netdev - Re: [PATCH] net: bonding: Fix transmit load balancing in balance-alb mode if specified by sysfs

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Date:   Sat, 9 Sep 2017 14:28:11 +0300
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     Kosuke Tatsukawa <tatsu@...jp.nec.com>,
        Jay Vosburgh <j.vosburgh@...il.com>,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Reinis Rozitis <r@...e.lv>
Subject: Re: [PATCH] net: bonding: Fix transmit load balancing in balance-alb
 mode if specified by sysfs

On 07/09/17 01:47, Kosuke Tatsukawa wrote:
> Commit cbf5ecb30560 ("net: bonding: Fix transmit load balancing in
> balance-alb mode") tried to fix transmit dynamic load balancing in
> balance-alb mode, which wasn't working after commit 8b426dc54cf4
> ("bonding: remove hardcoded value").
> 
> It turned out that my previous patch only fixed the case when
> balance-alb was specified as bonding module parameter, and not when
> balance-alb mode was set using /sys/class/net/*/bonding/mode (the most
> common usage).  In the latter case, tlb_dynamic_lb was set up according
> to the default mode of the bonding interface, which happens to be
> balance-rr.
> 
> This additional patch addresses this issue by setting up tlb_dynamic_lb
> to 1 if "mode" is set to balance-alb through the sysfs interface.
> 
> I didn't add code to change tlb_balance_lb back to the default value for
> other modes, because "mode" is usually set up only once during
> initialization, and it's not worthwhile to change the static variable
> bonding_defaults in bond_main.c to a global variable just for this
> purpose.
> 
> Commit 8b426dc54cf4 also changes the value of tlb_dynamic_lb for
> balance-tlb mode if it is set up using the sysfs interface.  I didn't
> change that behavior, because the value of tlb_balance_lb can be changed
> using the sysfs interface for balance-tlb, and I didn't like changing
> the default value back and forth for balance-tlb.
> 
> As for balance-alb, /sys/class/net/*/bonding/tlb_balance_lb cannot be
> written to.  However, I think balance-alb with tlb_dynamic_lb set to 0
> is not an intended usage, so there is little use making it writable at
> this moment.
> 
> Fixes: 8b426dc54cf4 ("bonding: remove hardcoded value")
> Reported-by: Reinis Rozitis <r@...e.lv>
> Signed-off-by: Kosuke Tatsukawa <tatsu@...jp.nec.com>
> Cc: stable@...r.kernel.org  # v4.12+
> ---
>  drivers/net/bonding/bond_options.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 

This fix is simpler and more suitable for -net, it fixes the case where
we switch to ALB mode with tlb_dynamic_lb = 0. After it is in I'll fix the
default tlb_dynamic_lb issue and restore the original behaviour.

Acked-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>