uctxt_offset
offset = offset_in_page((uctxt_offset(uctxt) + fd->subctxt) *
evs = dd->events + uctxt_offset(uctxt);
evs = dd->events + uctxt_offset(uctxt) + subctxt;
(dd->events + uctxt_offset(uctxt)) & PAGE_MASK;
ev = dd->events + uctxt_offset(uctxt) + fdata->subctxt;
(uctxt_offset(uctxt) + fd->subctxt);
(uctxt_offset(uctxt) + fdata->subctxt);