netdev - Re: [Patch bpf-next v6 02/12] skmsg: introduce a spinlock to protect ingress

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Message-ID: <93f9be88-2803-93cd-df6b-43f494c0f67d@huawei.com>
Date:   Tue, 23 Mar 2021 09:24:58 +0800
From:   Yunsheng Lin <linyunsheng@...wei.com>
To:     Cong Wang <xiyou.wangcong@...il.com>, <netdev@...r.kernel.org>
CC:     <bpf@...r.kernel.org>, <duanxiongchun@...edance.com>,
        <wangdongdong.6@...edance.com>, <jiang.wang@...edance.com>,
        Cong Wang <cong.wang@...edance.com>,
        John Fastabend <john.fastabend@...il.com>,
        "Daniel Borkmann" <daniel@...earbox.net>,
        Lorenz Bauer <lmb@...udflare.com>,
        "Jakub Sitnicki" <jakub@...udflare.com>
Subject: Re: [Patch bpf-next v6 02/12] skmsg: introduce a spinlock to protect
 ingress_msg

On 2021/3/23 8:37, Cong Wang wrote:
> From: Cong Wang <cong.wang@...edance.com>
> 
> Currently we rely on lock_sock to protect ingress_msg,
> it is too big for this, we can actually just use a spinlock
> to protect this list like protecting other skb queues.
> 
> __tcp_bpf_recvmsg() is still special because of peeking,
> it still has to use lock_sock.
> 
> Cc: John Fastabend <john.fastabend@...il.com>
> Cc: Daniel Borkmann <daniel@...earbox.net>
> Cc: Lorenz Bauer <lmb@...udflare.com>
> Acked-by: Jakub Sitnicki <jakub@...udflare.com>
> Signed-off-by: Cong Wang <cong.wang@...edance.com>
> ---
>  include/linux/skmsg.h | 46 +++++++++++++++++++++++++++++++++++++++++++
>  net/core/skmsg.c      |  3 +++
>  net/ipv4/tcp_bpf.c    | 18 ++++++-----------
>  3 files changed, 55 insertions(+), 12 deletions(-)
> 
> diff --git a/include/linux/skmsg.h b/include/linux/skmsg.h
> index 6c09d94be2e9..f2d45a73b2b2 100644
> --- a/include/linux/skmsg.h
> +++ b/include/linux/skmsg.h
> @@ -89,6 +89,7 @@ struct sk_psock {
>  #endif
>  	struct sk_buff_head		ingress_skb;
>  	struct list_head		ingress_msg;
> +	spinlock_t			ingress_lock;
>  	unsigned long			state;
>  	struct list_head		link;
>  	spinlock_t			link_lock;
> @@ -284,7 +285,45 @@ static inline struct sk_psock *sk_psock(const struct sock *sk)
>  static inline void sk_psock_queue_msg(struct sk_psock *psock,
>  				      struct sk_msg *msg)
>  {
> +	spin_lock_bh(&psock->ingress_lock);
>  	list_add_tail(&msg->list, &psock->ingress_msg);
> +	spin_unlock_bh(&psock->ingress_lock);
> +}
> +
> +static inline struct sk_msg *sk_psock_dequeue_msg(struct sk_psock *psock)
> +{
> +	struct sk_msg *msg;
> +
> +	spin_lock_bh(&psock->ingress_lock);
> +	msg = list_first_entry_or_null(&psock->ingress_msg, struct sk_msg, list);
> +	if (msg)
> +		list_del(&msg->list);
> +	spin_unlock_bh(&psock->ingress_lock);
> +	return msg;
> +}
> +
> +static inline struct sk_msg *sk_psock_peek_msg(struct sk_psock *psock)
> +{
> +	struct sk_msg *msg;
> +
> +	spin_lock_bh(&psock->ingress_lock);
> +	msg = list_first_entry_or_null(&psock->ingress_msg, struct sk_msg, list);
> +	spin_unlock_bh(&psock->ingress_lock);
> +	return msg;
> +}
> +
> +static inline struct sk_msg *sk_psock_next_msg(struct sk_psock *psock,
> +					       struct sk_msg *msg)
> +{
> +	struct sk_msg *ret;

Nit:
Use msg instead of ret to be consistently with sk_psock_dequeue_msg()
and sk_psock_next_msg().

> +
> +	spin_lock_bh(&psock->ingress_lock);
> +	if (list_is_last(&msg->list, &psock->ingress_msg))
> +		ret = NULL;
> +	else
> +		ret = list_next_entry(msg, list);
> +	spin_unlock_bh(&psock->ingress_lock);
> +	return ret;
>  }