Re: [PATCH v3 for-next 02/33] IB/core: Add kref to IB devices

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

On Fri, May 01, 2015 at 09:34:24AM +0300, Matan Barak wrote:

> > This current scheme is just so ugly, there are so many wonky
> > possibilities. What happens if I remove an IP and then add a new one?
> > The GID index will eventually be re-used, and QPs bound to that gid
> > index will silently change source IPs. Horrible.
> 
> This should be handled by the vendor's driver/other future ib_core part.
> This patchset introduces roce_gid_cache that manages the GID table and
> notify vendors about GID changes.
> 
> The vendor needs to:
> (a) Move all QPs that use GID x to error state when GID x is deleted from
>       the table.
> (b) Change all QPs that use GID x to use a special invalid GID entry.
> (c) Don't delete GIDs that are being used by a QP.

What about AH's for UD?

What about clients that discover and then hold the GID index
internally?

What about the impossible to fix race of returing the GID index in the
work completion and translating that back to an IP?

It is a terrible scheme, Sean is right, the clients should work with
the actual sock addr, somehow, at least kernel side. Converting from a
sockaddr to a gid index cannot really be done without some kind of
lock and ref count scheme.

At the very least, that should be the starting point, if we can't get
there then patch on a case by case basis why.

Jason
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