Subject: Re: [PATCH 5/6] bridge: new function to pack vlans using both IFLA_BRIDGE_VLAN_INFO and IFLA_BRIDGE_VLAN_RANGE_INFO

From: roopa <[email-masked]>
Date: Tue, 30 Dec 2014 05:57:56 -0800

On 12/30/14, 12:04 AM, Scott Feldman wrote:
> On Mon, Dec 29, 2014 at 9:31 PM, roopa <[email-masked]> wrote:
>> On 12/29/14, 3:25 PM, Scott Feldman wrote:
>>> On Mon, Dec 29, 2014 at 1:05 PM,  <[email-masked]> wrote:
>>>> From: Roopa Prabhu <[email-masked]>
>>>>
>>>> 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 <[email-masked]>
>>>> Signed-off-by: Roopa Prabhu <[email-masked]>
>>>> ---
>>>>    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.
They are all under rtnl_lock today. In any case, I do plan to change it 
to kzalloc in its current place.