Merge branch 'net-make-sure-we-retain-napi-ordering-on-netdev-napi_list'

Jakub Kicinski says:

====================
net: make sure we retain NAPI ordering on netdev->napi_list

I promised Eric to remove the rtnl protection of the NAPI list,
when I sat down to implement it over the break I realized that
the recently added NAPI ID retention will break the list ordering
assumption we have in netlink dump. The ordering used to happen
"naturally", because we'd always add NAPIs that the head of the
list, and assign a new monotonically increasing ID.

Before the first patch of this series we'd still only add at
the head of the list but now the newly added NAPI may inherit
from its config an ID lower than something else already on the list.

The fix is in the first patch, the rest is netdevsim churn to test it.
I'm posting this for net-next, because AFAICT the problem can't
be triggered in net, given the very limited queue API adoption.

v2:
 - [patch 2] allocate the array with kcalloc() instead of kvcalloc()
 - [patch 2] set GFP_KERNEL_ACCOUNT when allocating queues
 - [patch 6] don't null-check page pool before page_pool_destroy()
 - [patch 6] controled -> controlled
 - [patch 7] change mode to 0200
 - [patch 7] reorder removal to be inverse of add
 - [patch 7] fix the spaces vs tabs
v1: https://lore.kernel.org/20250103185954.1236510-1-kuba@kernel.org
====================

Link: https://patch.msgid.link/20250107160846.2223263-1-kuba@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Documentation/networking/netdevices.rst

@@ -297,3 +297,13 @@ napi->poll:
 	Context:
 		 softirq
 		 will be called with interrupts disabled by netconsole.
+
+NETDEV_INTERNAL symbol namespace
+================================
+
+Symbols exported as NETDEV_INTERNAL can only be used in networking
+core and drivers which exclusively flow via the main networking list and trees.
+Note that the inverse is not true, most symbols outside of NETDEV_INTERNAL
+are not expected to be used by random code outside netdev either.
+Symbols may lack the designation because they predate the namespaces,
+or simply due to an oversight.

drivers/net/netdevsim/netdev.c

@@ -20,6 +20,7 @@
 #include <linux/netdevice.h>
 #include <linux/slab.h>
 #include <net/netdev_queues.h>
+#include <net/netdev_rx_queue.h>
 #include <net/page_pool/helpers.h>
 #include <net/netlink.h>
 #include <net/net_shaper.h>
@@ -29,6 +30,8 @@
 
 #include "netdevsim.h"
 
+MODULE_IMPORT_NS("NETDEV_INTERNAL");
+
 #define NSIM_RING_SIZE		256
 
 static int nsim_napi_rx(struct nsim_rq *rq, struct sk_buff *skb)
@@ -69,7 +72,7 @@ static netdev_tx_t nsim_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	rxq = skb_get_queue_mapping(skb);
 	if (rxq >= peer_dev->num_rx_queues)
 		rxq = rxq % peer_dev->num_rx_queues;
-	rq = &peer_ns->rq[rxq];
+	rq = peer_ns->rq[rxq];
 
 	skb_tx_timestamp(skb);
 	if (unlikely(nsim_forward_skb(peer_dev, skb, rq) == NET_RX_DROP))
@@ -359,25 +362,24 @@ static int nsim_poll(struct napi_struct *napi, int budget)
 	return done;
 }
 
-static int nsim_create_page_pool(struct nsim_rq *rq)
+static int nsim_create_page_pool(struct page_pool **p, struct napi_struct *napi)
 {
-	struct page_pool_params p = {
+	struct page_pool_params params = {
 		.order = 0,
 		.pool_size = NSIM_RING_SIZE,
 		.nid = NUMA_NO_NODE,
-		.dev = &rq->napi.dev->dev,
-		.napi = &rq->napi,
+		.dev = &napi->dev->dev,
+		.napi = napi,
 		.dma_dir = DMA_BIDIRECTIONAL,
-		.netdev = rq->napi.dev,
+		.netdev = napi->dev,
 	};
+	struct page_pool *pool;
 
