Subject: [PATCH net-next v2 2/8] net: designate XSK pool pointers in queues as "ops protected"

From: Jakub Kicinski <[email-masked]>
Date: Tue, 8 Apr 2025 12:59:49 -0700

Read accesses go via xsk_get_pool_from_qid(), the call coming
from the core and gve look safe (other "ops locked" drivers
don't support XSK).

Write accesses go via xsk_reg_pool_at_qid() and xsk_clear_pool_at_qid().
Former is already under the ops lock, latter is not (both coming from
the workqueue via xp_clear_dev() and NETDEV_UNREGISTER via xsk_notifier()).

Acked-by: Stanislav Fomichev <[email-masked]>
Signed-off-by: Jakub Kicinski <[email-masked]>
Signed-off-by: Stanislav Fomichev <[email-masked]>
---
v2:
 - move the locking to xp_clear_dev()
v1: https://lore.kernel.org/[email-masked]
---
 include/linux/netdevice.h     | 1 +
 include/net/netdev_rx_queue.h | 6 +++---
 net/xdp/xsk_buff_pool.c       | 6 +++++-
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 8e9be80bc167..7242fb8a22fc 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -688,6 +688,7 @@ struct netdev_queue {
 	/* Subordinate device that the queue has been assigned to */
 	struct net_device	*sb_dev;
 #ifdef CONFIG_XDP_SOCKETS
+	/* "ops protected", see comment about net_device::lock */
 	struct xsk_buff_pool    *pool;
 #endif
 
diff --git a/include/net/netdev_rx_queue.h b/include/net/netdev_rx_queue.h
index b2238b551dce..8cdcd138b33f 100644
--- a/include/net/netdev_rx_queue.h
+++ b/include/net/netdev_rx_queue.h
@@ -20,12 +20,12 @@ struct netdev_rx_queue {
 	struct net_device		*dev;
 	netdevice_tracker		dev_tracker;
 
+	/* All fields below are "ops protected",
+	 * see comment about net_device::lock
+	 */
 #ifdef CONFIG_XDP_SOCKETS
 	struct xsk_buff_pool            *pool;
 #endif
-	/* NAPI instance for the queue
-	 * "ops protected", see comment about net_device::lock
-	 */
 	struct napi_struct		*napi;
 	struct pp_memory_provider_params mp_params;
 } ____cacheline_aligned_in_smp;
diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
index 25a76c5ce0f1..cbf2129e808b 100644
--- a/net/xdp/xsk_buff_pool.c
+++ b/net/xdp/xsk_buff_pool.c
@@ -266,13 +266,17 @@ int xp_assign_dev_shared(struct xsk_buff_pool *pool, struct xdp_sock *umem_xs,
 
 void xp_clear_dev(struct xsk_buff_pool *pool)
 {
+	struct net_device *netdev = pool->netdev;
+
 	if (!pool->netdev)
 		return;
 
+	netdev_lock_ops(netdev);
 	xp_disable_drv_zc(pool);
 	xsk_clear_pool_at_qid(pool->netdev, pool->queue_id);
-	dev_put(pool->netdev);
 	pool->netdev = NULL;
+	netdev_unlock_ops(netdev);
+	dev_put(netdev);
 }
 
 static void xp_release_deferred(struct work_struct *work)
-- 
2.49.0