Re: [PATCH 1/5] IB/core: Introduce Fast Indirect Memory Registration verbs API

[Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>]

On Tue, Jun 30, 2015 at 02:47:00PM +0300, Sagi Grimberg wrote:
> Kernel 4.1 introduced the new pmem driver for byte addressable storage
> (https://lwn.net/Articles/640115/). It won't be long before we see HA
> models where secondary persistent memory devices will sit across an
> RDMA fabric. (http://www.snia.org/sites/default/files/DougVoigt_RDMA_Requirements_for_HA.pdf)

And what does this bullshitting slide have to do with our memory models?
In it's current form the pmem driver can't even be used as a (R)DMA
target, so it's totally irrelevant for now.

Let's get a proper in-kernel interface for generic memory registrations
in place as a first step. le this will be a significant amount of work
it'll help greatly with moving nasty implementation details out of
the drivers.  Adding additional registrations methods will be easy
behind the back of a proper abstraction.

> Do we want to live with this limitation forever?

I don't think anyone has refused additional support.  Just the way how
it's done in your patches is a giant nightmare.  The whole RDMA stack
needs a healthy dose of software engineering instead of blindly
following a working group of a marketing organisation.
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