteCount;

                    if (NewValidDataToDisk > FileSize) {
                        NewValidDataToDisk = FileSize;
                    }

                    if (FcbOrDcb->ValidDataToDisk < NewValidDataToDisk) {
                        FcbOrDcb->ValidDataToDisk = NewValidDataToDisk;
                    }
                }

                //
                // The transfer is either complete, or the Iosb contains the
                // appropriate status.
                //

                try_return( Status );

            } // if No Intermediate Buffering


            //
            // HANDLE CACHED CASE
            //

            else {

                NT_ASSERT( !PagingIo );

                //
                // We delay setting up the file cache until now, in case the
                // caller never does any I/O to the file, and thus
                // FileObject->PrivateCacheMap == NULL.
                //

                if ( FileObject->PrivateCacheMap == NULL ) {

                    DebugTrace(0, Dbg, "Initialize cache mapping.\n", 0);

                    //
                    //  Get the file allocation size, and if it is less than
                    //  the file size, raise file corrupt error.
                    //

                    if (FcbOrDcb->Header.AllocationSize.QuadPart == FCB_LOOKUP_ALLOCATIONSIZE_HINT) {

                        FatLookupFileAllocationSize( IrpContext, FcbOrDcb );
                    }

                    if ( FileSize > FcbOrDcb->Header.AllocationSize.LowPart ) {

                        FatPopUpFileCorrupt( IrpContext, FcbOrDcb );

                        FatRaiseStatus( IrpContext, STATUS_FILE_CORRUPT_ERROR );
                    }

                    //
                    //  Now initialize the cache map.
                    //

                    FatInitializeCacheMap( FileObject,
                                           (PCC_FILE_SIZES)&FcbOrDcb->Header.AllocationSize,
                                           FALSE,
                                           &FatData.CacheManagerCallbacks,
                                           FcbOrDcb );

                    CcSetReadAheadGranularity( FileObject, READ_AHEAD_GRANULARITY );

                    //
                    //  Special case large floppy tranfers, and make the file
                    //  object write through.  For small floppy transfers,
                    //  set a timer to go off in a second and flush the file.
                    //
                    //

                    if (!FlagOn( FileObject->Flags, FO_WRITE_THROUGH ) &&
                        FlagOn(Vcb->VcbState, VCB_STATE_FLAG_DEFERRED_FLUSH)) {

                        if (((StartingByte.LowPart & (PAGE_SIZE-1)) == 0) &&
                            (ByteCount >= PAGE_SIZE)) {

                            SetFlag( FileObject->Flags, FO_WRITE_THROUGH );

                        } else {

                            LARGE_INTEGER OneSecondFromNow;
                            PDEFERRED_FLUSH_CONTEXT FlushContext;

                            //
                            //  Get pool and initialize the timer and DPC
                            //

#ifndef __REACTOS__
                            FlushContext = FsRtlAllocatePoolWithTag( NonPagedPoolNx,
#else
                            FlushContext = FsRtlAllocatePoolWithTag( NonPagedPool,
#endif
                                                                     sizeof(DEFERRED_FLUSH_CONTEXT),
                                                                     TAG_DEFERRED_FLUSH_CONTEXT );

                            KeInitializeTimer( &FlushContext->Timer );

                            KeInitializeDpc( &FlushContext->Dpc,
                                             FatDeferredFlushDpc,
                                             FlushContext );


                            //
                            //  We have to reference the file object here.
                            //

                            ObReferenceObject( FileObject );

                            FlushContext->File = FileObject;

                            //
                            //  Let'er rip!
                            //

                            OneSecondFromNow.QuadPart = (LONG)-1*1000*1000*10;

                            KeSetTimer( &FlushContext->Timer,
                                        OneSecondFromNow,
                                        &FlushContext->Dpc );
                        }
                    }
                }

                //
                // If this write is beyond valid data length, then we
                // must zero the data in between.
                //

                if ( StartingVbo > ValidDataToCheck ) {

                    //
                    // Call the Cache Manager to zero the data.
                    //

                    if (!FatZeroData( IrpContext,
                                      Vcb,
                                      FileObject,
                                      ValidDataToCheck,
                                      StartingVbo - ValidDataToCheck )) {

