Commit 7a9dcb05 authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Jens Axboe
Browse files

io_uring: return -EAGAIN to continue multishot 



Multishot errors can be mapped 1:1 to normal errors, but there are not
identical. It leads to a peculiar situation where all multishot requests
has to check in what context they're run and return different codes.

Unify them starting with EAGAIN / IOU_ISSUE_SKIP_COMPLETE(EIOCBQUEUED)
pair, which mean that core io_uring still owns the request and it should
be retried. In case of multishot it's naturally just continues to poll,
otherwise it might poll, use iowq or do any other kind of allowed
blocking. Introduce IOU_RETRY aliased to -EAGAIN for that.

Apart from obvious upsides, multishot can now also check for misuse of
IOU_ISSUE_SKIP_COMPLETE.

Signed-off-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/da117b79ce72ecc3ab488c744e29fae9ba54e23b.1741453534.git.asml.silence@gmail.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 0396ad37

io_uring/io_uring.c

+1 −3
Original line number Diff line number Diff line
@@ -1791,10 +1791,8 @@ int io_poll_issue(struct io_kiocb *req, io_tw_token_t tw) 


	ret = __io_issue_sqe(req, issue_flags, &io_issue_defs[req->opcode]);



	WARN_ON_ONCE(ret == IOU_ISSUE_SKIP_COMPLETE);

	WARN_ON_ONCE(ret == IOU_OK);



	if (ret == IOU_ISSUE_SKIP_COMPLETE)

		ret = 0;

	return ret;

}

io_uring/io_uring.h

+8 −0
Original line number Diff line number Diff line
@@ -22,6 +22,14 @@ enum { 
	IOU_OK			= 0,

	IOU_ISSUE_SKIP_COMPLETE	= -EIOCBQUEUED,



	/*

	 * The request has more work to do and should be retried. io_uring will

	 * attempt to wait on the file for eligible opcodes, but otherwise

	 * it'll be handed to iowq for blocking execution. It works for normal

	 * requests as well as for the multi shot mode.

	 */

	IOU_RETRY		= -EAGAIN,



	/*

	 * Requeue the task_work to restart operations on this request. The

	 * actual value isn't important, should just be not an otherwise

io_uring/net.c

+14 −33
Original line number Diff line number Diff line
@@ -898,8 +898,7 @@ static inline bool io_recv_finish(struct io_kiocb *req, int *ret, 
	 */

	if ((req->flags & REQ_F_APOLL_MULTISHOT) && !mshot_finished &&

	    io_req_post_cqe(req, *ret, cflags | IORING_CQE_F_MORE)) {

		int mshot_retry_ret = IOU_ISSUE_SKIP_COMPLETE;



		*ret = IOU_RETRY;

		io_mshot_prep_retry(req, kmsg);

		/* Known not-empty or unknown state, retry */

		if (cflags & IORING_CQE_F_SOCK_NONEMPTY || kmsg->msg.msg_inq < 0) {
@@ -907,12 +906,9 @@ static inline bool io_recv_finish(struct io_kiocb *req, int *ret, 
				return false;

			/* mshot retries exceeded, force a requeue */

			sr->nr_multishot_loops = 0;

			mshot_retry_ret = IOU_REQUEUE;

		}

			if (issue_flags & IO_URING_F_MULTISHOT)

			*ret = mshot_retry_ret;

		else

			*ret = -EAGAIN;

				*ret = IOU_REQUEUE;

		}

		return true;

	}
@@ -1070,16 +1066,15 @@ int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags) 


	if (ret < min_ret) {

		if (ret == -EAGAIN && force_nonblock) {

			if (issue_flags & IO_URING_F_MULTISHOT) {

			if (issue_flags & IO_URING_F_MULTISHOT)

				io_kbuf_recycle(req, issue_flags);

				return IOU_ISSUE_SKIP_COMPLETE;

			}

			return -EAGAIN;



			return IOU_RETRY;

		}

		if (ret > 0 && io_net_retry(sock, flags)) {

			sr->done_io += ret;

			req->flags |= REQ_F_BL_NO_RECYCLE;

			return -EAGAIN;

			return IOU_RETRY;