-	rq->page_pool = page_pool_create(&p);
-	if (IS_ERR(rq->page_pool)) {
-		int err = PTR_ERR(rq->page_pool);
+	pool = page_pool_create(&params);
+	if (IS_ERR(pool))
+		return PTR_ERR(pool);
 
-		rq->page_pool = NULL;
-		return err;
-	}
+	*p = pool;
 	return 0;
 }
 
@@ -388,15 +390,15 @@ static int nsim_init_napi(struct netdevsim *ns)
 	int err, i;
 
 	for (i = 0; i < dev->num_rx_queues; i++) {
-		rq = &ns->rq[i];
+		rq = ns->rq[i];
 
-		netif_napi_add(dev, &rq->napi, nsim_poll);
+		netif_napi_add_config(dev, &rq->napi, nsim_poll, i);
 	}
 
 	for (i = 0; i < dev->num_rx_queues; i++) {
-		rq = &ns->rq[i];
+		rq = ns->rq[i];
 
-		err = nsim_create_page_pool(rq);
+		err = nsim_create_page_pool(&rq->page_pool, &rq->napi);
 		if (err)
 			goto err_pp_destroy;
 	}
@@ -405,12 +407,12 @@ static int nsim_init_napi(struct netdevsim *ns)
 
 err_pp_destroy:
 	while (i--) {
-		page_pool_destroy(ns->rq[i].page_pool);
-		ns->rq[i].page_pool = NULL;
+		page_pool_destroy(ns->rq[i]->page_pool);
+		ns->rq[i]->page_pool = NULL;
 	}
 
 	for (i = 0; i < dev->num_rx_queues; i++)
-		__netif_napi_del(&ns->rq[i].napi);
+		__netif_napi_del(&ns->rq[i]->napi);
 
 	return err;
 }
@@ -421,7 +423,7 @@ static void nsim_enable_napi(struct netdevsim *ns)
 	int i;
 
 	for (i = 0; i < dev->num_rx_queues; i++) {
-		struct nsim_rq *rq = &ns->rq[i];
+		struct nsim_rq *rq = ns->rq[i];
 
 		netif_queue_set_napi(dev, i, NETDEV_QUEUE_TYPE_RX, &rq->napi);
 		napi_enable(&rq->napi);
@@ -448,7 +450,7 @@ static void nsim_del_napi(struct netdevsim *ns)
 	int i;
 
 	for (i = 0; i < dev->num_rx_queues; i++) {
-		struct nsim_rq *rq = &ns->rq[i];
+		struct nsim_rq *rq = ns->rq[i];
 
 		napi_disable(&rq->napi);
 		__netif_napi_del(&rq->napi);
@@ -456,8 +458,8 @@ static void nsim_del_napi(struct netdevsim *ns)
 	synchronize_net();
 
 	for (i = 0; i < dev->num_rx_queues; i++) {
-		page_pool_destroy(ns->rq[i].page_pool);
-		ns->rq[i].page_pool = NULL;
+		page_pool_destroy(ns->rq[i]->page_pool);
+		ns->rq[i]->page_pool = NULL;
 	}
 }
 
@@ -595,6 +597,182 @@ static const struct netdev_stat_ops nsim_stat_ops = {
 	.get_base_stats		= nsim_get_base_stats,
 };
 
