netdev - Re: [PATCH 5/6] bridge: new function to pack vlans using both IFLA_BRIDGE_VLAN_INFO and IFLA_BRIDGE_VLAN_RANGE

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Date:	Tue, 30 Dec 2014 00:04:05 -0800
From:	Scott Feldman <sfeldma@...il.com>
To:	roopa <roopa@...ulusnetworks.com>
Cc:	Netdev <netdev@...r.kernel.org>, shemminger@...tta.com,
	"vyasevic@...hat.com" <vyasevic@...hat.com>,
	Wilson kok <wkok@...ulusnetworks.com>
Subject: Re: [PATCH 5/6] bridge: new function to pack vlans using both
 IFLA_BRIDGE_VLAN_INFO and IFLA_BRIDGE_VLAN_RANGE_INFO

On Mon, Dec 29, 2014 at 9:31 PM, roopa <roopa@...ulusnetworks.com> wrote:
> On 12/29/14, 3:25 PM, Scott Feldman wrote:
>>
>> On Mon, Dec 29, 2014 at 1:05 PM,  <roopa@...ulusnetworks.com> wrote:
>>>
>>> From: Roopa Prabhu <roopa@...ulusnetworks.com>
>>>
>>> This patch adds new function to compress vlans into ranges.
>>> Vlans are compressed into ranges only if the fill request is called with
>>> RTEXT_FILTER_BRVLAN_COMPRESSED in filtermask.
>>>
>>> Old vlan packing code is moved to a new function and continues to be
>>> called when filter_mask is RTEXT_FILTER_BRVLAN
>>>
>>> Signed-off-by: Wilson kok <wkok@...ulusnetworks.com>
>>> Signed-off-by: Roopa Prabhu <roopa@...ulusnetworks.com>
>>> ---
>>>   net/bridge/br_netlink.c |  157
>>> +++++++++++++++++++++++++++++++++++++++++------
>>>   1 file changed, 137 insertions(+), 20 deletions(-)
>>>
>>> diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
>>> index 4c47ba0..16bdd5a 100644
>>> --- a/net/bridge/br_netlink.c
>>> +++ b/net/bridge/br_netlink.c
>>> @@ -67,6 +67,133 @@ static int br_port_fill_attrs(struct sk_buff *skb,
>>>          return 0;
>>>   }
>>>
>>> +static int br_fill_ifvlaninfo_bitmap(struct sk_buff *skb,
>>> +                                    const unsigned long *vlan_bmp, u16
>>> flags)
>>> +{
>>> +       struct bridge_vlan_range_info vinfo_range;
>>> +       struct bridge_vlan_info vinfo;
>>> +       u16 vid, start = 0, end = 0;
>>
>> One per line?
>
> ack
>
>>> +       u16 pvid;
>>
>> Aren't you getting an "unused" compile warning on this ^^^?
>
> will double check..
>
>>> +
>>> +       /* handle the untagged */
>>
>> This comment ^^^ doesn't make sense here.
>>
>>> +       for_each_set_bit(vid, vlan_bmp, VLAN_N_VID) {
>>> +               if (start == 0) {
>>> +                       start = vid;
>>> +                       end = vid;
>>> +               }
>>> +               if ((vid - end) > 1) {
>>> +                       memset(&vinfo_range, 0, sizeof(vinfo_range));
>>> +                       vinfo_range.flags |= flags;
>>> +                       vinfo_range.vid = start;
>>> +                       vinfo_range.vid_end = end;
>>> +                       if (nla_put(skb, IFLA_BRIDGE_VLAN_RANGE_INFO,
>>> +                                   sizeof(vinfo_range), &vinfo_range))
>>> +                               goto nla_put_failure;
>>> +                       start = vid;
>>> +                       end = vid;
>>> +               } else {
>>> +                       end = vid;
>>> +               }
>>> +       }
>>
>> What happens with this set {1-10, 12, 20-25, 30}?  On vid 12, will
>> that put a VLAN_RANGE_INFO with start=end=12?  Seems strange to use
>> RANGE_INFO for single vlan.
>>
>> Can the algorithm be simplified?  Maybe there are other examples in
>> the kernel of finding ranges/singles from a bitmap we could borrow
>> code from?
>
> let me see...
>
>>> +       if (start != 0 && end != 0) {
>>> +               if (start != end) {
>>> +                       memset(&vinfo_range, 0, sizeof(vinfo_range));
>>> +                       vinfo_range.flags |= flags;
>>> +                       vinfo_range.vid = start;
>>> +                       vinfo_range.vid_end = end;
>>> +                       if (nla_put(skb, IFLA_BRIDGE_VLAN_RANGE_INFO,
>>> +                                   sizeof(vinfo_range), &vinfo_range))
>>> +                               goto nla_put_failure;
>>> +               } else {
>>> +                       memset(&vinfo, 0, sizeof(vinfo));
>>> +                       vinfo.flags |= flags;
>>> +                       vinfo.vid = start;
>>> +                       if (nla_put(skb, IFLA_BRIDGE_VLAN_INFO,
>>> +                                   sizeof(vinfo), &vinfo))
>>> +                               goto nla_put_failure;
>>
>> How many IFLA_BRIDGE_VLAN_INFOs can you fit into skb?   It seems the
>> worst case is you'll have 4094/2 = 2047 VLAN_INFOs if using all
>> even-numbered vids, for example.  Will that fit?  I guess the original
>> code had the same concern...wonder if anyone checked this worst-case?
>
>
> I will check this again. Remember doing worst case tests for setlinks. will
> get back with some worst cases tests in the next submission.
>>
>>
>>> +               }
>>> +       }
>>> +
>>> +nla_put_failure:
>>> +       return -EMSGSIZE;
>>> +}
>>> +
>>> +static int br_fill_ifvlaninfo_compressed(struct sk_buff *skb,
>>> +                                        const struct net_port_vlans *pv)
>>> +{
>>> +       unsigned long vlan_bmp_copy[BR_VLAN_BITMAP_LEN];
>>> +       unsigned long untagged_bmp_copy[BR_VLAN_BITMAP_LEN];
>>
>> Lots of automatic space on the stack...can you use dynamic mem
>> (kzalloc) for these?
>
> Let me see. Or make it a static global ?

Static global would be bad news for multiple threads doing a vlan fill.
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