Re: [PATCH] net: convert netdev_nl_sock bindings list to xarray

[Shivaji Kant]

On Mon, Aug 10, 2026 at 12:48 PM Nikolay Aleksandrov
<razor@xxxxxxxxxxxxx> wrote:
>
> On 10/08/2026 09:57, Shivaji Kant wrote:
> > netdev_nl_sock previously used a struct list_head bindings to keep
> > track of active netdev netlink bindings, protected by a per-socket
> > struct mutex lock (priv->lock).
> >
> > Since list modifications and iterations are not concurrency-safe,
> > priv->lock was introduced to serialize operations on priv->bindings.
> > However, xarray manages its own internal locking (xa_lock) for store,
> > erase, and iteration operations.
> >
> > Convert bindings in struct netdev_nl_sock from struct list_head to
> > struct xarray and remove priv->lock. This simplifies the code by
> > removing explicit mutex locking in netdev_nl_bind_rx_doit(),
> > netdev_nl_bind_tx_doit(), and socket initialization/teardown functions.
> >
> > Reviewed-by: Mina Almasry <almasrymina@xxxxxxxxxx>
> > Signed-off-by: Shivaji Kant <shivajikant@xxxxxxxxxx>
> > ---
> >   include/net/netdev_netlink.h |  5 ++---
> >   net/core/devmem.c            | 13 ++++++++++---
> >   net/core/devmem.h            |  4 ++--
> >   net/core/netdev-genl.c       | 25 ++++++-------------------
> >   4 files changed, 20 insertions(+), 27 deletions(-)
> >
>
> This patch should target net-next.

Ack, I will correct this in v2.


>
> > diff --git a/include/net/netdev_netlink.h b/include/net/netdev_netlink.h
> > index 075962dbe743..45a4a482d42e 100644
> > --- a/include/net/netdev_netlink.h
> > +++ b/include/net/netdev_netlink.h
> > @@ -2,11 +2,10 @@
> >   #ifndef __NET_NETDEV_NETLINK_H
> >   #define __NET_NETDEV_NETLINK_H
> >
> > -#include <linux/list.h>
> > +#include <linux/xarray.h>
> >
> >   struct netdev_nl_sock {
> > -     struct mutex lock;
> > -     struct list_head bindings;
> > +     struct xarray bindings;
> >   };
> >
> >   #endif      /* __NET_NETDEV_NETLINK_H */
> > diff --git a/net/core/devmem.c b/net/core/devmem.c
> > index 957d6b96216b..52fda18b80ef 100644
> > --- a/net/core/devmem.c
> > +++ b/net/core/devmem.c
> > @@ -134,8 +134,8 @@ void net_devmem_unbind_dmabuf(struct net_devmem_dmabuf_binding *binding)
> >        */
> >       synchronize_net();
> >
> > -     if (binding->list.next)
> > -             list_del(&binding->list);
> > +     if (binding->sock_priv)
> > +             xa_erase(&binding->sock_priv->bindings, binding->id);
> >
> >       xa_for_each(&binding->bound_rxqs, xa_idx, rxq) {
> >               const struct pp_memory_provider_params mp_params = {
> > @@ -193,6 +193,7 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
> >       struct dma_buf *dmabuf;
> >       unsigned int sg_idx, i;
> >       unsigned long virtual;
> > +     void *res;
> >       int err;
> >
> >       if (!dma_dev) {
> > @@ -325,7 +326,13 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
> >       if (err < 0)
> >               goto err_free_chunks;
> >
> > -     list_add(&binding->list, &priv->bindings);
> > +     binding->sock_priv = priv;
> > +     res = xa_store(&priv->bindings, binding->id, binding, GFP_KERNEL);
> > +     if (xa_is_err(res)) {
> > +             err = xa_err(res);
> > +             xa_erase(&net_devmem_dmabuf_bindings, binding->id);
> > +             goto err_free_chunks;
>
> This error cleans up after the previous xa_alloc_cyclic call itself instead
> of following the style of the rest of the error cleanups. I'd move the xa_erase()
> into its own err_ label and goto there.

Ack, will follow this consistent style.

