linux-kernel - Re: [PATCH net-next v2 1/2] net: mana: introduce helper to get a master netdev

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Message-ID: <5b418472-4370-4626-9373-064e7aaf9ae5@linux.dev>
Date: Tue, 2 Jul 2024 04:14:07 +0800
From: Zhu Yanjun <yanjun.zhu@...ux.dev>
To: Konstantin Taranov <kotaranov@...ux.microsoft.com>,
 kotaranov@...rosoft.com, pabeni@...hat.com, haiyangz@...rosoft.com,
 kys@...rosoft.com, edumazet@...gle.com, kuba@...nel.org,
 davem@...emloft.net, decui@...rosoft.com, wei.liu@...nel.org,
 sharmaajay@...rosoft.com, longli@...rosoft.com, jgg@...pe.ca, leon@...nel.org
Cc: linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
 netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2 1/2] net: mana: introduce helper to get a
 master netdev

在 2024/7/1 20:58, Konstantin Taranov 写道:
> From: Konstantin Taranov <kotaranov@...rosoft.com>
> 
> Add helper to get a master netdevice for a given port.
> When mana is used with netvsc, the VF netdev is controlled
> by an upper netvsc device. In a baremetal case, the VF
> netdev is the master device.
> 
> Signed-off-by: Konstantin Taranov <kotaranov@...rosoft.com>
> ---
>   drivers/net/ethernet/microsoft/mana/mana_en.c | 18 ++++++++++++++++++
>   include/net/mana/mana.h                       |  2 ++
>   2 files changed, 20 insertions(+)
> 
> diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
> index d087cf9..b893339 100644
> --- a/drivers/net/ethernet/microsoft/mana/mana_en.c
> +++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
> @@ -2948,3 +2948,21 @@ out:
>   	gd->gdma_context = NULL;
>   	kfree(ac);
>   }
> +
> +/* the caller should hold rcu_read_lock */
> +struct net_device *mana_get_master_netdev_rcu(struct mana_context *ac, u32 port_index)
> +{
> +	struct net_device *ndev;

 From the comments, this function requires rcu_read_lock. Can the 
following be added in this function?

RCU_LOCKDEP_WARN(!rcu_read_lock_held(), "no rcu read lock held");

If rcu_read_lock is not held, this function will notify the caller.
This can explicitly ensure that rcu_read_lock should be held before this 
fuction is called.

Best Regards,

Zhu Yanjun

> +
> +	if (port_index >= ac->num_ports)
> +		return NULL;
> +
> +	/* When mana is used in netvsc, the upper netdevice should be returned. */
> +	if (ac->ports[port_index]->flags & IFF_SLAVE)
> +		ndev = netdev_master_upper_dev_get_rcu(ac->ports[port_index]);
> +	else
> +		ndev = ac->ports[port_index];
> +
> +	return ndev;
> +}
> +EXPORT_SYMBOL_NS(mana_get_master_netdev_rcu, NET_MANA);
> diff --git a/include/net/mana/mana.h b/include/net/mana/mana.h
> index 46f741e..2d3625c 100644
> --- a/include/net/mana/mana.h
> +++ b/include/net/mana/mana.h
> @@ -797,4 +797,6 @@ void mana_destroy_wq_obj(struct mana_port_context *apc, u32 wq_type,
>   int mana_cfg_vport(struct mana_port_context *apc, u32 protection_dom_id,
>   		   u32 doorbell_pg_id);
>   void mana_uncfg_vport(struct mana_port_context *apc);
> +
> +struct net_device *mana_get_master_netdev_rcu(struct mana_context *ac, u32 port_index);
>   #endif /* _MANA_H */