io_uring/zcrx: extract netdev+area init into a helper

In preparation to following patches, add a function that is responsibly
for looking up a netdev, creating an area, DMA mapping it and opening a
queue.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://patch.msgid.link/88cb6f746ecb496a9030756125419df273d0b003.1774261953.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: isilence

io_uring/zcrx.c

@@ -751,10 +751,50 @@ static int import_zcrx(struct io_ring_ctx *ctx,
 	return ret;
 }
 
+static int zcrx_register_netdev(struct io_zcrx_ifq *ifq,
+				struct io_uring_zcrx_ifq_reg *reg,
+				struct io_uring_zcrx_area_reg *area)
+{
+	struct pp_memory_provider_params mp_param = {};
+	unsigned if_rxq = reg->if_rxq;
+	int ret;
+
+	ifq->netdev = netdev_get_by_index_lock(current->nsproxy->net_ns,
+						reg->if_idx);
+	if (!ifq->netdev)
+		return -ENODEV;
+
+	netdev_hold(ifq->netdev, &ifq->netdev_tracker, GFP_KERNEL);
+
+	ifq->dev = netdev_queue_get_dma_dev(ifq->netdev, if_rxq);
+	if (!ifq->dev) {
+		ret = -EOPNOTSUPP;
+		goto netdev_put_unlock;
+	}
+	get_device(ifq->dev);
+
+	ret = io_zcrx_create_area(ifq, area, reg);
+	if (ret)
+		goto netdev_put_unlock;
+
+	if (reg->rx_buf_len)
+		mp_param.rx_page_size = 1U << ifq->niov_shift;
+	mp_param.mp_ops = &io_uring_pp_zc_ops;
+	mp_param.mp_priv = ifq;
+	ret = __net_mp_open_rxq(ifq->netdev, if_rxq, &mp_param, NULL);
+	if (ret)
+		goto netdev_put_unlock;
+
+	ifq->if_rxq = if_rxq;
+	ret = 0;
+netdev_put_unlock:
+	netdev_unlock(ifq->netdev);
+	return ret;
+}
+
 int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 			  struct io_uring_zcrx_ifq_reg __user *arg)
 {
-	struct pp_memory_provider_params mp_param = {};
 	struct io_uring_zcrx_area_reg area;
 	struct io_uring_zcrx_ifq_reg reg;
 	struct io_uring_region_desc rd;
@@ -821,33 +861,9 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 	if (ret)
 		goto err;
 
-	ifq->netdev = netdev_get_by_index_lock(current->nsproxy->net_ns, reg.if_idx);
-	if (!ifq->netdev) {
-		ret = -ENODEV;
-		goto err;
-	}
-	netdev_hold(ifq->netdev, &ifq->netdev_tracker, GFP_KERNEL);
-
-	ifq->dev = netdev_queue_get_dma_dev(ifq->netdev, reg.if_rxq);
-	if (!ifq->dev) {
-		ret = -EOPNOTSUPP;
-		goto netdev_put_unlock;
-	}
-	get_device(ifq->dev);
-
-	ret = io_zcrx_create_area(ifq, &area, &reg);
-	if (ret)
-		goto netdev_put_unlock;
-
-	if (reg.rx_buf_len)
-		mp_param.rx_page_size = 1U << ifq->niov_shift;
-	mp_param.mp_ops = &io_uring_pp_zc_ops;
-	mp_param.mp_priv = ifq;
-	ret = __net_mp_open_rxq(ifq->netdev, reg.if_rxq, &mp_param, NULL);
+	ret = zcrx_register_netdev(ifq, &reg, &area);
 	if (ret)
-		goto netdev_put_unlock;
-	netdev_unlock(ifq->netdev);
-	ifq->if_rxq = reg.if_rxq;
+		goto err;
 
 	reg.zcrx_id = id;
 
@@ -867,8 +883,6 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 		goto err;
 	}
 	return 0;
-netdev_put_unlock:
-	netdev_unlock(ifq->netdev);
 err:
 	scoped_guard(mutex, &ctx->mmap_lock)
 		xa_erase(&ctx->zcrx_ctxs, id);