io_uring/zcrx: set pp memory provider for an rx queue

Set the page pool memory provider for the rx queue configured for zero
copy to io_uring. Then the rx queue is reset using
netdev_rx_queue_restart() and netdev core + page pool will take care of
filling the rx queue from the io_uring zero copy memory provider.

For now, there is only one ifq so its destruction happens implicitly
during io_uring cleanup.

Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: David Wei <dw@davidwei.uk>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20250215000947.789731-8-dw@davidwei.uk
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: spikeh

io_uring/zcrx.c

@@ -11,11 +11,12 @@
 #include <net/page_pool/helpers.h>
 #include <net/page_pool/memory_provider.h>
 #include <net/netlink.h>
-
-#include <trace/events/page_pool.h>
+#include <net/netdev_rx_queue.h>
 #include <net/tcp.h>
 #include <net/rps.h>
 
+#include <trace/events/page_pool.h>
+
 #include <uapi/linux/io_uring.h>
 
 #include "io_uring.h"
@@ -275,8 +276,34 @@ static void io_zcrx_drop_netdev(struct io_zcrx_ifq *ifq)
 	spin_unlock(&ifq->lock);
 }
 
+static void io_close_queue(struct io_zcrx_ifq *ifq)
+{
+	struct net_device *netdev;
+	netdevice_tracker netdev_tracker;
+	struct pp_memory_provider_params p = {
+		.mp_ops = &io_uring_pp_zc_ops,
+		.mp_priv = ifq,
+	};
+
+	if (ifq->if_rxq == -1)
+		return;
+
+	spin_lock(&ifq->lock);
+	netdev = ifq->netdev;
+	netdev_tracker = ifq->netdev_tracker;
+	ifq->netdev = NULL;
+	spin_unlock(&ifq->lock);
+
+	if (netdev) {
+		net_mp_close_rxq(netdev, ifq->if_rxq, &p);
+		netdev_put(netdev, &netdev_tracker);
+	}
+	ifq->if_rxq = -1;
+}
+
 static void io_zcrx_ifq_free(struct io_zcrx_ifq *ifq)
 {
+	io_close_queue(ifq);
 	io_zcrx_drop_netdev(ifq);
 
 	if (ifq->area)
@@ -291,6 +318,7 @@ static void io_zcrx_ifq_free(struct io_zcrx_ifq *ifq)
 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;
@@ -341,7 +369,6 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 		goto err;
 
 	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,
@@ -358,16 +385,20 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 	if (ret)
 		goto err;
 
+	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);
+	if (ret)
+		goto err;
+	ifq->if_rxq = reg.if_rxq;
+
 	reg.offsets.rqes = sizeof(struct io_uring);
 	reg.offsets.head = offsetof(struct io_uring, head);
 	reg.offsets.tail = offsetof(struct io_uring, tail);
 
 	if (copy_to_user(arg, &reg, sizeof(reg)) ||
-	    copy_to_user(u64_to_user_ptr(reg.region_ptr), &rd, sizeof(rd))) {
-		ret = -EFAULT;
-		goto err;
-	}
-	if (copy_to_user(u64_to_user_ptr(reg.area_ptr), &area, sizeof(area))) {
+	    copy_to_user(u64_to_user_ptr(reg.region_ptr), &rd, sizeof(rd)) ||
+	    copy_to_user(u64_to_user_ptr(reg.area_ptr), &area, sizeof(area))) {
 		ret = -EFAULT;
 		goto err;
 	}
@@ -444,6 +475,8 @@ void io_shutdown_zcrx_ifqs(struct io_ring_ctx *ctx)
 
 	if (ctx->ifq)
 		io_zcrx_scrub(ctx->ifq);
+
+	io_close_queue(ctx->ifq);
 }
 
 static inline u32 io_zcrx_rqring_entries(struct io_zcrx_ifq *ifq)