io_uring: refactor io_req_map_rw()

Set rw->free_iovec to @iovec, that gives an identical result and stresses
that @iovec param rw->free_iovec play the same role.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -3010,7 +3010,7 @@ static void io_req_map_rw(struct io_kiocb *req, const struct iovec *iovec,
 	struct io_async_rw *rw = &req->io->rw;
 
 	memcpy(&rw->iter, iter, sizeof(*iter));
-	rw->free_iovec = NULL;
+	rw->free_iovec = iovec;
 	rw->bytes_done = 0;
 	/* can only be fixed buffers, no need to do anything */
 	if (iter->type == ITER_BVEC)
@@ -3027,7 +3027,6 @@ static void io_req_map_rw(struct io_kiocb *req, const struct iovec *iovec,
 			memcpy(rw->fast_iov + iov_off, fast_iov + iov_off,
 			       sizeof(struct iovec) * iter->nr_segs);
 	} else {
-		rw->free_iovec = iovec;
 		req->flags |= REQ_F_NEED_CLEANUP;
 	}
 }