linux-kernel - Re: [PATCH v3 net-next] udp: introduce __sk_mem

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Date:   Tue, 07 Mar 2023 15:55:20 +0100
From:   Paolo Abeni <pabeni@...hat.com>
To:     Jason Xing <kerneljasonxing@...il.com>, simon.horman@...igine.com,
        willemdebruijn.kernel@...il.com, davem@...emloft.net,
        dsahern@...nel.org, edumazet@...gle.com, kuba@...nel.org
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org, Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH v3 net-next] udp: introduce __sk_mem_schedule() usage

On Tue, 2023-03-07 at 09:56 +0800, Jason Xing wrote:
> From: Jason Xing <kernelxing@...cent.com>
> 
> Keep the accounting schema consistent across different protocols
> with __sk_mem_schedule(). Besides, it adjusts a little bit on how
> to calculate forward allocated memory compared to before. After
> applied this patch, we could avoid receive path scheduling extra
> amount of memory.
> 
> Link: https://lore.kernel.org/lkml/20230221110344.82818-1-kerneljasonxing@gmail.com/
> Signed-off-by: Jason Xing <kernelxing@...cent.com>
> ---
> v3:
> 1) get rid of inline suggested by Simon Horman
> 
> v2:
> 1) change the title and body message
> 2) use __sk_mem_schedule() instead suggested by Paolo Abeni
> ---
>  net/ipv4/udp.c | 31 ++++++++++++++++++-------------
>  1 file changed, 18 insertions(+), 13 deletions(-)
> 
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index c605d171eb2d..60473781933c 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -1531,10 +1531,23 @@ static void busylock_release(spinlock_t *busy)
>  		spin_unlock(busy);
>  }
>  
> +static int udp_rmem_schedule(struct sock *sk, int size)
> +{
> +	int delta;
> +
> +	delta = size - sk->sk_forward_alloc;
> +	if (delta > 0 && !__sk_mem_schedule(sk, delta, SK_MEM_RECV))
> +		return -ENOBUFS;
> +
> +	sk->sk_forward_alloc -= size;

I think it's better if you maintain the above statement outside of this
helper: it's a bit confusing that rmem_schedule() actually consumes fwd
memory.

Side note

Cheers,

Paolo