to #26323578

commit 944e58bfeda0e9b97cd611adafc823c78e0bc464 upstream.

Make io_req_find_next() and io_req_link_next() to accept only non-null
nxt, and handle it in callers.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: NJoseph Qi <joseph.qi@linux.alibaba.com>
Acked-by: NXiaoguang Wang <xiaoguang.wang@linux.alibaba.com>