io_uring: clear IOCB_WAITQ for non -EIOCBQUEUED return

The callback can only be armed, if we get -EIOCBQUEUED returned. It's
important that we clear the WAITQ bit for other cases, otherwise we can
queue for async retry and filemap will assume that we're armed and
return -EAGAIN instead of just blocking for the IO.

Cc: stable@vger.kernel.org # 5.9+
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -3286,6 +3286,7 @@ static int io_read(struct io_kiocb *req, unsigned int issue_flags)
 		if (ret == -EIOCBQUEUED)
 			return 0;
 		/* we got some bytes, but not all. retry. */
+		kiocb->ki_flags &= ~IOCB_WAITQ;
 	} while (ret > 0 && ret < io_size);
 done:
 	kiocb_done(kiocb, ret, issue_flags);