Function Ext2BuildExtents

Ext4Fsd/memory.c:1204–1355

}

NTSTATUS
Ext2BuildExtents(
    IN PEXT2_IRP_CONTEXT    IrpContext,
    IN PEXT2_VCB            Vcb,
    IN PEXT2_MCB            Mcb,
    IN ULONGLONG            Offset,
    IN ULONG                Size,
    IN BOOLEAN              bAlloc,
    OUT PEXT2_EXTENT *      Chain
)
{
    ULONG       Start, End;
    ULONG       Total = 0;

    LONGLONG    Lba = 0;
    NTSTATUS    Status = STATUS_SUCCESS;

    PEXT2_EXTENT  Extent = NULL;
    PEXT2_EXTENT  List = *Chain = NULL;

    if (!IsZoneInited(Mcb)) {
        Status = Ext2InitializeZone(IrpContext, Vcb, Mcb);
        if (!NT_SUCCESS(Status)) {
            DbgBreak();
        }
    }

    if ((IrpContext && IrpContext->Irp) &&
            ((IrpContext->Irp->Flags & IRP_NOCACHE) ||
             (IrpContext->Irp->Flags & IRP_PAGING_IO))) {
        Size = (Size + SECTOR_SIZE - 1) & (~(SECTOR_SIZE - 1));
    }

    Start = (ULONG)(Offset >> BLOCK_BITS);
    End = (ULONG)((Size + Offset + BLOCK_SIZE - 1) >> BLOCK_BITS);

    if (End > (ULONG)((Mcb->Inode.i_size + BLOCK_SIZE - 1) >> BLOCK_BITS) ) {
        End = (ULONG)((Mcb->Inode.i_size + BLOCK_SIZE - 1) >> BLOCK_BITS);
    }

    while (Size > 0 && Start < End) {

        ULONG   Mapped = 0;
        ULONG   Length = 0;
        ULONG   Block = 0;

        BOOLEAN rc = FALSE;

        /* try to map file offset to ext2 block upon Extents cache */
        if (IsZoneInited(Mcb)) {
            rc = Ext2LookupBlockExtent(
                     Vcb,
                     Mcb,
                     Start,
                     &Block,
                     &Mapped);

            if (!rc) {