Re: [PATCH v6 00/25] RTRS (former IBTRS) rdma transport library and RNBD (former IBNBD) rdma network block device

Jinpu Wang
2020-01-02T09:20:21Z

On Tue, Dec 31, 2019 at 3:39 AM Bart Van Assche <bvanassche@acm.org> wrote:
>
> On 2019-12-30 02:29, Jack Wang wrote:
> > here is V6 of the RTRS (former IBTRS) rdma transport library and the
> > corresponding RNBD (former IBNBD) rdma network block device.
> >
> > Changelog since v5:
> > 1 rebased to linux-5.5-rc4
> > 2 fix typo in my email address in first patch
> > 3 cleanup copyright as suggested by Leon Romanovsky
> > 4 remove 2 redudant kobject_del in error path as suggested by Leon Romanovsky
> > 5 add MAINTAINERS entries in alphabetical order as Gal Pressman suggested
>
> Please always include the full changelog when posting a new version.
> Every other Linux kernel patch series I have seen includes a full
> changelog in version two and later versions of its cover letter.
Sorry, it was my mistake, will include the full changelog next time.
>
> Information about how this patch series has been tested would be
> welcome. How big were the changes between v4 and v5 and how much testing
> have these changes received? Was this patch series tested in the Ionos
> data center or is it the out-of-tree version of these drivers that runs
> in the Ionos data center?
As mentioned in the v5 cover letter, the changes between v4 and v5
"'
Main changes are the following:
1. Fix the security problem pointed out by Jason
2. Implement code-style/readability/API/etc suggestions by Bart van Assche
3. Rename IBTRS and IBNBD to RTRS and RNBD accordingly
4. Fileio mode support in rnbd-srv has been removed.

The main functional change is a fix for the security problem pointed out by
Jason and discussed both on the mailing list and during the last LPC
RDMA MC 2019.
On the server side we now invalidate in RTRS each rdma buffer before we hand it
over to RNBD server and in turn to the block layer. A new rkey is generated and
registered for the buffer after it returns back from the block layer and RNBD
server. The new rkey is sent back to the client along with the IO result.
The procedure is the default behaviour of the driver. This invalidation and
registration on each IO causes performance drop of up to 20%. A user of the
driver may choose to load the modules with this mechanism switched off
(always_invalidate=N), if he understands and can take the risk of a malicious
client being able to corrupt memory of a server it is connected to. This might
be a reasonable option in a scenario where all the clients and all the servers
are located within a secure datacenter.

Huge thanks to Bart van Assche for the very detailed review of both RNBD and
RTRS. These included suggestions for style fixes, better readability and
documentation, code simplifications, eliminating usage of deprecated APIs,
too many to name.

The transport library and the network block device using it have been renamed to
RTRS and RNBD accordingly in order to reflect the fact that they are based on
the rdma subsystem and not bound to InfiniBand only.

Fileio mode support in rnbd-server is not so efficent as pointed out by Bart,
and we can use loop device in between if there is need, hence we just
removed the fileio mode support.
"'
Regarding testing, all the changes have been tested with our
regression tests in our staging environment in IONOS data center.
it's around 200 test cases, for both always_invalidate=N and
always_invalidate=Y configurations.

I will mention it in the cover letter next time.

Thanks for your comments, Bart.
>
> Thanks,
>
> Bart.