to #26323588

commit 8cdf2193a3335b4cfb6e023b41ac293d0843d287 upstream.

Draining the middle of a link is tricky, so leave a comment there
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>