linux-kernel - Re: [PATCH net] net: Remove redundant calls of sk_tx_queue

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Date:   Wed, 27 Jan 2021 15:54:32 +0100
From:   Eric Dumazet <edumazet@...gle.com>
To:     Kuniyuki Iwashima <kuniyu@...zon.co.jp>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, Amit Shah <aams@...zon.de>,
        Kuniyuki Iwashima <kuni1840@...il.com>,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Tariq Toukan <tariqt@...lanox.com>,
        Boris Pismenny <borisp@...lanox.com>
Subject: Re: [PATCH net] net: Remove redundant calls of sk_tx_queue_clear().

On Wed, Jan 27, 2021 at 1:50 PM Kuniyuki Iwashima <kuniyu@...zon.co.jp> wrote:
>
> The commit 41b14fb8724d ("net: Do not clear the sock TX queue in
> sk_set_socket()") removes sk_tx_queue_clear() from sk_set_socket() and adds
> it instead in sk_alloc() and sk_clone_lock() to fix an issue introduced in
> the commit e022f0b4a03f ("net: Introduce sk_tx_queue_mapping"). However,
> the original commit had already put sk_tx_queue_clear() in sk_prot_alloc():
> the callee of sk_alloc() and sk_clone_lock(). Thus sk_tx_queue_clear() is
> called twice in each path currently.

Are you sure ?

I do not clearly see the sk_tx_queue_clear() call from the cloning part.

Please elaborate.

In any case, this seems to be a candidate for net-next, this is not
fixing a bug,
this would be an optimization at most, and potentially adding a bug.

So if you resend this patch, you can mention the old commit in the changelog,
but do not add a dubious Fixes: tag


>
> This patch removes the redundant calls of sk_tx_queue_clear() in sk_alloc()
> and sk_clone_lock().
>
> Fixes: 41b14fb8724d ("net: Do not clear the sock TX queue in sk_set_socket()")
> CC: Tariq Toukan <tariqt@...lanox.com>
> CC: Boris Pismenny <borisp@...lanox.com>
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.co.jp>
> Reviewed-by: Amit Shah <aams@...zon.de>
> ---
>  net/core/sock.c | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/net/core/sock.c b/net/core/sock.c
> index bbcd4b97eddd..5c665ee14159 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -1759,7 +1759,6 @@ struct sock *sk_alloc(struct net *net, int family, gfp_t priority,
>                 cgroup_sk_alloc(&sk->sk_cgrp_data);
>                 sock_update_classid(&sk->sk_cgrp_data);
>                 sock_update_netprioidx(&sk->sk_cgrp_data);
> -               sk_tx_queue_clear(sk);
>         }
>
>         return sk;
> @@ -1983,7 +1982,6 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
>                  */
>                 sk_refcnt_debug_inc(newsk);
>                 sk_set_socket(newsk, NULL);
> -               sk_tx_queue_clear(newsk);
>                 RCU_INIT_POINTER(newsk->sk_wq, NULL);
>
>                 if (newsk->sk_prot->sockets_allocated)
> --
> 2.17.2 (Apple Git-113)
>