Re: [RFC ABI V5 01/10] RDMA/core: Refactor IDR to be per-device

[Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>]

On Fri, Oct 28, 2016 at 10:53:13PM +0000, Hefty, Sean wrote:
> > The current code creates an IDR per type. Since types are currently
> > common for all vendors and known in advance, this was good enough.
> > However, the proposed ioctl based infrastructure allows each vendor
> > to declare only some of the common types and declare its own specific
> > types.
> > 
> > Thus, we decided to implement IDR to be per device and refactor it to
> > use a new file.
> 
> I think this needs to be more abstract.  I would consider
> introducing the concept of an 'ioctl provider', with the idr per
> ioctl provider.  You could then make each ib_device an ioctl
> provider.  (Just embed the structure).  I believe this will be
> necessary to support the rdma_cm, ib_cm, as well as devices that
> export different sets of ioctls, where an ib_device isn't
> necessarily available.
> 
> Essentially, I would treat plugging into the uABI independent from
> plugging into the kernel verbs API.  Otherwise, I think we'll end up
> with multiple ioctl 'frameworks'.

Matan,

I think you should change things so that all the *general* code uses
'urdma_' as a prefix instead of uverbs_. Only use uverbs_ on things
that truely only apply to uverbs. This will make things much
clearer how the code sharing is expected to work with rdma_cm

Sean is right, this shows why having the IDR be per device does not
work, rdma-cm really does need a per-file or global IDR - both
approaches should really be the same, and I think per-file has better
locking characteristics, so I'd recommend that.

Jason

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