[ofa-general] Re: [openib-general] [RFC] [PATCH v2] IB/ipoib: Add bonding support to IPoIB

[Moni Shoua]

Michael S. Tsirkin wrote:
>> Quoting Moni Shoua <monisonlists at gmail.com>:
>> Subject: Re: [openib-general] [RFC] [PATCH v2] IB/ipoib: Add bonding support to IPoIB
>>
>> Michael S. Tsirkin wrote:
>>>> Quoting Moni Shoua <monisonlists at gmail.com>:
>>>> Subject: Re: [openib-general] [RFC] [PATCH v2] IB/ipoib: Add bonding support to IPoIB
>>>>
>>>> This version of the patch tracks the allocs and releases of ipoib_neigh and
>>>>  keeps a list of them.  Before IPoIB net device unregisters the list is passed
>>>> to destroy ipoib_neighs that ride on on a bond neighbour.
>>>>
>>>> This is a replacement to the method of scanning the arp and ndisc
>>>> tables.
>>> Why does the list need to be global?
>>> We already have a per-device list of paths, and each of these in turn
>>> has a list of neighbours. Can't this be used?
>>>
>> OK, It's a good point but coming to think of it now I have a question
>>
>> When a device unregisters ipoib_stop() is called and all ipoib_neighs are destroyed.
>>    Isn't it enough to ensure that ipoib_neigh_destructor will not try to
>>    "touch" one of the ib devs?  or in other words: Isn't it that the work to
>>    clean ipoib_neighs is unnecessary?
>>
Michael, Do you agree that destroying the ipoib_neighs 
through (a call trace that starts with) ipoib_stop() is enough for safety
and that there is no need to do that just before calling to unregister_netdev() ?

>> BTW: I guess that idea of global list was influenced from the ipoib_8111... patch. 
>> Why was it used there?
> 
> AFAIK, the point is to check whether (in pre-2.6.17 kernels) some neighbour
> shares the same ops pointer. Only after no such neighbours are left is it safe
> to set the destructor to NULL.
> 
> This backport is not raceless BTW - some neighbour not related to IPoIB could
> be running the destructor. But I think it's the best I could come up with
> for these old kernels.
>