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SubjectRe: [PATCH] net: bonding: Fix transmit load balancing in balance-alb mode if specified by sysfs
On Fri, Sep 8, 2017 at 7:30 AM, Nikolay Aleksandrov
<nikolay@cumulusnetworks.com> wrote:
> On 08/09/17 17:17, Kosuke Tatsukawa wrote:
>> Hi,
>>
>>> On 08/09/17 13:10, Nikolay Aleksandrov wrote:
>>>> On 08/09/17 05:06, Kosuke Tatsukawa wrote:
>>>>> Hi,
>>>>>
>>>>>> On 7.09.2017 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@roze.lv>
>>>>>>> Signed-off-by: Kosuke Tatsukawa <tatsu@ab.jp.nec.com>
>>>>>>> Cc: stable@vger.kernel.org # v4.12+
>>>>>>> ---
>>>>>>> drivers/net/bonding/bond_options.c | 3 +++
>>>>>>> 1 files changed, 3 insertions(+), 0 deletions(-)
>>>>>>>
>>>>>>
>>>>>> I don't believe this to be the right solution, hardcoding it like this
>>>>>> changes user-visible behaviour. The issue is that if someone configured
>>>>>> it to be 0 in tlb mode, suddenly it will become 1 and will silently
>>>>>> override their config if they switch the mode to alb. Also it robs users
>>>>>> from their choice.
>>>>>>
>>>>>> If you think this should be settable in ALB mode, then IMO you should
>>>>>> edit tlb_dynamic_lb option's unsuppmodes and allow it to be set in ALB.
>>>>>> That would also be consistent with how it's handled in TLB mode.
>>>>>
>>>>> No, I don't think tlb_dynamic_lb should be settable in balance-alb at
>>>>> this point. All the current commits regarding tlb_dynamic_lb are for
>>>>> balance-tlb mode, so I don't think balance-alb with tlb_dynamic_lb set
>>>>> to 0 is an intended usage.
>>>>>
>>>>>
>>>>>> Going back and looking at your previous fix I'd argue that it is also
>>>>>> wrong, you should've removed the mode check altogether to return the
>>>>>> original behaviour where the dynamic_lb is set to 1 (enabled) by
>>>>>> default and then ALB mode would've had it, of course that would've left
>>>>>> the case of setting it to 0 in TLB mode and switching to ALB, but that
>>>>>> is a different issue.
>>>>>
>>>>> Maybe balance-alb shouldn't be dependent on tlb_dynamic_lb.
>>>>> tlb_dynamic_lb is referenced in the following functions.
>>>>>
>>>>> + bond_do_alb_xmit() -- Used by both balance-tlb and balance-alb
>>>>> + bond_tlb_xmit() -- Only used by balance-tlb
>>>>> + bond_open() -- Used by both balance-tlb and balance-alb
>>>>> + bond_check_params() -- Used during module initialization
>>>>> + bond_fill_info() -- Used to get/set value
>>>>> + bond_option_tlb_dynamic_lb_set() -- Used to get/set value
>>>>> + bonding_show_tlb_dynamic_lb() -- Used to get/set value
>>>>> + bond_is_nondyn_tlb() -- Only referenced if balance-tlb mode
>>>>>
>>>>> The following untested patch adds code to make balance-alb work as if
>>>>> tlb_dynamic_lb==1 for the functions which affect balance-alb mode. It
>>>>> also reverts my previous patch.
>>>>>
>>>>> What do you think about this approach?
>>>>> ---
>>>>> Kosuke TATSUKAWA | 1st Platform Software Division
>>>>> | NEC Solution Innovators
>>>>> | tatsu@ab.jp.nec.com
>>>>>
>>>>
>>>> Logically the approach looks good, that being said it adds unnecessary tests in
>>>> the fast path, why not just something like the patch below ? That only leaves the
>>>> problem if it is zeroed in TLB and switched to ALB mode, and that is a one line
>>>> fix to unsuppmodes just allow it to be set for that specific case. The below
>>>> returns the default behaviour before the commit in your Fixes tag.
>>>>
>>>>
>>>
