netdev - Re: [PATCH net-next v5] net: psample: Introduce stubs to remove NIC driver dependency

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Date:   Sat, 30 Jan 2021 16:52:27 +0200
From:   Ido Schimmel <idosch@...sch.org>
To:     Chris Mi <cmi@...dia.com>
Cc:     netdev@...r.kernel.org, kuba@...nel.org, jiri@...dia.com,
        saeedm@...dia.com, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH net-next v5] net: psample: Introduce stubs to remove NIC
 driver dependency

On Sat, Jan 30, 2021 at 10:33:19AM +0800, Chris Mi wrote:
> In order to send sampled packets to userspace, NIC driver calls
> psample api directly. But it creates a hard dependency on module
> psample. Introduce psample_ops to remove the hard dependency.
> It is initialized when psample module is loaded and set to NULL
> when the module is unloaded.
> 
> Reported-by: kernel test robot <lkp@...el.com>

This belongs in the changelog (that should be part of the commit
message). Something like "Fix xxx reported by kernel test robot".

> Signed-off-by: Chris Mi <cmi@...dia.com>
> Reviewed-by: Jiri Pirko <jiri@...dia.com>
> ---
> v1->v2:
>  - fix sparse errors
> v2->v3:
>  - remove inline
> v3->v4:
>  - add inline back
> v4->v5:
>  - address Jakub's comments
> 
>  include/net/psample.h    | 26 ++++++++++++++++++++++++++
>  net/psample/psample.c    | 14 +++++++++++++-
>  net/sched/Makefile       |  2 +-
>  net/sched/psample_stub.c |  5 +++++
>  4 files changed, 45 insertions(+), 2 deletions(-)
>  create mode 100644 net/sched/psample_stub.c
> 
> diff --git a/include/net/psample.h b/include/net/psample.h
> index 68ae16bb0a4a..d0f1cfc56f6f 100644
> --- a/include/net/psample.h
> +++ b/include/net/psample.h
> @@ -14,6 +14,15 @@ struct psample_group {
>  	struct rcu_head rcu;
>  };
>  
> +struct psample_ops {
> +	void (*sample_packet)(struct psample_group *group, struct sk_buff *skb,
> +			      u32 trunc_size, int in_ifindex, int out_ifindex,
> +			      u32 sample_rate);
> +
> +};
> +
> +extern const struct psample_ops __rcu *psample_ops __read_mostly;
> +
>  struct psample_group *psample_group_get(struct net *net, u32 group_num);
>  void psample_group_take(struct psample_group *group);
>  void psample_group_put(struct psample_group *group);
> @@ -35,4 +44,21 @@ static inline void psample_sample_packet(struct psample_group *group,
>  
>  #endif
>  
> +static inline void
> +psample_nic_sample_packet(struct psample_group *group,
> +			  struct sk_buff *skb, u32 trunc_size,
> +			  int in_ifindex, int out_ifindex,
> +			  u32 sample_rate)
> +{
> +	const struct psample_ops *ops;
> +
> +	rcu_read_lock();
> +	ops = rcu_dereference(psample_ops);
> +	if (ops)
> +		ops->sample_packet(group, skb, trunc_size,
> +				   in_ifindex, out_ifindex,
> +				   sample_rate);
> +	rcu_read_unlock();
> +}
> +
>  #endif /* __NET_PSAMPLE_H */
> diff --git a/net/psample/psample.c b/net/psample/psample.c
> index 33e238c965bd..983ca5b698fe 100644
> --- a/net/psample/psample.c
> +++ b/net/psample/psample.c
> @@ -8,6 +8,7 @@
>  #include <linux/kernel.h>
>  #include <linux/skbuff.h>
>  #include <linux/module.h>
> +#include <linux/rcupdate.h>
>  #include <net/net_namespace.h>
>  #include <net/sock.h>
>  #include <net/netlink.h>
> @@ -35,6 +36,10 @@ static const struct genl_multicast_group psample_nl_mcgrps[] = {
>  
>  static struct genl_family psample_nl_family __ro_after_init;
>  
> +static const struct psample_ops psample_sample_ops = {
> +	.sample_packet	= psample_sample_packet,
> +};
> +
>  static int psample_group_nl_fill(struct sk_buff *msg,
>  				 struct psample_group *group,
>  				 enum psample_command cmd, u32 portid, u32 seq,
> @@ -456,11 +461,18 @@ EXPORT_SYMBOL_GPL(psample_sample_packet);
>  
>  static int __init psample_module_init(void)
>  {
> -	return genl_register_family(&psample_nl_family);
> +	int ret;
> +
> +	ret = genl_register_family(&psample_nl_family);
> +	if (!ret)
> +		RCU_INIT_POINTER(psample_ops, &psample_sample_ops);
> +	return ret;
>  }
>  
>  static void __exit psample_module_exit(void)
>  {
> +	rcu_assign_pointer(psample_ops, NULL);
> +	synchronize_rcu();
>  	genl_unregister_family(&psample_nl_family);
>  }
>  
> diff --git a/net/sched/Makefile b/net/sched/Makefile
> index dd14ef413fda..0d92bb98bb26 100644
> --- a/net/sched/Makefile
> +++ b/net/sched/Makefile
> @@ -3,7 +3,7 @@
>  # Makefile for the Linux Traffic Control Unit.
>  #
>  
> -obj-y	:= sch_generic.o sch_mq.o
> +obj-y	:= sch_generic.o sch_mq.o psample_stub.o

Why the stub is under net/sched/ when psample is at net/psample/?
psample is not the same as 'act_sample'.

>  
>  obj-$(CONFIG_INET)		+= sch_frag.o
>  obj-$(CONFIG_NET_SCHED)		+= sch_api.o sch_blackhole.o
> diff --git a/net/sched/psample_stub.c b/net/sched/psample_stub.c
> new file mode 100644
> index 000000000000..0541b8c5100d
> --- /dev/null
> +++ b/net/sched/psample_stub.c
> @@ -0,0 +1,5 @@
> +// SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB

psample has "// SPDX-License-Identifier: GPL-2.0-only"

> +/* Copyright (c) 2021 Mellanox Technologies. */
> +
> +const struct psample_ops __rcu *psample_ops __read_mostly;
> +EXPORT_SYMBOL_GPL(psample_ops);
> -- 
> 2.26.2
>