netdev - Re: [PATCH net] net: Do not clear the socket TX queue in sock

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Date:   Mon, 22 Jun 2020 08:53:01 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Tariq Toukan <tariqt@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, Saeed Mahameed <saeedm@...lanox.com>,
        Boris Pismenny <borisp@...lanox.com>
Subject: Re: [PATCH net] net: Do not clear the socket TX queue in
 sock_orphan()



On 6/21/20 7:09 AM, Tariq Toukan wrote:
> sock_orphan() call to sk_set_socket() implies clearing the sock TX queue.
> This might cause unexpected out-of-order transmit, as outstanding packets
> can pick a different TX queue and bypass the ones already queued.
> This is undesired in general. More specifically, it breaks the in-order
> scheduling property guarantee for device-offloaded TLS sockets.
> 
> Introduce a function variation __sk_set_socket() that does not clear
> the TX queue, and call it from sock_orphan().
> All other callers of sk_set_socket() do not operate on an active socket,
> so they do not need this change.
> 
> Fixes: e022f0b4a03f ("net: Introduce sk_tx_queue_mapping")
> Signed-off-by: Tariq Toukan <tariqt@...lanox.com>
> Reviewed-by: Boris Pismenny <borisp@...lanox.com>
> ---
>  include/net/sock.h | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> Please queue for -stable.
> 
> diff --git a/include/net/sock.h b/include/net/sock.h
> index c53cc42b5ab9..23e43f3d79f0 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -1846,10 +1846,15 @@ static inline int sk_rx_queue_get(const struct sock *sk)
>  }
>  #endif
>  
> +static inline void __sk_set_socket(struct sock *sk, struct socket *sock)
> +{
> +	sk->sk_socket = sock;
> +}
> +
>  static inline void sk_set_socket(struct sock *sk, struct socket *sock)
>  {
>  	sk_tx_queue_clear(sk);
> -	sk->sk_socket = sock;
> +	__sk_set_socket(sk, sock);
>  }
>  

Hmm...

I think we should have a single sk_set_socket() call, and remove
the sk_tx_queue_clear() from it.

sk_tx_queue_clear() should be put where it is needed, instead of being hidden
in sk_set_socket()

diff --git a/include/net/sock.h b/include/net/sock.h
index c53cc42b5ab92d0062519e60435b85c75564a967..3428619faae4340485b200f49d9cce4fb09086b3 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1848,7 +1848,6 @@ static inline int sk_rx_queue_get(const struct sock *sk)
 
 static inline void sk_set_socket(struct sock *sk, struct socket *sock)
 {
-       sk_tx_queue_clear(sk);
        sk->sk_socket = sock;
 }
 
diff --git a/net/core/sock.c b/net/core/sock.c
index 6c4acf1f0220b1f925ebcfaa847632ec0dbe0b9b..134de0d37f77ba781b2b3341c94a97a1b2d57a2d 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1767,6 +1767,7 @@ 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;
@@ -1990,6 +1991,7 @@ 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)