>>> Actually I'm fine with your approach, too. It will fix this regardless of the
>>> value of tlb_dynamic_lb which sounds good to me for the price of a test in
>>> the fast path.
>>
>> If you're concerned about the additional test in the fast path, how
>> about the patch below. I've added an arguemnt to bond_do_alb_xmit()
>> to handle both balance-tlb and balance-alb similary.
>>
>
> Even better, looks great! 1 question below though.
>
>> I'm not sure if this causes any problem if tlb_dynamic_lb is changed
>> while calling bond_do_alb_xmit() in balance-tlb mode.
>
> The option has the ifdown flag, you shouldn't be able to change it while
> the bond dev is up, but even if you could I don't think it will be an issue
> for the xmit.
>
>> ---
>> Kosuke TATSUKAWA | 1st Platform Software Division
>> | NEC Solution Innovators
>> | tatsu@ab.jp.nec.com
>>
>> ------------------------------------------------------------------------
>> drivers/net/bonding/bond_alb.c | 11 ++++++-----
>> drivers/net/bonding/bond_main.c | 5 +++--
>> 2 files changed, 9 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
>> index c02cc81..7710f20 100644
>> --- a/drivers/net/bonding/bond_alb.c
>> +++ b/drivers/net/bonding/bond_alb.c
>> @@ -1317,7 +1317,7 @@ void bond_alb_deinitialize(struct bonding *bond)
>> }
>>
>> static int bond_do_alb_xmit(struct sk_buff *skb, struct bonding *bond,
>> - struct slave *tx_slave)
>> + struct slave *tx_slave, int tlb_dynamic_lb)
>> {
>> struct alb_bond_info *bond_info = &(BOND_ALB_INFO(bond));
>> struct ethhdr *eth_data = eth_hdr(skb);
>> @@ -1325,7 +1325,7 @@ static int bond_do_alb_xmit(struct sk_buff *skb, struct bonding *bond,
>> if (!tx_slave) {
>> /* unbalanced or unassigned, send through primary */
>> tx_slave = rcu_dereference(bond->curr_active_slave);
>> - if (bond->params.tlb_dynamic_lb)
>> + if (tlb_dynamic_lb)
>> bond_info->unbalanced_load += skb->len;
>> }
>>
>> @@ -1339,7 +1339,7 @@ static int bond_do_alb_xmit(struct sk_buff *skb, struct bonding *bond,
>> goto out;
>> }
>>
>> - if (tx_slave && bond->params.tlb_dynamic_lb) {
>> + if (tx_slave && tlb_dynamic_lb) {
>> spin_lock(&bond->mode_lock);
>> __tlb_clear_slave(bond, tx_slave, 0);
>> spin_unlock(&bond->mode_lock);
>> @@ -1386,7 +1386,8 @@ int bond_tlb_xmit(struct sk_buff *skb, struct net_device *bond_dev)
>> break;
>> }
>> }
>> - return bond_do_alb_xmit(skb, bond, tx_slave);
>> + return bond_do_alb_xmit(skb, bond, tx_slave,
>> + bond->params.tlb_dynamic_lb);
>> }
>>
>> int bond_alb_xmit(struct sk_buff *skb, struct net_device *bond_dev)
>> @@ -1483,7 +1484,7 @@ int bond_alb_xmit(struct sk_buff *skb, struct net_device *bond_dev)
>> tx_slave = tlb_choose_channel(bond, hash_index, skb->len);
>> }
>>
>> - return bond_do_alb_xmit(skb, bond, tx_slave);
>> + return bond_do_alb_xmit(skb, bond, tx_slave, 1);
>> }
>>
>> void bond_alb_monitor(struct work_struct *work)
>> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>> index fc63992..bcb71e7 100644
>> --- a/drivers/net/bonding/bond_main.c
>> +++ b/drivers/net/bonding/bond_main.c
>> @@ -3305,7 +3305,8 @@ static int bond_open(struct net_device *bond_dev)
>> */
>> if (bond_alb_initialize(bond, (BOND_MODE(bond) == BOND_MODE_ALB)))
>> return -ENOMEM;
>> - if (bond->params.tlb_dynamic_lb)
>> + if (bond->params.tlb_dynamic_lb ||
>> + (BOND_MODE(bond) == BOND_MODE_TLB))
>
> mode == tlb ? shouldn't this check be for alb ?
>
Actually this is not needed since this is already inside if
(bond_is_lb()) condition.

