io_uring/zctx: separate notification user_data

People previously asked for the notification CQE to have a different
user_data value from the main request completion. It's useful to
separate buffer and request handling logic and avoid separately
refcounting the request.

Let the user pass the notification user_data in sqe->addr3. If zero,
it'll inherit sqe->user_data as before. It doesn't change the rules for
when the user can expect a notification CQE, and it should still check
the IORING_CQE_F_MORE flag.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: isilence

io_uring/net.c

@@ -1333,11 +1333,12 @@ int io_send_zc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	struct io_ring_ctx *ctx = req->ctx;
 	struct io_async_msghdr *iomsg;
 	struct io_kiocb *notif;
+	u64 user_data;
 	int ret;
 
 	zc->done_io = 0;
 
-	if (unlikely(READ_ONCE(sqe->__pad2[0]) || READ_ONCE(sqe->addr3)))
+	if (unlikely(READ_ONCE(sqe->__pad2[0])))
 		return -EINVAL;
 	/* we don't support IOSQE_CQE_SKIP_SUCCESS just yet */
 	if (req->flags & REQ_F_CQE_SKIP)
@@ -1346,7 +1347,11 @@ int io_send_zc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	notif = zc->notif = io_alloc_notif(ctx);
 	if (!notif)
 		return -ENOMEM;
-	notif->cqe.user_data = req->cqe.user_data;
+	user_data = READ_ONCE(sqe->addr3);
+	if (!user_data)
+		user_data = req->cqe.user_data;
+
+	notif->cqe.user_data = user_data;
 	notif->cqe.res = 0;
 	notif->cqe.flags = IORING_CQE_F_NOTIF;
 	req->flags |= REQ_F_NEED_CLEANUP | REQ_F_POLL_NO_LAZY;