[PATCH for-next 6/8] io_uring: add IOU_STOP_MULTISHOT return code

[Dylan Yudaken <dylany@fb.com>]

For multishot we want a way to signal the caller that multishot has ended
but also this might not be an error return.

For example sockets return 0 when closed, which should end a multishot
recv, but still have a CQE with result 0

Introduce IOU_STOP_MULTISHOT which does this and indicates that the return
code is stored inside req->cqe

Signed-off-by: Dylan Yudaken <dylany@fb.com>
---
 io_uring/io_uring.h | 7 +++++++
 io_uring/poll.c     | 9 +++++++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
index f77e4a5403e4..e8da70781fa3 100644
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -15,6 +15,13 @@
 enum {
 	IOU_OK			= 0,
 	IOU_ISSUE_SKIP_COMPLETE	= -EIOCBQUEUED,
+
+	/*
+	 * Intended only when both REQ_F_POLLED and REQ_F_APOLL_MULTISHOT
+	 * are set to indicate to the poll runner that multishot should be
+	 * removed and the result is set on req->cqe.res.
+	 */
+	IOU_STOP_MULTISHOT	= -ECANCELED,
 };
 
 struct io_uring_cqe *__io_get_cqe(struct io_ring_ctx *ctx);
diff --git a/io_uring/poll.c b/io_uring/poll.c
index fc3a5789d303..2054df9af291 100644
--- a/io_uring/poll.c
+++ b/io_uring/poll.c
@@ -195,6 +195,7 @@ static void io_poll_remove_entries(struct io_kiocb *req)
 enum {
 	IOU_POLL_DONE = 0,
 	IOU_POLL_NO_ACTION = 1,
+	IOU_POLL_REMOVE_POLL_USE_RES = 2,
 };
 
 /*
@@ -244,6 +245,8 @@ static int io_poll_check_events(struct io_kiocb *req, bool *locked)
 				return -ECANCELED;
 		} else {
 			ret = io_poll_issue(req, locked);
+			if (ret == IOU_STOP_MULTISHOT)
+				return IOU_POLL_REMOVE_POLL_USE_RES;
 			if (ret < 0)
 				return ret;
 		}
@@ -268,7 +271,7 @@ static void io_poll_task_func(struct io_kiocb *req, bool *locked)
 	if (ret == IOU_POLL_DONE) {
 		struct io_poll *poll = io_kiocb_to_cmd(req);
 		req->cqe.res = mangle_poll(req->cqe.res & poll->events);
-	} else {
+	} else if (ret != IOU_POLL_REMOVE_POLL_USE_RES) {
 		req->cqe.res = ret;
 		req_set_fail(req);
 	}
@@ -291,7 +294,9 @@ static void io_apoll_task_func(struct io_kiocb *req, bool *locked)
 	io_poll_remove_entries(req);
 	io_poll_tw_hash_eject(req, locked);
 
-	if (!ret)
+	if (ret == IOU_POLL_REMOVE_POLL_USE_RES)
+		io_req_complete_post(req);
+	else if (ret == IOU_POLL_DONE)
 		io_req_task_submit(req, locked);
 	else
 		io_req_complete_failed(req, ret);
-- 
2.30.2