io_uring/rw: return IOU_ISSUE_SKIP_COMPLETE for multishot retry

If read multishot is being invoked from the poll retry handler, then we
should return IOU_ISSUE_SKIP_COMPLETE rather than -EAGAIN. If not, then
a CQE will be posted with -EAGAIN rather than triggering the retry when
the file is flagged as readable again.

Cc: stable@vger.kernel.org
Reported-by: Sargun Dhillon <sargun@meta.com>
Fixes: fc68fcd ("io_uring/rw: add support for IORING_OP_READ_MULTISHOT")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: axboe

io_uring/rw.c

@@ -947,6 +947,8 @@ 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;
 	}