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

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Message-ID: <819E319E-B2EE-44FF-8616-03257E753E6C@cumulusnetworks.com>
Date:   Mon, 11 Sep 2017 19:30:08 +0300
From:   Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:     Mahesh Bandewar (महेश बंडेवार) 
        <maheshb@...gle.com>
CC:     Kosuke Tatsukawa <tatsu@...jp.nec.com>,
        Jay Vosburgh <j.vosburgh@...il.com>,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        "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 11 September 2017 19:07:33 EEST, "Mahesh Bandewar (महेश बंडेवार)" <maheshb@...gle.com> wrote:
>On Sat, Sep 9, 2017 at 4:28 AM, Nikolay Aleksandrov
><nikolay@...ulusnetworks.com> wrote:
>> 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.
>>
>Changing tlb_dyanamic_lb to initialize always is also safe for -net
>and can go in before or after this change (no dependency on this
>change as such)

I never said it was unsafe or dependent, it is simply my preference to wait. :-)
If you need it sooner feel free to post it.

>
>> Acked-by: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
>Acked-by: Mahesh Bandewar <maheshb@...gle.com>
>>
>>