io_uring: add memory barrier to synchronize io_kiocb's result and iopoll_completed
In io_complete_rw_iopoll(), stores to io_kiocb's result and iopoll completed are two independent store operations, to ensure that once iopoll_completed is ture and then req->result must been perceived by the cpu executing io_do_iopoll(), proper memory barrier should be used. And in io_do_iopoll(), we check whether req->result is EAGAIN, if it is, we'll need to issue this io request using io-wq again. In order to just issue a single smp_rmb() on the completion side, move the re-submit work to io_iopoll_complete(). Cc: stable@vger.kernel.org Signed-off-by: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com> [axboe: don't set ->iopoll_completed for -EAGAIN retry] Signed-off-by: Jens Axboe <axboe@kernel.dk>
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