                        DebugTrace( 0, Dbg, "Cached Write could not wait to zero\n", 0 );

                        try_return( PostIrp = TRUE );
                    }
                }

                WriteFileSizeToDirent = BooleanFlagOn(IrpContext->Flags,
                                                      IRP_CONTEXT_FLAG_WRITE_THROUGH);


                //
                // DO A NORMAL CACHED WRITE, if the MDL bit is not set,
                //

                if (!FlagOn(IrpContext->MinorFunction, IRP_MN_MDL)) {

                    DebugTrace(0, Dbg, "Cached write.\n", 0);

                    //
                    //  Get hold of the user's buffer.
                    //

                    SystemBuffer = FatMapUserBuffer( IrpContext, Irp );

                    //
                    // Do the write, possibly writing through
                    //

#if (NTDDI_VERSION >= NTDDI_WIN8)
                    if (!CcCopyWriteEx( FileObject,
                                        &StartingByte,
                                        ByteCount,
                                        Wait,
                                        SystemBuffer,
                                        Irp->Tail.Overlay.Thread )) {
#else
                    if (!CcCopyWrite( FileObject,
                                      &StartingByte,
                                      ByteCount,
                                      Wait,
                                      SystemBuffer )) {
#endif

                        DebugTrace( 0, Dbg, "Cached Write could not wait\n", 0 );

                        try_return( PostIrp = TRUE );
                    }

                    Irp->IoStatus.Status = STATUS_SUCCESS;
                    Irp->IoStatus.Information = ByteCount;

                    try_return( Status = STATUS_SUCCESS );

                } else {

                    //
                    //  DO AN MDL WRITE
                    //

                    DebugTrace(0, Dbg, "MDL write.\n", 0);

                    NT_ASSERT( Wait );

                    CcPrepareMdlWrite( FileObject,
                                       &StartingByte,
                                       ByteCount,
                                       &Irp->MdlAddress,
                                       &Irp->IoStatus );

                    Status = Irp->IoStatus.Status;

                    try_return( Status );
                }
            }
        }

        //
        //  These two cases correspond to a system write directory file and
        //  ea file.
        //

        if (( TypeOfOpen == DirectoryFile ) || ( TypeOfOpen == EaFile)
            ) {

            ULONG SectorSize;

#if FASTFATDBG
            if ( TypeOfOpen == DirectoryFile ) {
                DebugTrace(0, Dbg, "Type of write is directoryfile\n", 0);                
            } else if ( TypeOfOpen == EaFile) {
                DebugTrace(0, Dbg, "Type of write is eafile\n", 0);
            }
#endif

            //
            //  Make sure the FcbOrDcb is still good
            //

            FatVerifyFcb( IrpContext, FcbOrDcb );

            //
            //  Synchronize here with people deleting directories and
            //  mucking with the internals of the EA file.
            //

            if (!ExAcquireSharedStarveExclusive( FcbOrDcb->Header.PagingIoResource,
                                          Wait )) {

                DebugTrace( 0, Dbg, "Cannot acquire FcbOrDcb = %p shared without waiting\n", FcbOrDcb );

                try_return( PostIrp = TRUE );
            }

            PagingIoResourceAcquired = TRUE;

            if (!Wait) {

                IrpContext->FatIoContext->Wait.Async.Resource =
                    FcbOrDcb->Header.PagingIoResource;
            }

            //
            //  Check to see if we colided with a MoveFile call, and if
            //  so block until it completes.
            //

            if (FcbOrDcb->MoveFileEvent) {

                (VOID)KeWaitForSingleObject( FcbOrDcb->MoveFileEvent,
                                             Executive,
                                             KernelMode,
                                             FALSE,
                                             NULL );
            }

            //
            //  If we weren't called by the Lazy Writer, then this write
            //  must be the result of a write-through or flush operation.
            //  Setting the IrpContext flag, will cause DevIoSup.c to
            //  write-through the data to the disk.
            //

            if (!FlagOn((ULONG_PTR)IoGetTopLevelIrp(), FSRTL_CACHE_TOP_LEVEL_IRP)) {

                SetFlag( IrpContext->Flags, IRP_CONTEXT_FLAG_WRITE_THROUGH );
            }

            //
            //  For the noncached case, assert that everything is sector
            //  alligned.
            //
            