+static struct nsim_rq *nsim_queue_alloc(void)
+{
+	struct nsim_rq *rq;
+
+	rq = kzalloc(sizeof(*rq), GFP_KERNEL_ACCOUNT);
+	if (!rq)
+		return NULL;
+
+	skb_queue_head_init(&rq->skb_queue);
+	return rq;
+}
+
+static void nsim_queue_free(struct nsim_rq *rq)
+{
+	skb_queue_purge_reason(&rq->skb_queue, SKB_DROP_REASON_QUEUE_PURGE);
+	kfree(rq);
+}
+
+/* Queue reset mode is controlled by ns->rq_reset_mode.
+ * - normal - new NAPI new pool (old NAPI enabled when new added)
+ * - mode 1 - allocate new pool (NAPI is only disabled / enabled)
+ * - mode 2 - new NAPI new pool (old NAPI removed before new added)
+ * - mode 3 - new NAPI new pool (old NAPI disabled when new added)
+ */
+struct nsim_queue_mem {
+	struct nsim_rq *rq;
+	struct page_pool *pp;
+};
+
+static int
+nsim_queue_mem_alloc(struct net_device *dev, void *per_queue_mem, int idx)
+{
+	struct nsim_queue_mem *qmem = per_queue_mem;
+	struct netdevsim *ns = netdev_priv(dev);
+	int err;
+
+	if (ns->rq_reset_mode > 3)
+		return -EINVAL;
+
+	if (ns->rq_reset_mode == 1)
+		return nsim_create_page_pool(&qmem->pp, &ns->rq[idx]->napi);
+
+	qmem->rq = nsim_queue_alloc();
+	if (!qmem->rq)
+		return -ENOMEM;
+
+	err = nsim_create_page_pool(&qmem->rq->page_pool, &qmem->rq->napi);
+	if (err)
+		goto err_free;
+
+	if (!ns->rq_reset_mode)
+		netif_napi_add_config(dev, &qmem->rq->napi, nsim_poll, idx);
+
+	return 0;
+
+err_free:
+	nsim_queue_free(qmem->rq);
+	return err;
+}
+
+static void nsim_queue_mem_free(struct net_device *dev, void *per_queue_mem)
+{
+	struct nsim_queue_mem *qmem = per_queue_mem;
+	struct netdevsim *ns = netdev_priv(dev);
+
+	page_pool_destroy(qmem->pp);
+	if (qmem->rq) {
+		if (!ns->rq_reset_mode)
+			netif_napi_del(&qmem->rq->napi);
+		page_pool_destroy(qmem->rq->page_pool);
+		nsim_queue_free(qmem->rq);
+	}
+}
+
+static int
+nsim_queue_start(struct net_device *dev, void *per_queue_mem, int idx)
+{
+	struct nsim_queue_mem *qmem = per_queue_mem;
+	struct netdevsim *ns = netdev_priv(dev);
+
+	if (ns->rq_reset_mode == 1) {
+		ns->rq[idx]->page_pool = qmem->pp;
+		napi_enable(&ns->rq[idx]->napi);
+		return 0;
+	}
+
+	/* netif_napi_add()/_del() should normally be called from alloc/free,
+	 * here we want to test various call orders.
+	 */
+	if (ns->rq_reset_mode == 2) {
+		netif_napi_del(&ns->rq[idx]->napi);
+		netif_napi_add_config(dev, &qmem->rq->napi, nsim_poll, idx);
+	} else if (ns->rq_reset_mode == 3) {
+		netif_napi_add_config(dev, &qmem->rq->napi, nsim_poll, idx);
+		netif_napi_del(&ns->rq[idx]->napi);
+	}
+
+	ns->rq[idx] = qmem->rq;
+	napi_enable(&ns->rq[idx]->napi);
+
+	return 0;
+}
+
+static int nsim_queue_stop(struct net_device *dev, void *per_queue_mem, int idx)
+{
+	struct nsim_queue_mem *qmem = per_queue_mem;
+	struct netdevsim *ns = netdev_priv(dev);
+
+	napi_disable(&ns->rq[idx]->napi);
+
+	if (ns->rq_reset_mode == 1) {
+		qmem->pp = ns->rq[idx]->page_pool;
+		page_pool_disable_direct_recycling(qmem->pp);
+	} else {
+		qmem->rq = ns->rq[idx];
+	}
+
+	return 0;
+}
+
+static const struct netdev_queue_mgmt_ops nsim_queue_mgmt_ops = {
+	.ndo_queue_mem_size	= sizeof(struct nsim_queue_mem),
+	.ndo_queue_mem_alloc	= nsim_queue_mem_alloc,
+	.ndo_queue_mem_free	= nsim_queue_mem_free,
+	.ndo_queue_start	= nsim_queue_start,
+	.ndo_queue_stop		= nsim_queue_stop,
+};
+
+static ssize_t
+nsim_qreset_write(struct file *file, const char __user *data,
+		  size_t count, loff_t *ppos)
+{
+	struct netdevsim *ns = file->private_data;
+	unsigned int queue, mode;
+	char buf[32];
+	ssize_t ret;
+
+	if (count >= sizeof(buf))
+		return -EINVAL;
+	if (copy_from_user(buf, data, count))
+		return -EFAULT;
+	buf[count] = '\0';
+
+	ret = sscanf(buf, "%u %u", &queue, &mode);
+	if (ret != 2)
+		return -EINVAL;
+
+	rtnl_lock();
+	if (!netif_running(ns->netdev)) {
+		ret = -ENETDOWN;
+		goto exit_unlock;
+	}
+
+	if (queue >= ns->netdev->real_num_rx_queues) {
+		ret = -EINVAL;
+		goto exit_unlock;
+	}
+
+	ns->rq_reset_mode = mode;
+	ret = netdev_rx_queue_restart(ns->netdev, queue);
+	ns->rq_reset_mode = 0;
+	if (ret)
+		goto exit_unlock;
+
+	ret = count;
+exit_unlock:
+	rtnl_unlock();
+	return ret;
+}
+
+static const struct file_operations nsim_qreset_fops = {
+	.open = simple_open,
+	.write = nsim_qreset_write,
+	.owner = THIS_MODULE,
+};
+
 static ssize_t
 nsim_pp_hold_read(struct file *file, char __user *data,
 		  size_t count, loff_t *ppos)
@@ -628,7 +806,7 @@ nsim_pp_hold_write(struct file *file, const char __user *data,
 	if (!netif_running(ns->netdev) && val) {
 		ret = -ENETDOWN;
 	} else if (val) {
-		ns->page = page_pool_dev_alloc_pages(ns->rq[0].page_pool);
+		ns->page = page_pool_dev_alloc_pages(ns->rq[0]->page_pool);
 		if (!ns->page)
 			ret = -ENOMEM;
 	} else {
@@ -677,27 +855,35 @@ static int nsim_queue_init(struct netdevsim *ns)
 	struct net_device *dev = ns->netdev;
 	int i;
 
