Re: [PATCH rdma-next v1 2/4] RDMA/nldev: Allow different fill function per resource

[Leon Romanovsky <leon@kernel.org>]

On Mon, Sep 09, 2019 at 08:48:09AM +0000, Jason Gunthorpe wrote:
> On Fri, Aug 30, 2019 at 11:16:10AM +0300, Leon Romanovsky wrote:
> > From: Erez Alfasi <ereza@mellanox.com>
> >
> > So far res_get_common_{dumpit, doit} was using the default
> > resource fill function which was defined as part of the
> > nldev_fill_res_entry fill_entries.
> >
> > Add a fill function pointer as an argument allows us to use
> > different fill function in case we want to dump different
> > values then 'rdma resource' flow do, but still use the same
> > existing general resources dumping flow.
> >
> > If a NULL value is passed, it will be using the default
> > fill function that was defined in 'fill_entries' for a
> > given resource type.
> >
> > Signed-off-by: Erez Alfasi <ereza@mellanox.com>
> > Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
> >  drivers/infiniband/core/nldev.c | 42 +++++++++++++++++++++++----------
> >  1 file changed, 29 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/infiniband/core/nldev.c b/drivers/infiniband/core/nldev.c
> > index cc08218f1ef7..47f7fe5432db 100644
> > +++ b/drivers/infiniband/core/nldev.c
> > @@ -1181,7 +1181,10 @@ static const struct nldev_fill_res_entry fill_entries[RDMA_RESTRACK_MAX] = {
> >
> >  static int res_get_common_doit(struct sk_buff *skb, struct nlmsghdr *nlh,
> >  			       struct netlink_ext_ack *extack,
> > -			       enum rdma_restrack_type res_type)
> > +			       enum rdma_restrack_type res_type,
> > +			       int (*fill_func)(struct sk_buff*, bool,
> > +						struct rdma_restrack_entry*,
> > +						uint32_t))
>
> Use a typedef?

I'll take a look on that, but it is not fully clear to me what are the
gains here.

>
> >  {
> >  	const struct nldev_fill_res_entry *fe = &fill_entries[res_type];
> >  	struct nlattr *tb[RDMA_NLDEV_ATTR_MAX];
> > @@ -1244,7 +1247,12 @@ static int res_get_common_doit(struct sk_buff *skb, struct nlmsghdr *nlh,
> >  	}
> >
> >  	has_cap_net_admin = netlink_capable(skb, CAP_NET_ADMIN);
> > -	ret = fe->fill_res_func(msg, has_cap_net_admin, res, port);
> > +
> > +	if (fill_func)
> > +		ret = fill_func(msg, has_cap_net_admin, res, port);
> > +	else
> > +		ret = fe->fill_res_func(msg, has_cap_net_admin, res, port);
>
> Weird to now be choosing between two function pointers

I didn't like this either, but we didn't find an easy solution to do
chains of fill functions. In our case, we are requesting COUNTER object
which will call to MR object to fill statistic.

>
> > -#define RES_GET_FUNCS(name, type)                                              \
> > -	static int nldev_res_get_##name##_dumpit(struct sk_buff *skb,          \
> > +#define RES_GET_FUNCS(name, type)					       \
> > +	static int nldev_res_get_##name##_dumpit(struct sk_buff *skb,	       \
> >  						 struct netlink_callback *cb)  \
> > -	{                                                                      \
> > -		return res_get_common_dumpit(skb, cb, type);                   \
> > -	}                                                                      \
> > -	static int nldev_res_get_##name##_doit(struct sk_buff *skb,            \
> > -					       struct nlmsghdr *nlh,           \
> > +	{								       \
> > +		return res_get_common_dumpit(skb, cb, type, NULL);	       \
> > +	}								       \
> > +	static int nldev_res_get_##name##_doit(struct sk_buff *skb,	       \
> > +					       struct nlmsghdr *nlh,	       \
> >  					       struct netlink_ext_ack *extack) \
> > -	{                                                                      \
> > -		return res_get_common_doit(skb, nlh, extack, type);            \
> > +	{								       \
> > +		return res_get_common_doit(skb, nlh, extack, type, NULL);      \
> >  	}
>
> ie the NULL should be fill_entries[type]->fill_res_func?

The "if (fill_func) " above will do the trick.

>
> Jason