#ifdef _MSC_VER
#pragma prefast( suppress:28931, "needed for debug build" )
#endif
            SectorSize = (ULONG)Vcb->Bpb.BytesPerSector;

            //
            //  We make several assumptions about these two types of files.
            //  Make sure all of them are true.
            //

            NT_ASSERT( NonCachedIo && PagingIo );
            NT_ASSERT( ((StartingVbo | ByteCount) & (SectorSize - 1)) == 0 );


                //
                //  These calls must always be within the allocation size, which is
                //  convienently the same as filesize, which conveniently doesn't
                //  get reset to a hint value when we verify the volume.
                //

                if (StartingVbo >= FcbOrDcb->Header.FileSize.LowPart) {

                    DebugTrace( 0, Dbg, "PagingIo dirent started beyond EOF.\n", 0 );

                    Irp->IoStatus.Information = 0;

                    try_return( Status = STATUS_SUCCESS );
                }

                if ( StartingVbo + ByteCount > FcbOrDcb->Header.FileSize.LowPart ) {

                    DebugTrace( 0, Dbg, "PagingIo dirent extending beyond EOF.\n", 0 );
                    ByteCount = FcbOrDcb->Header.FileSize.LowPart - StartingVbo;
                }

            
            //
            //  Perform the actual IO
            //

            if (FatNonCachedIo( IrpContext,
                                Irp,
                                FcbOrDcb,
                                StartingVbo,
                                ByteCount,
                                ByteCount,
                                0 ) == STATUS_PENDING) {

                IrpContext->FatIoContext = NULL;

                Irp = NULL;

                try_return( Status = STATUS_PENDING );
            }

            //
            //  The transfer is either complete, or the Iosb contains the
            //  appropriate status.
            //
            //  Also, mark the volume as needing verification to automatically
            //  clean up stuff.
            //

            if (!NT_SUCCESS( Status = Irp->IoStatus.Status )) {

                FatNormalizeAndRaiseStatus( IrpContext, Status );
            }

            try_return( Status );
        }

        //
        // This is the case of a user who openned a directory. No writing is
        // allowed.
        //

        if ( TypeOfOpen == UserDirectoryOpen ) {

            DebugTrace( 0, Dbg, "FatCommonWrite -> STATUS_INVALID_PARAMETER\n", 0);

            try_return( Status = STATUS_INVALID_PARAMETER );
        }

        //
        //  If we get this far, something really serious is wrong.
        //

        DebugDump("Illegal TypeOfOpen\n", 0, FcbOrDcb );

#ifdef _MSC_VER
#pragma prefast( suppress:28159, "things are seriously wrong if we get here" )
#endif
        FatBugCheck( TypeOfOpen, (ULONG_PTR) FcbOrDcb, 0 );

    try_exit: NOTHING;


        //
        //  If the request was not posted and there is still an Irp,
        //  deal with it.
        //

        if (Irp) {

            if ( !PostIrp ) {

                ULONG ActualBytesWrote;

                DebugTrace( 0, Dbg, "Completing request with status = %08lx\n",
                            Status);

                DebugTrace( 0, Dbg, "                   Information = %08lx\n",
                            Irp->IoStatus.Information);

                //
                //  Record the total number of bytes actually written
                //

                ActualBytesWrote = (ULONG)Irp->IoStatus.Information;

                //
                //  If the file was opened for Synchronous IO, update the current
                //  file position.
                //

                if (SynchronousIo && !PagingIo) {

                    FileObject->CurrentByteOffset.LowPart =
                         StartingVbo + (NT_ERROR( Status ) ? 0 : ActualBytesWrote);
                }

                //
                //  The following are things we only do if we were successful
                //

                if ( NT_SUCCESS( Status ) ) {

                    //
                    //  If this was not PagingIo, mark that the modify
                    //  time on the dirent needs to be updated on close.
                    //

                    if ( !PagingIo ) {

                        SetFlag( FileObject->Flags, FO_FILE_MODIFIED );
                    }

                    //
                    //  If we extended the file size and we are meant to
                    //  immediately update the dirent, do so. (This flag is
                    //  set for either Write Through or noncached, because
                    //  in either case the data and any necessary zeros are
                    //  actually written to the file.)
                    //

                    if ( ExtendingFile && WriteFileSizeToDirent ) {

                        NT_ASSERT( FileObject->DeleteAccess || FileObject->WriteAccess );

