netdev - Re: [PATCH net-next v3 10/23] net: move netdev_config manipulation to dedicated helpers

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Message-ID: <CAHS8izPWODE0sdVe0KTT69Wm8-LJLnXGjNFi+j77PrVGzK1FgQ@mail.gmail.com>
Date: Tue, 19 Aug 2025 13:15:37 -0700
From: Mina Almasry <almasrymina@...gle.com>
To: Pavel Begunkov <asml.silence@...il.com>
Cc: Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org, 
	Eric Dumazet <edumazet@...gle.com>, Willem de Bruijn <willemb@...gle.com>, 
	Paolo Abeni <pabeni@...hat.com>, andrew+netdev@...n.ch, horms@...nel.org, 
	davem@...emloft.net, sdf@...ichev.me, dw@...idwei.uk, 
	michael.chan@...adcom.com, dtatulea@...dia.com, ap420073@...il.com, 
	linux-kernel@...r.kernel.org, io-uring@...r.kernel.org
Subject: Re: [PATCH net-next v3 10/23] net: move netdev_config manipulation to
 dedicated helpers

On Mon, Aug 18, 2025 at 6:56 AM Pavel Begunkov <asml.silence@...il.com> wrote:
>
> From: Jakub Kicinski <kuba@...nel.org>
>
> netdev_config manipulation will become slightly more complicated
> soon and we will need to call if from ethtool as well as queue API.
> Encapsulate the logic into helper functions.
>
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
> ---
>  net/core/Makefile        |  2 +-
>  net/core/dev.c           |  7 ++-----
>  net/core/dev.h           |  5 +++++
>  net/core/netdev_config.c | 43 ++++++++++++++++++++++++++++++++++++++++
>  net/ethtool/netlink.c    | 14 ++++++-------
>  5 files changed, 57 insertions(+), 14 deletions(-)
>  create mode 100644 net/core/netdev_config.c
>
> diff --git a/net/core/Makefile b/net/core/Makefile
> index b2a76ce33932..4db487396094 100644
> --- a/net/core/Makefile
> +++ b/net/core/Makefile
> @@ -19,7 +19,7 @@ obj-$(CONFIG_NETDEV_ADDR_LIST_TEST) += dev_addr_lists_test.o
>
>  obj-y += net-sysfs.o
>  obj-y += hotdata.o
> -obj-y += netdev_rx_queue.o
> +obj-y += netdev_config.o netdev_rx_queue.o
>  obj-$(CONFIG_PAGE_POOL) += page_pool.o page_pool_user.o
>  obj-$(CONFIG_PROC_FS) += net-procfs.o
>  obj-$(CONFIG_NET_PKTGEN) += pktgen.o
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 5a3c0f40a93f..7cd4e5eab441 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -11873,10 +11873,8 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
>         if (!dev->ethtool)
>                 goto free_all;
>
> -       dev->cfg = kzalloc(sizeof(*dev->cfg), GFP_KERNEL_ACCOUNT);
> -       if (!dev->cfg)
> +       if (netdev_alloc_config(dev))
>                 goto free_all;
> -       dev->cfg_pending = dev->cfg;
>
>         dev->num_napi_configs = maxqs;
>         napi_config_sz = array_size(maxqs, sizeof(*dev->napi_config));
> @@ -11947,8 +11945,7 @@ void free_netdev(struct net_device *dev)
>                 return;
>         }
>
> -       WARN_ON(dev->cfg != dev->cfg_pending);
> -       kfree(dev->cfg);
> +       netdev_free_config(dev);
>         kfree(dev->ethtool);
>         netif_free_tx_queues(dev);
>         netif_free_rx_queues(dev);
> diff --git a/net/core/dev.h b/net/core/dev.h
> index d6b08d435479..7041c8bd2a0f 100644
> --- a/net/core/dev.h
> +++ b/net/core/dev.h
> @@ -92,6 +92,11 @@ extern struct rw_semaphore dev_addr_sem;
>  extern struct list_head net_todo_list;
>  void netdev_run_todo(void);
>
> +int netdev_alloc_config(struct net_device *dev);
> +void __netdev_free_config(struct netdev_config *cfg);
> +void netdev_free_config(struct net_device *dev);
> +int netdev_reconfig_start(struct net_device *dev);
> +
>  /* netdev management, shared between various uAPI entry points */
>  struct netdev_name_node {
>         struct hlist_node hlist;
> diff --git a/net/core/netdev_config.c b/net/core/netdev_config.c
> new file mode 100644
> index 000000000000..270b7f10a192
> --- /dev/null
> +++ b/net/core/netdev_config.c
> @@ -0,0 +1,43 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +#include <linux/netdevice.h>
> +#include <net/netdev_queues.h>
> +
> +#include "dev.h"
> +
> +int netdev_alloc_config(struct net_device *dev)
> +{
> +       struct netdev_config *cfg;
> +
> +       cfg = kzalloc(sizeof(*dev->cfg), GFP_KERNEL_ACCOUNT);
> +       if (!cfg)
> +               return -ENOMEM;
> +
> +       dev->cfg = cfg;
> +       dev->cfg_pending = cfg;
> +       return 0;
> +}
> +
> +void __netdev_free_config(struct netdev_config *cfg)
> +{
> +       kfree(cfg);
> +}
> +
> +void netdev_free_config(struct net_device *dev)
> +{
> +       WARN_ON(dev->cfg != dev->cfg_pending);
> +       __netdev_free_config(dev->cfg);
> +}
> +
> +int netdev_reconfig_start(struct net_device *dev)
> +{
> +       struct netdev_config *cfg;
> +
> +       WARN_ON(dev->cfg != dev->cfg_pending);
> +       cfg = kmemdup(dev->cfg, sizeof(*dev->cfg), GFP_KERNEL_ACCOUNT);
> +       if (!cfg)
> +               return -ENOMEM;
> +
> +       dev->cfg_pending = cfg;
> +       return 0;

There are a couple of small behavior changes in this code. (a) the
WARN_ON is new, and (b) this helper retains dev->cfg_pending on error
while the old code would clear it. But both seem fine to me, so,

Reviewed-by: Mina Almasry <almasrymina@...gle.com>

--
Thanks,
Mina