linux-kernel - Re: [PATCH v6 14/25] rtrs: a bit of documentation

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Date:   Mon, 30 Dec 2019 15:19:45 -0800
From:   Bart Van Assche <bvanassche@....org>
To:     Jack Wang <jinpuwang@...il.com>, linux-block@...r.kernel.org,
        linux-rdma@...r.kernel.org
Cc:     axboe@...nel.dk, hch@...radead.org, sagi@...mberg.me,
        leon@...nel.org, dledford@...hat.com, danil.kipnis@...ud.ionos.com,
        jinpu.wang@...ud.ionos.com, rpenyaev@...e.de,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 14/25] rtrs: a bit of documentation

On 2019-12-30 02:29, Jack Wang wrote:
> diff --git a/drivers/infiniband/ulp/rtrs/README b/drivers/infiniband/ulp/rtrs/README

Other kernel driver documentation exists under the Documentation/
directory. Should this README file perhaps be moved to a subdirectory of
the Documentation/ directory?

> +****************************
> +InfiniBand Transport (RTRS)
> +****************************

The abbreviation does not match the full title. Do you agree that this
is confusing?

> +RTRS is used by the RNBD (Infiniband Network Block Device) modules.

Is RNBD an RDMA or an InfiniBand network block device?

> +
> +==================
> +Transport protocol
> +==================
> +
> +Overview
> +--------
> +An established connection between a client and a server is called rtrs
> +session. A session is associated with a set of memory chunks reserved on the
> +server side for a given client for rdma transfer. A session
> +consists of multiple paths, each representing a separate physical link
> +between client and server. Those are used for load balancing and failover.
> +Each path consists of as many connections (QPs) as there are cpus on
> +the client.
> +
> +When processing an incoming rdma write or read request rtrs client uses memory

A quote from
https://linuxplumbersconf.org/event/4/contributions/367/attachments/331/555/LPC_2019_RMDA_MC_IBNBD_IBTRS_Upstreaming.pdf:
"Only RDMA writes with immediate". Has the wire protocol perhaps been
changed such that both RDMA reads and writes are used? I haven't found
any references to RDMA reads in the "IO path" section in this file. Did
I perhaps overlook something?

Thanks,

Bart.