[ofa-general] [RFC/PATCH 2.6.24] ib/multicast: report errors on multicast groups if pkeys change

[Sean Hefty]

> > Pkey changes can invalidate multicast groups.  Report errors on any
> > multicast group affected by a pkey change.
>
>I'm missing some context here.  What is the issue that's being fixed
>here?  What's the impact of not having this patch?  (ie does this need
>to go into 2.6.24?  Also 2.6.23.x?  Or is 2.6.25 OK?)

If the pkey table changes, all existing multicast groups are potentially
invalidated.  Without this patch, subscribers to those groups are left
subscribed to a group that they can no longer communicate with.  This patch
determines which groups were affected by a pkey table change and reports errors
to the users.  IPoIB follows a similar process for pkey changes; see
ipoib_event() and __ipoib_ib_dev_flush(pkey_event = 1).

I don't think this is critical, but I'm assuming that changes to pkey tables
without other port events occurring are rare.  But since it is a fix and it's
early, I asked to merge into 2.6.24.

- Sean