-	ns->rq = kvcalloc(dev->num_rx_queues, sizeof(*ns->rq),
-			  GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL);
+	ns->rq = kcalloc(dev->num_rx_queues, sizeof(*ns->rq),
+			 GFP_KERNEL_ACCOUNT);
 	if (!ns->rq)
 		return -ENOMEM;
 
-	for (i = 0; i < dev->num_rx_queues; i++)
-		skb_queue_head_init(&ns->rq[i].skb_queue);
+	for (i = 0; i < dev->num_rx_queues; i++) {
+		ns->rq[i] = nsim_queue_alloc();
+		if (!ns->rq[i])
+			goto err_free_prev;
+	}
 
 	return 0;
+
+err_free_prev:
+	while (i--)
+		kfree(ns->rq[i]);
+	kfree(ns->rq);
+	return -ENOMEM;
 }
 
-static void nsim_queue_free(struct netdevsim *ns)
+static void nsim_queue_uninit(struct netdevsim *ns)
 {
 	struct net_device *dev = ns->netdev;
 	int i;
 
 	for (i = 0; i < dev->num_rx_queues; i++)
-		skb_queue_purge_reason(&ns->rq[i].skb_queue,
-				       SKB_DROP_REASON_QUEUE_PURGE);
+		nsim_queue_free(ns->rq[i]);
 
