Function Ext2QueryExtentMappings

Ext4Fsd/fsctl.c:667–769

NTSTATUS
Ext2QueryExtentMappings(
    IN PEXT2_IRP_CONTEXT   IrpContext,
    IN PEXT2_VCB           Vcb,
    IN PEXT2_FCB           Fcb,
    IN PLARGE_INTEGER      RequestVbn,
    OUT PLARGE_INTEGER *   pMappedRuns
)
{
    PLARGE_INTEGER      MappedRuns = NULL;
    PLARGE_INTEGER      PartialRuns = NULL;

    PEXT2_EXTENT        Chain = NULL;
    PEXT2_EXTENT        Extent = NULL;

    LONGLONG            Vbn = 0;
    ULONG               Length = 0;
    ULONG               i = 0;

    NTSTATUS            Status = STATUS_SUCCESS;

    __try {

        /* now building all the request extents */
        while (Vbn < RequestVbn->QuadPart) {

            Length = 0x80000000; /* 2g bytes */
            if (RequestVbn->QuadPart < Vbn + Length) {
                Length = (ULONG)(RequestVbn->QuadPart - Vbn);
            }

            /* build extents for sub-range */
            Extent = NULL;
            Status = Ext2BuildExtents(
                         IrpContext,
                         Vcb,
                         Fcb->Mcb,
                         Vbn,
                         Length,
                         FALSE,
                         &Extent);

            if (!NT_SUCCESS(Status)) {
                __leave;
            }

            if (Chain) {
                Ext2JointExtents(Chain, Extent);
            } else {
                Chain = Extent;
            }

            /* allocate extent array */
            PartialRuns = Ext2AllocatePool(
                              NonPagedPool,
                              (Ext2CountExtents(Chain) + 2) *
                              (2 * sizeof(LARGE_INTEGER)),
                              'RE2E');