On Tue, Feb 27, 2018 at 03:27:42PM -0700, Jason Gunthorpe wrote:
> On Tue, Feb 27, 2018 at 04:21:36PM -0600, Steve Wise wrote:
> > >
> > > On Mon, Feb 26, 2018 at 03:22:42PM -0800, Steve Wise wrote:
> > >
> > > > +static int fill_res_mr_entry(struct sk_buff *msg, struct
> > netlink_callback
> > > *cb,
> > > > + struct rdma_restrack_entry *res, uint32_t port)
> > > > +{
> > > > + struct ib_mr *mr = container_of(res, struct ib_mr, res);
> > > > + struct nlattr *entry_attr;
> > > > +
> > > > + entry_attr = nla_nest_start(msg,
> > > RDMA_NLDEV_ATTR_RES_MR_ENTRY);
> > > > + if (!entry_attr)
> > > > + goto out;
> > > > +
> > > > + if (netlink_capable(cb->skb, CAP_NET_ADMIN)) {
> > > > + if (nla_put_u32(msg, RDMA_NLDEV_ATTR_RES_RKEY, mr-
> > > >rkey))
> > > > + goto err;
> > > > + if (nla_put_u32(msg, RDMA_NLDEV_ATTR_RES_LKEY, mr-
> > > >lkey))
> > > > + goto err;
> > > > + if (nla_put_u64_64bit(msg, RDMA_NLDEV_ATTR_RES_IOVA,
> > > > + mr->iova, 0))
> > >
> > > ?? is '0' right here? Expecting a defined attribute constant for padding.
> >
> >
> > What does the pad do exactly? I replicated other code I saw that use 0 for
> > the pad. But I can add a NLDEV_ATTR_RES_PAD if that is the correct way to
> > go.
>
> Sometimes netlink will try to align the u64s to 8 bytes in the skb. If
> it needs to make an alignment adjustment then it stuffs a dummy
> attribute with the given ID. The ID should never be used for any other
> attribute and must be ignored by userspace.
>
> Safest to put it in the general enum to ensure it isn't re-used.
It is already done but not really explicitly as you would like.
0 is equal to RDMA_NLDEV_ATTR_UNSPEC and user space is ignoring this
attribute.
Thanks
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