[ofa-general] Re: [PATCH for-2.6.22] IB/cm: improve local id allocation

[Roland Dreier]

 > IB/cm uses idr for local id allocations, with a running counter
 > as start_id. This fails to generate distinct ids in the scenario where
 > 1. An id is constantly created and destroyed
 > 2. A chunk of ids just beyond the current next_id value is occupied
 > 
 > This in turn leads to an increased chance of connection request being mis-detected
 > as a duplicate, sometimes for several retries, until next_id gets past
 > the block of allocated ids. This has been observed in practice.
 > 
 > As a fix, remember the last id allocated and start immediately above it.

OK I guess but this needs some explanation about why the impact is so
severe we want to merge it after rc2 is already out.

 > +			next_id = (unsigned)id + 1;

what happens when this wraps and becomes negative?

in fact the idr stuff all works with plain signed ints -- could
idr_get_new() ever give a negative id?  (too lazy too look at the
source right now)

 - R.