[PATCH net-next v10 18/22] io_uring/zcrx: set pp memory provider for an rx queue

[David Wei <dw@davidwei.uk>]

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>
---
 io_uring/zcrx.c | 83 ++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 75 insertions(+), 8 deletions(-)

diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index 036de2981e64..caaec528cc3c 100644
--- a/io_uring/zcrx.c
+++ b/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"
@@ -139,6 +140,65 @@ static void io_zcrx_get_niov_uref(struct net_iov *niov)
 	atomic_inc(io_get_user_counter(niov));
 }
 
+static int io_open_zc_rxq(struct io_zcrx_ifq *ifq, unsigned ifq_idx)
+{
+	struct netdev_rx_queue *rxq;
+	struct net_device *dev = ifq->dev;
+	int ret;
+
+	ASSERT_RTNL();
+
+	if (ifq_idx >= dev->num_rx_queues)
+		return -EINVAL;
+	ifq_idx = array_index_nospec(ifq_idx, dev->num_rx_queues);
+
+	rxq = __netif_get_rx_queue(ifq->dev, ifq_idx);
+	if (rxq->mp_params.mp_priv)
+		return -EEXIST;
+
+	ifq->if_rxq = ifq_idx;
+	rxq->mp_params.mp_ops = &io_uring_pp_zc_ops;
+	rxq->mp_params.mp_priv = ifq;
+	ret = netdev_rx_queue_restart(ifq->dev, ifq->if_rxq);
+	if (ret)
+		goto fail;
+	return 0;
+fail:
+	rxq->mp_params.mp_ops = NULL;
+	rxq->mp_params.mp_priv = NULL;
+	ifq->if_rxq = -1;
+	return ret;
+}
+
+static void io_close_zc_rxq(struct io_zcrx_ifq *ifq)
+{
+	struct netdev_rx_queue *rxq;
+	int err;
+
+	if (ifq->if_rxq == -1)
+		return;
+
+	rtnl_lock();
+	if (WARN_ON_ONCE(ifq->if_rxq >= ifq->dev->num_rx_queues)) {
+		rtnl_unlock();
+		return;
+	}
+
+	rxq = __netif_get_rx_queue(ifq->dev, ifq->if_rxq);
+
+	WARN_ON_ONCE(rxq->mp_params.mp_priv != ifq);
+
+	rxq->mp_params.mp_ops = NULL;
+	rxq->mp_params.mp_priv = NULL;
+
+	err = netdev_rx_queue_restart(ifq->dev, ifq->if_rxq);
+	if (err)
+		pr_devel("io_uring: can't restart a queue on zcrx close\n");
+
+	rtnl_unlock();
+	ifq->if_rxq = -1;
+}
+
 static int io_allocate_rbuf_ring(struct io_zcrx_ifq *ifq,
 				 struct io_uring_zcrx_ifq_reg *reg,
 				 struct io_uring_region_desc *rd)
@@ -275,6 +335,8 @@ static struct io_zcrx_ifq *io_zcrx_ifq_alloc(struct io_ring_ctx *ctx)
 
 static void io_zcrx_ifq_free(struct io_zcrx_ifq *ifq)
 {
+	io_close_zc_rxq(ifq);
+
 	if (ifq->area)
 		io_zcrx_free_area(ifq->area);
 
@@ -337,7 +399,6 @@ 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->dev = netdev_get_by_index(current->nsproxy->net_ns, reg.if_idx,
@@ -349,16 +410,20 @@ int io_register_zcrx_ifq(struct io_ring_ctx *ctx,
 	if (ret)
 		goto err;
 
+	rtnl_lock();
+	ret = io_open_zc_rxq(ifq, reg.if_rxq);
+	rtnl_unlock();
+	if (ret)
+		goto err;
+
 	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))) {
+		io_close_zc_rxq(ifq);
 		ret = -EFAULT;
 		goto err;
 	}
@@ -435,6 +500,8 @@ void io_shutdown_zcrx_ifqs(struct io_ring_ctx *ctx)
 
 	if (ctx->ifq)
 		io_zcrx_scrub(ctx->ifq);
+
+	io_close_zc_rxq(ctx->ifq);
 }
 
 static inline u32 io_zcrx_rqring_entries(struct io_zcrx_ifq *ifq)
-- 
2.43.5