io_uring: make io_fill_cqe_aux honour CQE32

Don't let io_fill_cqe_aux() post 16B cqes for CQE32 rings, neither the
kernel nor the userspace expect this to happen.

Fixes: 76c68fb ("io_uring: enable CQE32")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/64fae669fae1b7083aa15d0cd807f692b0880b9a.1655287457.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: isilence

fs/io_uring.c

@@ -2518,6 +2518,11 @@ static noinline bool io_fill_cqe_aux(struct io_ring_ctx *ctx, u64 user_data,
 		WRITE_ONCE(cqe->user_data, user_data);
 		WRITE_ONCE(cqe->res, res);
 		WRITE_ONCE(cqe->flags, cflags);
+
+		if (ctx->flags & IORING_SETUP_CQE32) {
+			WRITE_ONCE(cqe->big_cqe[0], 0);
+			WRITE_ONCE(cqe->big_cqe[1], 0);
+		}
 		return true;
 	}
 	return io_cqring_event_overflow(ctx, user_data, res, cflags, 0, 0);