                        FatSetFileSizeInDirent( IrpContext, FcbOrDcb, NULL );

                        //
                        //  Report that a file size has changed.
                        //

                        FatNotifyReportChange( IrpContext,
                                               Vcb,
                                               FcbOrDcb,
                                               FILE_NOTIFY_CHANGE_SIZE,
                                               FILE_ACTION_MODIFIED );
                    }

                    if ( ExtendingFile && !WriteFileSizeToDirent ) {

                        SetFlag( FileObject->Flags, FO_FILE_SIZE_CHANGED );
                    }

                    if ( ExtendingValidData ) {

                        ULONG EndingVboWritten = StartingVbo + ActualBytesWrote;

                        //
                        //  Never set a ValidDataLength greater than FileSize.
                        //

                        if ( FileSize < EndingVboWritten ) {

                            FcbOrDcb->Header.ValidDataLength.LowPart = FileSize;

                        } else {

                            FcbOrDcb->Header.ValidDataLength.LowPart = EndingVboWritten;
                        }

                        //
                        //  Now, if we are noncached and the file is cached, we must
                        //  tell the cache manager about the VDL extension so that
                        //  async cached IO will not be optimized into zero-page faults
                        //  beyond where it believes VDL is.
                        //
                        //  In the cached case, since Cc did the work, it has updated
                        //  itself already.
                        //

                        if (NonCachedIo && CcIsFileCached(FileObject)) {
                            CcSetFileSizes( FileObject, (PCC_FILE_SIZES)&FcbOrDcb->Header.AllocationSize );
                        }
                    }
                    
                }
                
                //
                //  Note that we have to unpin repinned Bcbs here after the above
                //  work, but if we are going to post the request, we must do this
                //  before the post (below).
                //

                FatUnpinRepinnedBcbs( IrpContext );

            } else {

                //
                //  Take action if the Oplock package is not going to post the Irp.
                //

                if (!OplockPostIrp) {

                    FatUnpinRepinnedBcbs( IrpContext );

                    if ( ExtendingFile ) {

                        //
                        //  We need the PagingIo resource exclusive whenever we
                        //  pull back either file size or valid data length.
                        //

                        NT_ASSERT( FcbOrDcb->Header.PagingIoResource != NULL );

                        (VOID)ExAcquireResourceExclusiveLite(FcbOrDcb->Header.PagingIoResource, TRUE);

                        FcbOrDcb->Header.FileSize.LowPart = InitialFileSize;

                        NT_ASSERT( FcbOrDcb->Header.FileSize.LowPart <= FcbOrDcb->Header.AllocationSize.LowPart );

                        //
                        //  Pull back the cache map as well
                        //

                        if (FileObject->SectionObjectPointer->SharedCacheMap != NULL) {

                            *CcGetFileSizePointer(FileObject) = FcbOrDcb->Header.FileSize;
                        }

                        ExReleaseResourceLite( FcbOrDcb->Header.PagingIoResource );
                    }

                    DebugTrace( 0, Dbg, "Passing request to Fsp\n", 0 );

                    Status = FatFsdPostRequest(IrpContext, Irp);
                }
            }
        }

    } _SEH2_FINALLY {

        DebugUnwind( FatCommonWrite );

        if (_SEH2_AbnormalTermination()) {

            //
            //  Restore initial file size and valid data length
            //

            if (ExtendingFile || ExtendingValidData) {

                //
                //  We got an error, pull back the file size if we extended it.
                //

                FcbOrDcb->Header.FileSize.LowPart = InitialFileSize;
                FcbOrDcb->Header.ValidDataLength.LowPart = InitialValidDataLength;

                NT_ASSERT( FcbOrDcb->Header.FileSize.LowPart <= FcbOrDcb->Header.AllocationSize.LowPart );

                //
                //  Pull back the cache map as well
                //

                if (FileObject->SectionObjectPointer->SharedCacheMap != NULL) {

                    *CcGetFileSizePointer(FileObject) = FcbOrDcb->Header.FileSize;
                }
            }
        }