-	kvfree(ns->rq);
+	kfree(ns->rq);
 	ns->rq = NULL;
 }
 
@@ -713,6 +899,7 @@ static int nsim_init_netdevsim(struct netdevsim *ns)
 	ns->phc = phc;
 	ns->netdev->netdev_ops = &nsim_netdev_ops;
 	ns->netdev->stat_ops = &nsim_stat_ops;
+	ns->netdev->queue_mgmt_ops = &nsim_queue_mgmt_ops;
 
 	err = nsim_udp_tunnels_info_create(ns->nsim_dev, ns->netdev);
 	if (err)
@@ -741,7 +928,7 @@ static int nsim_init_netdevsim(struct netdevsim *ns)
 	nsim_macsec_teardown(ns);
 	nsim_bpf_uninit(ns);
 err_rq_destroy:
-	nsim_queue_free(ns);
+	nsim_queue_uninit(ns);
 err_utn_destroy:
 	rtnl_unlock();
 	nsim_udp_tunnels_info_destroy(ns->netdev);
@@ -798,6 +985,9 @@ nsim_create(struct nsim_dev *nsim_dev, struct nsim_dev_port *nsim_dev_port)
 
 	ns->pp_dfs = debugfs_create_file("pp_hold", 0600, nsim_dev_port->ddir,
 					 ns, &nsim_pp_hold_fops);
+	ns->qr_dfs = debugfs_create_file("queue_reset", 0200,
+					 nsim_dev_port->ddir, ns,
+					 &nsim_qreset_fops);
 
 	return ns;
 
@@ -811,6 +1001,7 @@ void nsim_destroy(struct netdevsim *ns)
 	struct net_device *dev = ns->netdev;
 	struct netdevsim *peer;
 
+	debugfs_remove(ns->qr_dfs);
 	debugfs_remove(ns->pp_dfs);
 
 	rtnl_lock();
@@ -823,7 +1014,7 @@ void nsim_destroy(struct netdevsim *ns)
 		nsim_macsec_teardown(ns);
 		nsim_ipsec_teardown(ns);
 		nsim_bpf_uninit(ns);
-		nsim_queue_free(ns);
+		nsim_queue_uninit(ns);
 	}
 	rtnl_unlock();
 	if (nsim_dev_port_is_pf(ns->nsim_dev_port))

drivers/net/netdevsim/netdevsim.h

@@ -101,7 +101,9 @@ struct netdevsim {
 	struct nsim_dev *nsim_dev;
 	struct nsim_dev_port *nsim_dev_port;
 	struct mock_phc *phc;
-	struct nsim_rq *rq;
+	struct nsim_rq **rq;
+
+	int rq_reset_mode;
 
 	u64 tx_packets;
 	u64 tx_bytes;
@@ -134,6 +136,7 @@ struct netdevsim {
 
 	struct page *page;
 	struct dentry *pp_dfs;
+	struct dentry *qr_dfs;
 
 	struct nsim_ethtool ethtool;
 	struct netdevsim __rcu *peer;

net/core/dev.c

@@ -6736,13 +6736,14 @@ static void napi_restore_config(struct napi_struct *n)
 	n->gro_flush_timeout = n->config->gro_flush_timeout;
 	n->irq_suspend_timeout = n->config->irq_suspend_timeout;
 	/* a NAPI ID might be stored in the config, if so use it. if not, use
-	 * napi_hash_add to generate one for us. It will be saved to the config
-	 * in napi_disable.
+	 * napi_hash_add to generate one for us.
 	 */
-	if (n->config->napi_id)
+	if (n->config->napi_id) {
 		napi_hash_add_with_id(n, n->config->napi_id);
-	else
+	} else {
 		napi_hash_add(n);
+		n->config->napi_id = n->napi_id;
+	}
 }
 
 static void napi_save_config(struct napi_struct *n)
@@ -6750,10 +6751,39 @@ static void napi_save_config(struct napi_struct *n)
 	n->config->defer_hard_irqs = n->defer_hard_irqs;
 	n->config->gro_flush_timeout = n->gro_flush_timeout;
 	n->config->irq_suspend_timeout = n->irq_suspend_timeout;
-	n->config->napi_id = n->napi_id;
 	napi_hash_del(n);
 }
 
