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: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/da117b79ce72ecc3ab488c744e29fae9ba54e23b.1741453534.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 14 insertions, 33 deletions

diff --git a/io_uring/net.c b/io_uring/net.c
index 34a28689ec99..d9befb6fb8a7 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -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 = IOU_REQUEUE;
 		}
-		if (issue_flags & IO_URING_F_MULTISHOT)
-			*ret = mshot_retry_ret;
-		else
-			*ret = -EAGAIN;
 		return true;
 	}
 
@@ -1070,16 +1066,15 @@ retry_multishot:
 
 	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 @@ retry_multishot:
 	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 @@ retry:
 			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 @@ retry:
 	    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);