>> queue_delayed_work(bond->wq, &bond->alb_work, 0);
>> }
>>
>> @@ -4601,7 +4602,7 @@ static int bond_check_params(struct bond_params *params)
>> }
>> ad_user_port_key = valptr->value;
>>
>> - if ((bond_mode == BOND_MODE_TLB) || (bond_mode == BOND_MODE_ALB)) {
>> + if (bond_mode == BOND_MODE_TLB) {
>> bond_opt_initstr(&newval, "default");
>> valptr = bond_opt_parse(bond_opt_get(BOND_OPT_TLB_DYNAMIC_LB),
>> &newval);
>>
>
I think the underlying issue is that tlb_dynamic_lb should be set to 1
for all modes which was not the case when it was getting initialized
only forTLB mode. So from that perspective I prefer Nik's patch with a
small variation that guards the case when mode transitions from TLB to
ALB. The reason why I like that patch is because it's simple and
avoids complications.

Here is what I meant -

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index fc63992ab0e0..c99dc59d729b 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -4289,7 +4289,7 @@ static int bond_check_params(struct bond_params *params)
int bond_mode = BOND_MODE_ROUNDROBIN;
int xmit_hashtype = BOND_XMIT_POLICY_LAYER2;
int lacp_fast = 0;
- int tlb_dynamic_lb = 0;
+ int tlb_dynamic_lb;

/* Convert string parameters. */
if (mode) {
@@ -4601,16 +4601,13 @@ static int bond_check_params(struct bond_params *params)
}
ad_user_port_key = valptr->value;

- if ((bond_mode == BOND_MODE_TLB) || (bond_mode == BOND_MODE_ALB)) {
- bond_opt_initstr(&newval, "default");
- valptr = bond_opt_parse(bond_opt_get(BOND_OPT_TLB_DYNAMIC_LB),
- &newval);
- if (!valptr) {
- pr_err("Error: No tlb_dynamic_lb default value");
- return -EINVAL;
- }
- tlb_dynamic_lb = valptr->value;
+ bond_opt_initstr(&newval, "default");
+ valptr = bond_opt_parse(bond_opt_get(BOND_OPT_TLB_DYNAMIC_LB), &newval);
+ if (!valptr) {
+ pr_err("Error: No tlb_dynamic_lb default value");
+ return -EINVAL;
}
+ tlb_dynamic_lb = valptr->value;

if (lp_interval == 0) {
pr_warn("Warning: ip_interval must be between 1 and
%d, so it was reset to %d\n",
diff --git a/drivers/net/bonding/bond_options.c
b/drivers/net/bonding/bond_options.c
index a12d603d41c6..7feacd262182 100644
--- a/drivers/net/bonding/bond_options.c
+++ b/drivers/net/bonding/bond_options.c
@@ -754,6 +754,12 @@ static int bond_option_mode_set(struct bonding *bond,
bond->params.miimon);
}

+ /* Guard against transition TLB/tlb_dynamic_lb=0 -> ALB mode.
+ * In ALB mode, tlb_dynamic_lb must be set to 1.
+ */
+ if (newval->value == BOND_MODE_ALB && bond->params.tlb_dynamic_lb != 1)
+ bond->params.tlb_dynamic_lb = 1;
+
/* don't cache arp_validate between modes */
bond->params.arp_validate = BOND_ARP_VALIDATE_NONE;
bond->params.mode = newval->value;
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