This is a note to let you know that I've just added the patch titled io_uring: fix hanging iopoll in case of -EAGAIN to the 5.7-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: io_uring-fix-hanging-iopoll-in-case-of-eagain.patch and it can be found in the queue-5.7 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 7544a902aad6b1b080bd1bbce66093ca588218fc Author: Pavel Begunkov <asml.silence@xxxxxxxxx> Date: Thu Jun 25 12:37:10 2020 +0300 io_uring: fix hanging iopoll in case of -EAGAIN [ Upstream commit cd664b0e35cb1202f40c259a1a5ea791d18c879d ] io_do_iopoll() won't do anything with a request unless req->iopoll_completed is set. So io_complete_rw_iopoll() has to set it, otherwise io_do_iopoll() will poll a file again and again even though the request of interest was completed long time ago. Also, remove -EAGAIN check from io_issue_sqe() as it races with the changed lines. The request will take the long way and be resubmitted from io_iopoll*(). io_kiocb's result and iopoll_completed") Fixes: bbde017a32b3 ("io_uring: add memory barrier to synchronize Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/fs/io_uring.c b/fs/io_uring.c index 1829be7f63a35..4ab1728de247c 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1942,10 +1942,8 @@ static void io_complete_rw_iopoll(struct kiocb *kiocb, long res, long res2) WRITE_ONCE(req->result, res); /* order with io_poll_complete() checking ->result */ - if (res != -EAGAIN) { - smp_wmb(); - WRITE_ONCE(req->iopoll_completed, 1); - } + smp_wmb(); + WRITE_ONCE(req->iopoll_completed, 1); } /* @@ -5425,9 +5423,6 @@ static int io_issue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe, if ((ctx->flags & IORING_SETUP_IOPOLL) && req->file) { const bool in_async = io_wq_current_is_worker(); - if (req->result == -EAGAIN) - return -EAGAIN; - /* workqueue context doesn't hold uring_lock, grab it now */ if (in_async) mutex_lock(&ctx->uring_lock);