> Quoting Roland Dreier <[EMAIL PROTECTED]>:
> Subject: Re: [PATCH for-2.6.22] IB/cm: improve local id allocation
>
> > A quick looks makes it look like idr stuff is *really* not designed to
> > get a negative input: and note that old code has the wrap-around problem,
> too.
> > So, I think the following would be a better fix:
>
> Yes, that's basically what I just proposed (although see below). It
> all looks pretty safe to me... Sean, what do you think about this for
> 2.6.22?
>
> > diff --git a/drivers/infiniband/core/cm.c b/drivers/infiniband/core/cm.c
> > index eff591d..5e77b01 100644
> > --- a/drivers/infiniband/core/cm.c
> > +++ b/drivers/infiniband/core/cm.c
> > @@ -306,7 +306,9 @@ static int cm_alloc_id(struct cm_id_private
> *cm_id_priv)
> > do {
> > spin_lock_irqsave(&cm.lock, flags);
> > ret = idr_get_new_above(&cm.local_id_table, cm_id_priv,
> > - next_id++, &id);
> > + next_id, &id);
> > + if (!ret)
> > + next_id = id == 0x7ffffff ? 0 : id + 1;
>
> ...except I used MAX_INT here, and indeed your patch only has 6 'f's
> in that constant. Actually digging a little I see that we should use
> MAX_ID_MASK to be really correct.
And since it's a *mask*, we can do it this way if you like:
> > + if (!ret)
> > + next_id = ((unsigned)id + 1) & MAX_ID_MASK;
which might generate a bit less code.
--
MST
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