commit a278682dad37fd2f8d2f30d8e84e376a856ab472 upstream.

If io_copy_iov() fails, it will break the loop and report success,
albeit partially completed operation.
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>
Reviewed-by: NXiaoguang Wang <xiaoguang.wang@linux.alibaba.com>