netdev - Re: [PATCH net-next v3 3/4] bridge: push bridge setting ageing

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Message-ID: <CAE4R7bC9zjQ+oQsRV=aBrJj2LRmqXPLKTs7zSr0rnKZt1d10gw@mail.gmail.com>
Date:	Sun, 11 Oct 2015 22:43:16 -0700
From:	Scott Feldman <sfeldma@...il.com>
To:	Jiri Pirko <jiri@...nulli.us>
Cc:	Premkumar Jonnala <pjonnala@...adcom.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"siva.mannem.lnx@...il.com" <siva.mannem.lnx@...il.com>,
	"stephen@...workplumber.org" <stephen@...workplumber.org>,
	"roopa@...ulusnetworks.com" <roopa@...ulusnetworks.com>,
	"andrew@...n.ch" <andrew@...n.ch>,
	"f.fainelli@...il.com" <f.fainelli@...il.com>,
	"vivien.didelot@...oirfairelinux.com" 
	<vivien.didelot@...oirfairelinux.com>
Subject: Re: [PATCH net-next v3 3/4] bridge: push bridge setting ageing_time
 down to switchdev

On Sat, Oct 10, 2015 at 12:04 AM, Jiri Pirko <jiri@...nulli.us> wrote:
> Sat, Oct 10, 2015 at 04:53:52AM CEST, sfeldma@...il.com wrote:
>>On Thu, Oct 8, 2015 at 9:38 PM, Premkumar Jonnala <pjonnala@...adcom.com> wrote:
>>>
>>>
>>>> -----Original Message-----
>>>> From: sfeldma@...il.com [mailto:sfeldma@...il.com]
>>>> Sent: Friday, October 09, 2015 7:53 AM
>>>> To: netdev@...r.kernel.org
>>>> Cc: davem@...emloft.net; jiri@...nulli.us; siva.mannem.lnx@...il.com;
>>>> Premkumar Jonnala; stephen@...workplumber.org;
>>>> roopa@...ulusnetworks.com; andrew@...n.ch; f.fainelli@...il.com;
>>>> vivien.didelot@...oirfairelinux.com
>>>> Subject: [PATCH net-next v3 3/4] bridge: push bridge setting ageing_time down
>>>> to switchdev
>>>>
>>>> From: Scott Feldman <sfeldma@...il.com>
>>>>
>>>> Use SWITCHDEV_F_SKIP_EOPNOTSUPP to skip over ports in bridge that don't
>>>> support setting ageing_time (or setting bridge attrs in general).
>>>>
>>>> If push fails, don't update ageing_time in bridge and return err to user.
>>>>
>>>> If push succeeds, update ageing_time in bridge and run gc_timer now to
>>>> recalabrate when to run gc_timer next, based on new ageing_time.
>>>>
>>>> Signed-off-by: Scott Feldman <sfeldma@...il.com>
>>>> Signed-off-by: Jiri Pirko <jiri@...nulli.us>
>>
>><snip>
>>
>>>> +int br_set_ageing_time(struct net_bridge *br, u32 ageing_time)
>>>> +{
>>>> +     struct switchdev_attr attr = {
>>>> +             .id = SWITCHDEV_ATTR_ID_BRIDGE_AGEING_TIME,
>>>> +             .flags = SWITCHDEV_F_SKIP_EOPNOTSUPP,
>>>> +             .u.ageing_time = ageing_time,
>>>> +     };
>>>> +     unsigned long t = clock_t_to_jiffies(ageing_time);
>>>> +     int err;
>>>> +
>>>> +     if (t < BR_MIN_AGEING_TIME || t > BR_MAX_AGEING_TIME)
>>>> +             return -ERANGE;
>>>> +
>>>> +     err = switchdev_port_attr_set(br->dev, &attr);
>>>
>>> A thought - given that the ageing time is not a per-bridge-port attr, why are we using a "port based api"
>>> to pass the attribute down?  May be I'm missing something here?
>>
>>I think Florian raised the same point earlier.  Sigh, I think this
>>should be addressed....v4 coming soon...thanks guys for keeping the
>>standard high.
>
> Scott, can you tell us how do you want to address this? I like the
> current implementation.

I like it also, but there is some awkwardness in calling
switchdev_port_attr_set() with the first argument being the bridge
netdev, not a port netdev.  But, the basic algorithm to recurse from
_this_ netdev down to its lower netdevs works great in this case; it's
just the name "switchdev_port_attr_set" implies a port netdev for
top-level netdev.  So I was thinking about adding another call,
something like "switchdev_master_attr_set", which basically just does
the same thing as switchdev_port_attr_set, except maybe skips the
check to call the ops->switchdev_port_attr_add on the top-level
netdev.  But now I don't like that idea so much as "master" would be
confusing when your passing a bond netdev (which is also a master),
but the bond _is_ the port netdev this time, a port on the bridge.

So let's scrap v4 and go with v3.  I think I can live with this naming
awkwardness, given that we got something for essentially free by using
switchdev_port_attr_set() in a new way.

Davem, I think we're OK going with v3.

(There is a follow-on discussion about a switch device, which we'll
continue but it shouldn't block this v3 version).
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