io_uring/zcrx: grab a net device

Zerocopy receive needs a net device to bind to its rx queue and dma map
buffers. As a preparation to following patches, resolve a net device
from the if_idx parameter with no functional changes otherwise.

Reviewed-by: Jens Axboe <[email protected]>
Signed-off-by: Pavel Begunkov <[email protected]>
Signed-off-by: David Wei <[email protected]>
Acked-by: Jakub Kicinski <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: isilence

io_uring/zcrx.c

@@ -3,6 +3,8 @@
 #include <linux/errno.h>
 #include <linux/mm.h>
 #include <linux/io_uring.h>
+#include <linux/netdevice.h>
+#include <linux/rtnetlink.h>
 
 #include <uapi/linux/io_uring.h>
 
@@ -128,13 +130,28 @@ static struct io_zcrx_ifq *io_zcrx_ifq_alloc(struct io_ring_ctx *ctx)
 
 	ifq->if_rxq = -1;
 	ifq->ctx = ctx;
+	spin_lock_init(&ifq->lock);
 	return ifq;
 }
 
+static void io_zcrx_drop_netdev(struct io_zcrx_ifq *ifq)
+{
+	spin_lock(&ifq->lock);
+	if (ifq->netdev) {
+		netdev_put(ifq->netdev, &ifq->netdev_tracker);
+		ifq->netdev = NULL;
+	}
+	spin_unlock(&ifq->lock);
+}
+
 static void io_zcrx_ifq_free(struct io_zcrx_ifq *ifq)
 {
+	io_zcrx_drop_netdev(ifq);
+
 	if (ifq->area)
 		io_zcrx_free_area(ifq->area);
+	if (ifq->dev)
+		put_device(ifq->dev);
 
 	io_free_rbuf_ring(ifq);
 	kfree(ifq);
@@ -195,6 +212,17 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 	ifq->rq_entries = reg.rq_entries;
 	ifq->if_rxq = reg.if_rxq;
 
+	ret = -ENODEV;
+	ifq->netdev = netdev_get_by_index(current->nsproxy->net_ns, reg.if_idx,
+					  &ifq->netdev_tracker, GFP_KERNEL);
+	if (!ifq->netdev)
+		goto err;
+
+	ifq->dev = ifq->netdev->dev.parent;
+	if (!ifq->dev)
+		return -EOPNOTSUPP;
+	get_device(ifq->dev);
+
 	reg.offsets.rqes = sizeof(struct io_uring);
 	reg.offsets.head = offsetof(struct io_uring, head);
 	reg.offsets.tail = offsetof(struct io_uring, tail);

io_uring/zcrx.h

@@ -4,6 +4,7 @@
 
 #include <linux/io_uring_types.h>
 #include <net/page_pool/types.h>
+#include <net/net_trackers.h>
 
 struct io_zcrx_area {
 	struct net_iov_area	nia;
@@ -27,6 +28,10 @@ struct io_zcrx_ifq {
 	u32				rq_entries;
 
 	u32				if_rxq;
+	struct device			*dev;
+	struct net_device		*netdev;
+	netdevice_tracker		netdev_tracker;
+	spinlock_t			lock;
 };
 
 #if defined(CONFIG_IO_URING_ZCRX)