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

[Mahesh Bandewar (àààà ààààààà)]

On Sat, Sep 9, 2017 at 4:28 AM, Nikolay Aleksandrov
<nikolay@xxxxxxxxxxxxxxxxxxx> 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@xxxxxxx>
>> Signed-off-by: Kosuke Tatsukawa <tatsu@xxxxxxxxxxxxx>
>> Cc: stable@xxxxxxxxxxxxxxx  # 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)

> Acked-by: Nikolay Aleksandrov <nikolay@xxxxxxxxxxxxxxxxxxx>
Acked-by: Mahesh Bandewar <maheshb@xxxxxxxxxx>
>
>