		}

		if (ret == -ERESTARTSYS)

			ret = -EINTR;
@@ -1207,12 +1202,10 @@ int io_recv(struct io_kiocb *req, unsigned int issue_flags) 
	ret = sock_recvmsg(sock, &kmsg->msg, flags);

	if (ret < min_ret) {

		if (ret == -EAGAIN && force_nonblock) {

			if (issue_flags & IO_URING_F_MULTISHOT) {

			if (issue_flags & IO_URING_F_MULTISHOT)

				io_kbuf_recycle(req, issue_flags);

				return IOU_ISSUE_SKIP_COMPLETE;

			}



			return -EAGAIN;

			return IOU_RETRY;

		}

		if (ret > 0 && io_net_retry(sock, flags)) {

			sr->len -= ret;
@@ -1312,10 +1305,7 @@ int io_recvzc(struct io_kiocb *req, unsigned int issue_flags) 
			return IOU_STOP_MULTISHOT;

		return IOU_OK;

	}



	if (issue_flags & IO_URING_F_MULTISHOT)

		return IOU_ISSUE_SKIP_COMPLETE;

	return -EAGAIN;

	return IOU_RETRY;

}



void io_send_zc_cleanup(struct io_kiocb *req)
@@ -1692,16 +1682,9 @@ int io_accept(struct io_kiocb *req, unsigned int issue_flags) 
			put_unused_fd(fd);

		ret = PTR_ERR(file);

		if (ret == -EAGAIN && force_nonblock &&

		    !(accept->iou_flags & IORING_ACCEPT_DONTWAIT)) {

			/*

			 * if it's multishot and polled, we don't need to

			 * return EAGAIN to arm the poll infra since it

			 * has already been done

			 */

			if (issue_flags & IO_URING_F_MULTISHOT)

				return IOU_ISSUE_SKIP_COMPLETE;

			return ret;

		}

		    !(accept->iou_flags & IORING_ACCEPT_DONTWAIT))

			return IOU_RETRY;



		if (ret == -ERESTARTSYS)

			ret = -EINTR;

	} else if (!fixed) {
@@ -1720,9 +1703,7 @@ int io_accept(struct io_kiocb *req, unsigned int issue_flags) 
	    io_req_post_cqe(req, ret, cflags | IORING_CQE_F_MORE)) {

		if (cflags & IORING_CQE_F_SOCK_NONEMPTY || arg.is_empty == -1)

			goto retry;

		if (issue_flags & IO_URING_F_MULTISHOT)

			return IOU_ISSUE_SKIP_COMPLETE;

		return -EAGAIN;

		return IOU_RETRY;

	}



	io_req_set_res(req, ret, cflags);

io_uring/poll.c

+2 −1
Original line number Diff line number Diff line
@@ -289,11 +289,12 @@ static int io_poll_check_events(struct io_kiocb *req, io_tw_token_t tw) 
			}

		} else {

			int ret = io_poll_issue(req, tw);



			if (ret == IOU_STOP_MULTISHOT)

				return IOU_POLL_REMOVE_POLL_USE_RES;

			else if (ret == IOU_REQUEUE)

				return IOU_POLL_REQUEUE;

			if (ret < 0)

			if (ret != IOU_RETRY && ret < 0)

				return ret;

		}

io_uring/rw.c

+4 −7
Original line number Diff line number Diff line
@@ -1068,9 +1068,7 @@ int io_read_mshot(struct io_kiocb *req, unsigned int issue_flags) 
		 */

		if (io_kbuf_recycle(req, issue_flags))

			rw->len = 0;

		if (issue_flags & IO_URING_F_MULTISHOT)

			return IOU_ISSUE_SKIP_COMPLETE;

		return -EAGAIN;

		return IOU_RETRY;

	} else if (ret <= 0) {

		io_kbuf_recycle(req, issue_flags);

		if (ret < 0)
@@ -1088,16 +1086,15 @@ int io_read_mshot(struct io_kiocb *req, unsigned int issue_flags) 
		rw->len = 0; /* similarly to above, reset len to 0 */



		if (io_req_post_cqe(req, ret, cflags | IORING_CQE_F_MORE)) {

			if (issue_flags & IO_URING_F_MULTISHOT) {

			if (issue_flags & IO_URING_F_MULTISHOT)

				/*

				 * Force retry, as we might have more data to

				 * be read and otherwise it won't get retried

				 * until (if ever) another poll is triggered.

				 */

				io_poll_multishot_retry(req);

				return IOU_ISSUE_SKIP_COMPLETE;

			}

			return -EAGAIN;



			return IOU_RETRY;

		}

	}