+/* Netlink wants the NAPI list to be sorted by ID, if adding a NAPI which will
+ * inherit an existing ID try to insert it at the right position.
+ */
+static void
+netif_napi_dev_list_add(struct net_device *dev, struct napi_struct *napi)
+{
+	unsigned int new_id, pos_id;
+	struct list_head *higher;
+	struct napi_struct *pos;
+
+	new_id = UINT_MAX;
+	if (napi->config && napi->config->napi_id)
+		new_id = napi->config->napi_id;
+
+	higher = &dev->napi_list;
+	list_for_each_entry(pos, &dev->napi_list, dev_list) {
+		if (pos->napi_id >= MIN_NAPI_ID)
+			pos_id = pos->napi_id;
+		else if (pos->config)
+			pos_id = pos->config->napi_id;
+		else
+			pos_id = UINT_MAX;
+
+		if (pos_id <= new_id)
+			break;
+		higher = &pos->dev_list;
+	}
+	list_add_rcu(&napi->dev_list, higher); /* adds after higher */
+}
+
 void netif_napi_add_weight(struct net_device *dev, struct napi_struct *napi,
 			   int (*poll)(struct napi_struct *, int), int weight)
 {
@@ -6780,7 +6810,7 @@ void netif_napi_add_weight(struct net_device *dev, struct napi_struct *napi,
 	napi->list_owner = -1;
 	set_bit(NAPI_STATE_SCHED, &napi->state);
 	set_bit(NAPI_STATE_NPSVC, &napi->state);
-	list_add_rcu(&napi->dev_list, &dev->napi_list);
+	netif_napi_dev_list_add(dev, napi);
 
 	/* default settings from sysfs are applied to all NAPIs. any per-NAPI
 	 * configuration will be loaded in napi_enable

net/core/netdev_rx_queue.c

@@ -79,3 +79,4 @@ int netdev_rx_queue_restart(struct net_device *dev, unsigned int rxq_idx)
 
 	return err;
 }
+EXPORT_SYMBOL_NS_GPL(netdev_rx_queue_restart, "NETDEV_INTERNAL");

tools/testing/selftests/net/nl_netdev.py

@@ -18,6 +18,23 @@ def lo_check(nf) -> None:
     ksft_eq(len(lo_info['xdp-rx-metadata-features']), 0)
 
 
+def napi_list_check(nf) -> None:
+    with NetdevSimDev(queue_count=100) as nsimdev:
+        nsim = nsimdev.nsims[0]
+
+        ip(f"link set dev {nsim.ifname} up")
+
+        napis = nf.napi_get({'ifindex': nsim.ifindex}, dump=True)
+        ksft_eq(len(napis), 100)
+
+        for q in [50, 0, 99]:
+            for i in range(4):
+                nsim.dfs_write("queue_reset", f"{q} {i}")
+                napis = nf.napi_get({'ifindex': nsim.ifindex}, dump=True)
+                ksft_eq(len(napis), 100,
+                        comment=f"queue count after reset queue {q} mode {i}")
+
+
 def page_pool_check(nf) -> None:
     with NetdevSimDev() as nsimdev:
         nsim = nsimdev.nsims[0]
@@ -89,7 +106,7 @@ def page_pool_check(nf) -> None:
 
 def main() -> None:
     nf = NetdevFamily()
-    ksft_run([empty_check, lo_check, page_pool_check],
+    ksft_run([empty_check, lo_check, page_pool_check, napi_list_check],
              args=(nf, ))
     ksft_exit()