IoCompleteRequest rollback process, if not installed in current IO_Stack complete routines, then the current Control of IO_Stack. SL_PENDING_RETURNED mark is how to deal with it?

There are two: 1: it is the stack pointer forward to a layer of the stack unit 2: make a copy of the current stack unit SL_PENDING_RETURNED marks on a layer of the stack in the cell

Saw some WRK and many articles, didn't find the right explanation, please, dear god grant instruction, wish: the work is smooth, happy happy life!