Re: [PATCH v4 for-next 3/3] IB/core: Obtain subnet_prefix from cache in IB devices

[Anand Khoje]

On 6/16/2021 1:00 PM, Leon Romanovsky wrote:
> On Wed, Jun 16, 2021 at 12:22:13PM +0530, Anand Khoje wrote:
> > ib_query_port() calls device->ops.query_port() to get the port
> > attributes. The method of querying is device driver specific.
> > The same function calls device->ops.query_gid() to get the GID and
> > extract the subnet_prefix (gid_prefix).
> >
> > The GID and subnet_prefix are stored in a cache. But they do not get
> > read from the cache if the device is an Infiniband device. The
> > following change takes advantage of the cached subnet_prefix.
> > Testing with RDBMS has shown a significant improvement in performance
> > with this change.
> >
> > The function ib_cache_is_initialised() is introduced because
> > ib_query_port() gets called early in the stage when the cache is not
> > built while reading port immutable property.
> >
> > In that case, the default GID still gets read from HCA for IB link-
> > layer devices.
> >
> > In the situation of an event causing cache update, the subnet_prefix
> > will get retrieved from newly updated GID cache in ib_cache_update(),
> > so that we do not end up reading a stale value from cache via
> > ib_query_port().
> >
> > Fixes: fad61ad ("IB/core: Add subnet prefix to port info")
> > Suggested-by: Leon Romanovsky <leonro@xxxxxxxxxx>
> > Suggested-by: Aru Kolappan <aru.kolappan@xxxxxxxxxx>
> > Signed-off-by: Anand Khoje <anand.a.khoje@xxxxxxxxxx>
> > Signed-off-by: Haakon Bugge <haakon.bugge@xxxxxxxxxx>
> > ---
>
> <...>
>
> > @@ -1523,13 +1526,21 @@ static int config_non_roce_gid_cache(struct ib_device *device,
> >   	device->port_data[port].cache.lmc = tprops->lmc;
> >   	device->port_data[port].cache.port_state = tprops->state;
> >   
> > -	device->port_data[port].cache.subnet_prefix = tprops->subnet_prefix;
> > +	ret = rdma_query_gid(device, port, 0, &gid);
> > +	if (ret) {
> > +		write_unlock_irq(&device->cache.lock);
>
> And this patch can't compile. It should be cache_lock and not cache.lock.
>
> Thanks
Unfortunate typo from my end. Thanks for pointing this out. I will share 
the updated patch.