selftest/net: adjust io_uring sendzc notif handling

It's not currently possible but in the future we may get
IORING_CQE_F_MORE and so a notification even for a failed request, i.e.
when cqe->res <= 0. That's precisely what the documentation says, so
adjust the test and do IORING_CQE_F_MORE checks regardless of the main
completion cqe->res.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/aac948ea753a8bfe1fa3b82fe45debcb54586369.1663953085.git.asml.silence@gmail.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

tools/testing/selftests/net/io_uring_zerocopy_tx.c

@@ -400,7 +400,6 @@ static void do_tx(int domain, int type, int protocol)
 						   cfg_payload_len, msg_flags);
 				sqe->user_data = NONZC_TAG;
 			} else {
-				compl_cqes++;
 				io_uring_prep_sendzc(sqe, fd, payload,
 						     cfg_payload_len,
 						     msg_flags, zc_flags);
@@ -430,18 +429,23 @@ static void do_tx(int domain, int type, int protocol)
 			if (cqe->flags & IORING_CQE_F_NOTIF) {
 				if (cqe->flags & IORING_CQE_F_MORE)
 					error(1, -EINVAL, "invalid notif flags");
+				if (compl_cqes <= 0)
+					error(1, -EINVAL, "notification mismatch");
 				compl_cqes--;
 				i--;
-			} else if (cqe->res <= 0) {
-				if (cqe->flags & IORING_CQE_F_MORE)
-					error(1, cqe->res, "more with a failed send");
-				error(1, cqe->res, "send failed");
-			} else {
-				if (cqe->user_data == ZC_TAG &&
-				    !(cqe->flags & IORING_CQE_F_MORE))
-					error(1, cqe->res, "missing more flag");
+				io_uring_cqe_seen(&ring);
+				continue;
+			}
+			if (cqe->flags & IORING_CQE_F_MORE) {
+				if (cqe->user_data != ZC_TAG)
+					error(1, cqe->res, "unexpected F_MORE");
+				compl_cqes++;
+			}
+			if (cqe->res >= 0) {
 				packets++;
 				bytes += cqe->res;
+			} else if (cqe->res != -EAGAIN) {
+				error(1, cqe->res, "send failed");
 			}
 			io_uring_cqe_seen(&ring);
 		}