>
> > +     }
> >
> >       return binding;
> >
> > diff --git a/net/core/devmem.h b/net/core/devmem.h
> > index 3852a56036cb..bf77e5a9a8fe 100644
> > --- a/net/core/devmem.h
> > +++ b/net/core/devmem.h
> > @@ -49,10 +49,10 @@ struct net_devmem_dmabuf_binding {
> >        */
> >       struct percpu_ref ref;
> >
> > -     /* The list of bindings currently active. Used for netlink to notify us
> > +     /* The socket priv this binding belongs to. Used for netlink to notify us
> >        * of the user dropping the bind.
> >        */
> > -     struct list_head list;
> > +     struct netdev_nl_sock *sock_priv;
> >
> >       /* rxq's this binding is active on. */
> >       struct xarray bound_rxqs;
> > diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
> > index c15d8d4ca1f8..d3f3a91a6d93 100644
> > --- a/net/core/netdev-genl.c
> > +++ b/net/core/netdev-genl.c
> > @@ -1044,13 +1044,11 @@ int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info)
> >               goto err_genlmsg_free;
> >       }
> >
> > -     mutex_lock(&priv->lock);
> > -
> >       err = 0;
> >       netdev = netdev_get_by_index_lock(genl_info_net(info), ifindex);
> >       if (!netdev) {
> >               err = -ENODEV;
> > -             goto err_unlock_sock;
> > +             goto err_genlmsg_free;
> >       }
> >       if (!netif_device_present(netdev))
> >               err = -ENODEV;
> > @@ -1102,8 +1100,6 @@ int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info)
> >
> >       netdev_unlock(netdev);
> >
> > -     mutex_unlock(&priv->lock);
> > -
> >       return err < 0 ? err : 0;
> >
> >   err_unbind:
> > @@ -1112,8 +1108,6 @@ int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info)
> >       bitmap_free(rxq_bitmap);
> >   err_unlock:
> >       netdev_unlock(netdev);
> > -err_unlock_sock:
> > -     mutex_unlock(&priv->lock);
> >   err_genlmsg_free:
> >       nlmsg_free(rsp);
> >       return err;
> > @@ -1185,12 +1179,10 @@ int netdev_nl_bind_tx_doit(struct sk_buff *skb, struct genl_info *info)
> >               goto err_genlmsg_free;
> >       }
> >
> > -     mutex_lock(&priv->lock);
> > -
> >       netdev = netdev_get_by_index_lock(genl_info_net(info), ifindex);
> >       if (!netdev) {
> >               err = -ENODEV;
> > -             goto err_unlock_sock;
> > +             goto err_genlmsg_free;
> >       }
> >
> >       if (!netif_device_present(netdev)) {
> > @@ -1233,7 +1225,6 @@ int netdev_nl_bind_tx_doit(struct sk_buff *skb, struct genl_info *info)
> >       if (bind_dev != netdev)
> >               netdev_unlock(bind_dev);
> >       netdev_unlock(netdev);
> > -     mutex_unlock(&priv->lock);
> >
> >       return genlmsg_reply(rsp, info);
> >
> > @@ -1242,8 +1233,6 @@ int netdev_nl_bind_tx_doit(struct sk_buff *skb, struct genl_info *info)
> >               netdev_unlock(bind_dev);
> >   err_unlock_netdev:
> >       netdev_unlock(netdev);
> > -err_unlock_sock:
> > -     mutex_unlock(&priv->lock);
> >   err_genlmsg_free:
> >       nlmsg_free(rsp);
> >       return err;
> > @@ -1418,19 +1407,17 @@ int netdev_nl_queue_create_doit(struct sk_buff *skb, struct genl_info *info)
> >
> >   void netdev_nl_sock_priv_init(struct netdev_nl_sock *priv)
> >   {
> > -     INIT_LIST_HEAD(&priv->bindings);
> > -     mutex_init(&priv->lock);
> > +     xa_init(&priv->bindings);
> >   }
> >
> >   void netdev_nl_sock_priv_destroy(struct netdev_nl_sock *priv)
> >   {
> >       struct net_devmem_dmabuf_binding *binding;
> > -     struct net_devmem_dmabuf_binding *temp;
> >       netdevice_tracker dev_tracker;
> >       struct net_device *dev;
> > +     unsigned long xa_idx;
> >
> > -     mutex_lock(&priv->lock);
> > -     list_for_each_entry_safe(binding, temp, &priv->bindings, list) {
> > +     xa_for_each(&priv->bindings, xa_idx, binding) {
> >               mutex_lock(&binding->lock);
> >               dev = binding->dev;
> >               if (!dev) {
> > @@ -1446,7 +1433,7 @@ void netdev_nl_sock_priv_destroy(struct netdev_nl_sock *priv)
> >               netdev_unlock(dev);
> >               netdev_put(dev, &dev_tracker);
> >       }
> > -     mutex_unlock(&priv->lock);
> > +     xa_destroy(&priv->bindings);
> >   }
> >
> >   static int netdev_genl_netdevice_event(struct notifier_block *nb,
>