        //
        //  Check if this needs to be backed out.
        //

        if (UnwindOutstandingAsync) {

            ExInterlockedAddUlong( &FcbOrDcb->NonPaged->OutstandingAsyncWrites,
                                   0xffffffff,
                                   &FatData.GeneralSpinLock );
        }

        //
        //  If the FcbOrDcb has been acquired, release it.
        //

        if (FcbOrDcbAcquired && Irp) {

            FatReleaseFcb( NULL, FcbOrDcb );
        }

        if (PagingIoResourceAcquired && Irp) {

            ExReleaseResourceLite( FcbOrDcb->Header.PagingIoResource );
        }

        //
        //  Complete the request if we didn't post it and no exception
        //
        //  Note that FatCompleteRequest does the right thing if either
        //  IrpContext or Irp are NULL
        //

        if ( !PostIrp && !_SEH2_AbnormalTermination() ) {

            FatCompleteRequest( IrpContext, Irp, Status );
        }

        DebugTrace(-1, Dbg, "FatCommonWrite -> %08lx\n", Status );
    } _SEH2_END;

    return Status;
}

FatDeferredFlush()

VOID NTAPI FatDeferredFlush

(

_In_ PVOID

Parameter

)

Definition at line 3032 of file write.c.

{

    PFILE_OBJECT File;
    PVCB Vcb;
    PFCB FcbOrDcb;
    PCCB Ccb;

    PAGED_CODE();

    File = ((PDEFERRED_FLUSH_CONTEXT)Parameter)->File;

    FatDecodeFileObject(File, &Vcb, &FcbOrDcb, &Ccb);
    NT_ASSERT( FcbOrDcb != NULL );
    
    //
    //  Make us appear as a top level FSP request so that we will
    //  receive any errors from the flush.
    //

    IoSetTopLevelIrp( (PIRP)FSRTL_FSP_TOP_LEVEL_IRP );

    ExAcquireResourceExclusiveLite( FcbOrDcb->Header.Resource, TRUE );
    ExAcquireResourceSharedLite( FcbOrDcb->Header.PagingIoResource, TRUE );
    
    CcFlushCache( File->SectionObjectPointer, NULL, 0, NULL );

    ExReleaseResourceLite( FcbOrDcb->Header.PagingIoResource );
    ExReleaseResourceLite( FcbOrDcb->Header.Resource );

    IoSetTopLevelIrp( NULL );

    ObDereferenceObject( File );

    ExFreePool( Parameter );

}

FatDeferredFlushDpc()

VOID NTAPI FatDeferredFlushDpc	(	_In_ PKDPC	Dpc,
		_In_opt_ PVOID	DeferredContext,
		_In_opt_ PVOID	SystemArgument1,
		_In_opt_ PVOID	SystemArgument2
	)

Definition at line 2977 of file write.c.

{
    PDEFERRED_FLUSH_CONTEXT FlushContext;

    UNREFERENCED_PARAMETER( SystemArgument1 );
    UNREFERENCED_PARAMETER( SystemArgument2 );
    UNREFERENCED_PARAMETER( Dpc );

    FlushContext = (PDEFERRED_FLUSH_CONTEXT)DeferredContext;

    //
    //  Send it off
    //

    ExInitializeWorkItem( &FlushContext->Item,
                          FatDeferredFlush,
                          FlushContext );

#ifdef _MSC_VER
#pragma prefast( suppress:28159, "prefast indicates this API is obsolete, but it's ok for fastfat to keep using it" )
#endif
    ExQueueWorkItem( &FlushContext->Item, CriticalWorkQueue );
}

Variable Documentation

FatDeferredFlush

VOID NTAPI FatDeferredFlush

Definition at line 63 of file write.c.

Referenced by FatDeferredFlushDpc().

FatDeferredFlushDpc

VOID NTAPI FatDeferredFlushDpc

Definition at line 52 of file write.c.

Referenced by _Requires_lock_held_().

FatNoAsync

BOOLEAN FatNoAsync = FALSE

Definition at line 46 of file write.c.

Referenced by _Requires_lock_held_().