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

[Michael S. Tsirkin]

>  > +			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)

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:

Hmm?

Signed-off-by: Michael S. Tsirkin <mst at dev.mellanox.co.il>


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;
 		spin_unlock_irqrestore(&cm.lock, flags);
 	} while( (ret == -EAGAIN) && idr_pre_get(&cm.local_id_table, GFP_KERNEL) );
 

-- 
MST